Biology: Unit 1

All of B1 For AQA Biology.

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1a - Diet and Exercise

You need the right balance of different foods in a healthy diet: 

·       Carbohydrates, fats and proteins are used by the body to release energy and to build cells.

·       Mineral ions and vitamins are needed in small amounts for healthy functioning of the body.


·       The metabolic rate (MR) is the rate at which all chemical reactions in the cells of the body are carried out.

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Factors Affecting Health:

  • Unbalanced diet - Malnourished.
  • Not enough exercise.
  • Inheritance factors.

You inherit:      

  • Factors that affect your metabolic rate (eg. Lower inherited MR could cause obesity)      
  • Factors that affect blood cholesterol level (LDLs {bad} and HDLs {good})


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Defending Against Infection

Microorganisms that cause infectious diseases are called pathogens.

White blood cells defend against pathogens by:

·       Ingesting pathogens.

·       Producing antibodies which destroy particular bacteria or viruses.

·       Producing antitoxins which counteract the toxins released by the pathogens.


·       People can be immunised against a disease by by introducing small quantities of dead or inactive forms of the pathogen into the body.

·       Vaccines stimulate the white blood cells to produce antibodies that destroy the pathogens. This makes the person immune to future infections by the microorganism.

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Antibiotics can only help cure bacterial diseases. NOT Viral pathogens.

Overuse and inappropriate use of antibiotics,(eg. Using it for the flu or a cough) has increased the rate of development of antibiotic resistant strains of bacteria.

MRSA: A type of bacteria resistant to antibiotics

Antibiotics kill individual pathogens of the non-resistant strain.

Individual resistant pathogens survive and reproduce, so the population of the resistant strain increases.

Now, antibiotics are not used to treat non-serious infections,(eg. Mild throat infections) so that the rate of development of resistant strains is slowed down.


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The Nervous System

Cells called receptors are groups of specialised cells which detect stimuli and turn them into electrical impulses.

 Receptors and the stimuli the detect include:

 (1)-{Eyes - Light}    (2)-{Ears - Sound} (3)-{Ears - Position(Balance)}          (4)-{Tongue and Nose - Chemicals (Taste and Smell)}                                           (5)-{Skin - Touch, Pressure, Pain and Temperature changes}

In a simple reflex action

 Receptor detects a stimulus and impulses from the receptor pass along a sensory neuron (SN) to the central nervous system (CNS). At a junction (synapse) between a SN and a relay neuron (RN) a chemical is released that causes a impulse to be sent along the RN. A chemical is then released between a RN and the motor neuron (MN) in the CNS, at a synapse, causing impulses to be sent along a motor neuron to the organ (the effector) that brings about the response(The effector is either a muscle or gland).

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Homeostasis: All the functions of your body which try to maintain a "constant internal environment". 

Internal conditions that are controlled are:

  • The water content of the body- Water leaves the body via the lungs when we respire, via the skin when we sweat and excess water is lost via kidneys in the urine
  • The ion content of the body- Ions are lost via the skin when we sweat and excess ions are lost via the kidneys in the urine.
  • Temperature- To maintain the temperature at which enzymes work best.
  • Blood sugar levels- To provide the cells with a constant supply of energy.
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Hormones are chemical messengers which travel in the blood to activate target cells.

FSH: -Produced by the pituitary gland.

 -Causes an egg to mature in one of the ovaries.

 -Stimulates the ovaries to produce oestrogen.

LH:  -Produced by the pituitary gland.

-Stimulates the release of an egg at around the middle of the menstrual cycle from the ovaries.

Oestrogen: -Produced in the ovaries.

-Causes the pituitary gland to produce LH.

-Inhibits the further release of FSH.

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The Menstrual Cycle

The Menstrual Cycle has four stages:

1- Day 1 is when the bleeding starts. The uterus lining breaks down for about four days.

2- The lining of the uterus builds up again, from day 4 to 14, into a think spongy layer full of blood vessels, ready to receive a fertilised egg.

3- An egg is released from the ovary at day 14.

4- The wall is then maintained until day 28. If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts again.

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Controlling Fertility

Hormones can be used to reduce fertility:

Oestrogen can be used to prevent the release of an egg, because it inhibits the production of FSH and after a while egg development and production stop and stay stopped.

Progesterone also reduces fertility  by stimulating the of thick cervical mucus which prevents any sperm getting through and reaching an egg.

Or Increase fertility chances:

If FSH and LH are injected into a women who's levels of FSH are too low to cause their eggs to mature, it will stimulate egg release in their ovaries.

IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs. The eggs are then collected from the mother and fertilised by the father. The fertilised eggs develop into embryos. At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother's uterus (womb).

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Plant Hormones

Plants are sensitive to lightmoisture and gravity.

