Notes for Quarter I - Quia



Notes for Quarter 4

Information Posted on 6/6/06

Notes for Chapter 17 – Birds and Mammals

Section 1 – Characteristics of Birds

One familiar characteristic of birds is their feathers – they help birds stay dry and warm, attract mates, and fly. In the act of preening, birds use their beaks to spread oil on their feathers. The oil is made by a gland near the bird’s tail. When feathers wear out, birds replace them by molting. Most birds shed their feathers this way at least once a year.

Birds have two main kinds of feathers – down feathers and contour feathers. Down feathers are fluffy, and lie next to the bird’s body, helping it stay warm. Contour feathers are stiff, and cover a bird’s body and wings. Contour feathers have a stiff central shaft with side branches called barbs.

Birds need a lot of energy to fly. To get the energy, their bodies must break down food quickly. This creates a lot of body heat. To cool off, birds lay their feathers flat and pant like dogs do. To sustain the energy needed to fly, birds must eat a lot. Birds have a unique digestive system (Fig. 3, p. 443) to help them get energy quickly. Since modern birds don’t have teeth, food goes from the mouth to the crop, where it’s stored until it moves to the gizzard. Many gizzards have small stones inside that grind food up so that it can be easily digested in the intestine.

Most birds can fly, and have adaptations such as large eyes, wing shape, a rapidly beating heart, air sacs, hollow bones, and powerful flight muscles (Fig. 4, p. 444-445). Birds are able to stay in the air because their wings cause lift – an upward force on a bird’s wings.

Most birds build nests in which to lay their eggs (Fig. 6, p. 446). They keep their eggs warm by brooding – the act of sitting on eggs and using body heat to keep them warm. Some birds, such as chickens and ducks, are active soon after they hatch. These active chicks are called precocial. Others, such as hawks and songbirds, are weak and helpless for a while after hatching. These weaker chicks are called altricial.

Section 2 – Kinds of Birds

There are about 10,000 species of birds on Earth. Songbirds, such as robins and bluebirds, make up the largest order – about 60%. Bird species can be grouped into four categories: flightless birds, water birds, perching birds, and birds of prey.

Flightless birds: Not all birds fly. Instead of flying, some flightless birds run quickly to move around. Fig. 1, p. 448 shows three flightless birds – the penguin, the kiwi, and the ostrich.

Water birds: Many flying birds are comfortable in the water. These include ducks, cranes, geese, pelicans, and loons. Many eat plants, invertebrates, or fish (Fig. 2, p. 449).

Perching birds: These birds have special adaptations for resting on branches (Fig. 3, p. 450). Songbirds, such as robins, warblers, and sparrows make up a large part of this group of birds. When a perching bird lands on a branch, its feet automatically close around a branch. Even while asleep, the bird’s feet still grip the branch, so that the bird doesn’t fall off.

Birds of Prey: These birds (Fig. 4, p. 451) hunt and eat other vertebrates, such as mammals, fish, reptiles, and birds. Birds of prey like owls and ospreys have good vision, sharp, curved beaks, and sharp talons on their feet. Most hunt during the day, like the osprey, but owls hunt at night.

Section 3 – Characteristics of Mammals

Mammals live in a wide variety of climates on Earth. There are approximately 5,000 modern species, all of which share certain characteristics, despite varying in many ways. Mammals appeared in the fossil record more than 225 million years ago, and were about the size of mice. When the dinosaurs died out, more land and food became available for the mammals.

Mammals share many common characteristics. These include:

Mammary glands – structures that make milk. All female mammals feed their young with this milk (Fig. 2, p. 453). Milk is made of water, proteins, fats, and sugars.

Like birds and reptiles, mammals use lungs to get oxygen from the air. But mammals have a diaphragm, a large muscle that helps bring air into the lungs. It lies at the bottom of the rib cage.

All mammals are endothermic. This means that internal chemical changes keep their body temperature constant.

Mammals have a few characteristics that keep them from losing heat. One way they stay warm is by having hair. Mammals are the only animals that have hair. Mammals that live in cold climates, such as the fox in Figure 3, p. 454, have thick coats of hair called fur. Most mammals also have a layer of fat under their skin to keep them warm.

Mammals have specialized teeth, with different shapes and sizes for different jobs. The three kinds of teeth are incisors – cutting teeth, in the front of your mouth; canines are stabbing teeth, and the flat, grinding back teeth are called molars.

All mammals reproduce sexually – sperm fertilizes eggs inside the female’s body. Most mammals give birth to live young, and newborn mammals stay with at least one parent until they are grown.

A mammal’s brain size is much larger than that of most other animals that are the same size. The larger brain size allows them to learn and think quickly, and also to respond quickly to events around them.

Section 4 – Placental Mammals

A placental mammal is a mammal whose embryos develop inside the mother’s body, growing inside an organ called the uterus. An organ called the placenta – which carries food and oxygen to the embryo - attaches the embryos to the uterus.

The time in which an embryo develops within the mother is called a gestation period, and lasts a different amount of time for each kind of placental mammal. It is 9 months for humans. The most common orders of placental mammals are:

Armadillos, Anteaters, and Sloths: This group of mammals have unique backbones that have special connections between the vertebrae. Most mammals in this group eat insects that they catch with their long, sticky tongues (Fig. 1, p. 456).

Insectivores: This group of mammals includes moles, shrews, and hedgehogs (Fig. 2, p. 457). Most are small, and have long, pointed noses that help them smell their food. They have small brains and simple teeth, and eat worms, fish, frogs, lizards, and small mammals in addition to insects.

Rodents: This group makes up one-third of mammal species (Fig. 3, p. 457). They include squirrels, chinchillas, porcupines, rats, mice, and guinea pigs. They have one set of incisors, which get worn down because of continual gnawing and chewing. They grow continuously, however.

Rabbits, Hares, and Pikas: Like rodents, this group of mammals (Fig. 4,p. 458) have sharp, gnawing teeth. However, unlike rodents, they have two sets of incisors and a shorter tail.

Flying Mammals: Bats are the only mammals that fly (Fig. 5, p. 458). Most eat insects or other small animals. Most bats use echolocation to find things. When flying, bats make clicking noises that echo off of trees, rocks, and insects.

Carnivores: This group of mammals (Fig. 6, p. 459) have large canine teeth and special molar teeth for slicing meat. Some are omnivores – like the black bear – and some are even herbivores that eat plants. Fish-eating ocean mammals such as walruses are called pinnipeds.

Trunk-Nosed Mammals: Elephants alone among the mammals possess a trunk – a combination of an upper lip and nose (Fig. 7, p. 459). It uses its trunk like we use our hands, to put food in its mouth. It also uses it to spray its back with water to cool off.

Hoofed Mammals: This group of mammals have at least one hoof – a thick, hard pad that covers the entire toe (Fig. 8, p. 460). Odd-toed hoofed mammals include horses and zebras, and even-toed hoofed mammals include pigs, deer, cattle, camels, and giraffes. Most are fast runner, and have large, flat molars to grind the plants they eat.

Cetaceans: This group of mammals are made up of whales, dolphins, and porpoises. All live in the water, have lungs, and nurse their young (Fig. 9, p. 461).

Manatees and Dugongs: This is the smallest group of mammals that live in the water. They use their front flippers and tails to swim, and eat seaweed and water plants (Fig. 10, p. 461).

Primates: This group of highly intelligent placental mammals (Fig. 11, p. 462) consist of prosimians, monkeys, apes, and humans. They have five fingers on each hand, and five toes on each foot. Most have flat fingernails, and have a larger brain than most other mammals their size. They have forward-facing eyes for focusing, and opposable thumbs for holding things. Many primates live in trees, aided by adaptations of flexible shoulder joints and grasping hands and feet.

Section 5 – Monotremes and Marsupials

A monotreme is a mammal that lays eggs. They have all the traits of other mammals, such as mammary glands, a diaphragm, and hair. They are also endothermic. The eggs laid by a monotreme have a thick, leathery shell. Monotremes don’t have nipples, so the babies lick milk from the skin and hair around the mother’s mammary glands.

There are three living species of monotremes. Two of these are echidnas. Their large claws and long snouts help them dig ants and termites out of nests (Fig. 1, p. 464). The other monotreme is the platypus, which lives in Australia. It has webbed feet and a flat tail to help it swim. It uses its flat, rubbery bill to search for food, and lays its eggs in tunnels that it digs out along riverbanks.

Marsupials are kangaroos and other mammals with pouches. Unlike monotremes, marsupials give birth to live young. Newborn marsupials continue their development in a mother’s pouch; newborns can stay in the pouch for several months. They’re born at an early stage of development, just days or weeks after fertilization (Fig. 3, p. 466).

Commonly known marsupials are kangaroos, koalas, and opossums (Fig. 4, p. 466). But less-well known marsupials include wallabies, bettongs, numbats, and Tasmanian devils. At least 22 of Australia’s native mammal species have become extinct in the last 400 years (Fig. 5, p. 467). Exotic species and habitat destruction continue to threaten marsupials in Australia.

Information Posted on 5/21/06

Notes for Chapter 16 – Fishes, Amphibians, and Reptiles

Section 1 – Fishes: The First Invertebrates

The skeletons of humans, fish, and dinosaurs all have something in common: they all have a backbone. Animals that have a backbone are called vertebrates. Vertebrates belong to the phylum Chordata; members of this phylum are called chordates.

Vertebrates make up the largest group of chordates, but there are two other groups as well – lancelets and tunicates (Fig. 1, p. 412). These two groups of chordates are much simpler than vertebrates, lacking a backbone and well-developed head. These three groups share certain characteristics; namely four particular body parts (pharyngeal pouches, hollow nerve cord, notochord, and tail) at some point in their life (Fig. 2, p. 413).

Fishes, amphibians, reptiles, birds, and mammals are vertebrates. One major difference between vertebrates and the other types of chordates is a strong, flexible column of bones called vertebrae. These vertebrae surround and protect the spinal cord, and help to support the rest of the body. Another major difference is the head – vertebrates have a well-developed head protected by a skull, which is made up of either cartilage or bone. Cartilage is a tough material that the flexible parts of our ears and nose are made of. Bone is much harder than cartilage, and so it can be easily fossilized. Fossil evidence shows that fishes were the first vertebrates on Earth, first appearing about 500 million years ago.

Some vertebrates are warm-blooded animals called endotherms – animals that have a stable body temperature. They use energy released by the chemical reactions in their cells to warm their bodies. Other animals depend on the surroundings to stay warm, since their body temperature changes as the temperature of the environment changes. These animals that do not control body temperature through activity in their cells are cold-blooded animals called ectotherms.

There are over 25,000 species of fishes, and many look different from each other. But all fishes share several characteristics: Fishes use fins – fan-shaped structures – to steer, stop, and balance. Many fishes also have bodies covered by bony structures called scales. Fishes have a brain to process information coming in from the senses of vision, hearing, and smell. Most also have a lateral line system – a row of tiny sense organs that detect water vibrations. Fishes use gills to breathe. A gill is an organ that removes oxygen from the water, and is also used to remove carbon dioxide from the blood. Most fish reproduce by external fertilization (where the female lays unfertilized eggs in the water, and the male drops sperm on them). But some species use internal fertilization, where the male deposits sperm inside the female.

There are five very different classes of fish. Two of these classes are extinct, and so we’ll focus only on the three that are living. These are: the jawless fishes, cartilaginous fishes, and bony fishes.

Jawless fishes, like the hagfish and lampreys (Fig. 6, p. 416), are eel-like. Hagfish eat dead fish on the ocean floor, and lampreys suck other animals’ blood and flesh using a tooth-lined suction cup mouth.

Cartilaginous fishes have skeletons that lack bone, their skeletons being made of cartilage alone. Sharks, skates, and rays are examples of this class of fish (Fig. 7, p. 417). They are strong swimmers and excellent predators, possessing fully functional jaws. They store oil in their liver to help stay afloat.

Bony fishes make up 95% of all fishes. They have skeletons made of bone, and their bodies are covered by bony scales. They possess a swim bladder, a balloon-like organ that is filled with oxygen and other gases. The bladder inflates to make the fish more buoyant (and rise up in the water), and deflates to allow the fish to sink to a deeper depth. There are two groups of bony fishes: ray-finned fishes and lobe-finned fishes (Fig. 8, p. 418).

Section 2 – Amphibians

Amphibians are animals that can live in water and have lungs and legs. A lung is a saclike organ that takes oxygen from the air and delivers oxygen to the blood. These fishes also had strong fins that could have evolved into legs.

The word “amphibian” means ‘double life.’ Most amphibians live part of their lives in water and part of their lives on land. Embryos must develop in a wet environment, since eggs do not have a shell or a membrane that prevents water loss. Most amphibians live in the water after hatching and then develop later into adults that can live on land.

Amphibians have thin, smooth, moist skin. The skin is so thin, in fact, that amphibians absorb water through it instead of drinking. But they can also lose water through their skin and become dehydrated. For this reason, most amphibians live in water or in damp habitats. Many amphibians also have brightly colored skin, which serves to warn predators that their skin contains poison glands.

A tadpole is an immature frog or toad that must live in water, getting oxygen through gills and using its long tail to swim. Later, the tadpole loses its gills and develops lungs and legs that allow it to live on land. The change from an immature form to an adult form is metamorphosis (Fig. 4, p. 422). A few amphibians don’t go through a full metamorphosis, rather hatching as tiny versions of adults.

There are more than 5,400 species of amphibians alive today, and these belong to three groups: caecilians, salamanders, and frogs and toads. Caecilians live in tropical areas of Asia, Africa, and South America. Looking like earthworms or snakes, they lack legs (Fig. 6, p. 423). Salamanders (Fig. 7, p. 423) live in wooded areas of North America. They don’t develop as tadpoles, but most of them lose gills and grow lungs during their development. Frogs and Toads make up about 90% of all amphibians. They are very similar to one another; in fact toads are a type of frog. They live all over the world, except for very cold places. Some frogs sing to communicate messages that help in attracting mates and marking territories.

