Cells: - Edward Burns Biology/Science



Biology notes

7 Characteristics of living things:

1. Feeding

2. Respiration

3. Movement

4. Sensitivity

5. Growth

6. Reproduction

7. Excretion

Cells:

1: Plants and animals are made up of cells.

2. Animal cells are composed of:

Cell membrane keeps the parts of the cell together and allows oxygen and food into the cell, and carbon dioxide and water out of the cell.

The nucleus controls the cell and it contains genetic material.

Temporary Vacuoles contain food and waste products of cell metabolism.

Cytoplasm is everything within the cell membrane except the nucleus.

3. Plant cells are composed of:

All components found in the animal cell, + the cell wall protects the cell and gives it support. It contains cellulose.

Vacuole contains water and helps to give the cell its rigidity.

The chloroplast contains chlorophyll necessary for photosynthesis

Animal Cell Plant cell

Differences between plant and animal cells

Cell organisation

A tissue is a group of similar cells with a special function, e.g. muscle cells, nerve cells and blood cells.

An organ is a group of tissues that work together to perform a special function, e.g. a nose contains skin tissue, bone tissue and blood tissue; a leaf contains phloem and xylem tissue.

A system is a group of organs working together, e.g. the digestive system consists of intestines, stomach, oesophagus and other organs.

Biologists study cells using a microscope.

[pic]

The parts of a typical microscope are shown in the diagram.

• Eyepiece lens:

You look through this to see the object (animal or plant cells) being magnified.

• Focusing knob:

This is used to lower and raise the stage. This brings the object into focus.

• Objective lens:

The magnifying power can be changed by using different lenses.

• Stage:

This is used to hold the glass slide and the object being magnified in position. A small opening allows light through.

• Light source:

The light source may be an electric light bulb or natural light reflected through a mirror.

Food

A balanced diet is one that contains the right amounts of all the food types needed to stay healthy.

Types of Food:

The Food Pyramid shows the amounts of different foods we should eat

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Enzymes are complex chemicals which break down foods to simple molecules. They are

produced in the mouth, stomach, pancreas and the small intestine. Amylase breaks down starch into a sugar called maltose.

Starch is called the substrate.Amylase is the enzyme and Maltose is the product

Amylase is found in our saliva in our mouth and it breaks down carbohydrates

Food labels show us what is in our food. The food listed first is present in the greatest amount. Foods are listed in order of amounts present. Labels must also show the energy content of food per 100g. Energy is shown as KJ or KCals.

The Digestive System

Teeth:

There are four types of teeth in a human being

incisors, canines, premolars, molars.

The incisors bite food.

The canines tear food (these teeth are well developed in carnivores, e.g. dogs and lions).

The premolars and molars grind up the food.

Plaque is a build up of sugar and bacteria on the teeth

The end products of digestion

Carbohydrates are broken down to sugars.

Proteins are broken down to amino acids.

Fats are broken down to fatty acids and glycerol.

The mouth breaks up food physically. The digestion of starch by the enzyme amylase begins.

The oesophagus is the tube which brings the food from the mouth to the stomach.

The stomach is where protein digestion begins. The contents of the stomach are acidic. Food is churned up by the stomach muscles.

The small intestine is where the digestion of carbohydrates, proteins and fats is completed. he digested food is absorbed into the bloodstream.

The large intestine is where water is reabsorbed into the body.

Faeces are stored in the rectum.

Undigested food is egested from the body at the anus.

Feeding for humans and most other animals involves the following processes.

Ingestion: Food is taken into the mouth.

Digestion: Food is broken up into soluble substances by the teeth and by digestive enzymes.

Absorption: Soluble substances are absorbed into the bloodstream.

Assimilation: The soluble products of digestion are reorganised and used for growth new cells, for energy and for repair of tissues and organs.

Egestion: Undigested material is got rid of (excreted) through the anus.

The Respiratory System[pic]

1. Energy is required by all living organisms.

2. Respiration is the release of energy from food using oxygen.

Glucose + Oxygen Carbon dioxide + water + energy

Aerobic Respiration requires the presence of oxygen

3. When a person breathes, oxygen is taken into the body by the lungs. Carbon dioxide and water vapour are expired from the body.

