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Diet and Exercise

  • PROTEIN: Meat, fish, eggs, pulses etc. Their role is to build new tissue, and they are important for growth, and well as repairing tissue. Proteins are made of amino acids.
  • CARBOHYDRATES: Rice, pasta, bread, sugars. They provide energy.
  • FATS: Butter, margerine, oils, lard. They provide stored energy.
  • WATER: Important for chemical reactions as all happen in a watery environment. 
  • FIBRE: Fruit, vegetables. Gives bulk to faeces to prevent constipation.
  • VITAMINS AND MINERALS: Important for general health - if you don't have enough, you could get deficiency diseases.

If you don't have a balanced diet, you can become malnourished (overweight or underweight). You can become overweight is you take in more energy than you give out, and underweight if you take in less energy than you give out. 

Metabolism is the rate of chemical reactions in the body - it is affected by exercise, genetics, gender and muscle to fat ratio (women have a lower muscle to fat ratio = lower metabolism).

Too high cholesterol can lead to blocked arteries which can lead to heart attacks. Type II diabetes is linked to being overweight, and is where the body doesn't recognise insulin and cannot control blood sugar. 

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Infectious Diseases

Microorganisms include bacteria, viruses, and fungi.

Disease-causing microorganisms are called pathogens. Bacteria produce toxins, and viruses infect body cells and reproduce rapidly, until the cell breaks open and is permanently damaged.

The body uses white blood cells to defend itself. It does this in three ways:

  • INGESTING PATHOGENS: the white blood cells surround and engulf the invading bacteria. They release enzymed to digest the pathogen.
  • PRODUCING ANTIBODIES: There are antigens on the surface of the invading cells. The shapes of these match the shape of the antibodies that the white blood cells produce. These attach together and the bacteria is destroyed.
  • PRODUCING ANTITOXINS: The antitoxins deactivate the toxins to make them harmless.

Vaccines contain a dead/inactive form of a pathogen. The pathogen still has antigens on the surface, so the white blood cells produce antibodies to fight these. In the future, it can then do this much more rapidly, protecting you. The more people that are vaccinated, the harder it is for the disease to spread. 

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Antibiotic Resistance

Pathogens can cause symptoms, for which medicine can be taken, which relieve the symptoms. However, taking antibiotics also affect the bacteria and remove the pathogen. 

However, if antibiotics are prescribed too much or if a course of antibiotics isnt finished, antibiotic resistance can occur, caused by a mutation - a random change in the DNA.

1. A bacteria has developed resistance to an antibiotic.

2. It can divide/reproduce.

3. A population of antibiotic resistant bacteria is caused, produced by natural selection. 

4. Scientists must then develop new antibiotics to fight this resistant strain. 

To slow the rate of development of resistant strains, you should avoid taking antibiotics for non-serious infections. 

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Growing Microbes

We often grow microbes to test antibiotics and disinfectants.


  • Sterilise the agar and the petri dish to prevent contamination.
  • Kill all bacteria on the inoculating loop by putting it through a bunsen burner.
  • Leave the loop to cool and then place into a sample of microbes. Transfer to the agar, making straight lines.
  • Place the lid on top of the petri dish and seal with tape to prevent contamination or harmful substances from coming out. 
  • Incubate at 25°C (in a school lab), to avoid growing pathogens. It should be 37°C in industry.

This can be done to test disinfectants, where the agar is filled with bacteria. Where the area is clear, the bacteria are dead and the disinfectant is successful. 

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The Nervous System

The Nervous System detects stimuli to coordinate behaviour. 

The body has many receptors,e.g sound receptors, light receptors etc. Light receptors can be rods or cones, and have nuclei, cytoplasms and cell membranes.

The receptor detects a stimulus and sends an electrical impulse through the sensory neurone to the central nervous system - the impulse is then sent through the relay neurone, to the motor neurone and then to the effector. The effector can be a muscle (which contracts) or a gland (which secretes hormones), producing a response.

E.G: Receptor - Sensory Neurone - CNS - Relay Neurone - Motor Neurone - Effector

A synapse is a junction of two neurones. An electrical impulse travels along the axon, and triggers the release of chemicals called neurotransmitters, which diffuse across the synapse. This stimulates the second neurone to transmit the electrical impulse.

Reflexes are designed for protection, and do not use the brain for maximum speed. 

E.G: Stimulus - Sensory Neurone - Spinal Chord - Relay Neurone - Motor Neurone - Effector

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Controlling Body Conditions

HOMEOSTASIS - keeping constant conditions in the body.

  • Water: since all chemical reactions in the body happen in a watery environment, reducing the amount of water reduces the amount of reactions. It can cause dehydration. We gain water through drinking and food, and lose it through breathing, sweating and urination (via our kidneys, which filter out excess water). 

The body has control mechanisms meaning it doesn't produce too much urine if dehydrated, but produces more if you have an excess. Key organ - KIDNEYS.