Amphibians are often called ecological indicators because they are very sensitive to changes in the environment. Their thin skin absorbs chemicals in the water or air, and their lungs also take in any chemicals present in the air. Climate change is another factor that may affect amphibians.

Section 3 - Reptiles

About 35 million years after amphibians moved onto land, some of them began to change, growing thick, dry skin that reduced water loss. Their legs also grew stronger, and they laid eggs that didn’t dry out on dry land – they had become reptiles, the first animals to live out of the water. Many reptiles are now extinct, such as the dinosaurs. They and other ancient reptiles were in some cases similar to reptiles alive today, such as snakes, tortoises, and crocodiles (Fig. 1, p. 426).

Reptiles have characteristics that make them well adapted for life on land. Their thick, dry skin prevents water loss. Since nearly all reptiles are ectotherms, they can’t keep their bodies at a stable temperature. They are active when it’s warm outside, and slow down when it’s cool. The most important adaptation to life on land is the amniotic egg – an egg that holds fluid that protects the embryo. Reptiles, as well as birds and mammals, have amniotic eggs. Reptiles’ amniotic eggs have a shell (Fig. 3, p. 427), which protects the embryo and keeps the egg from drying out. There are several other parts of the amniotic egg, which are shown and described in Fig. 4, p. 428). Reptiles lay their eggs under rocks, in the ground, or even in the desert.

Reptiles usually reproduce by internal fertilization. Once the female lays the egg, it is often buried in soil or sand. A few reptiles do not lay eggs; instead, the embryos develop inside the mother, and the young are born alive. In either case, the embryo develops into a tiny young reptile that looks like a small adult. Therefore, reptiles don’t go through metamorphosis.

Today there are some 8,000 known species of reptiles known to exist. Turtles and tortoises, crocodiles and alligators, lizards and snakes, and tuataras make up the four groups of reptiles. Tortoises generally live on land, and turtles (Fig 6, p. 429) spend all or much of their lives in the water. Their shell is what makes these creatures unique, providing a defensive adaptation against predators. Crocodiles and alligators (Fig. 7, p. 429) spend most of their time in the water. Since their eyes and nostrils are on the top of their flat head, they are able to watch their surroundings while most of their body is underwater. Today, the most common reptiles are snakes and lizards. Snakes (Fig. 8, p. 430) are carnivores. They use their tongues to tell them when prey is nearby. Some snakes kill with venom, others squeeze their prey until it suffocates. Lizards (Fig. 9, p. 430) eat mostly small insects and worms, but some lizards eat plants. Tuataras (Fig. 10, p. 431) look similar to lizards, although the two reptiles are classified into different groups. Unlike reptiles, tuataras don’t have visible ear openings on the outside of the body, and most are active when the temperature is low.

Information Posted on 5/3/06

Notes for Chapter 15 – Invertebrates

Section 1 – Simple Invertebrates

Invertebrates are animals that don’t have backbones. They make up about 96% of all animal species in Earth. More than 1 million species have been named, and millions more have not been identified yet.

Invertebrates have three basic body plans, or types of symmetry (see Fig. 1, p. 380): bilateral symmetry (where two sides of the body mirror each other); radial symmetry (where the body is organized around the center, like wheel spokes), and asymmetry (not symmetrical). Most animals have bilateral symmetry. Some, like the sea star, have radial symmetry, and some have no symmetry at all.

All animals except sponges have special tissues that make fibers called neurons, which allow animals to sense their environment and carry messages around the body. Simple invertebrates have neurons arranged in networks or in nerve cords – packs of neurons that carry messages along a single path. In some invertebrates, many nerve cells come together as ganglia (singular ganglion), a concentrated mass of nerve cells.

Almost all animals digest food in a gut – a pouch lined with cells that release chemicals that break food down into small particles. In complex animals, the gut is inside a coelom – a body cavity that surrounds the gut. The coelom contains many organs, such as the heart and lungs (see Fig. 2, p. 381 for an earthworm’s coelom).

Sponges are the simplest invertebrates. They are asymmetrical, and have no tissues, gut, or neurons. Despite appearances (Fig. 3, p. 381), because sponges can’t make their own food, they are classified as animals. Sponges feed on tiny plants and animals, sweeping water into its body through holes on its outside called pores. This water carries both oxygen and food for the sponge. Collar cells filter and digest food from the water that enters the body. Water leaves the body through a hole at the top of the sponge called an osculum. Sponges can regenerate, or grow back, a part that is broken off. The pieces of a sponge can cause new sponges to form. So sponges can use regeneration as a form of reproduction, as well as sexual reproduction. While all sponges live in water, they come in many different shapes and sizes (Fig. 5, p. 383). They have a skeleton made of hard, small fibers called spicules. The skeleton protects the sponge from predators and supports its body.

Cnidarians are more complex than sponges. They have complex tissues and a gut for digesting food. They have two forms – the medusa and polyp (see Fig. 6, p. 383). Medusas (like jellyfish) swim through the water, whereas polyps (such as coral) usually attach to a surface. All cnidarians have tentacles covered with stinging cells. When an organism brushes against the tentacles, hundreds of stinging cells are activated. Each stinging cell fires a tiny, barbed, poison bearing spear into an organism. These stinging cells are use for protection, and to catch food. There are three classes of cnidarians: jellyfish, hydrozoans, and sea anemones and corals.

Flatworms are the simplest type of worms. They all have bilateral symmetry. Many flatworms have a clearly defined head and two large eyespots, as well as sensory lobes in the sides of the head used for detecting food (Fig. 9, p. 385).

There are three types of flatworms: planarians, flukes, and tapeworms. Planarians live in freshwater lakes and streams or in damp places on land. Most are predators, and even have a brain for processing information about their surroundings. Flukes are parasites, meaning that they feed on the body of another living organism called a host. They have special suckers and hooks for attaching to animals. Tapeworms are similar to flukes, in that they have a small head and no eyespots or sensory lobes. Tapeworms attach to the intestines of other animals and absorb nutrients (see Fig. 11, p. 386).

Roundworms have bodies that are long, slim, and round (Fig. 12, p. 386). They have a simple nervous system, and most are very small. A single apple could contain 100,000 roundworms! These tiny worms break down the dead tissues of plants and animals, helping to make the soil rich and healthy. Some roundworms, however, are parasites. Some can be passed to people from infected pork, causing a disease called trichinosis.

Section 2 – Mollusks and Annelid Worms

Snails, slugs, clams, oysters, squids, and octopuses are all mollusks. Most live in the ocean, but some live in fresh water or even on land. They can be divided into three classes: (1) gastropods include snails and slugs; (2) bivalves include clams and other shellfish that have two shells; and (3) cephalopods include squids and octopuses.

Each kind of mollusk has its own way of eating. Snails and slugs eat with a ribbon-like organ called a radula – a tongue covered with curved teeth. Clams and oysters attach to one place can use gills to filter tiny plants, bacteria, and other particles from the water. Octopuses and squids use tentacles to grab their food and place it in their jaws.

All mollusks have complex ganglia – masses of nerve cells – to control breathing, movement, and digestion. Cephalopods have large brains that connect all of their ganglia, and are thought to be the smartest invertebrates.

Unlike simple invertebrates, mollusks have a circulatory system, which transports materials through the body in the blood. Most mollusks have an open circulatory system, a simple heart that pumps blood through blood vessels that empty into sinuses, or spaces in the animal’s body. Squids and octopuses have a closed circulatory system, a heart that pumps blood through a network of blood vessels that form a closed loop.

Although a snail, a clam, and squid look very different from one another, their bodies actually have similar structures. They have a broad, muscular foot for movement. The gills, gut, and other organs form the visceral mass, which lies in the body’s center. The mantle – a layer of tissue – covers the visceral mass. In most mollusks, the outside of the mantle secretes a shell, which provides protection and keeps the mollusk from drying out.

Annelid worms are often called segmented worms, because their bodies have segments – identical, or nearly identical, repeating body parts. They have bilateral symmetry like roundworms and flatworms, but are more complex, having a closed circulatory system and a complex nervous system with a brain. Annelid worms can live in salt or fresh water, or on land. They eat plants or animals.

There are three major groups of annelid worms: (1) earthworms, (2) marine worms, and (3) leeches. Earthworms have 100 to 175 segments, which have special jobs, such as eating or reproducing. They eat material in the soil, and break down plant and animal material and leave behind wastes called castings, which helps to make the soil richer. Earthworms use stiff hairs called bristles to move. Marine worms, called polychaetes (“many bristles”) are brightly colored. Most live in the ocean, and eat mollusks and other small animals. Others filter small pieces of food from the water. Some leeches are parasites, sucking the blood from a host organism; others are scavengers that eat dead animals, and others are predators, eating insects, slugs, and snails. Leeches have some medical uses; for example, they can prevent swelling near a wound, keep clots from forming, and help break down clots that already exist.

Section 3 - Arthropods

Arthropods such as insects, spiders, crabs, and centipedes have been on Earth for hundreds of millions of years. At least 75% of all animal species are arthropods! They all share four basic characteristics: a segmented body with specialized parts, jointed limbs, an exoskeleton, and a well-developed nervous system.

Most arthropod species have segments that include specialized structures such as wings, antennae, gills, pincers, and claws. Suring development, some segments grow together, forming the three main body parts (the head, thorax, and abdomen – see Fig. 1, p. 392).

Jointed limbs give arthropods their name. Arthro means “joint” and pod means “foot.” Jointed limbs are legs or other body parts that bend at the joints – this makes it easier for arthropods to move. Arthropods have a hard outer covering called an exoskeleton. It serves as a support for the body and allows the animal to move. In addition, it protects the organs and keeps water inside the body. Finally, all arthropods have a well-developed brain and nerve cord. The nervous system receives information from sense organs such as eyes and bristles, which can detect motion, vibration, and chemicals. Some arthropods have simple eyes (which can detect light but not form images), and some have compound eyes made of many identical, light-sensing units. Compound eyes can see images.

Arthropods are classified by the kinds of body parts they have. One can tell the difference between them by looking at the number of legs, eyes, and antennae that they have. An antenna is a feeler that senses touch, taste, or smell. Four basic kinds of arthropods are centipedes and millipedes, crustaceans, arachnids, and insects.

Centipedes and millipedes (Fig. 4, p. 394) have one pair of antennae, a hard head, and one pair of mandibles – mouthparts that can pierce and chew food. Centipedes have one pair of legs on each segment, and can have 30 – 354 legs. Millipedes have two pairs of legs on each segment, and can have up to 752 legs.

Crustaceans (Fig. 5, p. 394) include shrimp, barnacles, crabs, and lobsters. Most live in the water; have gills for breathing, mandibles for eating, and two compound eyes, each of which is located on one end of an eyestalk.

Arachnids (Fig. 6, p. 395) are spiders, scorpions, mites, and ticks. The two main body parts of arachnids are the cephalothorax (made of both a head and thorax), and the abdomen. Most arachnids have four pairs of legs, have no antennae, and instead of mandibles have a pair of claw-like mouthparts called chelicerae. Arachnids have simple eyes, sometimes up to 8!

Insects make up the largest group of arthropods. In fact, if you put all of the insects in the world together, they would weigh more than all the other animals combined! Although as Fig. 7, p. 395 shows, despite looking different, they all have three main body parts, six legs, and two antennae. The only place on Earth where insects do not live is in ocean water. While most are beneficial (pollinating crops, for example), some insects destroy crops and spread disease.

The three main body parts of the insect are shown in Fig. 8, p. 396. The head has one pair of antennae, one pair of compound eyes, and mandibles. The thorax is made of three segments, each of which has one pair of legs.

As an insect develops, it changes form. This process is called metamorphosis. Most insects go through complete metamorphosis (Fig. 9, p. 396). It has four main stages: egg, larva, pupa, and adult. Butterflies, beetles, bees, wasps, and ants go through this change. But some insects, such as grasshoppers and cockroaches, go through incomplete metamorphosis (Fig. 10, p. 397). It has three main stages: egg, nymph, and adult. Some nymphs shed their exoskeleton several times in a process called molting. An insect in the nymph stage looks very much like an adult insect, unlike in complete metamorphosis, where the larva looks very different from an adult.

Section 4 - Echinoderms

Echinoderms are spiny, invertebrate marine animals. The name echinoderm means “spiny skinned.” The skin is not the spiny part. Rather, the spines are on the animal’s skeleton. An echinoderm’s internal skeleton is called an endoskeleton. Endoskeletons can be hard and bony, or stiff and flexible. The spines covering these skeletons can be long and sharp, or short and bumpy. The animal’s skin covers the endoskeleton.

Adult echinoderms have radial symmetry, but they develop from larvae that have bilateral symmetry (Fig. 1, p. 398). Echinoderms have a simple nervous system similar to that of a jellyfish. Around the mouth is a circle of nerve fibers called the nerve ring.

In sea stars, a radial nerve runs from the nerve ring to the tip of each arm (Fig. 2, p. 399). The radial nerves control the movements of the sea star’s arms. A light-sensing simple eye can be found at the tip of each arm. The rest of the body is covered with cells that sense touch and chemical signals in the water.

One unique characteristic of echinoderms is the water vascular system – a system of canals filled with fluid. It uses water pumps to help the animal move, eat, breathe, and sense its environment (see Fig. 3, p. 399).

There are five major classes of echinoderms. Brittle stars and basket stars (Fig. 4, p. 400) have long, slim arms, and don’t have suckers on their tube feet. Sea urchins and sand dollars (Fig. 5, p. 400) are round, and their endoskeletons form a solid, shell-like structure. They have no arms, and use their tube feet to move in the same way that sea stars move. Sea lilies and feather stars (Fig. 6, p. 401) may have 5 to 200 feathery arms. These arms stretch away from their body and trap small pieces of food. Sea cucumbers (Fig. 7, p. 401), like some other echinoderms, have no arms. They have a soft, leathery body.

Information Posted on 4/10/06

Notes for Chapter 14 – Animals and Behavior

Section 1 – What is an Animal?

