Ecology - C. Shirley Science EJCHS
Ecology
Ecology is the study of the interactions of living organisms with one another and with their environment. An environment is composed of both biotic and abiotic factors. Biotic factors are the living and once living parts of an environment (i.e. plants, animals, dead organisms). Abiotic factors are the nonliving parts of the environment (i.e. air, water, rocks, sand, light & temperature).
Organism - an individual living thing. A species is a group of organisms that can mate to produce fertile offspring. Every organism is a member of a species.
Population – all the members of the same species that LIVE in the same place at the same time
Community – a group of various species that live in the same place and interact with each other. It’s only made of biotic components.
Ecosystems - are all of the organisms living in an area together with their physical environment. Ecosystems do NOT have clear boundaries and components move from one ecosystem into another.
Biomes - are large climatic regions that contain a number of smaller ecosystems. Biomes may exist in more than one location and are distinguished by plants and animals, rarely have distinguished boundaries.
Biosphere - the thin layer of Earth and the atmosphere that supports life.
Evolution
Organisms tend to be well suited to where they live and what they do. In 1859, English naturalist Charles Darwin observed that organisms in a population differ slightly from each other in form, function and behavior. Some of these differences are hereditary……passed on from parent to offspring.
Darwin proposed that the environment exerts a strong influence over which individuals survive to produce offspring. Some individuals with certain traits are more likely to survive and reproduce than other individuals. Darwin called this NATURAL SELECTION which describes the survival and reproduction of organisms with particular traits. Nature selects which traits it deems fit for the particular environment.
o Darwin proposed that over many generations natural selection causes the characteristics of populations to change. A change in the genetic characteristics of a population from one generation to the next is known as EVOLUTION.
NATURE SELECTS – Darwin thought that nature selects for certain traits because organisms with these traits are more likely to survive and reproduce. Over time, populations will see a greater proportion of organisms with certain traits. As the population of a given species change, so does the species.
o The “fittest” individuals will survive and reproduce allowing them to pass its genes on to their offspring. The fittest is the one most adapted to its current or changing environment.
Adaptations are inherited traits that increase an organism’s chance of survival and reproduction in a certain environment.
o Physical adaptations are body structures that allow an animal to find and consume food, defend itself, and to reproduce its species. For example: camouflage (blending in with surroundings), mimicry (looking or sounding like another organism), chemical defenses (venom, ink, sprays), body parts (claws, beaks, armor plates)
o Behavioral adaptations allow animals to respond to life needs. Each organism has unique methods of adapting to its environment by means of different actions. For example: methods of obtaining food, defending oneself, hibernation, migration
|Evolution by Natural Selection |
|1. Individuals in a population vary in each generation. |Conclusion – Individuals with genetic traits that make them |
| |more likely to survive and reproduce in the existing |
| |environment will become more common in the population from |
| |one generation to the next. |
|2. Some of theses variations are genetic or inherited. These inherited traits are called | |
|adaptations. | |
|3. More individuals are produced than live to grow up and reproduce. | |
|4. Individuals with some genes are more likely to survive and reproduce than individuals with| |
|other genes. | |
CASE STUDY: Darwin’s Finches
For 5 years, Darwin served as a naturalist aboard the H.M.S. Beagle on a British science expedition. In South America, Darwin found fossils of extinct animals that were similar to modern species. On the Galapagos Islands, he noticed unique variations of plants and animals. The islands contained 13 species of finches with specialized bills adapted to eating certain types of food. Darwin speculated that all the Galapagos finches had evolved from a single species of seed-eating finch that found its way to the islands from the South American mainland. Populations of the finches became established on the various islands and the finches that survived were those able to eat what they found on their island.
Coevolution – Organisms evolve adaptations to other organisms and to their physical environment. The process of two species evolving in response to long-term interactions with each other is called coevolution. (i.e. honeycreeper’s beak & lobelia flower)
Artificial Selection – Over thousands of years, humans bred the ancestors of today’s wolves to produce the variety of dog breeds. The selective breeding or organisms by humans for specific characteristics is called artificial selection. By selecting certain traits such as size and sweetness of vegetables, fruits and grains, farmers directed the evolution of crop plants.