  • Ions: Mineral ions are needed for teeth and bones. We can these through our food, and lose it through sweating and urination - urination is controlled to ensure you have enough ions.
  • Blood sugar: We gain this through food and drink, and lose it through exercise and insulin, a hormone that helps reduce blood sugar when it is too high.
  • Temperature is a condition, and is increased through exercise or weather. It is decreased through sweating, or other ways (e.g if too hot, blood flows to the surface of the skin, and if too cold, it moves away from the surface of the skin.) The body has to be kept at 37°C, where enzymes work the best. 
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The Menstrual Cycle




Produced in the pituitary gland

Produced by the ovaries

Produced in the pituitary gland

Causes egg to mature

Thickens lining of the womb

Releases the egg

Stimulates production of oestrogen

Stimulates production of LH

Inhibits production of FSH (makes sure only one egg is matured at a time)


  (http://media.tumblr.com/296aaa60470259adff32415524e0b3e2/tumblr_inline_mlrmjxW57b1qz4rgp.gif) (http://www.bbc.co.uk/staticarchive/54b53307d8c7dc5ffbc8686c0408537bb1823490.gif)

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Hormones and Fertility

Oral contraceptives are used for stopping contraceptives.

  • In the past, high doses of oestrogen were used, as they inhibit FSH production, stopping the egg from maturing. However, this has many side effects (headaches, high blood pressure, etc.)
  • As a result, pills now usually contain only progesterone of a mixture of progesterone and low amounts of oestrogen, which have less side effects.

IVF is used a method of encouraging pregnancy.

  • This is used when the female does not produce enough FSH.
  • The woman is given a fertility drug containing FSH, which causes the eggs to mature.
  • The eggs are removed and put in a petri dish.
  • The eggs are fertilised and grow into embryos.
  • They are then implanted back into the womb.
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Drugs in Medicine

Drugs can be divided into three categories: medical, recreational and performance enhancing.

New drugs must go through testing before being approved.

  • First, they are tested on cells, tissues and animals for toxicity.
  • If they pass this, clinical trials are completed of volunteers, given low doses.
  • Further clinical trials are then completed, such as double blind trials.
  • Double blind trials are when neither the doctor nor the patients know who has the drug and who has the placebo. 
  • The drug is then approved, if it gets through this stage.

Thalidomide was originally a sleeping pill, and was given approval through these trials. It was theng given to treat morning sickness, however wasn't tested on pregnant women. As a result, many babies were born with limb deformities. It is still banned in many countries, however has been proved to help treat leprosy. 

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Drugs in Recreation and Sport

People take recreational drugs to make your mood happier or more relaxed, or to give the user a sense of euphoria.

Nicotine, alcohol and caffeine are legal recreational drugs. They have a bigger impact on society, as more people take them and therefore it is more expensive when they need to be treated. They can become addictive, and you become dependent on them - however they withdrawal effects are usually quite mild if you stop.

Cocaine, heorine, cannabis and ecstasy are all illegal recreational drugs. Cocaine and heroine are highly addictive and have severe withdrawal effects. Many also believe cannabis and ecstasy have negative effects on the heart/circulatory system, and may lead to mental illness. Cannabis can also be a gateway drug.

People take performance enhancing drugs for various reason. Steroids are taken to build muscle, stimulants are used for stamina and beta blockers are used to stay calm, however have many ethical issues. 

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Competition is seen in animals and plants in order to survive and reproduce. Plants compete for light and water (for photosynthesis), space and nutrients. Animals compete for food, territory and mates. Extremophiles can avoid competition.

Extremophiles may live in salty conditions (seas/lakes), e.g bacteria and mangroves, which have roots that absorb water but no salt - they have adapted. They may also live in pressurised conditions (bottom of the sea), e.g certain bacteria, fish, sea mammals etc.

They may also live in hot conditions. Most living things aim to stay at a body temperature of 37°C. Camels are adapted to survive at up to 40°C, and certain bacteria that contain special enzymes can survive up to 80°C. If the heat is too high, the enzymes can become denatured.

COLD CLIMATES: thick fur to reduce heat loss and trap air (good insulator). Whales have a thick layer of fat (good insulator.) Many are white for camouflage. Small SA to reduce heat loss.

HOT CLIMATES: high surface area to increase heat loss. Cacti are adapted to hot climates. They have thick stems which store water. Their leaves are in the shape of spikes which have a low SA to prevent water loss. They also have large root systems near the surface of the earth, that allows water to be absorbed quickly. 

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Environmental Change

The population size of living things in a particular area is affected by...

NON LIVING FACTORS: temperature, nutrients, rainfall, pollution. 

LIVING FACTORS: competition, predators, disease.

A movement in living things due to these factors may have implications. They may compete with those that already live there, causing these living things to move, or they may act as pests, causing problems.

POLLUTION INDICATORSLichens can detect air pollution, as they are sensitive to sulphur dioxide. There will be more of a variety of lichen if there is less pollution. Invertebrates can detect water pollution.