There is a great amount of diversity, or variety, among Earth’s animal species. Scientists have named more than 1 million different species of animals, and many more have not yet been named. There may be more than 3 million total animal species on the Earth.

Animals can be classified into two major groups; vertebrates and invertebrates. A vertebrate is an animal that has a backbone, and include fishes, amphibians, reptiles, birds, and mammals. We humans are one of about 5,000 species of mammals. Less than 5% of known animal species are vertebrates. The vast majority (over 95%) of animal species belong to the second group, the invertebrates – animals without backbones. This group includes insects, snails, jellyfish, and worms.

Among the shared characteristics of animals include being multicellular – made up of many cells. Animal cells are eukaryotic, which means they have a nucleus. Unlike plant cells, animal cells lack a cell wall. Almost all animals reproduce sexually. When an egg and sperm join during fertilization, they form the first cell of a new organism. This first cell divides into many cells to form an embryo – an organism at an early stage of development. A few animals can reproduce asexually. For example, the hydra can reproduce by budding, a process where part of an organism breaks off and develops as a new organism. An animal’s body has specialized parts that do different things. For example, muscle cells in an animal form muscle tissue, and nerve cells form nerve tissue. Most animals also have organs – a group of tissues that carry out a special function of the body.

Most animals can move from place to place, flying, running, swimming, or jumping. Nearly all animals use movement to search for food, shelter, or mates at some stage of life. Since animals can’t make their own food, they must survive by eating other organisms or parts and products of other organisms. So animals are consumers – organisms that eat other organisms or organic matter.

Section 2 – Animal Behavior

Sometimes animals instinctively know how to behave, but sometimes they learn how. Innate behavior is behavior that doesn’t depend on learning or experience. Innate behavior is inherited through genes. Some examples of this include bees inheriting the tendency to fly, and newborn whales having the innate ability to swim. Learned behavior is behavior that has been learned from experience or from observing other animals. For example, humans inherit the tendency to speak (an innate behavior). But the language we use is not inherited, but rather learned – we might learn English, Spanish, or sign language.

Animals depend on their behaviors to survive. Animals must find food, and this is done in many ways. Some animals fly from flower to flower to get food (bees), some climb trees to get eucalyptus leaves (koalas), and some animals hunt for their food. Animals that eat other animals are known as predators. The animal being eaten is the prey. Animals that are predators can also be prey for another animal (eagle ( snake ( mouse).

Sometimes, members of the same species must compete for food and mates. In order to save energy and avoid this competition, some animals claim territories – areas occupied by one animal or a group of animals that do not allow other members of the species to enter. Animals may mark territories in different ways. For example, some birds do so by singing, which lets other birds know not to enter the area. Animals use their territories for mating, raising young, and finding food.

Defensive behavior allows animals to protect resources, including territories, from other animals. Animals defend food, mates, and offspring. Some animals might use distraction (to draw a predator’s attention away from their young); others use camouflage, blending into their environment. Skunks spray irritating chemicals at predators, and rabbits try to outrun them.

Animals need to find mates to reproduce, as reproduction is essential for the survival of an individual’s genes. Animals use courtship - special behaviors to help them find a mate. Some animals use movement to find a mate, others build nests, while others display rich colors.

Finally, while some animals, such as caterpillars, begin life with the ability to take care of themselves, many young animals depend on their parents for survival. Examples of this parenting include adult birds bringing food to their young. Others, such as the killer whale in Fig. 5, p. 363, teach their young how to hunt.

The third major type of animal behavior is seasonal behavior. Seasonal behaviors help animals adjust to the environment. Many animals avoid cold weather by traveling to warmer places. These animals migrate – travel from one place to another – to find food, water, or safe nesting grounds. To help them find their way, animals use landmarks – fixed objects such as mountain ranges, rivers, and coastlines.

Some animals deal with food and water shortages by hibernating. Hibernation is a period of inactivity and decreased body temperature that some animals experience in winter. Hibernating animals survive on stored body fat. While hibernating, an animal’s temperature, heart rate, and breathing rate drops. Winter, however, is not the only time that resources can be hard to find. Some animals, such as desert squirrels and mice, experience a similar internal slowdown in the hottest part of the summer. This period of reduced activity in the summer is called estivation.

Animals need to keep track of time so that they know when to store food and when to migrate. The internal control of an animal’s natural cycles is called a biological clock. Animals may use such clues as the length of the day and the temperature to set their clocks. Some biological clocks keep track of daily cycles – these daily cycles are called circadian rhythms. An example would be waking up and getting sleepy at the same time each day and night. Seasonal cycles are nearly universal among animals – many animals hibernate at certain times of the year, and reproduce at other times.

Section 3 – Social Relationships

Animals often interact with one another. This behavior is called social behavior – the interaction among animals of the same species. Central to social behavior is communication. In communication, a signal must travel from one animal to another, and the receiver of the signal must respond in some way. While animals do not use a language with complex words and grammar (like humans), they communicate in many ways.

Communication helps animals survive, find food, warn others of danger, identify family members, frighten predators, and find mates. Animals communicate by signaling to other animals through sound, touch, chemicals, and sight. Each of these methods can be used convey specific information.

Animals communicate through sound – making noises. For example, wolves howl, dolphins use complex clicking noises and whistles, and birds use song to claim territory or attract a mate. Sound is a signal that can reach many animals over a large area. Animals use touch to communicate friendship or support. Grooming is an important way for primates such as chimpanzees to communicate through touch. Animals can also communicate through chemicals called pheromones. They do this to find a mate, as well as warn other members of a group of danger. Animals also use sight – visual communication, through the use of body language. Animals use body language to scare other animals, to engage in courtship, to find food, and to play (Fig. 5, p. 368).

While some animals, like the tiger, live alone, many animals like lions live in groups. There are both positive points and negative points to living in a group. On the positive side, living in groups can be safer than living alone – large groups can spot a predator quickly because there are so many pairs of eyes watching for danger. Living in groups also helps animals find food. On the negative side, animals in large groups must compete with each other for food and mates. Also, animals in groups more easily attract predators, so they must always be on the lookout. Disease also spreads more easily among animals in a large group.

Information Posted on 3/31/06

Notes for Chapter 13 – Plant Processes

Section 1 – Photosynthesis

Photosynthesis is the process by which plants make their own food. Energy from sunlight is used to make the sugar glucose (C6H12O6) from carbon dioxide (CO2) and water (H2O). In addition to glucose, the chemical reaction of photosynthesis occurring in plant cells gives off oxygen gas (O2) – see Fig. 2, p. 333. Six molecules of carbon dioxide and six molecules of water are needed to form one molecule of glucose and six molecules of oxygen. This process is summarized in the chemical equation below:

6CO2 + 6H2O + light energy ( C6H12O6 + 6O2

Plants have organelles called chloroplasts to capture sunlight (see Fig. 1, p. 332). They are surrounded by two membranes Inside the chloroplast, another membrane forms stacks called grana. Grana contain the green pigment chlorophyll, which absorbs light energy. Sunlight is made up of many different wavelengths of light. Chlorophyll absorbs most of these wavelengths, but reflects back more wavelengths of green light than wavelengths of other colors, which is why most plants look green.

Glucose molecules store energy. Plants break down glucose using oxygen in a process called cellular respiration. During this process, plant cells give off water and carbon dioxide. Excess glucose is converted to another type of sugar, sucrose, or stored as starch.

Many above-ground plant surfaces are covered by a waxy cuticle, which helps protect the plant from water loss. Despite this outer covering, plants are able to obtain the carbon dioxide needed for photosynthesis through stomata (singular, stoma), which are openings in the leaf’s epidermis and cuticle. Each stoma is surrounded by two guard cells, which function as doors, opening and closing the stoma. Carbon dioxide enters the leaf when the stomata are open, and oxygen produced during photosynthesis exits. Water vapor also exits through the stomata. Water loss from leaves is called transpiration. Most of the water absorbed by the roots replaces water lost during transpiration. If, however, more water is lost than is absorbed, then the plant wilts.

Plants and other photosynthetic organisms such as bacteria and many protists form the base of nearly all food chains on Earth. Indeed, most organisms could not survive without photosynthetic organisms. Plants store light energy as chemical energy, which animals receive when they eat plants. Other animals get energy from plants indirectly, when animals eat animals that eat plants (see Fig. 4, p. 335 for an example of a food chain).

Section 2 - Reproduction of Flowering Plants

Flowers are adaptations for sexual reproduction. During sexual reproduction, an egg is fertilized by a sperm. Pollination happens when the pollen is moved from anthers to stigmas. Usually, wind or animals move pollen. Pollen contain sperm. After pollen land on the stigma, a tube grows from each pollen grain. The tube grows through the style to the ovary. Each ovule inside the ovary contains an egg. Sperm from the pollen grain move down the pollen tube and into an ovule. Fertilization happens when a sperm fuses with the egg in the ovule (see Fig. 1, p. 336).

After fertilization takes place, the ovule develops into a seed, which contains a tiny, undeveloped plant. The ovary surrounding the ovule becomes a fruit (see Fig. 2, p. 337). As a fruit swells and ripens, it protects the developing seeds.

Once a seed is fully developed, the young plant inside stops growing. The seed may become dormant,, meaning that they are inactive. Dormant seeds often survive long periods of drought or freezing temperatures. When a seed becomes dormant they are inactive. When the environment becomes suitable for growth the seed will sprout, or germinate (see Fig. 4, p. 338). A suitable environment includes water, air, and warm temperatures. Each type of plant has its ideal temperature for growth. For many plants, this ideal temperature is about 27o C (80.6oF).

Flowering plants may also reproduce asexually. Plantlets fall off and grow on their own. Underground stems or tubers can produce new plants. Runners are above-ground stems from which new plants can grow (see Fig. 5, p. 339).

Section 3 - Plant Responses to the Environment

Plants respond to certain stimuli such as light, gravity, and changing seasons. Tropism is growth in response to an external stimulus. Tropisms are either positive or negative. Plant growth toward a stimulus is a positive tropism, and plant growth away from a tropism is a negative tropism.

A change in the direction a plant grows that is caused by light is called phototropism (see Fig. 1, p. 340). Plant growth in response to the direction of gravity is called gravitropism. Most shoot tips have negative gravitropism. They grow upward, away from the center of the Earth. Most root tips have positive gravitropism. Roots grow downward, toward the center of the Earth.

Plants respond to seasonal changes. Plants living in colder regions can detect changes in seasons. As fall and winter approach, the days get shorter, and the nights get longer. The opposite happens when spring and summer approach. Plants respond to the change in the length of day. The difference between day length and night length is an important environmental stimulus for many plants, one that can cause plants to begin reproducing. Plants that flower in the winter are called short-day plants. Examples of short-day plants include Poinsettias and Chrysanthemums. Long-day plants flower in spring or early summer, when night is short. Clover, lettuce and spinach are examples of long-day plants.

Some trees lose their leaves all year long so there are always leaves on the tree. These trees, of which holly and pines are an example, are called evergreens. These leaves usually have a thick cuticle for protection. Deciduous trees lose all of their leaves before winter. The loss of leaves helps the plant survive low temperatures or long periods without rain. Deciduous leaves may change color before they are lost. The green pigment chlorophyll breaks down which then exposes the orange and yellow pigments that were always present but not seen.

Notes for Quarter 3

Information Posted on 3/16/06

Notes for Chapter 12 – Introduction to Plants

Section 1 – What is a Plant?

Plants come in a variety of shapes and sizes, from cactuses, water lilies, ferns, and many others. Despite this wide diversity, plants share certain characteristics. Among these is the way that plants obtain food. Plant cells contain chlorophyll. Chlorophyll is a green pigment that captures energy from sunlight. Chlorophyll is found in chloroplasts – organelles found in many plant cells and some protists. Through the process called photosynthesis, plants use energy from sunlight to make food from carbon dioxide and water. Plants are therefore producers – organisms that make their own food.

Most plants live on dry land and need sunlight to survive. Constant exposure to air would seem to eventually dry them out. However, a cuticle – a protective waxy layer that coats most of the surface of plants that are exposed to air – keeps them from drying out.

Another plant characteristic has to do with the way that plants stay upright. Plant cells are surrounded by a rigid cell wall. Lying outside the cell membrane (Fig. 2, p. 301), cell walls support and protect the plant cell.

A fourth plant characteristic is reproduction. Plants have two stages in their life cycle – the sporophyte stage and the gametophyte stage. During the sporophyte stage, plants make spores, which can then grow and become new plants called gametophytes. During the gametophyte stage, female gametophytes produce eggs, and male gametophytes produce sperm. The sperm fertilizes the egg, and the fertilized egg grows into a sporophyte. The sporophyte makes more spires, and the cycle starts again.

Although plants share the above basic characteristics, they can be classified into four groups (see Fig. 3, p. 302). The first classification is two-fold – nonvascular plants and vascular plants. Vascular plants are further divided into three groups – seedless plants, nonflowering seed plants, and flowering seed plants.

Nonvascular plants are plants that don’t have specialized tissues to move water and nutrients through the plant. Instead, they rely on a process called diffusion to do this. Diffusion is possible because of the small size of nonvascular plants. Examples of nonvascular plants are mosses, liverworts, and hornworts. Vascular plants have specialized tissues that can deliver water and other nutrients from one part of the plant to another. Because of these tissues, vascular plants can grow to almost any size. Vascular plants are divided into three groups – seedless plants and two types of seed plants. Seedless vascular plants include ferns, horsetails, and club mosses. Nonflowering seed plants are called gymnosperms. Flowering seed plants are called angiosperms.

Because of many shared similarities, scientists believe that green algae and plants share a common ancestor. They have the same kind of chlorophyll, they have similar cell walls, they make their food through photosynthesis, they store energy in the form of starch, and they have a two-stage life cycle.

Section 2 – Seedless Plants

Seedless plants can be both nonvascular and vascular. Nonvascular plants such as mosses, liverworts, and hornworts, are small in size. They grow on soil, tree bark, and rocks. Since they don’t have vascular tissue, they live in damp places – each cell of the plant has to get water from the environment or a nearby cell. Lacking true stems, roots, or leaves, these plants do have structures that carry out similar functions.