Evolution of Resistance – Sometimes humans cause populations of organisms to evolve unwanted adaptations. Resistance is the ability of one or more organisms to tolerate a particular chemical designed to kill it. An organism may be resistant to a chemical when it contains a gene that allows it to break the chemical down into harmless substances. (i.e. By trying to control pests and bacteria with chemicals, humans promote the evolution of resistant populations.)
o Pesticide resistance – A pesticide is sprayed on corn to kill grasshoppers. Most of the grasshoppers die, but a few survive. The survivors happen to have a version of a gene that protects them from the pesticide. Each time the corn is sprayed, insects that are resistant to the pesticide have a greater chance of survival and reproduction. As a result, insect populations will evolve to include more and more resistant members.
Kingdoms of Life
| |Kingdom |Characteristics |Environmental Contribution |
|Domain |Archaebacteria |Prokaryotes - unicellular, no nucleus |Decomposers - break down the remains and waste of other |
|Archae | |Found in harsh environments such as hot springs, swamps |organisms and recycle nutrients to the soil. |
| | |Autotrophs & Heterotrophs |Recycle mineral nutrients, such as nitrogen and |
| | | |phosphorus. |
| | | |Allow organisms to extract certain nutrients from food. |
|Domain |Eubacteria |Prokaryotes – unicellular, no nucleus | |
|Bacteria | |Common type of bacteria | |
| | |Autotrophs & Heterotrophs | |
|Domain |Protist |Eukaryotes – unicellular or multicellular, have a nucleus |Algae use photosynthesis to make their own food and |
|Eukarya | |Autotrophs & Heterotrophs |produce majority of Earth’s oxygen. |
| |Fungi |Eukaryotes – unicellular or multicellular, have a nucleus |Fungi release enzymes into the soil breaking down organic |
| | |Heterotrophs |matter, then absorb the nutrients. (aka. decomposer) |
| |Plant |Eukaryotes – multicelluar, have a nucleus |Plants use photosynthesis to make their own food and |
| | |Autotrophs |produce oxygen. |
| |Animal |Eukaryotes – multicellular, have a nucleus | |
| | |Heterotrophs | |
Energy Flow in Ecosystems
The primary source of energy for an ecosystem is the sun. Photosynthetic organisms change light energy from the sun into energy that they can use to grow. Photosynthesis is the process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce carbohydrates and oxygen.
As organisms consume food and use energy from carbohydrates, the energy travels from one organism to another. Plants produce carbohydrates in their leaves. When an animal eats a plant, some energy is transferred from the plant to the animal. Organisms use this energy to move, grow and reproduce.
← Because plants make their own food, they are called autotrophs or producers. A producer is an organism that can make carbohydrates (organic compounds) from the sun’s energy or inorganic compounds. (i.e. Bacteria in deep-ocean vents use hydrogen sulfide, an inorganic compound) as the energy source to perform chemosynthesis).
← A heterotroph or consumer is an organism that eats other organisms or organic matter instead of producing its own nutrients. Consumers get their energy indirectly by eating producers or other consumers.
|Types of Consumers |
|Herbivore |eats producers |
|Carnivore |eats consumers |
|Omnivore |eats consumers and producers |
|Decomposers |break down dead organisms and returns nutrients to the soil, water |
|(fungi & bacteria) |and air |
An organism obtains energy from the food it eats. This food must be broken down within its body. The process of breaking down food to yield energy is called cellular respiration. Cellular Respiration is the process by which cells produce energy from carbohydrates; atmospheric oxygen combines with glucose to form water and carbon dioxide.
Through cellular respiration, cells use glucose (sugar) and oxygen to produce carbon dioxide, water, and energy (ATP). Part of the energy obtained through cellular respiration is used to carry out daily activities. Excess energy is stored as fat or sugar. All living things use cellular respiration to get the energy they need from food molecules.