  • Their shoots grow towards light and against the force of gravity.
  • Their roots grow towards moisture and in the direction of the force of gravity.

Auxin: A plant hormone that controls growth near the tips of the shoots and roots and controls the growth of a plant in response to light, moisture and gravity.

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Clinical Trial

Drugs are first tested on human cells and tissues in a lab. 

The next step is to test the drug on live animals. This is to prove that the drug works, to find out about its toxicity and the best dosage.

If the drug passes those tests, its tested on human volunteers in a clinical trial. It's first tested healthy volunteers, just in case it has harmful side affects when the body is working normally. At the start of the trial, a very low dose of the drug is given then gradually increased. If the drug is found to be safe further clinical trials are carried out on people suffering from the illness. To test this people are split into two groups. One group is given the new drug, and the other is given a placebo ( a substance that's like the drug being tested but doesn't do anything, "dummy drug"). This is so the doctor can see the actual difference the drug makes - it allows for the placebo effect. These clinical trials are sometimes blind or double blind so that doctors monitoring the patients and analysing the results aren't subconsciously influenced by their knowledge.

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Testing Medicinal Drugs

Thalidomide is a drug that was developed as a sleeping pill but was also found to be effective in relieving morning sickness in pregnant women. It wasn't tested in pregnant women. Many babies born to mothers who took this were born with severe limb abnormalities. It's now being used to cure leprosy and other diseases.

Statins: Prescribed drugs used to lower the risk of heart and circulatory disease.

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Recreational Drugs

Drugs change the chemical processes in peoples' bodies so that they may become dependent  or addicted to the drug and suffer withdrawal symptoms without them. 

Heroin and Cocaine are very addictive. 

Cannabis is an illegal drug. Cannabis smoke contains chemicals which cause mental illness in some people.

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1b - Adaptations in Animals

An adaptation is a particular feature that enables and organism to survive in its environment.

The polar bear

Polar bears are well adapted for survival in the Arctic:

  • A white appearance as camouflage from prey on the snow and ice.
  • Thick layers of fat and fur for insulation against the cold.
  • A small surface area to volume ratio, to minimise heat loss.
  • A greasy coat that sheds after after swimming.
  • Large furry feet to distribute their load and increase grip on the ice.

The camel

  • Large, flat feet to spread their weight on the sand.
  • A large surface are to volume ratio, to maximise heat loss.
  • The ability to tolerate body temperatures up to 42 degrees.
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Adaptions in Plants

Desert Plants

Cacti are well adapted for survival in the Desert:

  • Stems that can store water.
  • Widespread root systems that can collect water from a large area.
  • Have spines instead of leaves. These minimise surface area and so reduce water loss by transpiration. Also these spines help protect the cacti from animals that might eat them.

Arctic Plants

The Arctic is cold and windy with very little rainfall. Plants in the Artic often grow very close to ground and have small leaves. This helps to conserve water and to avoid damage by the wind.

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Animals compete for:

  • Food
  • Water
  • Space
  • Mates

Plants compete for:

  • Light
  • Water
  • Space
  • Mineral salts
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Environmental change

Environmental changes are caused by different factors.

Living factors:

  • A change in the occurrence of infectious diseases.
  • A change in the number of predators. 
  • A change in the number of prey or the availability of food sources.
  • A change in the number of types of competitors.

Non-Living factors:

  • A change in the average temperature.
  • A change in the average rainfall.
  • A change in the level of air or water pollution.

Environmental changes affect populations in different ways.

  • Population SIZE INCREASES.
  • Population SIZE DECREASES.
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Measuring Environmental Change

Environmental changes can be measured using living indicators...

  • Air pollution can be monitored by looking at particular types of lichen that are sensitive to the concentration of sulphur dioxide in the atmosphere.The number and type of lichen at a particular location will indicate how clean the air is. ( the air is clean if there are lots of lichen.)
  • Invertebrate animals (such as the mayfly larvae) can be used as water pollution indicators and are used as indicators of the concentration of dissolved oxygen in water. If you find mayfly larvae in river or lake, it indicates that the water is clean.

Environmental changes can be measures using non-living indicators...

  • Oxygen levels
  • Temperature 
  • Rainfall

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Energy and Biomass

Radiation from the sun is the source of energy for most living organisms. Green plants and algae absorb a small amount of the light that reaches them. The transfer from light energy to chemical energy occurs during photosynthesis. This energy is stored in the substances that make up the cells of the plants.

Pyramid of biomass: There's less energy, less biomass and fewer organisms every time you move up a stage in a food chain.

  • Some materials and energy are always lost in the organisms' waste materials.
  • Respiration energy. Much of this energy is eventually transferred to the surroundings.

Decay processes:

Living things remove materials from the environment for growth and other processes. These materials go back to the environment either in waste materials or when living things die and decay. Materials decay because they're broken down by microorganisms.