4. The respiratory system consists of:

(a) the nose: where air is filtered and warmed.

(b) the mouth: air is also taken in here.

(c) the epiglottis: stops food and drink entering the lungs.

(d) the trachea: connects the mouth and nose to the bronchi.

(e) the bronchi: connects the trachea to each lung.

(f) rings of cartilage: keeps the trachea and bronchi open.

(g) alveoli: where gas exchange takes place.

(h) ribs: protect the lungs and assist in the breathing process.

(i) diaphragm: is a sheet of muscle which assists in the breathing process.

(j) the respiratory system is lined with mucus and tiny hairs which filter and clean the incoming air.

5. Effects of Smoking:

(a) can cause lung cancer.

(b) cancause heart disease as cigarette smoke replaces the oxygen in the blood with carbon monoxide, this means the heart has to work much harder

(c ) lung disease. Smoking produces more mucus which in not easy to clear.

(d) produces toxic gases which affect the smoker and other people

(e) gives people smoker's cough.

(f) In pregnancy it reduces the amount of oxygen available leading to stunted growth in the baby.

The Respiratory system

Gas exchange in the alveoli

Gas exchange take place in the alveoli. The alveolis are only one cell thick and are surrounded by blood capillaries which are also one cell thick. Oxygen passes through the walls of the alveoli and into the blood capillaries by diffusion. Carbon dioxide passes the other way by diffusion.

The Circulatory system

Composition of Blood(what blood is made up of)

Red blood cells – have haemoglobin to carry oxygen

White blood cells – to fight infection

Platelets – to clot the blood

Plasma – is a liquid in which all the components of blood are held

Functions of the blood Blood:

1. transports food, oxygen, hormones, antibodies, carbon dioxide and unwanted substances like urea.

2. protects against loss of fluid by clotting and also against disease by killing germs. 3. controls the amounts of water and chemicals in the tissues.

4. regulates body temperature.

THE CIRCULATORY SYSTEM

1. The heart pumps blood around the body.

2. The heart is divided into two sections so that blood does not flow directly from one side to the other.

3. Arteries carry blood away from the heart to the tissues. They have thick muscular walls and narrow lumens (centres)

4. Capillaries are only one cell thick and carry blood through the tissues.

5. Veins carry blood back to the heart. They have thinner walls and have wider lumens than arteries. They have valves to prevent the blood from flowing backwards.

The right ventricle has thick walls because it pumps blood to the lungs. The left ventricle has very thick walls because it pumps blood all around the body.

The average pulse rate of a person is 70 beats per minute. If we exercise our pulse rate increases as we need more energy. Our heart beats faster to pump more oxygen around our body so that we can produce more energy.

Our body temperature is normally 37º Celsius

When our food is digested the products are released into our blood stream and are transported by the blood around the body for use.

Heart disease

Heart disease can be prevented by:

1. regular exercise.

2. a healthy diet.

3 . not smoking.

The Excretory System

1. Excretion is the removal of waste materials from the cells of the body.

2. There are three excretory organs

(a)The lungs get rid of carbon dioxide and water vapour.

(b) The Skin gets rid of water, salts and some urea

.

(c) The kidneys get rid of urine which is made up of water, salts and urea.

3. The blood enters the kidneys via the renal arteries. The blood is filtered, and the filtered blood is taken back to the heart by the renal vein. The urine is taken to the bladder by the ureter. Urine is stored in the bladder. When the bladder is full the urine is expelled from the body by the urethra.

The Skeletal System

1: The skeleton has three main functions:

(a) Support

(b) Movement - muscles and bones enable us to move.

(c) Protection - examples, the skull protects the brain and the ribs protect the heart and lungs.

2: Joints:

A joint is where two bones meet.

3: Types of joint:

(a) Ball and socket joint, e.g. hip, shoulder.

(b) Hinge joint, e.g. knee.

(c) Gliding joint, e.g. wrist.

(d) Pivot joint, e.g. between the skull and the vertebral column.

(e) Fused joint, e.g. found in the skull.

4: Joints have a lubricating fluid called synovial fluid, and the ends of the bones are covered with cartilage.

