AS AQA Biology unit 2- Variation

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  • Created by: Ruth Butt
  • Created on: 23-05-13 10:23

Terminology

Interspecific Variation- Variation between species
Intraspecific Variation- Variation within species

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Making measurements

Sampling sometimes contains error and may not be representative, two main reasons why data may be unrepresentative are: Sampling bias where scientists will either purposely or accidentally make biased choices, e.g. when taking a sample of buttercups, they are likely to avoid a muddy area rather than a dry area. Chance where individuals chosen may have been down to chance, making it unrepresentative, e.g. 50 buttercups chosen are the 50 tallest.

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Reducing sampling bias

The way to eliminate or reduce any chances of bias or chance is to use random sampling. This can be done either by using a random number grid or random number generator. Also using a large sample size, the probability of chance occurring will decrease. Also by analysing the data collected we can spot any anomalies or other unusual patterns.

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Causes of variation

Genetic differences are due to variation in genes each inidividual possesses. Genetic variation arises due to mutation, meisos (nuclear division when a gamete is formed) and the fusion of gametes (when fertilisation occurs, and gametes fuse). 

Enviromental influences e.g. a buttercup has a gene allowing it grow tall, but because it germinates in poor light, it will be short. 

In most cases, variation is a result of environmental and genetic factors...

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