Energy Transfer – Each time an organism eats another organism, an energy transfer occurs. This transfer of energy can be traced by studying food chains, food webs, and trophic levels. Studying the paths of energy between organisms can tell us how much energy is transferred and which organisms depend on other organisms for survival in an ecosystem.
A food chain is a sequence in which energy is transferred from one organism to the next as each organism eats another organism.
Energy flow in an ecosystem is more complex than energy flow in a simple chain. So a food web includes multiple food chains linked together to show many feeding relationships in an ecosystem.
← Each step in the transfer of energy through a food chain or food web is known as a trophic level. Energy flows from one trophic level to the next.
← Find one food chain in the web --- label the trophic levels.
Each time energy is transferred, some of the energy is lost as heat. Therefore, less energy is available to organisms at higher trophic levels. One way to visualize this is with an energy pyramid.
← When energy is used, about 90% of the energy at each trophic level is converted into heat energy and dispersed into the environment. Only about 10% of energy is stored in the animal’s body as fat or as tissue and is the amount of energy available to the next trophic level.
← Decreasing amounts of energy at each trophic level affects the number of organisms at each level and limits the number of trophic levels in an ecosystem. Big predators are rare because a lot more energy is required to support a single predator than a single herbivore. Many ecosystems do not have enough energy to support a large population of predators.
The Cycling of Matter
Carbon Cycle
Carbon is an essential component of fats, proteins and carbohydrates, which make up all organisms. The carbon cycle is a process by which carbon is cycled between the atmosphere, land, water and organisms.
o Carbon cycles between the process of photosynthesis and cellular respiration. Photosynthesis removes CO2 and respiration releases CO2.
o Carbon is converted into carbonates which make up bones and shells. Over millions of years, carbonate deposits have produced large formations of limestone rocks resulting in one of the largest carbon reservoirs on Earth.
o Some carbohydrates in organisms are converted to fats that store energy. When an organism dies and decomposition occurs, this carbon is returned to the soil and air. Over millions of years, these deposits will form coal, oil, and natural gas (fossil fuels). Burning of these fossil fuels release carbon dioxide back into the atmosphere.
How humans affect the Carbon Cycle?
Cars, factories and power plants rely on fossil fuels to operate. Each year, about 6 billion metric tons of carbon is released into the atmosphere as CO2 by the burning of fossil fuels and the burning of wood in forest fires. As a result, the amount of CO2 levels in the atmosphere has steadily increased. Increased levels of CO2 may contribute to global warming, which is an overall increase in temperature of the Earth.
Nitrogen Cycle
All organisms need nitrogen to build proteins, which are used to build new cells. However, most organisms can not use atmospheric nitrogen, which makes up 78% of atmospheric gases. It must be altered or fixed before organisms can use it. Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia or nitrate, a usable form of nitrogen. The nitrogen cycle is a process in which nitrogen is cycled between the atmosphere, bacteria and other organisms.
o Nitrogen-fixing bacteria live in the soil or in nodules on the roots of plants called legumes. The bacteria use sugars provided by the legumes to produce nitrates. The excess nitrogen fixed by the bacteria is released into the soil. Nitrification – The process of bacteria converting ammonia (NH3) (toxic to plants) to nitrites (toxic to plants) (NO2-) and then finally to nitrates (NO3-).
o Animals get nitrogen by eating plants or other animals. Decomposers in the soil break down waste or decaying organisms and return the nitrogen to the soil.
o Denitrification - The process of releasing fixed nitrogen back to atmospheric nitrogen gas. Denitrifying bacteria transform nitrogen in the soil back into atmospheric nitrogen gas.
How humans affect the Nitrogen Cycle?
Humans have impacted this cycle due to agricultural fertilization, burning of fossil fuels, wastewater etc. Excessive nitrogen contributes to acid precipitation, contamination of water, removal of nitrogen from topsoil, and destruction of plant through the release of excess nitrogen.