5: Bones are attached to one another by ligaments, and muscles are attached to bones by tendons.

6: Ligaments connect bone to bone

7: Tendons connect muscle to bone

8: Synovial fluid lubricates the joints and allows the joints to move freely

Muscles act by contracting. They work in pairs called antagonistic pairs, e.g. the biceps raises the forearm and the triceps lowers the forearm. When one of the pair of muscles contracts, the other muscle relaxes and vice versa.

THE NERVOUS SYSTEM

The nervous system consists of the brain, the spinal cord and the peripheral nerve (nerves connected to the brain and the spinal cord). The function of the nervous System is to transmit messages rapidly to all parts of the body and to co-ordinate the body's responses.

Nerves are made up of millions of nerve cells called neurons. Messages travel very quickly along neurons as tiny electrical pulses.

Sensory nerves carry messages from the sense organ to the brain.

Motor nerves carry messages from the brain back to the sense organ.

Sensory and motor functions

The sense organ receives a stimulus. A message is sent from the sense organ to the brain or spinal cord via a sensory nerve. The brain or spinal cord decides what to do then sends a message along the motor nerves to the muscles and glands.

The sense organs

|Sense |Sight |Hearing |Smell |Taste |Touch |

|Sense organ |Eye |Ear |Nose |Tongue |Skin |

The Eye

The Reproductive system

1. Reproduction is the process where new individuals are produced

2. The female reproductive system produces eggs and carries the developing foetus until birth.

(a) Eggs are produced and released in the ovary by a process called ovulation.

(b) Fallopian tubes carry the egg to the uterus (womb). Fertilisation occurs in the fallopian tubes.

(c) The foetus develops in the uterus.

(d) Sperm enters the woman's body through the vagina, and the baby is also born through the vagina.

3. The male reproductive system produces sperm.

(a) Sperm are produced in the testes. The testes are held in a sack called the scrotum. The scrotum is outside the body so that the testes are at a lower temperature than the body.

(b) Sperm ducts carry the sperm from the testes to the penis, which is capable of transferring sperm into the body of the female.

4. Intercourse, occurs when the male's penis is inserted into the vagina, and sperm are released.

5. Fertilisation occurs when the sperm and the egg unite to become a zygote.

6. Pregnancy is when the baby develops in the uterus of the female. Pregnancy lasts

nine months in humans. (40 weeks)

7. Birth occurs after approximately nine months, when the muscles of the uterus contract. This is called labour. The cervix dilates. The bag of amniotic fluid bursts and contractions push the baby out through the vagina. The umbilical cord is clamped and the cut. The placenta ( the afterbirth) is also pushed out.

8. The menstrual cycle begins by the lining of the uterus breaking down and is expelled through the vagina. This is known as menstruation and it lasts approximately five days. The lining of the uterus regenerates and is ready for possible implantation of an embryo. The woman's most fertile period is just after ovulation which occurs from approx. day 13-15 of the cycle. If fertilisation does not occur, the lining of the uterus breaks down and the lining is expelled and the cycle begins again. If fertilisation occurs, the embryo is implanted into the wall of the uterus where it develops. Menstruation then ceases until after the birth of the baby.

The fertile period is usually between the 13th and 15th day of the menstrual cycle and this is the time when pregnancy is most likely to occur

9. Contraception is the prevention of fertilisation.

Methods:

1. Rhythm method: This involves the women taking her body temperature with a special thermometer daily. When ovulation occurs the body temperature rises. If a women avoids intercourse at this stage fertilistaion of the egg will not take place.

2. The Contraceptive pill: The pill contains hormones stop ovulation

3. The condom: This is a rubber sheath that is placed on the penis before intercourse. This prevents the sperm from meeting an egg and therefore fertilisation cannot take place.

4. Sterilisation: Males are sterilized by having their sperm ducts cut and tied. This prevents the release of sperm. Females are sterilized by having their fallopian tubes cut and tied.

Inheritance

Genetics is the study of heredity

1. This is the transfer of characteristics from parent to child, and it is the reason why children resemble their parents.

2. Some characteristics are inherited, e.g. eye colour, hair colour etc. and some characteristics are non-inherited, e.g. a way of speaking, interest in sprt etc.

