Revison careds for my biology exam in june B3, B4, B5

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B1 Fitness And Health

The Circulatory System

The chirculatory system carries oxygen and glucose to all your body's cells so that energy can be released through aerobic respiration.

Blood Pressure

Blood pressure is a measure of the force of blood per unit area as it flows through the arteries. It's measured in mm Hg (millimeters of mercury)

  • Systolic blood pressure (the first number) is the pressure in your arteries when your heart contracts ( when it is at it;s highest)
  • Diastolic (blood pressure the second number) is the pressure in your arteries when your heart relaxes.
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B1 Human Health and Diet

Balanced Diet

How to calculate BMI (BMI=Mass(kg) divided by Height (m)2)

How to calculate your estimated average daily requirement (EAR)

(EAR= 0.6 x Body Mass (kg) )


If pathogens enter the body, white blood cells start fighting the invasion. the symptoms of a disease are caused by pathogens damaging cells and producing toxins (poisons) before the white blood cells can destroy them.

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B1 The Nervous System

The Nervous System

Your nervous system allows you to react to your surroundings and coordinate your behaviour. It comprises the central nervous system (CNS) and the peripheral nervous system (PNS) which included receptors and neurones

What receptors do we have?

  • Light receptors in your eyes
  • Sound receptors and balance receptors in your ears
  • Taste receptors on your tongue
  • Smell receptors in your nose
  • Touch,Pressure,Pain and Temperature receptors in your skin.
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The Nervous System

The nervous System

Neurones (nerve cells) are specially adapted cells that can carry a nerve impulse. Nerve impulses are electrical messages/signals and are carried along the axon (the long thin part of the cell)

There are three types of neurone:

  • Sensory Neurones carry nerve impulses from the receptors to your brain
  • Relay Neurones make connections between neurones inside your brain and your spinal cord
  • Motor neurones carry nerve impulses from your brain to your muscles and glands
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B1 The Eye

The Eye

Your iris (the coloured part of your eye) controls the amount of light that enters your eye). The rays of light are refracted by your cornea and the lens focuses light onto the retina so the rays come together at a signal point and produce a clear image on your retina. The light sensitive receptor cells on your retina then cause the nerve impulses to pass along sensory neurones in the optic nerve to your brain. The retina contains the light sensitive receptors. some are sensitive to colour.

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B1 Staying In Balance

Temperature Control

Enzymes in your body work best at 37 degrees Celsius so it is essential that your body remains at this temperature. If your body temperature becomes to high blood vessels widen and the blood flows closer to the skin so heat can be transferred to the environment. Getting to hot can be dangerous if too much water is lost through sweating the body becomes dehydrated this can lead to heat stroke and even death. If the body temperature falls too low blood vessels constrict and the blood flow near the skin is reduced, sweating stops and muscles start making contractions, commonly known as shivers, these contractions need energy from respiration, and heat is released as a by-product. Hypothermia occurs when the body's temperature falls below 35 degrees Celsius this can cause unconsciousness and sometimes even death. 

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B2 The Carbon Cycle


The constant recycling of carbon is called the carbon cycle

  • Carbon dioxide is removed from the atmosphere by green plants for photosynthesis
  • Plants and animals respire, releasing carbon dioxide into the atmosphere.
  • Soil, bacteria and fungi (decomposers) feed on dead plants and animals causing them to break down decay and release carbon dioxide into the air ( the micro-organisms respire as they feed passing carbon compounds along the food chain) This decay process makes elements available again to living organisms.

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B2 The Nitrogen Cycle

The Nitrogen Cycle

The air is made up of approximately 78% nitrogen, Nitrogen is a vital element used in the production of proteins which are needed for growth in plants and animals a lot of nitrogen is stored in the air but animals and plants can't use it because it's so un reactive

  • Plants absorb nitrates from the soil to make protein for growth 
  • Animals eat plants and use the nitrogen to make animal protein feeding passes nitrogen compounds along the food chain
  • Dead animals and plants are broken down by decomposers, releasing nitrates back into the soil.
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B2 Mutualistic Relationships

Mutalistic Relationships

In mutualistic relationships, two organisms form a relationship from which both organisms benefit.

