AQA GCSE Biology 2

I made these notes for my B2 revision, they're pretty much the same as the AQA GCSE Biology revision guide, but I made them so it was easier to understand in a format that I responded to. Hope this helps anyone with upcoming exams and hope its useful :-)

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  • Created on: 19-05-11 09:07
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B2 AQA GCSE Biology
Chapter One : Cells
Animal and plant cells have structures that enable them to function and do their jobs.

Plant cells have some structures that you will not find in an animal cell.

Similarities;

A nucleus (the brain of the cell) is used to control the…

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When an egg is fertilised, it begins to grow and develop.

At first, there's just a growing ball of cells. Then as the organism gets bigger, some of the cells
change and become specialised.

Some e.g's of specialised cells:

Xylem
Root hair cells
Nerve/sperm cells




2 | Biology Unit 2

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Molecules move randomly because of the energy they have.

Diffusion is the random movement of molecules from an area of high concentration to an area
of lower concentration.

The larger the difference in concentration, the fast the rate of diffusion.
E.g's are:

the diffusion of oxygen into the cells of…

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Chapter Two : How plants produce food
The equation for photosynthesis is


carbon dioxide + water (+ light energy) glucose + oxygen


Carbon dioxide taken in by leaves. Water taken up by roots.

Chlorophyll traps the energy needed for photosynthesis.

Glucose (a carbohydrate) is produced; oxygen is given off as…

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If there is too little CO2, then the rate will SLOW DOWN. May be limited in enclosed spaces, e.g. in a
greenhouse on a sunny day or in a rapidly photosynthesising rain forest.




When growing plants, there is no point increasing one of these factors if the photosynthesis is still…

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Organism Number Biomass ­ dry mass in g
Oak tree 1 500,000
Aphids 10,000 1,000
Ladybirds 200 50




Pyramid of numbers Pyramid of biomass



You can draw pyramids of biomass to scale to give an even more accurate picture.

Not all of the food eaten can be digested, so energy…

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Keeping the animal at a warmer temperature so it doesn't use as much energy from food to
keep itself at a constant temperature



Detritus feeders (such as some types of worm) may start the process of decay by eating dead animals or
plants and producing waste materials. Decay organisms then…

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Too high a temperature will change the enzymes shape, and it will no longer work. We say it has been
destroyed or denatured.

Enzymes can catalyse the build up of small molecules into large molecules or the break down of large
molecules into small molecules.

Enzymes lower the amount of…

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Amylase (a carbohydrase) is produced by the salivary glands, the pancreas and the small
intestine. Amylase catalyses the digestion of starch into sugars in the mouth and small intestine.
Protease is produced by the stomach, the pancreas and the small intestine. Protease catalyses
the breakdown of proteins into amino acids…

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Chapter Five : Homeostasis
The processes in your body that help to maintain a constant internal environment are known as
homeostasis.

Just think of the different temperatures we experience:




Your body also has to cope with varying rates of respiration needed in different activities:




Carbon dioxide is a waste product…

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