3. The male and female gametes are called the sperm and the egg respectively. These gametes contain chromosomes and in the human each gamete contains 23 chromosomes.

4. The chromosomes are made up of genes which are made up of (DNA).

[pic]

Introduction to plants

1: There are many different types of plants. They are living organisms and they exhibit the characteristics of life: movement, respiration, feeding, growth, reproduction, excretion, sensitivity to their environment.

2: Uses of plants

1. They recycle oxygen.

2. They are a food source.

3. They are used in medicine.

4. Many useful products are produced from plants, e.g. timber, linen, paper, coffee, tea.

5. Plants provide us with many leisure activities, e.g. gardening, walking in the countryside.

6. Plants may be recognised by their distinctive flowers and leaves.

Generally a plant has a root, stem, leaves, flowers and stems.

| Structure |Function |

|Root |(a) |anchors the plant. |

| |(b) |absorbs water and minerals from the |

| | |ground. |

| |(c) |stores food. |

|Leaves |(a) |make food (photosynthesis) |

| |(b) |gases diffuse into and out of the |

| | |leaves. |

|Flowers | |reproduction |

|Stems |(a) |transport water and minerals from the |

| | |root to the leaves. |

| |(b) |transport food to the root for storage. |

[pic]

Plant Nutrition:

1. Photosynthesis is the process by which green plants make their food. Carbon dioxide and water are the new materials. Sunlight provides the energy and the green pigment, chlorophyll, traps the sun's energy. Oxygen and starch (food) are produced. This replaces the oxygen which is used up in respiration.

energy/chlorophyll

Carbon dioxide + water Food + oxygen

6CO2 + 6H[pic]0 energy C[pic]H[pic]0[pic] + 6O[pic]

chlorophyll

Plants need minerals for healthy growth. These include nitrogen, phosphorous potassium and others. If plants do not get sufficient minerals they will not grow well they will not photosynthesise properly.

Transport in plants

A transport system is necessary in plants to bring water and minerals from the roots to the leaves (through the xylem) and food from the leaves to the root for storage (through phloem).

Transpiration is the process by which water evaporates from the leaves of plants. There are tiny holes in the leaves of plants called stoma which allow water out into atmosphere.

Factors which affect transpiration:

(a) Temperature: a hot day increases the rate of transpiration.

(b) Wind: a breeze will remove water vapour from around the leaf. More water vapour will replace it so that the rate of transpiration is higher than on a calm day with little wind.

(c) Humidity: high humidity with a lot of water vapour in the atmosphere lowers the rate of transpiration. Low humidity raises the rate of transpiration.

Tropisms

Tropism is the response of a plant to a stimulus.

Phototropism is the growth response of a plant to light.

Geotropism is the growth response of plant to gravity.

Reproduction in plants

[pic]

1: Reproduction is the way plants produce new organisms similar to themselves

2. Plant reproduction may be asexual or sexual.

Asexual reproduction involves one parent only without the union of gametes.

Examples include cuttings and strawberry runners.

Sexual reproduction involves the union of two gametes, one from each parent.

In the case of plants the pollen is the male cell and the egg is the female cell.

3: The flower is the organ of reproduction of the plant.

Parts of the flower.

The sepal protects the flower when it is a bud.

The petal attracts insects to the flower for pollination.

The carpel is the female part of the flower and it produces the egg.

4: The stamen is the male part of the flower and it produces the pollen. The carpel is the female part of the flower and it consists of the stigma, the style and the ovary. Pollen lands on the stigma, a pollen tube grows down through the style to the ovary (where the egg is produced).

5: There are four stages in the sexual reproduction of plants.

(a) Pollination is the transfer of pollen from the anther of one flower to the stigma of a second flower of the same species. This may happen by wind or by insect.

(b) Fertilisation is the union of the male and female gamete to produce a fertilised cell (zygote). After fertilisation the ovary is called a fruit.

(c) Dispersal is the scattering of the fruit or individual seeds.

This may occur by:

Wind: e.g. dandelion, or winged fruits, e.g. sycamore.

Animal: the seeds may stick to an animal and be carried some distance, animals may eat the seeds which are undigested and are found in the faeces of the animal.