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Food chains and biomass

During photosynthesis, plants covert light energy from the sun into chemical energy in the form of glucose. Glucose can make proteins, fats and carbohydrates, which are used to make new living tissue in the body of the plant - this is called BIOMASS, and it leads to growth. 

Biomass decreases at every level of the food chain. Biomass is lost:

  • through respiration
  • through movement
  • as heat
  • as faeces and urine 


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Plants need nutrients (e.g nitrates and mineral ions) for healthy growth. Animals get their nutrients from eating these plants. 

Over time, leaves fall off of trees, animals produce waste, and all living things die. The nutrients in their bodies must get back into the environment so their community can continue - DECAY.

  • Microorganisms break down/digest decaying living things, putting them back into soil.
  • A stable community has the same amount of nutrients out and in.
  • Microorganisms work best in warm, moist conditions and when there is plenty of oxygen.
  • A compost bin shows the use of decay. Compost is plant material broken down by microorganisms. It can be put on soil to encourage growth. 

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The Carbon Cycle

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Genetic Variation

Characteristics are the features of every living thing (e.g height, petal size etc).

Parent pass on their characteristics to their offspring - they pass this genetic information through genes. 

Every cell contains a nucleus - inside the nucleus are chromosomes, which are made of tightly coiled DNA. Genes are found in the chromosomes, and control all different features.

Genes produce molecules in the body that show as certain features.

Individuals can have genetic and environmental features. Genetic features include eye colour, ear shape, dimple, tongue rolling etc. Environmental features include accent. 


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Modern Cloning Techniques

Cloning plants:

TISSUE CULTURE: You take a group of cells from the leaf or stem, and put these balls of cells into a dish of nutrient agar (which contains sugars, vitamins and hormones). The aseptic technique is used to ensure sterile conditions, as cells will be destroyed if the agar becomes infected. Small plants can then be planted in soil. This can produce thousands of clones but it is expensive. 

Cloning animals:

EMBRYO PLANTS: Take the egg and sperm cell and fertilise them to make a fertilised egg that grows into an embryo (a ball of unspecialised cells). The embryo can then be split into smaller balls of cells. These are planted into the wombs of host mothers, causing all the individuals to have the required features.

ADULT CELL CLONING: Take the skin cell of an animal with the required features. Since the nucleus contains all the genes and DNA, after going through an electric shock, it can be implanted into the egg cell of another animal and then put into a host mother. This produces a clone. 

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Genetic Engineering

Genetic engineering is the transfer of genes from one type of living thing to another. 

  • EXAMPLE: INSULIN (hormone that controls blood sugar levels in the body.)
  • Some people are unable to produce insulin so must take an external source. In the past, it was obtained from the pancreas of a pig but now new methods have been found. 
  • The gene responsible for producing insulin was isolated and removed from the chromosome it was in through an enzyme that could cut through DNA.
  • A bacterium has DNA with a circular shape - once the DNA is removed, an enzyme can be used to cut a gap, to which the human gene can be inserted into.
  • This is placed back into the bacterium and reproduces rapidly, and can be put into humans.
  • EXAMPLE: CROP PLANTS (spraying chemicals to kill insects on plants can kill other things).
  • Take out a plant cell in the early development of a plant. Remove a chromosome and insert a gene (this gene is often found in bacteria and produces a protein to kill insects.)
  • Place the gene into the plant chromosome using enzymes and insert back into the plant. These cells can reproduce and make the plant insect repellent - GENETICALLY MODIFIED CROPS. Some people object to this, arguing that we don't know long term effects, and could be dangerous if this got into other plants, and then animals, and then humans. 
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Sexual and ASexual reproduction

SEXUAL REPRODUCTION requires male and female GAMETES (sex cells). Sexual reproduction in pants required an egg cell and pollen. The gametes contain genes which have all the genetic information.The gametes must fuse together, and the new offspring will have VARIATION (different features from the parents, they are not CLONES.)

ASEXUAL REPRODUCTION required one parent - there are no gametes, and no mixing of genes. All the new individuals formed will be CLONES. In plants, the parent plant will grow a runner, and will produce a new plant at the end of a runner. Many plants develop underground food storage organs that later develop into the following year's plants. 


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Darwin vs Lamarck - Evolution

Darwin's theory of evolution - NATURAL SELECTION:

  • Individuals in a species show variation in features.
  • Advantageous features help individuals to live longer and then reproduce.
  • Advantageous features are passed on to offspring. 
  • Darwin believed that the different species that exist today were all originally simple, single-celled life forms that evolved, 3500million years ago.
  • Many didn't believe the theory, as they believed the Creation story, and there wasn't enough evidence, and there was no way of understand variation or inheritance. 
  • Other impacts on evolution may have been environments that living things were in, and MUTATION (random, spontaneous change in genes) that may give advntageous features.

Lamark's theory of evolution: THEORY OF INHERITANCE

  • Individuals in a species can change their features over their lifetime.
  • These changes, made by the living thing themself, can be passed on to the offspring. 
  • This is basically saying that if you build muscle in your lifetime, your children will have big muscles. 
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