Mosses often live together in large groups. They cover soil or rocks with a mat of tiny green plants. They have leafy stalks and rhizoids - rootlike structures that hold nonvascular plants in place, and help them get water and nutrients. As Fig. 1, p. 304 shows, mosses have a two-stage life cycle. Like mosses, liverworts and hornworts are small in size and live in damp places. They also have similar life cycles. Both liverworts and hornworts have rhizoids.

Nonvascular plants have an important role in the environment. They’re usually the first plants to live in a new environment, such as newly exposed rock. When they die, they form a thin layer of soil, where new plants can grow. These new plants hold the soil in place, reducing soil erosion. Additionally, some animals eat nonvascular plants, and others use them for nesting material.

Vascular plants (ferns, horsetails, and club mosses) living in ancient times grew very tall. Club mosses, for example, could grow up to 40 meters tall. Today, these three seedless vascular plants are much smaller. But because they have vascular tissue, they are often larger than nonvascular plants.

Ferns grow in a variety of places, from the cold Arctic to warm, tropical forests. Most ferns have a rhizome – an underground stem from which new leaves and roots grow. Initially, fern leaves, or fronds, are tightly coiled, resembling the end of a violin, and so are called fiddleheads. The fern life cycle is shown in Fig. 3, p. 306). Modern horsetails can be as tall as 8 meters, although many are smaller. Usually found in wet, marshy places, their stems contain silica, which gives horsetails a gritty texture. Club mosses are often about 20 centimeters tall. Found in woodlands, club mosses are not actually mosses – despite the name. Club mosses contain vascular tissue – unlike mosses. They have a life cycle similar to that of ferns.

Seedless vascular plants also play important roles in the environment. Ferns, horsetails, and club mosses help form soil, and help prevent soil erosion. Seedless vascular plants that lived and died about 300 million years ago are among the most important to humans, as these became the fossil fuels that we mine today – coal, petroleum, and natural gas that rely on for energy.

Section 3 – Seed Plants

Seed plants differ from seedless plants in three key ways: (1) seed plants produce seeds, which nourish and protect young sporophytes. (2) the gametophytes of seed plants are tiny, and do not live independently of the sporophyte. The gametophytes form within the reproductive structures of the sporophyte. (3) The sperm of seed plants do not need water to reach an egg. Instead, sperm form inside tiny structures called pollen, which can be transported by wind or by animals. These three characteristics allow seed plants to live almost anywhere. They are therefore the most common type of plant on Earth today.

As Figure 2, p. 309 shows, a seed plant is made up of three parts: the first part is the young plant, or sporophyte; the second part is stored food in the cotyledon; and the third part is the seed coat, which surrounds and protects the young plant. One of the advantages that seed plants have over seedless plants is that the young plant can use the food stored in the seed. Another advantage of seed plants is that seeds can be spread by animals more efficiently than the wind spreads the spores of seedless plants.

Gymnosperms are seed plants that do not have flowers or fruit. Their seeds are usually protected by a cone. The four groups of gymnosperms are conifers, ginkgoes, cycads, and gnetophytes (see diagram on p. 310). Conifers are the most economically important gymnosperms. Conifer wood is used for building materials and paper products. Some conifers produce an anticancer drug. Pine trees produce a sticky fluid called resin, which is used to make soap, turpentine, paint, and ink. Some gnetophytes produce anti-allergy drugs. Conifers, cycads, and ginkgoes are often found in gardens and parks.

In the gymnosperm life cycle, the male gametophytes are found in pollen, which contains sperm. The female gametophytes produce eggs. Wind carries the pollen from the male to the female cones. This transfer of pollen is called pollination. The female cones can be on the same plant, or they can be on a different plant of the same species.

Angiosperms are vascular plants that produce flowers and fruits, and are the most abundant plants today with about 235,000 species. Flowers help angiosperms reproduce. Some angiosperms depend on the wind for pollination, while others have flowers that attract animals (Fig. 5, p. 312). There are two kinds of angiosperms – monocots and dicots. These two classes differ in the number of cotyledons, or seed leaves, that their seeds have (Fig. 6, p. 312). Monocot seeds have one cotyledon, and dicot seeds have two. Examples of monocots include orchids, lilies, onions, grasses, and palms. Examples of dicots include roses, sunflowers, cactuses, peanuts, and peas. Angiosperms are important to both animals and humans. Flowering plants provide many land animals with food. We also depend on flowering plants to provide food such as corn, wheat, and rice. Additional ways that flowering plants are beneficial to us include building materials, fiber for clothing, medicines, rubber, and perfume oils.

Section 4 – Structures of Seed Plants

A plant’s root system and shoot system supply the plant with what it needs to survive. The root system is made up of roots, and the shoot system includes stems and leaves. The vascular tissues of the root and shoot systems are connected. There are two kinds of vascular tissues – xylem and phloem. Xylem transports water and minerals through the plant. It moves materials from the roots to the shoots. Phloem transports food molecules to all parts of a plant.

Most roots are underground, as Fig. 1, p. 314 shows. There are three main functions of roots: (1) Roots supply plants with water and dissolved minerals. (2) Roots hold plants securely in the soil. (3) Roots store surplus food during photosynthesis. The structures of a root are shown in Fig. 2, p. 315. Covering the surface of roots is a layer of cells called the epidermis. A root absorbs water and minerals, which move into the xylem. Growth occurs at the tip of a root. The root cap releases a slimy substance that helps the root grow through soil.

There are two kinds of root systems-taproot systems and fibrous root systems. A taproot system has one main root, or a taproot, that grows downward. Dicots and gymnosperms usually have taproot systems. A fibrous root system has several roots that spread out from the base of a plant’s stem. Monocots usually have fibrous roots.

Stems, usually located above ground, connect a plant’s roots to its leaves and flowers. It also has the following functions: (1) Stems support the plant body. (2) Stems transport materials between the root system and the shoot system. (3) Some stems store materials like water. Many plants such as wildflowers, as well as crops such as beans, tomatoes, and corn, have herbaceous stems that are soft, thin, and flexible (Fig. 4, p. 316). Trees and shrubs have woody stems – rigid stems made of wood and bark (Fig. 5, p. 317).

Leaves vary greatly in shape; they can be round, narrow, heart-shaped, or fan-shaped. They also vary in size. The raffia palm has leaves that can be over twenty feet tall, whereas the leaves of duckweed could fit on your fingernail. The main function of leaves is to make food for the plant through the process of photosynthesis. The structure of leaves is shown in Fig. 7, p. 318. The cuticle prevents water loss. Light passes through the epidermis. Tiny openings in the epidermis, called stomata, let carbon dioxide enter the leaf. Most photosynthesis takes place in the middle of the leaf. This middle part has two layers. Cells in the upper layer (the palisade layer) contain many chloroplasts – this is where photosynthesis takes place. Carbon dioxide moves freely in the space between the cells of the second layer, the spongy layer. Xylem and phloem are found in the spongy layer.

Plants have flowers because flowers are adaptations for sexual reproduction. Flowers come in many shapes, colors, and fragrances. Brightly colored and fragrant flowers usually rely on animals for pollination. Flowers usually have the following basic parts: sepals, petals, stamens, and one or more pistils. Be sure to look over Figure 9, p. 320. Sepals are modified leaves that make up the outermost ring of flower parts and protect the bud. Petals are broad, flat, thin leaf-like parts of a flower. Varying in color and shape, petals attract insects or other animals to the flower. These animals help plants reproduce by carrying pollen from flower to flower. A stamen is a male reproductive structure of flowers. Each stamen has a thin stalk called a filament, which is topped by an anther. Anthers produce pollen. Found in the center of most flowers is one or more pistils – the female reproductive structure of flowers. The tip of the pistil is the stigma. This is where pollen grains collect. The long, slender part of the pistil is the style. The rounded base of a pistil contains one or more ovules called the ovary. Each ovule contains an egg. When the egg is fertilized, the ovule develops into a seed. The ovary develops into a fruit. Humans use flowers for many things, from floral arrangements, to making tea, and in products such as shampoo, perfumes and lotions.

Information Posted on 3/1/06

Notes for Chapter 11 – Protists and Fungi

Section 1 - Protists

A protist is a member of the kingdom Protista. They differ from other living things in many ways, as Fig. 1 p. 270 shows. Being very diverse, protists have few traits in common. Most are single-celled, but some are multi-cellular. Some are producers, while others eat other organisms or decaying matter. One thing that all protists have in common is that they are eukaryotic, which means that their cells have a nucleus.

Those protists that cam make, or produce their own food, are called producers. They have chloroplasts in their cells that they use to capture energy from the sun and make food in a process called photosynthesis. Other protists must get their food from their environment, and are called heterotrophs – organisms that cannot make their own food. They eat other organisms, parts of other organisms, or the remains of other organisms. Some protist heterotrophs are parasites. A parasite invades another organism to get the nutrients that it needs. An organism that a parasite invades is called a host. Parasites are harmful to their hosts, and may invade fungi, plants, or animals.

Some protists reproduce asexually, while others reproduce sexually. Some even change the way that they reproduce at different stages in their life cycle. Most protists reproduce asexually (offspring come from only one parent). The Euglena shown in Fig. 3, p. 272 is reproducing asexually by fission. In binary fission, a single-celled protists divides into two cells. In some cases, single-celled protists use multiple fission to make more than two offspring from one parent. Each new cell is a single-celled protist.

Some protists reproduce sexually (offspring come from two parents). Members of the genus Paramecium sometimes reproduce sexually by a process called conjugation (see Fig. 4 p. 272). During this process, tow individuals join together and exchange genetic material by using a small, second nucleus. They then divide to produce four protists that have new combinations of genetic material.

Some protists have complex reproductive cycles, and these protists may change forms many times. Look at Fig. 5, p. 273, which shows the life cycle of P. vivax, the protist that causes the disease malaria. This protist depends on both humans and mosquitoes to reproduce.

Section 2 – Kinds of Protists

Scientists group protists according to shared traits. The three groups are producers, heterotrophs that can move, and heterotrophs that can’t move. Most protists are producers, able to make their own food through photosynthesis. Protist producers are known as algae – eukaryotes that do not have roots, stems, or leaves. Many-celled algae live in shallow water along the shore, and are known as seaweeds. Free-floating single-celled algae are called phytoplankton. Usually floating near the water’s surface, phytoplankton provides food for most other organisms in the water, and produces much of the world’s oxygen.

Red algae comprise most of the world’s seaweeds. A red pigment gives them their color, and they usually grow less than 1 meter in length. Green algae are the most diverse group of protist producers. Since chlorophyll is the main pigment in their cells, they are green in color. Most live in water or most soil, but others can live in melting snow, on tree trunks, or inside organisms. Many are single-celled, but others are made of many cells. The many-celled species can grow up to 8 meters long. Individual cells of some species of green algae, such as Volvox, live in groups called colonies (see Fig. 3, p. 275). Brown algae are found in cool climates, and attach to rocks or form free floating beds in ocean waters. Like the other types of algae, brown algae have the green pigment chlorophyll, but they also have a yellow-brown pigment. Some grow up to 60 meters in length.

Diatoms are single-celled producers that are found in fresh and salt water (see Fig. 4, p. 276). The cell walls of diatoms contain a glasslike substance called silica. Dinoflagellates live in both salt and fresh water. They contain two whip-like strands called flagella that they use to move through the water. Most dinoflagellates are producers, but a few are consumers, decomposers, or parasites. Euglenoids are single-celled protists that live in fresh water. They use flagella to move around. Many are producers, but when there’s not enough sunlight, they can get food as heterotrophs. Other euglenoids don’t contain chlorophyll, and so can’t make their own food. These types of euglenoids are consumers or decomposers (see Fig. 5, p. 276).

Some heterotrophic protists are able to move around in their environments, while others are unable to. The mobile, or moving protists are sometimes called protozoans. Amoebas are soft, jellylike protozoans found in salt and fresh water, in soil, and as parasites in animals. They move with pseudopodia, or “false feet.” An amoeba stretches out a pseudopod from the cell, and the cell then flows into the pseudopod (see Fig. 6, p. 277). In addition to movement, amoebas use their pseudopodia to catch food. Surrounding its food with its pseudopodia, a food vacuole is formed. Here, enzymes digest the food (see Fig. 7, p. 277). Not all amoeba-like protists look shapeless. Some have an outer shell, like the radiolarian (Fig. 8 p. 287). Others, like the foraminiferans, have snail-like shells.

Zooflagellates are protists that wave flagella back and forth to move. Some live in water, while others live inside organisms. Some zooflagellates, like G. lamblia, are parasites that cause disease. Some zooflagellates live in mutualism with other organisms. In mutualism, each organism helps the other live; they provide a benefit to each other.

Ciliates are complex protists. They have hundreds of tiny, hair-like structures known as cilia. Beating up to 60 times per second, these cilia move to propel the organism forward. The Paramecium, shown in Fig. 10, p. 279, is a common ciliate. They have two types of nuclei – the macronucleus controls the cell’s functions, and the micronucleus passes genes to another paramecium during sexual reproduction.

The final group of protists are heterotrophs that can’t move. Many spore-forming protists are parasites, absorbing nutrients from their hosts. Having no cilia or flagella, they are unable to move. They have complicated life cycles that usually include two or more hosts. Water molds are small, single-celled organisms that live in water, moist soil, or other organisms. Some are decomposers, but many are parasites. Slime molds are heterotrophic protists that can move only in certain phases of their life cycles. They live in cool, moist places in the woods.

Section 3 - Fungi

Fungi are eukaryotic heterotrophs that have rigid cell walls and no chlorophyll. As Fig. 1 p. 282 shows, fungi come in a variety of shapes, sizes, and colors. Although they are heterotrophs, fungi can’t catch or surround food. Instead, they secrete digestive juices onto a food source, and then absorb the dissolved food. Many fungi are decomposers, feeding on dead plants and animals, while others are parasites. Some live in mutualism with other organisms. For example, some fungi grow on or in the roots of a plant. The plant provides nutrients to the fungus, and the fungus helps the root absorb minerals and protects the plant from disease-causing organisms.