Some seeds are self dispersed by the plant. The seed pods shrivel in the sun and pop, scatter the seeds, e.g. peas, lupins.

(d) Germination:

given favourable conditions the seeds will grow to form new plants. The conditions necessary for germination are:

(i) heat

(ii) water

(iii) oxygen

Features of wind pollinated flowers

(a) Small inconspicuous flowers with no smell which do not produce nectar.

(b) Small light pollen grains which do not stick together.

(c) Large stigmas to aid pollination.

Features of insect pollinated flowers

(a) Large flowers with coloured petals, a smell and nectary to attract insects.

(b) Less pollen is produced.

(c) Smaller stigmas inside the flower.

Ecology

1. A habitat is a place where plants and animals live. There are many different types of habitat, e.g. a pond, a seashore, a hedge, a field.

2. Animals and plants can be specific to certain habitats, e.g. crabs may be found in a seashore habitat.

3. There is a need for conservation in a number of habitats, e.g. bogland. Conservation is an attempt to preserve animals and plants from extinction.

4. Living things depend on one another for food, shelter, etc. This is called interrelationships.

5. Pollution is where the environment is damaged by such things as effluent, waste materials, slurry leaking into lakes and rivers, etc.

Habitat Study

1. Collecting animals:

A pit fall trap is used to collect small animals, e.g. insects, beetles

A pooter collects small animals by suction

A sweep net collects insects.

A butterfly net collects butterflies.

A mammal trap collects small mammals, e.g. mice

2. Plants

The distribution of plants is found using a transect line.

This is a piece of string which is laid across the habitat. The type of vegetation that touches the line is noted. The combination of several transect lines should give a good picture of the type of vegetation in the habitat.

[pic]

A quadrat may also be used to sample the vegetation in a habitat.

This consists of four pieces of timber joined together to form one metre squares. The quadrat is thrown at random and the type of vegetation inside the quadrat is noted.

The DAFOR scale is used to determine the frequency of each species. This stands for Dominant, Abundant, Frequent, Occasional and Rare.

3. Food Chains

Food chains always start with a producer, i.e. a plant. The next level is a primary consumer which eats plants, i.e. a herbivore. The next level is an animal that eats other animals, i.e. a carnivore, which is a secondary consumer.

e.g. Grass --> Rabbit --> Fox

4. Trophic levels

The primary producers are a solar energy trap, making organic material for the next level, i.e. the herbivores or primary consumers. These in turn provide food for the next level, the carnivores or secondary consumers. These levels are known as trophic levels.

5. Food webs

A food web gives a more accurate account of the feeding patterns in a habitat. It consists of a series of food chains which are interlinked.

6. Adaptation to the environment.

Animals and plants have certain features that allow them to survive in a particular environment. Some animals are coloured so as to camouflage themselves. Birds may have specially adapted beaks for feeding. Some water birds have webbed feet for swimming, e.g. swans. A hawk has good eyesight for hunting.

7. Competition

Plants compete with one another for light, water and space. This occurs within the same species and between different species.

Animals compete for food (within the same species and between species) and mates (within the same species).

8. Interdependence

This is where animals and plants are dependent on one another, e.g. plants are dependent on animals (insects) for pollination and animals (bees) are dependent on plants for food (nectar)

MICRO-ORGANISMS

Micro-organisms are very small organisms. Some are beneficial to humans can be harmful.

Viruses are micro-organisms that multiply only in living cells by making replicas of themselves. Viruses cause influenza, colds, polio, AIDS, and many other illnesses

Bacteria are single cells that can reproduce very quickly. Harmful bacteria cause diseases such as pneumonia and tuberculosis.

Many fungi, such as mushrooms, are not micro-organisms. Fungi have no chlorophyll and cannot produce food by photosynthesis.

Biotechnology is the use of animals , plants and microorganisms to produce useful products.

Uses of Biotechnology

|In Industry |In medicine |

|Yeast to make alcohol and bread |Bacteria and fungi to make antibiotics |

|Bacteia are used to make enzymes in |Bacteria and yeast are used to make hormones, insulin and |

|Washing powder |antibodies |

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