AQA Biology Unit 2 Variation

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What is interspecific variation?
This is when there are differences between members of different species, e.g. a cat and a dog
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What is intraspecific variation?
This is when there are differences between members of the same species e.g. every human looks different.
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When sampling variation data, what factors must be considered?
sample size and no biased data
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Advantages of random sampling?
Removes biased, eg placing quadrat on a grid in a random fashion by using a random number table to select each coordinate.
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Why should a large sample size be used?
Allows for a more reliable mean, reduces the effect of extreme values and helps to identify anomalies.
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What causes variation?
1. genetic factors 2. Differences in environment 3. Combination of both
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How is variation caused by genetic factors alone?
1. Small number of distinct phenotypes 2. No intermediate phenotypes 3. Variation is due to many alleles of a single gene
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Examples of variation causes by genes?
Eye and hair colour, blood group
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What is a phenotype?
A characteristic that is due to a gene e.g. brown is my phenotype for the eye colour gene.
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How is variation caused by both genetic and environmental factors?
Phenotypes have a continuous range rather than discrete grouping. There are no separate categories e.g. blood type has separate categories whereas height is continuous. Factors such as height or mass are polygenic (controlled by more than one gene).
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How might the environment affect height or mass?
Lack of food or particular food types will lead to less growth, regardless of a persons phenotype.
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Why use twins in an investigation about variation?
Identical twins can show genetic influence as they have the same genetic information. So any differences between them is caused by the environment. Whereas non- identical twins show a non-genetic or environmental influence.
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Main causes of genetic variation?
1. Mutation 2. Meiosis:- crossing over and independent segregation of homologous chromosomes 3. Random fusion of gametes at fertilisation
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How does mutation of a gene occur?
1. Change in the base sequence of DNA leads to a change in amino acid sequence ( which is the primary structure of a protein). 2. This mean thats hydrogen/ionic/disulphide bonds between amino acids are different.
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How does mutation of a gene occur? (continued)
3. Change in primary structure causes change in the tertiary structure of a protein 4. If the protein is an enzyme, the substrate can no longer bind so no E-S complexes are formed.
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How does mutation cause variation?
Changes in the base sequence give rise to new alleles which code for different gene products e.g. polypeptides
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What is crossing over and how does it lead to genetic variation?
Crossing over mixes alleles of genes of homologous pairs during meiosis. This leads to new combinations of alleles and exchange of genetic material.
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What is independent segregation and how does it cause genetic variation?
This is when the paternal and maternal chromosomes line up randomly upon fertilisation. This leads to many different combinations ( 2 to the power of n when n is the number of homologous pairs)
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How does the random fusion of gametes at fertilisation cause variation?
As a result of meiosis, all gametes are genetically unique. When they fuse, no two fertilised eggs (zygotes) can have the same genotype except twins.
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What calculation can be used to show variation?
Standard deviation formula
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Other cards in this set

Card 2

Front

What is intraspecific variation?

Back

This is when there are differences between members of the same species e.g. every human looks different.

Card 3

Front

When sampling variation data, what factors must be considered?

Back

Preview of the front of card 3

Card 4

Front

Advantages of random sampling?

Back

Preview of the front of card 4

Card 5

Front

Why should a large sample size be used?

Back

Preview of the front of card 5
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