Some fungi are single-celled, but most are made up of many cells. These many-celled fungi are made up of chains of cells called hyphae – threadlike fungal filaments. Most of the hyphae that forms a fungus grows together to form a twisted mass called the mycelium. Although hidden underground, the mycelium makes up the major part of the fungus.

Reproduction in fungi can be either asexual or sexual. Asexual reproduction can happen in two ways: in one type, hyphae break apart, and each new piece becomes a new fungus. In another type, spores can be produced. Spores are small reproductive cells protected by a thick cell wall. Sexual reproduction in fungi happen when special structures form to make new sex cells. The sex cells join to produce sexual spores that grow into a new fungus. Figure 3 p. 282 shows a puffball releasing sexual spores that can produce new fungi.

Fungi are classified based on their shape and the way that they reproduce. There are four main groups of fungi. The first is the threadlike fungi, can reproduce asexually. Parts of the hyphae grow into the air and form round spore cases called sporangia at the tips. When these sporangia break open, tiny spores are released into the air. This type of fungi can also reproduce sexually, when a hypha from one individual joins with the hypha from another individual.

Sac fungi are the second group, and are the largest group of fungi. Sac fungi can reproduce both asexually and sexually. Most of the time, they reproduce asexually. When they reproduce sexually, they form a sac called an ascus. Sexually produced spores develop within this ascus. Some sac fungi are helpful to humans, such as yeasts used in making bread. Some, however, are harmful. Many sac fungi are disease causing parasites.

Mushrooms belong to club fungi, so named because of the structures that the fungi grow during reproduction. Reproducing sexually, they grow special hyphae that form clublike structures called basidia (Greek for ‘clubs’). Sexual spores develop on the basidia. The most familiar mushrooms are gill fungi. The basidia of these mushrooms develop in structures called gills, under the mushroom cap. Not all members of the club fungi group are mushrooms. The non-mushroom club fungi are bracket fungi (which grow outward from wood and form small shelves), and smuts and rusts (common plant parasites). Smuts and rusts often attack crops such as corn and wheat (Fig. 12 p. 287).

The imperfect fungi group includes all fungi species that do not quite fit in the other groups. These fungi do not reproduce sexually. Most are parasites that cause disease in animals. Some imperfect fungi are helpful, however. For example, Penicillium, shown in Fig. 13 p. 287, is the source of the antibiotic penicillin.

A lichen is a combination of a fungus and an alga that grow together. The alga lives inside the protective walls of the fungus. The resulting organism is different from either organism growing alone. The lichen is the result of this mutualistic relationship. Unlike fungi, lichens are producers - the algae in the lichens are able to make food through photosynthesis. Found in almost every type of land environment, lichens need only air, light, and minerals to grow, and so can usually be found growing on rocks. Lichens absorb minerals and water from the air. As a result, lichens are easily affected by air pollution. So their presence or absence can be a good measure of air quality in an area.

Information Posted on 2/13/06

Notes for Chapter 10 – Bacteria and Viruses

Section 1 - Bacteria

There are more types of bacteria on Earth than all other living things combined. While most are too small to be seen without a microscope, they nonetheless display a wide variety in sizes. For example, the largest known bacteria are 1,000 times larger than the average bacterium.

Bacteria make up the kingdoms eubacteria and archaebacteria. These two kingdoms make up the oldest forms of life on Earth. All bacteria are single-celled organisms, and are usually one of three main shapes: bacilli (rod shaped); cocci (spherical); spirilla (long, spiral shaped). Most bacteria have a rigid cell wall that gives them their characteristic shape (see Fig. 2, p. 247). Some bacteria have hair-like flagella that help them to move around, pushing them through water or other liquids.

All bacteria are single-celled organisms lacking a nucleus. Such organisms are called prokaryotes. Prokaryotes are able to move, get energy, and reproduce like cells that contain a nucleus, which are called eukaryotes. Bacteria reproduce by the process of binary fission, shown in Figure 3, p. 248. Binary fission is a form of asexual reproduction in which one single-celled organism splits into two single-celled organisms.

Most bacteria do quite well in warm, moist places. Some bacteria species will die in cold, dry environments. In these cases, other bacteria become inactive and form endospores. Endospores contain genetic material and proteins and are covered by a thick, protective coat. Many endospores can survive in hot, cold, and even dry places. When conditions improve, the endospores break open, and the bacteria become active again.

Most bacteria are eubacteria, which as a kingdom has more individuals than all of the other five kingdoms combined! They have also been on the Earth for more than 3.5 billion years. Eubacteria are classified by the way that they get food. Most are consumers, meaning that they get their food by eating other organisms. Some eubacteria, however, make their own food, and so are producers. Like plants, these bacteria use sunlight to make food, and are often green in color. Cyanobacteria are producers that usually live in water. These bacteria contain the green pigment chlorophyll, which is important in the photosynthesis process. Many cyanobacteria have other colored pigments as well.

Archaebacteria make up the second bacterial kingdom. There are three main types of archaebacteria: heat lovers, salt lovers, and methane makers. Archaebacteria live often where nothing else can, and prefer environments with little or not oxygen. They are also different from eubacteria in that some lack cell walls. Those that do have cell walls are chemically different from those of eubacteria.

Section 2 – Bacteria’s Role in the World

While bacteria are often thought as a negative influence on the world, in reality life as we know it couldn’t exist without them. They help recycle dead plants and animals, and also play a role in the nitrogen cycle Nitrogen gas makes up about 78% of the atmosphere, but most plants can’t use nitrogen directly from the air. So in a process called nitrogen fixation, bacteria take in nitrogen from the air and change it into a form that plants can use (see Fig. 1, p. 252).

Besides nitrogen fixation, certain types of bacteria break down dead plant and animal matter, and in the process make those nutrients available to other living things. Additionally, bacteria are sometimes used to fight pollution. In a process called bioremediation, microorganisms are used to change harmful chemicals into harmless ones (see Fig. 2, p. 253).

Bacteria also help produce many of the foods we eat every day, such as cheese and yogurt. Some bacteria are even used to fight disease-causing bacteria through antibiotics – medicines used to kill bacteria and other microorganisms. In another health-related example of bacteria serving helpful purposes, scientists in the 1970’s discovered how to put genes into bacteria so that the bacteria would make human insulin, a substance used to break down and use sugar and carbohydrates. And in the practice of genetic engineering, scientists can change the genes of bacteria to make new products such as insecticides, cleansers, and adhesives.

There are, however, some types of bacteria that are quite harmful. These bacteria are called pathogenic bacteria, meaning that they cause disease. These bacteria get inside a host organism and take nutrients from the host’s cells, harming the host in the process. We are protected from many bacterial diseases by vaccination (Fig. 5, p. 254), and many bacterial diseases can also be treated with antibiotics. Bacteria can also cause disease in other organisms as well, such as plants, animals, fungi, protists, and even other bacteria. They can cause damage to grain, fruit, and vegetable crops, as shown in Fig. 6, p. 255).

Section 3 - Viruses

A virus is a microscopic particle that gets inside a cell and often destroys the cell. Many viruses cause diseases, such as the common cold, flu, and acquired immune deficiency syndrome (AIDS). Viruses are tiny, even smaller than the smallest bacteria. About 5 billion virus particles could into a single drop of blood! Being able to change quickly, a virus’s effect on living things can also change. So their small size, combined with this ability to change, or mutate so often, makes them difficult to fight.

Like living things, viruses contain protein and genetic material. But viruses, like those shown in Figure 1, p. 256, don’t act like living things – they can’t eat, grow, break down food, or use oxygen. In fact, a virus can’t function on its own – it can reproduce only inside a living cell that serves as a host. A host is a living thing that a virus or parasite lives on or in. Using a host’s cell as a tiny factory, the virus forces the host to make viruses rather than healthy new cells.

Viruses can be classified by their shape, the type of disease they cause, their life cycle, or the kind of genetic material that they contain. Figure 2, p. 257 shows the four main shapes of viruses. Every virus is made up of genetic material inside a protein coat. The coat protects the genetic material and also helps the virus enter a host cell. In fact, many viruses have a protein coat that matches characteristics of their specific host.

The genetic material contained in viruses is either DNA or RNA. Both contain information for making proteins. The viruses that cause warts and chickenpox contain DNA, whereas the viruses that cause colds and the flu contain RNA. The virus which causes AIDS also contains RNA.

The one thing that viruses do that living things also do is make more of themselves. The cycle in which viruses attack living cells and turn them into virus factories is called the lytic cycle (Fig. 3, p. 158). Some viruses don’t go straight into the lytic cycle. These viruses put their genetic material in the host cell, but new viruses aren’t made right away. Rather, in the lysogenic cycle, each new cell get s copy of the virus’s genes when the cell divides. The genes can stay inactive for a long time. When they do become active, they begin the lytic cycle and make copies of the virus.

Unlike bacteria, antibiotics do not kill viruses. However, scientists have recently developed antiviral medications, which can stop viruses from reproducing.

Information Posted on 2/1/06

Notes for Chapter 9 – Classification

Section 1 – Sorting it All Out

Classification is putting things into orderly groups based on similar characteristics. Scientists classify organisms to help make sense and order of the many kinds of living things in the world. Prior to the 1600’s, many scientists divided organisms into two groups: plants and animals. But, as more organisms were discovered, some of them didn’t fit into either group. In the 1700’s, a Swedish scientist named Carolus Linnaeus founded modern taxonomy. Taxonomy is the science of describing, classifying, and naming living things. He described a seven-level system of classification, which is still used today. Branching diagrams, like the one shown in Figure 2, p. 223, are also used by scientists to show similarities and differences between different species of organisms.

The seven levels of classification are: (1) Kingdom (2) Phylum (3) Class (4) Order (5) Family (6) Genus (7) Species. Every living thing is classified into one of six kingdoms, which are the largest, most general groups. All living things in a kingdom are sorted into several phyla (singular, phylum). All living things in a phylum are further sorted into classes. Each class includes one or more orders. Orders are separated into families. Families are broken into genera (singular, genus). Finally, genera are sorted into species. Look at Figure 3, p. 224-225 for an example of how this classification system works for a cat.

By classifying organisms, biologists are able to give organisms scientific names. A scientific name is always the same for a specific kind of organism no matter how many common names there might be. Before the time of Linnaeus, scholars used names that were as long as 12 words to identify species! Linnaeus simplified the naming of living things by giving each a two-part scientific name. For example, the scientific name of the Asian elephant is Elephas maximus. The first part of the name, Elephas, is the genus name, and it is always capitalized. The second part, maximus, is the species name, and it is always written in lower-case letters. Usually, both names are underlined or italicized. Scientific names, usually in Greek or Latin, contain information about an organism. Scientific names can also abbreviated, as in E. maximus, or T. rex.

A dichotomous key is an identification aid that uses sequential pairs of descriptive statements. There are only two alternative responses for each statement. From each pair of statements, the person trying to identify the organism chooses the statement that describes the organism. Either the chosen statement identifies the organism, or the person is directed to another pair of statements. Figure 5, p. 226 gives an example of how we can use dichotomous keys to identify organisms.

Organisms are still being discovered and classified today. Some newly discovered organisms fit into existing categories. Occasionally, however, a new organism differs so much from other organisms that it doesn’t fit into existing categories. In the case of Symbion pandora (see p. 227), a new phylum was created to accommodate it.

Section 2 – The Six Kingdoms

Organisms are classified by their characteristics. As scientists continued to learn about living things, they added kingdoms that account for the characteristics of different organisms. Living things are grouped into one of six kingdoms: (1) Archaebacteria (2) Eubacteria (3) Protista (4) Fungi (5) Plantae, and (6) Animalia.

Prokaryotes that can live in extreme environments are in the kingdom Archaebacteria. These bacteria love to live in places where the temperature is either extremely cold or extremely hot, like those living in the hot springs in Yellowstone National Park. Bacteria not in the kingdom Archaebacteria are in the kingdom Eubacteria. These are prokaryotes that live in the soil, in water, and even on and inside the human body, like Escherichia coli (Figure 3, p. 229).

Members of the kingdom Protista, called protists, are single celled or simple multicellular organisms that don’t fit into any other kingdom. Protists are eukaryotes, organisms whose cells have a nucleus and membrane-bound organelles. Animal-like protists are called protozoans, and plant-like protists are called algae. Members of the kingdom Fungi , like molds and mushrooms, do not perform photosynthesis (like plants), and do not eat food (unlike animals). Instead, they absorb nutrients from substances in their surroundings. Fungi use digestive juices to break down the substances.

Organisms in the kingdom Plantae are eukaryotic, have cell walls, cannot move around, and make food through photosynthesis. Plants also provide habitats for other organisms, like the giant Sequoia trees in Figure 6, p. 231. The kingdom Animalia, whose members are commonly called animals, contains complex, multicellular organisms that don’t have cell walls, are usually able to move around, and have specialized sense organs. These sense organs help most animals respond quickly to their environment. Sponges are thought of as the simplest animals. They don’t have sense organs, and most can’t move. Although they used to be considered plants, sponges cannot make food – they must eat other organisms to survive, which is one reason that they are classified as animals.

Notes for Quarter 2

Information Posted 1/16/06

Notes for Chapter 7 – The Evolution of Living Things

Section 1 – Change Over Time

“Change over time” – this is the briefest way to define what evolution is. Although chapter 7 focuses on evolutionary changes in living things, it is important to understand that all material things in the Universe change over time – from galaxies, stars, planets, to living things. Nature has risen to ever-greater states of complexity ever since the origin of the Universe some 14 billion years ago. From atoms of hydrogen and helium gas forming soon after the Big Bang, to enormous clouds of these gases condensing into galaxies like our Milky Way, to stars forming within the galaxies, to planets forming around some of those stars, and (at least on Earth) chemical and biological conditions suited for the origin and development of life forms, one of which has developed a technological civilization.

