AQA Biology Unit 2

biology gcse unit 2 higher tier notes

  • Created by: Hannah
  • Created on: 09-01-11 17:22

Adaptation (Hot and Cold)

Animals and plants have adapted over time to different living conditions.

Animals like the Arctic fox are adapted to survive the cold, the fox has a small compact shape so the surface area is smaller and a layer of fat under its fur for insulation

Camels however, are adapted for life in a desert. Fat is stored in the hump and can be converted into metabolic water, there is no insulating fat under the skin, they have long legs which keep it above hot ground, can drink 20 litres of water in a few minutes and so their stomach can also hold 20 litres of water. They also have very little urine

Plants like the cactus have adapted to hot weather by being able to conserve & store water they do this because they have a swollen stem to store water, thick waxy cuticle to reduce water evaporation, spines instead of leaves to reduce water loss and shallow roots to absorb water when it rains.

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Adapt or Die

All living things have one main purpose in life: to survive. They do ths by competing for 3 main things . Food . territory . a mate

An adaptation helps an animal to survive for example Moles survive by digging through the ground to find food. they have poor eyesight but an excellent sense of smell which helps them survive. 

Plants whihc are better adapted will ave leaves that don't over lap each other, this is so photosynthesis is carried out more effectivly becasue the leaves aren't blocking one anothers sunlight and a large root system so more water can be collected

Special adaptations such as poisonous chemicals help ward off other animals, often brightly coloured animals are poisionous and so won't be eaten by predators. This trait is obviously very useful and so other animals mimic the trait of a poisionous animal such as the coral snake (poisonous) and the kingsnake (mimic)

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Animal and Plant Cell

diagram.jpg animal cell 

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Animal and Plant Cell

imgres.jpg plant cell 

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Two Ways to Reproduce

Living things need to reproduce they do this by passing genes from one generation to the next

Sexual reproduction means that the offspring gets genes from both parents meaning it will inherit features from both parents

Asexual reproduction means that the offspring are clones of the parent as they have exactly the same genes as the parent does meaning they have the same genetic information

Sexual reproduction works when female gametes (sex cells) called eggs fertilize with male gametes called sperm and then eventually form a zygote

Asexual reprodction works either an individual splits in 2 like baceria does or a part divides off, and this is the offspring. So no gametes are involved.

The advantages of Asexual reproduction is only one parent is required and thy are all clones however because there is no variation if a new disease struck they would all be killed.

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offspring inherit characteristics from their parents because of genes. Genes are linked together in long chains called chromosomes. The nucleus of a cell normally has 2 sets of chromosones in it. genes and chromosones are made from a chemical called DNA. 

One set of genes comes from our mother's egg cell the other from our fathers sperm cell when the two gametes fertilize the new cell now has two sets of chromosomes 

In a human we have 46 chromosomes this is the diploid number the haploid number is half so a humans haploid number is 23. So we give 23 chromosomes to our infant and our partner also gives 23

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The most obvious way to produce new plants is by planting seeds, unfortunately these are produed by sexual reproduction so might not be exactly how you want them to be

Taking cuttings is a great soloution they will be exactly the same as the parent plant. To take a cutting you have to get a healthy plant and cut off a small bit of stem making sure the leaves are on the stem then you ip the end of the stem into hormone rooting pwder then put the stem into a flowerpot full of damp compost and eventually this will grow into a new plant.

The advantages of taking cuttings are: the new plants are all clones, they will all grow at the same rate, making cuttings is easy and cheap.

You can take cuttings from the stem, leaves and roots of a plant

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tissue culture

If you cut off the very top of a carrot and put it in water after a few days it would of grown a stem and leaves. Tissue culture is a bit like this, it is a way of growing plants from small groups of cells. You place the cells on a special jelly which contains all the nutrients it needs to grow and the cells divide and grow. Eventually you will have lots of identical plants. They have the same genes so they are clones Tissue culture and cuttings only happen in plants 

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Embryo transplant is basically  when an egg and sperm are fertilized then you get  the zygote from a female cow for example and letting it divide a few times so you have a ball of cells then splitting those cells apart so the separate cells each divide to form a new ball of cells. You then transplant a ball of cells into a surrogate mother  and identical calves are produced. These calves are clones of each other.

Adult cell cloning is when the nucleus of an egg is removed (enucleated) and replaced with the nucleus of another body cell ie a liver cell. When this new cell eventually develops into an individual it will be a clone and will have the same genes as the liver cell for example had. This new cell will then divide into a ball of cells which will be planted into a surrogate mother.

 If someone has been badly burnt they might need a skin graft. This means skin is 'harvested' from a donor and transplanting it to the burns victim. Sadly, the body's immune system can reject the skin graft if it does not recognize it. An other option is to grow new skin, undamaged skin is taken from the victim and then the cells are able to divide and grow because they are given the raw materials the skin can then be transplanted onto the victim when big enough

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Clones .

Cloning is a very controversial subject and many are either for or against it. Some say cloning is unethical because you are playing God also the cloned individual might not be wanted but instead just a scientific experiment.

If a parents child had died scientists are trying to discover if they could clone that child. However, cloning involves many implications and problems. You might have to use hundreds of embryos before one finally works. In my opinion this is unmoral because those embryos are the start of a new life which has now been destroyed.

A clone is an exact copy in its genetic makeup but not in its personality so a clone will not be exactly the same. 

Cloning is also very expensive and many countries such as the UK have banned the practice of cloning on humans but have permitted the practice of cloning on animals for scientific experiments. 

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genetic engineering

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This is pretty good so far, maybe add a bit of colour to it as you go along:)



Hardly enough information, not covered all of the subjects, good information on the sections you have covered.



This is mostly unit 1 not 2

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