Slides in this set
· Taking measurements of individuals from the population
that is being sampled.
· In theory these samples should be representative but are
· Sampling Bias: The investigators may have deliberately
or unwittingly made unrepresentative choices e.g.
avoiding muddy areas when sampling buttercups.
· Chance: Even if a sampling bias is avoided
They may be unrepresentative by pure chance.…read more
Preventing a Sampling Bias
· 1. Divide study area into grid and give each square co-
· 2. Generate random numbers to select co-ordinates of
· 3. Take samples at each co-ordinate
· We can minimise the chance of bias by:
· Using a large sample size: Means there is a smaller
probability that chance will influence result
· Analysis of data collected: Use statistics to analyse
how much chance has influenced the results.…read more
Causes of Variation (Genetic
These are due to the different genes each individual has
and genetic variation arises as a result of:
Mutations: These may or may not
Be passed to the next gen.
Meiosis: This nuclear division forms
Gametes by mixing up genetic material.
Fusion of Gametes: Variation occurs when the genetic
material of the mother fuses with the genetic material of the
father during sexual reproduction.…read more
Causes of Variation
The environment affects how an individuals genes
are expressed. Although genes set limits the
environment determines where within the limits
e.g. Hair colour may be lighter in the sun
Height may be shorter because of
Weight may be heavier/lighter due to diet
... a plant may not grow as tall as it should due to
environmental factors such as temperature, rainfall,
sunlight and pH.…read more