Looking now at chapter 7, section 1, a characteristic that helps an organism survive and reproduce in its environment is called an adaptation. Adaptations may be physical (such as a long neck or striped fur), or behaviors that help an organism find food, protect itself, or reproduce. Living things that have the same characteristics may be members of the same species, which is a group of organisms that can mate with one another to produce fertile offspring. For example, all strawberry poison dart frogs are members of the same species, and so can mate with each other to produce more poison dart frogs. Groups of individuals of the same species living in the same place make up a population.

Scientists believe that the Earth has changed a great deal in its 4.6 billion year history. Since life first appeared, many species have died out, and many new species have appeared. Scientists observe that species have changed over time, and that inherited characteristics in populations also change over time. As populations change over time, new species form. Thus, newer species descend from older species. Evolution is the process in which populations gradually change over time. Evidence that evolution has occurred is buried within Earth’s crust, which is arranged in layers. These layers, made up of rock and soil, are stacked on top of each other. Older layers are deposited, or set down, before newer layers, and so are buried deeper within the Earth. Within these layers, fossils - the remains or imprints of once-living organisms - are found (see Fig. 5, p. 168). By studying fossils, scientists have a timeline of life that is known as the fossil record.

Scientists observe that all living organisms have characteristics in common and inherit characteristics in similar ways. So, scientists think that all living species descended from common ancestors. Scientists draw models, like the one in Figure 6, p. 169, to help them figure out the relationships between extinct and living organisms. For example, by studying large numbers of fossils and making comparisons to modern whales, scientists can confidently assert that the ancient ancestor of whales was probably a mammal that lived on land and that could run on four legs. When one examines the hip bones of modern whales, they are observed to be very tiny. Fossils of ancestor creatures show larger hip bones, such as would be needed for walking on land (see Fig. 7, p. 170-171). Evidence that groups of organisms have common ancestors can also be found by comparing the groups’ DNA (see Fig. 8, p. 172).

Section 2 – How Does Evolution Happen?

By the 1800’s, scientists began to realize that the Earth is much older than anyone previously thought. But while evidence showed that gradual processes shaped the Earth’s surface over millions of years, and some scientists saw evidence of evolution in the fossil record, no one could really explain how evolution happens – until Charles Darwin came along. After deciding against careers in both medicine and the ministry, Darwin signed on for a five-year voyage as a naturalist aboard the British ship HMS Beagle. On this voyage (Fig. 3, p. 175), Darwin collected thousands of plant and animal samples, and kept careful notes of his observations. One of the places that the Beagle visited was the Galapagos Islands, a string of 13 volcanically-formed islands off of the coast of Ecuador, a country in South America.

Darwin noticed that the animals and plants found on the Galapagos were similar, but not identical to, those found in Ecuador. One notable case study involved finches – finches differed from island to island (see Fig. 4, p. 175). Specifically, the beak of each finch was observed by Darwin to be uniquely adapted to the way the bird gets food. So Darwin hypothesized that the Island finches were probably blown over from South America during a storm (thus explaining similarities between the two finch populations). But over many generations, the finches may have adapted to different ways of life on the Islands.

Darwin drew from different ideas, and the work of other scientists, to help him make sense of his observations. For example, traits – specific characteristics that can be passed from parent to offspring through genes. In Darwin’s time, farmers and breeders produced many different kinds of farm animals and plants. These plants and animals had traits desired by the farmers and breeders. This is known as selective breeding – when humans select which plants or animals to reproduce based on certain desired traits. Another thing that influenced Darwin was a work written by Thomas Malthus on human population and food supply (see Fig. 6, p. 177). After reading Malthus’ work, Darwin realized that any species can produce many offspring, and that populations of all species are limited by starvation, disease, competition, and predation. Only a limited number of offspring survive to reproduce. Thus, there is something special about the survivors – Darwin reasoned that the offspring of the survivors inherit traits that help the offspring survive in the environment. A third key area that influenced Darwin had to do with the Earth’s age. Charles Lyell, in his work Principles of Geology, showed that the age of the Earth was much greater than anyone previously thought.

After returning to England following his five-year voyage aboard the Beagle, Darwin tried to make some sense out of all his notes and observations for the next twenty years. After receiving a letter from Alfred Wallace, who independently came to the same conclusions that Darwin did about changes in living things, Darwin grew more motivated to present his ideas. In 1859, he published his famous On the Origin of Species by Means of Natural Selection. In this work, Darwin proposed the theory that evolution happens through a process called natural selection. This helps to explain the mechanism of evolution, and essentially states that individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do (see Figure 7, p. 178 for a description of the four parts of natural selection).

Darwin lacked evidence for parts of his theory. For example, he knew that organisms inherited traits, but not how they did. Today, scientists have found most of this lacking evidence. They know that variation happens as a result of differences in the genes.

Section 3 – Natural Selection in Action

The theory of natural selection explains how a population changes in response to its environment. So if natural selection is taking place, a population will tend to be well adapted to its environment. However, not all individuals are the same – the individuals that are likely to survive and reproduce are those that are best adapted at the time.

Changes in populations are sometimes observed when a new force affects the survival of individuals. For example, the hunting of African elephants for their tusks resulted in fewer of the elephants that have tusks surviving to reproduce, and more of the tuskless elephants surviving. When the tuskless elephants reproduce, they pass the tuskless trait to their offspring. Insect resistance is another example of natural selection work (see Fig. 2, p. 181). People use insecticides to control the insect populations around their homes and farms. As the diagram shows, over time insects develop a resistance to the chemicals in the insecticides – chemicals that used to be deadly to them. Insects can quickly develop resistance because they often reproduce and have short generation times. Generation time is the average time between one generation of offspring and the next.

Natural selection is also at work when individuals reproduce. In organisms that reproduce sexually, finding a mate is part of the struggle to reproduce. Many species have so much competition for mates that interesting adaptations result. For example, the females of many bird species prefer to mate with males that have certain types of colorful feathers.

Sometimes, drastic changes that can form a new species take place. In the animal kingdom, a species is a group of organisms that can mate with each other to produce fertile offspring. A new species may form after a group separates from the original population. This group forms a new population. Over time, the two populations adapt to their different environments. Eventually, the populations become so different that they can’t mate anymore. Each population may then be considered a new species. Speciation is the formation of a new species as a result of evolution. See Figure 3, p. 182 for a diagram of how new species of Galapagos finches may have formed.

Information Posted on 1/2/06

Notes for Chapter 6 – Genes and DNA

Section 1 – What Does DNA Look Like?

DNA (deoxyribonucleic acid) is the genetic material that determines inherited characteristics. Scientists initially thought that only complex molecules could explain the behavior of genes, which give instructions for building and maintaining cells, and the ability to be copied each time a cell divides. They were surprised that these important functions could be performed by the DNA molecule.

DNA is made of subunits called nucleotides. A nucleotide consists of a sugar, a phosphate, and a base. Except for the base, the nucleotides are identical. The four bases are adenine, thymine, guanine, and cytosine, and are often referred to by the first letter of their name (A, T, G, C). Each of these bases is shaped differently (see Fig. 1, p. 144). In the 1950’s, Erwin Chargaff determined that the amount of adenine in DNA always equals the amount of thymine. He found the same to be true of cytosine and guanine. His findings are known as Chargaff’s Rules.

Other scientists gave us information about DNA’s structure. Rosalind Franklin used the process of X-ray diffraction to make images of the DNA molecule. In this process, X- rays are aimed at the DNA molecule, bouncing off. The pattern made by the bouncing C-rays is captured on film, and the images that Franklin captured indicated that DNA has a spiral shape. After seeing Franklin’s images, James Watson and Francis Crick concluded that DNA must look like a long, twisted ladder. They built a model that perfectly fit both Chargaff’s and Franklin’s discoveries. Watson and Crick’s model would help us explain how DNA is copied and how it functions in the cell.

The shape of the DNA molecule is known as a double helix (see Fig. 4, p. 146). The two sides of the ladder are made of alternating sugar and phosphate parts, and the rungs of the ladder are made of a pair of bases. Adenine on one side of a rung is always paired with thymine on the other side, and guanine always pairs with cytosine to form a rung.

The pairing of bases allows the DNA molecule to replicate, or make copies. Each base always bonds with only one other base. So pairs of bases are complementary to each other, and both sides of a DNA molecule are complementary. For example, the sequence CGAC will bond to the sequence GCTG. During replication (see Fig. 5 p. 147), a DNA molecule is split down the middle, where the bases meet. The bases on each side of the molecule are used as a pattern for a new strand. And as these bases on the original molecule are exposed, complementary nucleotides are added to each side of the ladder. Two DNA molecules are now formed – half of each of the molecules is old DNA, and half is new DNA. DNA is copied every time that the cell divides. The job of unwinding, copying, and re-winding the DNA is done by proteins within the cell.

Section 2 – How DNA Works

Almost every cell in your body contains about 2 meters of DNA. DNA is often wound around proteins, coiled into strands, and then bundled up even more. In cells that lack a nucleus each strand of DNA forms a loose loop within the cell. In cells that contain a nucleus, however, the strands of DNA and proteins are bundled into chromosomes (see Fig. 1 p. 148-149).

The structure of DNA allows DNA to hold information. The order of the bases on one side of the molecule is a code that carries information. A gene consists of a string of nucleotides that give the cell information about how to make a certain trait (study Figure 1 on p. 148-149) so that you have a visual reference for how DNA is housed in a cell).

The DNA code is read much like a book – from one end to another and in one direction. The bases form the alphabet of the code. Groups of three bases are the codes for specific amino acids. So the three bases CCA form the code for the amino acid praline. The bases AGC form the code for the amino acid serine. A long string of amino acids forms a protein. So each gene is usually a set of instructions for making a protein. Proteins are related to traits, in that proteins act as chemical triggers and messengers for many of the processes within cells. Proteins help determine how tall you are, what colors you can see, and whether you have straight or curly hair.

Another molecule that helps make proteins is called RNA (ribonucleic acid). RNA is so similar to DNA that RNA can serve as a temporary copy of a DNA sequence. Several forms of RNA help in the process of changing the DNA code into proteins (study Figure 2 on p. 150-151, as this outlines the process protein making). The mirror-like copy of the DNA segment made out of RNA is called messenger RNA, or mRNA. It moves out of the nucleus and into the cytoplasm of the cell. Inside the cytoplasm, the mRNA is fed through a protein ‘assembly line.’ The ‘factory’ that runs this assembly line is the ribosome, which is a cell organelle composed of RNA and protein. The mRNA is fed through the ribosome three bases at a time, and code for one amino acid. Then, molecules of transfer RNA (tRNA) translate the RNA message. Each tRNA picks up a specific amino acid from the cytoplasm. Inside the ribosome, bases on the tRNA match up with bases on the mRNA like puzzle pieces. The tRNA molecules then release their amino acids. The amino acids become linked in a growing chain. As the entire segment of mRNA passes through the ribosome, the growing chain of amino acids folds up into a new protein molecule.

Changes in the number, type, or order of bases on a piece of DNA are known as mutations. Sometimes a base is left out (deletion). Or an extra base might be added (insertion). The most common change happens when the wrong base is used (substitution). See Figure 3, p. 152 for a graphic of these types of mutations. Mutations happen regularly because of random errors when DNA is copied. Damage to DNA can also be caused by abnormal things that happen to cells. Any physical or chemical agent that can cause a mutation is called a mutagen. Some examples would be X-rays, ultraviolet radiation, asbestos and the chemicals in cigarette smoke. Study Figure 4 on p. 153 to see how sickle cell disease results from a mutation.

When individual genes within organisms are manipulated, this is called genetic engineering. This process is used to create new products such as drugs, food, or fabrics. Since DNA is unique, it can be used like a fingerprint to identify you. So DNA fingerprinting identifies the unique patterns in an individual’s DNA (see Fig. 6 p. 154).

Information Posted on 12/5/05

Notes for Chapter 5 – Heredity

Section 1 – Mendel and His Peas –

Heredity is the passing on of traits from parents to offspring. Gregor Mendel conducted key experiments with pea plants in his monastery garden that would launch the science of genetics. In his first experiments, he crossed pea plants to study seven different characteristics (see Table 1, p. 118). He chose pea plants because they were plentiful in the gardens, but also because of their properties. They had the ability to self-pollinate – a self-pollinating plant has both male and female reproductive structures. So pollen from one flower can fertilize the ovule of the same flower. Pea plants can also cross-pollinate – here, one plant fertilizes the ovule of a flower on a different plant. (see Fig. 2, p. 115 for both cases).

He used plants that were true breeding for different traits for each characteristic. When a true breeding plant self-pollinates, all of its offspring will have the same trait as the parent. So a true breeding plant with purple flowers will always have offspring with purple flowers. Mendel, then, crossed plants that had purple flowers with plants that had white flowers (see Fig. 5, p. 117). The offspring of such a cross are called first generation plants. All the first generation plants in this cross had purple flowers.

Mendel got similar results for each cross. One trait was always present in the first generation, and the other trait seemed to disappear. The trait that was present in the first generation was called dominant, and the other trait, that seemed to disappear, was called recessive. Mendel was curious what happened to the recessive trait (which was the trait for white flowers), so he conducted another set of experiments.

In this second round of experiments, Mendel did the same experiment he did initially on each of seven characteristics (flower color, seed color, seed shape, pod color, pod shape, flower position, and plant height). In each case, some of the second generation plants had the recessive trait. Mendel then decided to figure out the ratio of dominant to recessive traits. As Figure 1, p. 118 shows, there is a 3:1 ratio of dominant to recessive trait for all seven characteristics.

Section 2 – Traits and Inheritance –

Mendel knew from his experiments with pea plants that there must be two sets of instructions for each characteristic. Scientists now call these instructions for an inherited trait genes. Each parent gives one set of genes to the offspring. The offspring then has two forms of the same gene for every characteristic-one from each parent. The different forms (often dominant and recessive) of a gene are known as alleles. Dominant alleles are shown with a capital letter, and recessive alleles are shown with a lowercase letter. So in Mendel’s experiments, purple, which was dominant in flower color, was represented with a capital R, and white, which was a recessive trait in flower color, was presented with a lowercase r.