Phosphorus Cycle
The phosphorus cycles fairly slowly through the earth’s water, soil and living organisms. It is an essential element for life, in molecules of DNA and ATP, and often is a limiting nutrient for plant growth. The phosphorus cycle is the movement of phosphorus form the environment to organisms and then back to the environment. Most phosphorus is stored in the Earth’s rocks/soils and is released to water via erosion and weathering. Phosphorus does NOT exist in the atmosphere!!
o When rocks erode, small amounts of phosphorus dissolve in soil and water. When organisms excrete waste or decompose, phosphorus is added in soil and water.
o Plants take up phosphorus in aquatic and terrestrial ecosystems and animals eat the plants; returning the phosphorus to the soil via urine, feces, and death.
How humans affect the Phosphorus Cycle?
Humans remove large amounts of phosphate from the earth through mining to make fertilizers, reduce phosphorus in tropical soils by clearing forests and then we add excess phosphates into aquatic systems. Phosphorus disrupts aquatic systems through runoff of animal wastes, fertilizers and discharges from sewage treatment systems.
Changes in Ecosystems
Ecosystems are constantly changing. Ecological succession is a gradual process of change and replacement of some or all of the species in a community. Ecological succession may take hundreds or thousands of years. Each new community that arises makes it harder for the previous community to survive, because of competition for resources. Succession provides opportunities for new resources and niches to become available for the next community.
Primary Succession – The initial establishment and development of an ecosystem. Begins in a place without any soil and no previous life exists. Starts with the arrival of living things such as lichen, moss or bacteria that do not need soil to survive…these first organisms are called pioneer species. Soil starts to form as pioneer species and the forces of weather and erosion help break down rocks into smaller pieces. Pioneer species decompose and add small amounts of organic matter to the rock to make soil. Simple plants like mosses and ferns grow in the new soil. When these plants decompose, it adds more organic material. The soil layer thickens and other plants begin to take over. These plants die, and they add more nutrients to the soil. Shrubs and tress can survive now. Insects, small birds, and mammals have begun to move in. What was once bare rock now supports a variety of life.
• Primary succession can occur on new islands created by volcanic eruptions, in areas exposed when a glacier retreats, sand dunes or any other surface that has not previously supported life. Slower process because it begins with no soil.
Secondary Succession – The reestablishment of an ecosystem where there are remnants of a previous biological community.….ecosystems have been disturbed or disrupted by humans or animals, or by natural processes such as storms, floods, fires, earthquakes, etc.
• Old-field succession – Occurs when farmland is abandoned….grasses and weeds grow rapidly and produce many seeds to cover large areas. Communities continue to grow and replace previous communities.
BIOMES
Terrestrial biomes are large regions characterized by specific type of climate and certain types of plants and animal communities.
• Vegetation -Biomes are described by their vegetation because the plants that grow in a certain region are the most noticeable characteristics of that region. Plants in a particular biome have characteristics, specialized structures, or adaptations such as size, shape, and color that allow the plants to survive in that biome.
• Climate – The climate is the main factor that determines which plants can grow in a certain area. Climate refers to the average weather conditions such as temperature, precipitation, humidity, and winds in an area. Most organisms are adapted to live within a certain temperature range and will not survive at temperatures outside this range. Precipitation limits the organisms that are found in a biome, because all organisms need water so the bigger the animal, the more water it needs. The higher the temperature and precipitation are, the taller and denser the vegetation is.
• Latitude & Altitude – Biomes and vegetation vary with latitude and altitude. Latitude is the distance north or south from the equator. Altitude is the height of an object above a reference point, such as sea level or the Earth’s surface. Climate varies with latitude and altitude (i.e. Climate gets colder as latitude and altitude increases.).
Tropical Rain Forest – It is the most widespread biome and has the greatest diversity of plants, animals and other organisms. This biome is located at the equator and helps to regulate world climate by playing a vital role in the nitrogen, oxygen and carbon cycles.
❖ Tropical rain forest are always humid, warm and gets about 200-450 cm of rain each year. This forest gets strong sunlight year-round and maintains a relatively constant temperature year-round.