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The Carbon Cycle

  • Firstly, Carbon dioxide is removed from the environment by green plants and algae for photosynthesis.
  • The carbon from the carbon dioxide is used to make carbohydrates, fats and proteins, which make up the body of plants and algae.
  • Respiration occurs with green plants and algae which releases some carbon dioxide into the atmosphere.
  • When green plants and algae are eaten by animals and these animals are eaten by other animals, some of the carbon becomes part of the fats and proteins that make up their bodies.
  • Respiration occurs when animals respire which releases carbon dioxide into the atmosphere.
  • When plants, algae and animals die, some animals (called detritus feeders) and microorganisms feed on the bodies.
  • When these animals respire carbon dioxide is released into the atmosphere.
  • Animals waste is too broken down by the detritus feeders and microorganisms. Compounds in the waste are then taken up up from the soil by plants as nutrients and are put back into the food chain.
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Variation and DNA

  • Genetic information is passed down by the sex cells(gametes) from which the offspring develop. 
  • In human beings, each gamete contains 23 chromosomes, so when the male and female gamete fuse the embryo contains the full 46 chromosomes.

The nucleus of a cell contains chromosomes. Chromosomes carry genes that control the characteristics of the body. The human cells contains 23 pairs of chromosomes.

Differences in the characteristics (Body weight, height, skin colour, academic or athletic prowess etc..) of different individuals of the same kind may be due to differences in:

  • Genetic causes: The genes they have inherited.
  • Environmental causes: The conditions in which they have developed.
  • Or both..

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Sexual reproduction happens when a male gamete and a female gamete join. This fusion of gametes is called fertilisation. Sexual reproduction allows some of the genetic information from each parent to mix, producing offspring that resemble their parents, but are not identical. Animals and plants can reproduce using sexual reproduction.

Asexual reproduction only needs one parent, and because of this, there is no fusion of gametes or mixing of genetic information. The offspring are clones.

  • X-shaped chromosomes have to identical halves.
  • So each chromosome splits down the middle to form two identical sets of half chromosomes.
  • A membrane forms around each set and the DNA replicates itself to form two identical cells with complete sets of X-shaped chromosomes.

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Tissue culture: This is where s few plant cells are put in a growth medium with hormones, and they grow into new plants plants, clones of the parent plant. These plants can be made quickly, in very little space and all year.

Cuttings: This is where you take cutting from a good parent plant, and then plant them to produce genetically identical copies (clones) of the parent plant. These plants can be produced very quickly and cheaply.

Embryo transplants: Farmers produce cloned offspring from their best (prize) bull and cow. Sperm cells are taken from a 'good bull' and egg cells are taken from a 'good cow'. The sperm is artificially fertilised with an egg cell. The embryo that develops is then split many times (to form clones) before any cells become specialised. These cloned embryos are implanted into lots of other cows where they grow into baby calves (which are genetically identical to each other).

Adult cell cloning: Involves taking an unfertilised egg and removing its nucleus (the genetic material) and inserting a complete set of chromosomes from an adult body cell ino the 'empty' egg cell. The egg cell is then stimulated by an electric shock, which makes it divide. Then gets implanted into a surrogate mother when the embryo is a ball of tiny cells.

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Genetic Engineering

Genetic engineering uses enzymes to cut out and paste genes: A useful gene is "cut" from one organism's chromosome using enzymes, Enzymes are then used to cut another organism's chromosome and then insert the useful gene.

Scientists use this method for all sorts of things, (eg. the human insulin gene can be inserted into bacteria to produce human insulin) including animals and plants:

  • GM crops have their genes modified, eg. to make them resistant to viruses, insects or herbicides (chemicals used to kill weeds).
  • GM crops can increase the yield of a crop, making more food.

Pros and Cons: GM crops could..

  • affect the number of weeds and flowers (and so the population of insects).
  • be engineered to contain nutrients that's missing in some people's diets.
  • let the transplanted genes get out in the natural environment, eg. the herbicide gene could get picked up by weeds making a new variety that does't get affected by weed killer.

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Darwin's idea...

Natural selection: A natural process where organisms with genetic characteristics best suited to their environment survive to reproduce and pass on their genes to the next generation.

Not everyone agreed with Darwin:

  • It was against religious beliefs.
  • There wasn't enough evidence to back up his theory.
  • He couldn't give a good explanation for why these new useful characteristics appeared or how organisms passed them on to their offspring.

Lamrack argued that if a characteristic was used alot by an organism it would become more developed during its lifetime, and that these characteristics would be then passed down to their offspring.

Mutations: A change in an organisms DNA.

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Benjamin Allen

Hope this helps anyone doing B1.


thank you this really helped :)


This was extremely helpful, thank you! :)


Thank you very much.its very understandable notes _


This is soooo usefull.  Your a savour. Thank you

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