An organism’s appearance is known as its phenotype. So for pea plants, possible phenotypes for flower color would be purple flowers or white flowers.

Both inherited alleles together form an organism’s genotype. Because the allele for purple flowers (P) is dominant, only one P allele is needed for the plant to have purple flowers. Two dominant or two recessive alleles (PP or pp) is said to be homozygous. A plant that has a hybrid genotype (Pp) is known as heterozygous.

Punnett Squares are tools used in genetics studies to organize the possible combinations of offspring from particular parents (see Fig. 2, p. 121 for an example). We can use Punnett Square to determine the probability, or likelihood that something will happen, in this case a particular genetic outcome. Each of the four squares that make up a Punnett Square represents a 25% probability that a certain outcome will occur. So the offspring of a Pp x Pp cross has a 50% chance of receiving either allele from either parent. So the probability of inheriting two p alleles is ½ x ½, or ¼ (25%). Traits in pea plants are easy to predict because there are only two choices for each trait, such as purple or white flowers, or round and wrinkled seeds.

Sometimes one trait is not completely dominant over another trait. These traits do not blend together, but each allele has its own degree of influence. This is known as incomplete dominance. Figure 5, p. 124 shows the result of incomplete dominance in true breeding snapdragons – a cross between true breeding red and white snapdragons yields pink flowers, because both alleles of the gene have some degree of influence.

Sometimes one gene can influence more than one trait (for example, the gene that causes the tiger in Fig. 6 p. 124 to have white fur also causes its blue eyes). Additionally, environment needs to be considered in studies of traits, as well as genes. For example, one may have the genes to be tall, but unless this is supplemented with a healthy diet, your full height potential will not be reached.

Section 3 – Meiosis -

In asexual reproduction, only one parent cell is needed. This parent cell divides in a process called mitosis, making two exact copies of itself. Most of the cells in your body reproduce in this way. However, in sexual reproduction, two parent cells join together to form offspring that are different from both parents. The parent cells are called sex cells. Sex cells are different from ordinary body cells. Human body cells have 46, or 23 pairs, of chromosomes. Chromosomes that carry the same set of genes are called homologous chromosomes. Sex cells are different though. They have 23 chromosomes-half the usual number. Each sex cell, then, has only one of the chromosomes from each homologous pair.

Sex cells are made during meiosis – a copying process that produces cells with half the usual number of chromosomes. Each sex cell receives one-half of each homologous pair. A human egg cell has 23 chromosomes, and a sperm cell has 23 chromosomes. The new cell that forms when an egg cell and a sperm cell join has 46 chromosomes.

Genes, which carry sets of instructions for traits, are located on chromosomes. Understanding meiosis was critical to finding the location of genes. The steps of meiosis are illustrated in Figure 3, p. 128-129. During the meiosis process, chromosomes are copied once, and then the nucleus divides twice. The resulting sperm and eggs have half the number of chromosomes of a normal body cell.

The steps in meiosis explain Mendel’s results that he obtained with his pea plants. Each fertilized egg in the first generation had one dominant allele and one recessive allele for seed shape. Only one genotype was possible because all sperm formed by the male parent during meiosis had the wrinkled-seed allele, and all of the female parent’s eggs had the round-seed allele.

Sex chromosomes carry genes that determine sex. In humans, females have two X chromosomes (XX). Human males have one X chromosome and one Y chromosome (XY). Figure 5 p. 131 shows that there is a 50% chance of the human offspring being male and 50% chance of offspring being female.

The genes for certain disorders, such as colorblindness and hemophilia, are carried on the X chromosome. These disorders are called sex-linked disorders. Because the gene for such disorders is recessive, men are more likely to have sex-linked disorders (because males have only one copy of each gene on their one X chromosome – females have two X’s, and so they carry two copies of each gene, and this makes a backup gene available if one becomes damaged).

Genetic disorders such as hemophilia can be traced through a family tree. Couples who are worried that they might pass a disease on to their children may consult a genetic counselor. These genetic counselors make use of a diagram called a pedigree, which is a tool for tracing a trait through generations of a family. By making a pedigree, a counselor can often predict whether a person is a carrier of a hereditary disease. Fig. 7 p. 132 shows a pedigree for the disease called cystic fibrosis, which affects the lungs.

When selective breeding is undertaken, organisms with desired characteristics are mated. Animals such as pets may be the result of selective breeding, as are flowers (see Fig 8 p. 132).

Notes for Chapter 4 – The Cell in Action

Section 1 – Exchange With the Environment –

Cells must exchange materials with their environment.

Diffusion – movement of a substance from an area of high concentration to low concentration (molecules move from crowded areas to less crowded areas); this process does not require energy

Ex. When the smell of baking cookies spreads throughout the house.

Osmosis – diffusion of water through a semipermeable (only certain substances can pass through) membrane. Look @ Figure 2 on p. 91.

The cell has different ways of moving small and large particles into and out of the cell.

Moving Small Particles…

Passive transport – small particles pass through channels in the membrane and energy is NOT required. Ex. Osmosis & diffusion

Active transport – small particles pass through channels in the membrane from low concentration to high concentration. This requires energy.

Moving Large Particles…

Endocytosis – active transport process where cell surrounds large particle (ex. Protein) and encloses it to bring the particle into the cell. See Figure 4 on p. 92.

Exocytosis – active transport process in which a vesicle forms around a large particle within the cell. Vesicle travels to and fuses w/ cell membrane to release the particle. See Figure 5 on p. 93.

Section 2 – Cell Energy –

Almost ALL energy that fuels life comes from the Sun

Plants capture sun energy and convert it to food during the process of:

PHOTOSYNTHESIS

Chlorophyll is a green pigment that is found in chloroplasts and it is crucial to photosynthesis.

Plants use the energy from the sun to convert carbon dioxide, CO2 and water, H2O, into glucose – food.

Glucose is a carbohydrate and can be stored by the plant. Oxygen (O2) is another product of photosynthesis.

CO2 + H2O ----( glucose + O2, in the presence of sunlight and chlorophyll

Cellular Respiration

- Process in which animal cells use oxygen to break down food.

Cellular respiration (CR) does NOT mean the cell is breathing! However, breathing supplies our cells with oxygen to perform cellular respiration. AND removes CO2 – waste product of CR.

In CR, food is broken down into CO2 and H2O and energy is released. Energy is used to maintain body T and produce ATP.

Cellular respiration occurs in the cell membranes of prokaryotic cells and in the mitochondria of eukaryotic cells.

Glucose + water ( CO2 + water + energy

So, Photosynthesis produces oxygen and glucose and uses carbon dioxide and water while CR produces carbon dioxide and water and uses oxygen and glucose.

The two processes support each other.

Fermentation

Fermentation is a process that enables organisms to perform CR without oxygen.

Two types:

1) When your muscle cells run out of oxygen – byproduct is lactic acid and causes muscle soreness.

2) When yeast perform CR without oxygen – byproduct is carbon dioxide.

Section 3 – The Cell Cycle –

• The life cycle of a cell is called the cell cycle.

• The cell cycle begins when the cell is formed and ends when the cell divides and forms new cells.

• Before cell division can occur, it must make a copy of its DNA.

• The DNA of a cell is organized into structures called chromosomes.

• Copying chromosomes that each new cell will be an exact copy of its parent cell.

How Does a Cell Make More Cells?

• Well, it depends on whether the cell is prokaryotic (no nucleus), or eukaryotic (has a nucleus).

• Prokaryotic cells are less complex than eukaryotic cells.

• Bacteria (which are prokaryotes), have ribosomes and a single circular DNA molecule.

• Cell division in bacteria is called binary fission (“splitting into two parts”). This results in two cells that each contain one copy of the circle of DNA.

• Eukaryotic cells are more complex than prokaryotic cells are – the chromosomes of eukaryotic cells contain more DNA than those of prokaryotic cells.

• Different kinds of eukaryotes have different numbers of chromosomes. IN humans, there are 46 chromosomes (23 pairs). These pairs made up of similar chromosomes are known as homologous chromosomes.

Making More Eukaryotic Cells

• The eukaryotic cell cycle includes three stages.

Phase One: Interphase

1) Chromosomes appear as threadlike chromatin

2) In animal cells, centrioles appear outside the nucleus

3) All the chromosomes are duplicated and each chromosome is attached with its sister

Phase Two: Prophase

1) Each chromosome is made up of two identical chromatids attached at the centromere

2) The two centrioles begin to move to opposite ends of the cell in an animal cell and a spindle begins to form in plant and animal cells

3) A nuclear membrane begins to break down and the nucleolus begins to disappear

Phase Three: Metaphase

1) The chromosomes attach to the spindle

2) They are attached by the centromere

3) Each chromatid is still connected to its sister

Phase Four: Anaphase

1) Sister chromatids separate

2) The chromatids move to opposite ends of the cell

3) Chromatids are called chromosomes again

Phase Five: Telophase

1) Chromosomes begin to uncoil and appear again as chromatin

2) A nuclear membrane forms around the chromatin at each end of the cell

3) In each nucleus, a nucleolus reappears

Phase Six: Cytokinesis

1) The cell membrane moves inward until the cytoplasm is divided equally

2) Two new daughter cells are produced with their own nucleus and identical chromosomes

3) In plant cells, each daughter cell also forms a cell wall

Notes for Quarter I

Information Posted on 10/19/05

Notes for Chapter 3 – Cells: The Basic Units of Life

Section 1 – The Diversity of Cells – Cells are the smallest unit that can perform all life processes. They are membrane covered and have DNA and cytoplasm.

The Cell Theory

• All living things are made of one or more cells

• Cells are the basic units of structure and function in living things

• All cells come from existing cells

Cell size - Most cells cannot be seen without a microscope. The yolk of a chicken egg is an exception – it is one big cell.

• If cells get too large, then the cell’s surface area will not be large enough to take in enough food or pump out wastes

Parts of a Cell – The Cell Membrane and Cytoplasm

• The cell membrane is a phospholipid layer covering a cell’s surface-acts as a doorway to the cell

• It is a protective layer that covers the cell’s surface

• Fluid and almost all its contents inside cell is called cytoplasm

Parts of a Cell - Organelles

• Inside a cell’s cytoplasm are small bodies that are specialized to perform a specific function – these are the organelles

Parts of a Cell – Nucleus

• In eukaryotic cells, the nucleus is an organelle that contains the cell’s DNA.

• Control center, or ‘brain’ of cell. Has a role in processes such as growth, metabolism, and reproduction

• Genetic material DNA is enclosed inside the nucleus

Two Kinds of Cells – Prokaryotes and Eukaryotes

• The two basic types of cells are those without a nucleus (prokaryotes) and with a nucleus (eukaryotes)

• Prokaryotes are single-celled organisms that do not have a nucleus of membrane-bound organelles

• There are two types of prokaryotes – eubacteria (or just bacteria), and archaebacteria

• Eukaryotes are organisms made up of cells that have a membrane-enclosed nucleus

• Eukaryotes include animals, plants, and fungi – but not eubacteria or archaebacteria

Section 2 – Eukaryotic Cells - Some eukaryotic cells have cell walls. A cell wall is a rigid structure that gives support to a cell.

Cell Membrane -

• The cell membrane is a protective layer that encloses a cell

• Contains proteins, lipids, and phospholipids (lipid that contains phosphorus)

Cytoskeleton –

• The cytoskeleton is a web of proteins in the cytoplasm

• Keeps the cells’ membrane from collapsing

• Made up of three types of proteins – one is a hollow tube, other two are long, stringy fibers

Nucleus –

• The nucleus is a large organelle in a eukaryotic cell

• Contains the cell’s DNA (genetic material)

• DNA contains information

Ribosomes -

• Ribosomes are small grain-like body made of RNA

• Found in ER or free floating in cytoplasm

• produced in nucleolus

• Place where proteins are made

Endoplasmic Reticulum –

• The endoplasmic reticulum is a system of membranes found in a cell’s cytoplasm

• Tubular passage-way that lead out from nuclear membrane--spreads throughout cell

• Carries proteins from one part of cell to another

Mitochondrion -

• Mitochondrion is the main power source of a cell; it’s power house

• Rod-shaped

• located in cytoplasm

• Where food molecules are broken down to make energy

Chloroplasts –

• Chloroplasts are organelles in plant and algae cells

• Photosynthesis takes place in chloroplasts

• Chloroplasts are green because they contain chlorophyll, a green pigment

Golgi Complex -

• The Golgi complex packages and distributes proteins to be transported out of the cell

Cell Compartments -

• A vesicle is a small cavity or sac that contains materials in a eukaryotic cell

• A vacuole is a large vesicle. Some vacuoles act like large lysosomes; others store water and other liquids

Lysosomes -

• Lysosomes are organelles that contain digestive enzymes

• Destroy worn-out or damaged organelles

• Get rid of waste materials

• Protect cell from foreign invaders

Section 3 – The Organization of Living Things – Multicellular organisms (those made of many cells) grow by making more small cells, not by making their cells larger.

• There are several benefits to being multicellular, as opposed to being made up of only one cell (unicellular). One is larger size – larger organisms are prey for fewer predators. A second is longer life – the life span of a multicellular organism is not limited to the life span of any single cell. A third advantage is specialization – each type of cell has a specific job, and specialization makes the organism more efficient. For example, the cardiac muscle cell shown in Figure 1 on p. 76 is a specialized muscle cell.

• A tissue is a group of cells that work together to perform a specific job. Animals have four basic types of tissue: nerve, muscle, connective, and protective. Plants have three types of tissue: transport, protective, and ground.

• An organ is a structure that is made up of two or more tissues working together to perform a specific function. Some common animal organs are the heart and stomach. Examples of plant organs are leaves, stems, and roots.

• An organ system is a group of organs working together to perform a particular function. Each organ system has a specific job to do in the body.