❖ The soil is nutrient poor because the nutrients are within plants. Decomposers break down organic matter and return nutrients to the soil, but plants quickly absorb the nutrients.
❖ Four layers of the forest: Emergent layer (top) – tallest trees; Canopy (upper/lower) – epiphytes (plants) grow to help support life and most animals/plants life in the canopy; Understory – plants adapted to shade grow here.
❖ It has the greatest species diversity. This diversity of plants has led to the evolution of diverse animals that are specialized to use specific resources.
Temperate Rain Forest – It has the largest amount of precipitation, high humidity and moderate temperatures. This biome is found in North America, Australia and New Zealand.
❖ The Pacific Northwest is North America’s only temperate rain forest, where tree branches are draped with moss and tree trunks are covered in lichen. The forest floor is blanketed with lush ferns and evergreen trees can grow around 90 cm tall.
❖ It maintains a moderate temperature year-round and receives large amounts of rainfall.
Temperate Deciduous Forest – These forests are generally located between 30o-50o north latitudes.
❖ The range of temperatures can be extreme with the growing seasons lasting only 4 to 6 months. Summer temperatures can soar to 35oC, while winter temperatures can fall below freezing.
❖ Vegetation changes with the seasons. Trees are predominately are broad, flat leaf which fall during the fall. Plants are adapted to survive seasonal changes. Animals usually hibernate or migrate during the winter months.
❖ Decomposition of organic matter occurs slowly which causes the soil to contain more nutrients.
Taiga – This northern coniferous forest stretches in a band across the Northern Hemisphere just below the Arctic Circle.
❖ Winters are long (6-10 months) and have average temperatures below freezing.
❖ Plant growth is abundant during summer months because of nearly constant daylight and larger amounts of precipitation. Mostly conifers trees grow which have needle-like leaves and seeds that develop in cones. The shape of the leaves and their waxy coating (cuticle) prevent the tree from losing too much water. This is important during when the ground is frozen and the roots cannot replace lost water by absorbing more from the soil. Conifer needles contain substances that make the soil acidic when the needles fall to the ground. Most plants can not grow in acidic soil, which is one reason the forest floor has few plants. Soil forms very slowly because the climate and acidity of fallen leaves slows decomposition.
❖ This biome has many lakes and swamps which attract birds that feed on aquatic organisms. Animals usually hibernate or migrate during winter months.
Threats to the FOREST biomes -
❖ Deforestation is the clearing of trees. It reduces the amount of water that is absorbed by plants after it rains. The more trees that are cleared form a forest, the more likely a flood will occur in that area.
❖ Tropical rain forest once covered about 20% of Earth, but today it only covers about 7%. Every minute, about 100 acres of forest are cleared for logging operations, agriculture or oil exploration. Habitat destruction occurs when land inhabited by an organism is destroyed or altered and usually results in species endangerment or extinction.
Savannas – Grassland found in Africa, western India, northern Australia and South America.
❖ A tropical biome that is dominated by grasses, shrubs and small trees. Rain falls mainly during the wet season, which last for only a few months of the year. Because most rain falls during the wet season, plants must be able to survive prolonged periods without water. During the dry season, plants lose their leaves or die down to the ground. Many plants have horizontal root systems so they can draw water from a larger area. Most plants have vertical leaves to reduce water loss and thorns to keep herbivores away.
❖ Grazing herbivores have adopted a migratory way of life and follow the rains. Many animals give birth during the rainy season when food is abundant and the young are more likely to survive.
Temperate Grassland – This grassland covers a large area of the interior of continents, where there is moderate rainfall, but still too little for trees to grow. This includes the prairies in North America, the steppes of Asia, the veldt in South Africa and the pampas in South America.
❖ Vegetation consists of mainly grasses and wildflowers. Near the banks of streams, the soil contains more water so shrubs and trees can grow. The root systems form dense layers that survive drought and fire.
