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