Variation

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What is discontinuous variation?
Where the distinction between characteristics is clear-cut, such as the distinction between being hairy or hairless.
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What is continuous variation?
Where there is a range of variation, such as tall to short.
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What is a phenotype?
A physical/observable characteristic.
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What causes discontinuous variation?
Differences in a single gene.
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What is shown in a normal distribution curve?
In most cases, the interaction of different genes causes the majority of individuals to lie near the middle of the range, with a few at the extremes.
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What is the standard deviation?
A measure of how much measurements are spread out from the mean.
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What is variation?
The many differences between individuals of the same species.
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What 2 factors can variation result from?
Environmental and genetic.
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Name 2 reasons that measurements may not be representative.
Sampling bias and chance.
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Explain how sampling bias can affect representativeness.
The selection process may be bias - investigators may make unrepresentative choices deliberately or even by accident.
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Explain how chance can affect representativeness.
Even if sampling bias is avioded, the individuals chosen may not represent the whole population purely by chance.
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How can sampling bias be eliminated?
By using random sampling, in order to eliminate, as much as possible, human involvement in chosing samples.
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How can you minimise the effect of chance?
Using a large sample size and analysing data by accepting that chance will play a part, and using statistical tests to determine the extent to which chance has influenced the data.
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What three genetic differences can affect variation?
Mutations, meiosis and fusion of gametes.
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How do mutations cause genetic differences?
Sudden changes to genes and chromosomes may, or may not, be passed on to the next generation.
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How does meiosis cause genetic differences?
This form of nuclear division forms the gametes, and mixes up genetic material before it is passed into the gametes, all of which are therefore different.
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How does the fusion of gametes cause genetic differences?
In sexual reproduction, the offspring inherit some characteristics from each parent and are therefore different from both of them. Which gamete fuses at fertilisation is also random, further adding to variation.
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How can variety in asexually reproducing organisms be increased?
By mutation.
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Card 2

Front

What is continuous variation?

Back

Where there is a range of variation, such as tall to short.

Card 3

Front

What is a phenotype?

Back

Preview of the front of card 3

Card 4

Front

What causes discontinuous variation?

Back

Preview of the front of card 4

Card 5

Front

What is shown in a normal distribution curve?

Back

Preview of the front of card 5
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