❖ Grasslands are highly productive because of their fertile soil. The summer is hot and the winter is cold, so the plants die back to their roots in winter. Low temperatures in the winter slow decomposition and organic matter accumulate in the soil making it the most fertile soil in the world. Grazing animals (herbivores) and burrowing animals are predominately found.
❖ Threats – Farming and overgrazing has caused soil erosion and depletion of nutrients from the soil making the soil less fertile.
Chaparral – Temperate shrub land that is found in areas that have moderately dry, coastal climates with little to no rainfall.
❖ Most plants are low-lying, evergreen shrubs and small trees that tend to grow in small patches. These plants have small, leathery leaves that retain water. The leaves contain natural oils that promote burning, which is an advantage because natural fires destroy trees that might compete with chaparral plants for light and space. These plants are well adapted to fire and can re-sprout from small bits of surviving plant tissue.
❖ Common adaptation of animals is camouflage, which is shape and coloring that allows animals to blend into its environment.
❖ Threats – Human development is the greatest threat.
Deserts – Areas that have widely scattered vegetation and receive very little rain. Even in hot deserts near the equator, there is little insulating moisture in the air that temperatures change rapidly in a 24-hour period. The temperature may go from 40oC in the day to near freezing at night. Deserts are often located near mountain ranges, which block the passage of rain clouds.
❖ Plants have adaptations for obtaining and conserving water, which allow the plants to live in dry desert conditions. Succulents are plants that have thick, fleshy stems and leaves that store water. Their leaves have a waxy coating that prevents water loss. Sharp spines protect the plants from animals. Rainfall rarely penetrates deep into the soil, so many plant roots spread out just under the surface to absorb as much rain as possible. Many shrubs drop their leaves during dry periods and grow new leaves when it rains again. When conditions are too dry, some plants die and drop seeds that stay dormant until the next rainfall.
❖ Reptiles have thick, scaly skin that prevents water loss. Amphibians survive summers by estivating – burying themselves in the ground and sleeping during the dry season. Desert insects and spiders are covered with body armor that helps retain water. Most desert animals are nocturnal which means they are active mainly at night when the air is cooler.
Tundra – In northern arctic regions, the winter is too cold and dry to permit the growth of trees. The deeper layers of soil called permafrost are permanently frozen throughout the year. In the summer the thin topsoil layer thaws and becomes a moist, spongy wet area ideal for insects and birds.
❖ Moss and lichen which can grow without soil cover vast areas of rock. The soil is thin, so plants have wide, shallow roots to anchor them against the icy winds. Most plants are short and grow close to the ground to keep out of wind and help absorb heat from the sunlit soil during the summer.
❖ Migratory birds and other animals are present during the summer. Some animals burrow underground during the winter, but are still active. Many animals that live in the tundra year-round lose their brown fur and grow white fur to camouflage them in the winter snow. These animals are also extremely well insulated.
❖ Threats – It’s the most fragile biome and is easily disrupted. Because conditions are so extreme, the lands is easily damaged and slow to recover. Until recently, the tundra was undisturbed by humans, but oil exploration, extraction and transport has disrupted the habitats of plants and animals. Pollution caused by spills of oil or other toxic materials may poison the food and water sources of organisms.
AQUATIC ECOSYSTEMS
Aquatic ecosystems are determined mainly by water’s salinity – the amount of dissolved salts. Freshwater ecosystems include waters of lakes, ponds, rivers, streams and wetlands. Marine ecosystems include the diverse coastal areas of marshes, swamps, coral reefs and oceans.
• Factors such as temperature, sunlight, oxygen and nutrients determine which organisms live in which areas of the water.
• Organisms are grouped by their location and by their adaptations. Plankton is the mass of mostly microscopic organisms that float or drift freely in the water, and can be microscopic animals called zooplankton or microscopic plants called phytoplankton.
• Nekton is a free-swimming organism in open water, independent of currents. Benthos is a bottom-dwelling organism that usually live attached to hard surfaces. Decomposers which break down dead organisms are also present.