E.G, oxpecker birds live on buffalo's backs,

The oxpecker gets a ready supply of food from flies and ticks on the buffalo's skin, 

The buffalo also benefits as the birds get rid of the pests and provide an early warning system hissing when lions or other predators approach,

Organisms performing this function such as oxpecker birds are known as 'cleaner' species.

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B2 Adaptations


Adaptations are special features or behaviours that make an organism particularly well suited to its environment. 

Examples of Adaptations.

Cold Environment:

  • Being well insulated to reduce heat loss
  • having a small surface area to volume ratio to prevent heat loss.
  • behavioural adaptations (hedgehogs hibernate) 

Hot and Dry Environment:

  • Body fat so there is little insulation under the skin which keeps it cooler
  • Drinks many litres of water at one time and stores the extra water in the blood
  • Behavioural adaptations so instead of hunting in the day they hunt at night to keep them cooler 
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B2 Natural Selection

Natural Selection

If animals and plants are better adapted to their environment they are more likely to survive this theory is called natural selection who was first put forward by Charles Darwin. Evolution is the specialisation of a population over many generations to become better adapted to its environment. Here are 4 points to Remember.

  • Individuals within a population show natural variation (differences between their genes)
  • There is competition between individuals for certain limited resources(food+mates) and keep population sizes constant ('struggle for survival' and weaker individuals die)
  • Individuals that are better adapted to the environment are more likely to survive this is termed 'survival of the fittest'
  • These survivors will therefore pass on their 'successful genes' to their offspring resulting in improved organism.
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B2 Population and Pollution


As more fossil fuels and oils are burned to produce energy a greater amount of pollution is produced in particular:

  • household waste and sewage
  • sulfur dioxide and carbon dioxide

Pollution can affect the number and type of organisms that can survive ( dark peppered moths will survive in polluted areas but pale ones will be eaten as they are not camoflaged.

Carbon footprint is the term used to refer to the amount of greenhouse gases a person or event is responsible for emitting in an amount of time the amount will depend on the persons lifestyle.

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B2 Pollution And Population

Ozone Depletion

Ozone is a natural gas found high up in the earth's atmosphere, it prevents too many harmful ultraviolet (UV) rays reaching the earth. Scientists have found out the ozone layer is becoming thinner (it is depleting) CFC'S (chlorofluorocarbons) could be held responsible. CFC'S are usually found in factories, fridges and aerosol cans. The consequence could be a rise in skin cancer.

Acid Rain

Acid rain is caused by burning fossil fuels which release acid gases like sulfur dioxide and nitrogen oxides, These dissolve in rainwater to form acid rain, this leads to metals corroding and dissolving of rocks and statues, destruction of forests and lakes becoming acidic this can cause fish and other wildlife to die.

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B2 Global Warming

Global Warming

The atmosphere keeps the earth warm this is known as the green house effect:

  • Heat energy from the sun is reflected from the earth's surface back out towards space.
  • When it reaches the atmosphere some rays can pass through but others are trapped in the carbon dioxide layer: These trapped rays keep the earth warmer than it would be otherwise and so allow life to exist.

The amount of carbon dioxide in the atmosphere has increased which has lead to more of the energy being reflected back this is known as 'global warming' because the earth is gradually getting hotter and this causes climate change.

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B2 Sustainability

Sustainable Development

A sustainable resource is one that can be used and replaced so it isnt used up completely.( if you cut down a tree you plant a new one) 

  • The size of fish nets have been increased to prevent young cod being caught before they reach breeding age

Education is important so that local people understand the importance of conservation. Sustainable development can help protect endangered species ( quotas can be set for whaling)

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