• An organism is anything that can perform life processes by itself. An organism made up of a single cell is called a unicellular organism. Bacteria, most protists, and some kinds of fungi are unicellular. Multicellular organisms are made up of many cells, and a multicellular organism has specialized cells that depend o each other for the organism to survive.

• In organisms, structure and function are related. Structure is the arrangement of parts in an organism. It includes the shape of a part and the material of which the part is made. Function is the job the part does.

Information Posted on 10/9/05

Notes for Chapter 2 – It’s Alive!! Or Is It?

Section 1 – Characteristics of Living Things –Living things can be said to share six basic characteristics. These include (1) Living things have cells – A cell is a membrane covered structure that contains all of the materials necessary for life. Some organisms are made of one cell, and are called unicellular. More complex organisms are made of billions, even trillions of cells, and are called multicellular. (2) Living things sense and respond to change – All organisms have the ability to sense change in their environment and to respond to that change. A change that affects the activity of the organism is called a stimulus. Stimuli can be chemicals, gravity, light, sounds, hunger – anything that causes an organism to respond in some way. Although an organism’s outside environment can change, conditions inside the organism’s body must remain the same. The maintenance of a stable internal environment is called homeostasis. (3) Living things reproduce – Organisms make other organisms similar to themselves. They do so in two ways. In sexual reproduction, two parents contribute sex cells that unite, producing offspring that share traits from both parents. In asexual reproduction, a single parent produces offspring that are identical to the parent. (4) Living things have DNA – DNA is present in the cells of all living things, and controls the structure and function of cells. When organisms reproduce, they pass copies of their DNA to their offspring. This passing on of traits from one generation to the next is called heredity. (5) Living things use energy – Organisms use energy to carry out the activities of life – things like making food, breaking down food, moving materials into and out of cells, and building cells. An organism’s metabolism is the total of all the chemical activities that the organism performs. (6) Living things grow and develop – all living things – whether single-celled or multi-celled – grow during periods of their lives. In single-celled organisms, the cell gets larger and divides, making other organisms. In multi-celled organisms, the number of cells gets larger, and the organism gets bigger.

Section 2 – The Necessities of Life – Every organism has the same basic needs – water, air, a place to live, and food. Some organisms, such as plants, are producers, meaning they can make their own food by using energy (either solar or chemical) from its surroundings. Other organisms are consumers because they eat (consume) other organisms to get food. Other organisms are decomposers, meaning that they get energy by breaking down the remains of dead plants and animals.

All organisms, whether they are producers, consumers, or decomposers, need to break down food in order to use the nutrients in it. These nutrients are made of molecules (substance made when two or more atoms combine). Molecules found in living things are usually made up of combinations of six elements – carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. These elements combine to firm proteins, carbohydrates, lipids, ATP, and nucleic acids. Proteins are large molecules that are made up of smaller molecules called amino acids. Organisms break down the proteins in food in order to supply their cells with amino acids. Carbohydrates are molecules made up of sugars. Cells use carbohydrates as a source of energy and for energy storage. There are two kinds of carbohydrates – simple and complex. Simple carbohydrates are made up of one sugar molecule or a few linked together (ex. Table sugar). When an organism has more sugar than it needs, its extra sugar is stored as complex carbohydrates. Lipids are compounds that cannot mix with water. Having important cellular functions, lipids, like carbohydrates, store energy. Some lipids form the membranes of cells; these lipids are called phospholipids. This special form of lipids is made up two main parts, a head and a tail (see p. 46). The head of a phospholipid molecule is attracted to water, while the tail is not. Fats and oils are lipids that store energy. When an organism has used up most of its carbohydrates, it can get energy from these lipids. ATP is another important molecule. It is the main energy-carrying molecule in the cell. The energy in carbohydrates and lipids must be transferred to ATP, which then provides fuel for cellular activities. Nucleic acids are called the blueprints of life because they have all the information needed for a cell to make proteins. Nucleic acids are made up of large molecules called nucleotides. A nucleic acid may have thousands of nucleotides. The order of these nucleotides stores information. DNA is a nucleic acid, and is like a recipe book for how to make proteins.

Information Posted on 9/27/05

Notes for Chapter 1 – The World of Life Science

Section 1 – Asking About Life – Science is a process of gathering knowledge about the natural world. Science includes making observations and asking questions about those observations. Life Science is the study of living things. A variety of people may become life scientists for a variety of reasons. Life Science can help solve problems such as disease or pollution, and it can be applied to help living things survive.

Section 2 – Scientific Methods – Scientific methods are the ways in which scientists follow steps to answer questions and solve problems. There are certain steps that scientists use whenever they are engaged in scientific inquiry. First, an observation is made – this is any use of the senses to gather information (for example, noting that the sky is blue or that a cotton ball feels soft). Scientists are then led to ask questions about their observations. After gathering preliminary information, scientists are then ready to form a hypothesis – a possible explanation or answer to a question. A good hypothesis is always testable. In other words, information can be gathered or an experiment can be designed to test the hypothesis. Scientists then make a prediction of what they think will happen before testing the hypothesis. One way to test a hypothesis is to do a controlled experiment, which tests only one factor at a time and consists of a control group and one or more experimental groups. All of the factors for both control and experimental groups are the same except for one. The one factor that differs is called the variable. –Pieces of information obtained through experimentation are called data. After testing a hypothesis, it is important to analyze your results by using calculations, tables, and graphs. Then, after analyzing your results, you should draw conclusions about whether your hypothesis is supported. Finally, communicating your results allows others to check or continue your work.

Section 3 – Scientific Models – A model is a representation of an object or system. Models are often used to represent things that are very small or very large. There are three kinds of scientific models: Physical, mathematical, and conceptual. A physical model might be a model space shuttle, or the human eye. Mathematical models are made up of equations and data, and sometimes use computers. A Punnett Square (p. 19) is an example of a mathematical model. Conceptual models are often ideas; for example, the big bang theory is a conceptual model. Some models are smaller than the objects they represent (i.e., globes, solar system models), while other models are larger than the objects they represent (i.e., molecules, DNA). A scientific theory is an explanation for many hypothesis and observations. A scientific law summarizes experimental results and observations. The different between the two is that a theory is an explanation of why something happened the way it did, and a law is a statement that tells how things work.

Section 4 – Tools, Measurement, and Safety – A tool is anything that helps you do a task. Scientists use many tools to help them in their experiments. The application of science for practical purposes is called technology. By using technology, life scientists are able to find information and solve problems in new ways. Some forms of technological tools used in life science are those that enable us to see fine details in things that are too small to be seen with the unaided eye. The compound light microscope is an instrument that magnifies small objects so that they can be easily seen. It has three main parts-a tube with two or more lenses, a stage, and a light. There are other more sophisticated microscopes that do not use light. In electron microscopes, tiny particles called electrons are used to produce magnified images clearer and more detailed than those made with light microscopes.

One way to collect data is to take measurements. But to do this, you need the proper tools, and a common system of measurement used throughout the world. (See metric information posted on 9/19 for detailed information on the International System of Units (SI), or metric system).

Length, volume, mass, and temperature are types of measurement used in science. The meter is the basic SI unit of length. Mass is the amount of matter in an object, and the kilogram (kg) is the basic unit for mass. The kilogram is used to describe the mass of large objects, and the gram is used to measure the mass of smaller objects. Volume is the amount of space that something occupies. Liquid volume is expressed in liters (L). Liters are based on the meter. A cubic meter is equal to 1,000 L. Volumes of solid objects are expressed in cubic meters. If you measure the mass and volume of an object, you have enough information to measure its density – the amount of matter in a given volume. Density is called a derived quantity because it is found by combining the two basic quantities of mass and volume. The equation that relates density to mass and volume is:

m

D = --------

V

The temperature of a substance is a measurement of hot or cold the substance is. Degrees Fahrenheit and degrees Celsius are often used to describe temperature. The SI unit for temperature is the Kelvin (K).

Area is a measure of how much surface an object has, and can be calculated from measurements such as length and width.

You will frequently encounter different safety symbols and rules when engaging in scientific investigations. Always pay attention to any safety labels on the sides of chemicals or other equipment – these alert you to what precautions you need to take, such as wearing goggles or gloves.

Information Posted on 9/19/05

Metric units of measurement

The French Academy of Sciences in the late 1700’s set out to make a simple and reliable measurement system. Over the next 200 years, the metric system was formed. This system is now the International System of Units (SI). We will be working with mass, volume, length, and temperature in our metric studies and conversions.

When working with mass, volume, and length, the “metric staircase” is a helpful visual tool, especially when doing conversions between units:

km

hm

dkm

m

dm

cm

mm

You can remember how the order of the units goes by remembering a simple mnemonic, or memory aide: King Henry Died Monday Drinking Chocolate Milk.

You can use the metric staircase for meters (as we did above), volume, or mass. Just be sure to substitute the ‘m’ on the right of the unit with ‘L’ for liters and ‘g’ for grams.

Common SI (Metric) units:

km (kilometer) = 1000 meters

hm (hectometer) = 100 meters

dkm (dekameter) = 10 meters

m (meter) = 1 meter (base unit)

dm (decimeter) = 1/10 of meter

cm (centimeter) = 1/100 of meter

mm (millimeter) = 1/1000 of meter

Information Posted 9/11/05

The Scientific Method is a useful tool for engaging in scientific inquiry. The traditional steps are:

• Observe

• Ask a question

• Research

• Form a hypothesis

• Test the hypothesis

• Record and analyze data

• Form a conclusion

It is also important to repeat your experiment, to exclude the possibility of error in your experimental setup. You also must communicate your results to the rest of the scientific community. In this way, you contribute to building up of knowledge and experience in a particular scientific discipline, and others benefit from your work.

Let’s put these steps into a practical example. You might observe that leaves are starting to change from green to shades of red, brown, and orange during the fall season. You then ask a question: “What is causing the leaves to change color during this time every year?” You then do some background research. You are now in a position to form a hypothesis: The leaves are changing color as a result of chemical reactions occurring. You must test this hypothesis, and then record and analyze data that you obtain. Only now can you form a reasonable conclusion: The leaves are changing color because of a breakdown in chlorophyll, and secondary chemical reactions that cause the green color to disappear and hues of red, brown, and orange to appear in its place.

Experiments are made up of variables, which are factors in an experiment that change. The Independent Variable (IV) is the factor that the experimenter changes on purpose. In an experiment that seeks to determine the effect of differing amounts of water on plant growth, the differing amounts of water would be the IV – the experimenter might give Plant A 10mL of water, Plant B 20mL, Plant C 30mL, and Plant D 40mL. The factor that changes as a result of the purposely-changed factor is called the Dependent Variable (DV). In other words, the experiment changes it. In our plant growth experiment example, plant growth would be the DV. The independent variable will have different levels, or ways that the experimenter changes it – this is referred to as Level of Independent Variable (LIV). In our example, the different ways that he/she changes, or manipulates the IV are applying 10, 20, 30, and 40mL of water to the different plants. Variables that do not change in an experiment are called Constants. In our sample experiment, some constants might be same type of water (distilled), same type of soil, same type of pot, etc.). An experiment will usually have a Control. A control group is used for comparison with the experimental groups. So in our example, Plant E might be the control – it is not given any water. It is a good idea to repeat our experiment, to reduce the possibility of error. So the Number of Repeated Trials (NRT) refers to the number of times that each level of independent variable is tested. In our example, Plants A-D will be given the specified amounts of water (10, 20, 30, and 40mL) of water a total of three times – so the NRT for this experiment would be 3.

υ We want to be able to formulate good title and hypothesis statements for our experiment. When you write an experimental title, you are basically stating what the effect of the independent variable is on the dependent variable, and you write it in this format:

The Effect of IV on DV.

So a good title for our plant experiment would be:

The Effect of Amount of Water on Plant Height.

| |

IV DV

We then can write a hypothesis statement for our experiment. Hypothesis statements follow an “If, then” format. Basically, in a hypothesis statement you are making a prediction about how the dependent variable will change if you make a certain change to the independent variable: If how you are changing the IV, then how you predict the DV will change. So a good hypothesis statement for our experiment would be:

If the amount of water given a plant is increased, then the height the plant will grow will be increased.

There are of course several different hypothesis statements that could be written for an experiment such as this. Some are written in such a way that a change in magnitude in the IV reflects a similar magnitude change in the DV. These are in direct proportion:

If IV increases, then DV increases.

If the amount of water given a plant is increased, then the plant height will be increased.

If IV decreases, then DV decreases.

If the amount of water given a plant is decreased, then the plant height will be decreased.

Others are written in such a way that a change in magnitude in the IV reflects the opposite change in magnitude in the DV. These are in inverse proportion:

If IV increases, then DV decreases.

If the amount of water given to a plant is increased, then the plant height will be decreased.

If IV decreases, then DV increases.

If the amount of water given a plant is decreased, then the plant height will be increased.

Let’s take all of this information and place it on an Experimental Design Diagram:

Experimental Design Frame/Diagram

Title: The Effect of Amount of Water on Plant Height

Hypothesis: If the amount of water given a plant is increased, then the plant height will be increased.

IV: Amount of water

Levels of IV

(LIV) 10mL 20mL 30mL 40mL No

water

(control)

# of Repeated 3 3 3 3 3

Trials (NRT)

DV: Plant height

Constants – C: Type of water, type of soil, type of pot

-----------------------

If going from a big to a smaller unit, move decimal point to RIGHT the number of times you jump down the staircase.

Ex.- 1 meter = _______millimeters

Meters to millimeters is 3 jumps. So there’s a decimal point after 1. Move decimal point 3 places to right.

1. _ _ _ = 1000.

So 1 meter = 1000 millimeters

If going from a smaller to a bigger unit, move decimal point to LEFT the number of times you jump up the staircase.

Ex. – 1 millimeter = _______meters

[€

Millimeters to meters is 3 jumps.

There’s a decimal point after 1.

Move decimal point 3 places to left.

_ _ _ 1.

So 1 millimeter = 0.001 meters

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