• Lakes, ponds, and wetlands can form naturally where groundwater reaches the Earth’s surface. Humans intentionally create artificial lakes by damming flowing rivers and streams.
Lakes and Ponds – In a nutrient-rich littoral zone near the shore, aquatic life can be diverse and abundant. Plants are rooted in mud underwater and their upper leaves and stems emerge above the water. In the open water, sunlight near the surface support drifting phytoplankton. Benthic zone is the bottom which is inhabited by decomposers, insect larvae and clams.
▪ Eutrophication is an increase in the amount of nutrients in an aquatic ecosystem. As the amount of plants and algae grows, the number of decomposers increases. These bacteria use oxygen dissolved in the water. The reduced amount of oxygen kills oxygen-loving organisms and the lake becomes eutrophic over time. This process can be accelerated due to runoff.
Freshwater Wetlands – Land is covered with freshwater for at least part of the year such as marshes and swamps. Marshes contain non-woody plants and swamps contain woody plants. Most freshwater wetlands in the U.S. are located in the Southeast. The Florida Everglades is the largest freshwater wetland in the U.S.
▪ Wetlands act as filters because they absorb and remove pollutants from the water that flows through them. Wetlands improve the water quality of lakes, rivers and reservoirs downstream. They control flooding by absorbing extra water when rivers overflow. Many game fish use wetlands for feeding and spawning. These areas provide habitats for native and migratory wildlife.
▪ Marshes tend to occur on low, flat lands and have little water movement. The benthic zones are nutrient rich and contain plants, numerous types of decomposers and scavengers. Water birds have flat beaks adapted for sifting through the water or spear-like beaks to probe or grasp fish or frogs in the mud. The salinity varies and the organisms are generally adapted to the specific range of salinities in the water.
▪ Swamps occur on flat, poorly drained land, often near streams. The species of trees and shrubs depend on the salinity of water and the climate of the area. Swamps are an ideal habitat for amphibians, birds and reptiles.
▪ Human Impact – Wetlands were previously considered to be wastelands that provide breeding grounds for disease-carrying insects. Therefore, many have been drained, filled and cleared for development. For example, the Florida Everglades once covered 8 million acres, but now covers less than 2 million acres. The government now protects many wetlands and prohibits their destruction.
Rivers – Many rivers originate from the snow melt in mountains. At its headwaters, a river is usually cold, full of oxygen and runs swiftly through a shallow riverbed. As the river flows down a mountain, it becomes warmer, wider, slower, contains more vegetation and less oxygen. A river changes with the land and the climate through which it flows. Runoff washes nutrients and sediments into rivers affecting the growth and health of organisms.
▪ Near the headwaters, moss anchor themselves to rocks using root-like structures called rhizoids. Trout and minnows are adapted to the cold, oxygen-rich headwaters. Downstream the plants set roots into the sediment and other species of fish live in the calmer waters.
▪ Human Impact – People draw water to use in homes and manufacturing. Sewage and garbage have been disposed of in rivers resulting in toxins that kill organisms and make the organisms unsuitable for eating. Runoff of pesticides and other poisons accumulate in sediments. Dams also alter ecosystems in rivers.
Coastal Wetlands – Coastal lands covered by salt water for all or part of the time. Coastal wetlands provide habitat and nesting areas for fish and other wildlife. Coastal wetlands absorb excess rain, protect areas from flooding, filter out pollutants and sediments and provide a recreational area for humans.
▪ Many coastal wetlands form in estuaries where fresh water rivers mix with the salt water from the ocean. As the two bodies meet, currents form and cause mineral-rich mud and dissolved nutrients to fall to the bottom. These nutrients become available to produces and in shallow areas, marsh grass will grow in the mud. Estuaries constantly receive fresh nutrients from the river. The surrounding land protects estuaries from the force of ocean waves. Estuaries support many marine organisms and these organisms are able to tolerate variations in salinity when tides go in and out. Estuaries provide protective harbors, access to the ocean and connection to a river.
▪ Threats to Estuaries – In populated areas, estuaries were often used as solid waste landfills which were filled and used as building sites. Pollutants such as sewage, industrial waste and agricultural runoff damage the ecosystem. Most pollutants are broken down over time, but estuaries cannot cope with the excessive amounts produced by humans.
Salt Marshes – In estuaries, where river deposit their load of mineral-rich mud, salt marshes form. The marsh supports a community of clams, fish and aquatic birds. It serves as a nursery for many species. It absorbs pollutants and protects inland areas.
Mangrove Swamps – Mangroves are small trees adapted for growing in shallow salt water (i.e. above-ground root systems for support). Dense growths of mangrove trees in swampy areas form mangrove swamps that grow in tropical and subtropical zones. These areas protect the coastline from erosion and reduce the damage from storms. They provide a habitat for about 2,000 species. Mangrove swamps have been filled with waste or used for development.
Rocky and Sandy Shores – Rocky shores have more plant and animal species than sandy shores do. The rocks anchor seaweed and many animals live on it. Life on sandy shores is abundant in the water, the sand and in sediments. Animals in these areas are adapted to the effects of drying and exposure at low tide. Barrier islands often run parallel to sandy shores and help protect the mainland and coastal wetlands from storms and ocean waves.
Coral Reefs – Reefs are limestone ridges built by tiny coral animals called polyps and the algae that live inside them. Coral polyps secrete skeletons of limestone (calcium carbonate) which slowly accumulates and form the reefs. Thousands of species live in the reefs making it one of the most diverse ecosystems. Reefs are found in shallow, clear tropical seas.
▪ Threats – If the water is too hot or cold for too long or if it is too polluted, muddy or high in nutrients, the algae that live in the coral will leave or die. As a result, the coral turn white causing coral bleaching. If bleaching occurs often or long enough, the animals and reef will die. Since the 20th century, bleaching events have occurred more frequently due to human activities. About 50% of the world’s coral reefs are now in danger of destruction. In addition, global warming, oil spills and polluting runoff have been linked to the destruction of coral reefs. Overfishing upsets the balance of reef ecosystem by devastating fish populations. Because coral reefs grow slowly, a reef may not be able to repair itself when stressed or destroyed.
Oceans – Much of ocean’s life is concentrated in the shallow, coastal waters were sunlight penetrates to the bottom and rivers wash nutrients form the land. Seaweed and algae grow anchored to rocks and phytoplankton drift on the surface. In the open ocean, phytoplankton grows only in areas where there is enough light and nutrients. Zooplankton and other herbivores feed and live in areas with more plant life. Fish and marine mammals feed on these herbivores. Deep ocean water organisms depend on food that drifts down from above.
▪ Threats – Pollution from agricultural runoff and industrial waste may cause algal blooms to occur depleting the nutrients from the water. Overfishing and certain fishing methods have reduced the number of ocean animals.
▪ Arctic and Antarctic Ecosystems – The Arctic Ocean is rich in nutrients from the surrounding land masses. It supports large populations of plankton which provide food for other organisms. The Antarctic is the only continent never colonized by humans. Even during the summer, only a few plants grow at rocky edges. As in the Arctic, plankton forms the basis of the food web and support a large numbers of organisms.
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All organisms live in particular places called habitats. Every habitat has specific biotic and abiotic factors that the organism living there needs to survive. Organisms tend to be very well suited to their natural habitats.
What does “survival of the fittest” mean?
How is artificial selection different from natural selection?
Autotrophs – use the processes of photosynthesis (light) or chemosynthesis (inorganic compounds) to make their own food.
Heterotrophs – obtain food from other sources.
CARBON CYCLE
NITROGEN CYCLE
PHOSPHORUS CYCLE
Excessive amounts of phosphorus and nitrogen in aquatic ecosystems can cause an algal bloom, overgrowth of algae. Algal blooms can deplete nutrients such as oxygen from the ecosystem.
Climax Community is composed of species best adapted to conditions in an area and has reached equilibrium. The ecosystem is established and changes are slow.
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