Variation

Question 1

Interspecific variation

Answer 1

Between species

Question 2

Intraspecific variation

Answer 2

• within species
• same genes, different alléles
• May be caused by genetic or environmental factors (can change phenotype)
• mutations may result in the change or loss of a protein

Question 3

Sampling

Answer 3

• taking a small sample of the population

* multiple measurements allow reliable, valid conclusions

Question 4

How to take a sample

Answer 4

Take a selection of individuals from the population that will provide an accurate representation of the entire population; normally done by random sampling

Question 5

Issues with sampling

Answer 5

sampling bias -> investigators may be making unrepresentative choices, either deliberately or unwittingly

chance -> individuals chosen may not be representative

Question 6

Random sampling

Answer 6

• aims to prevent bias and eliminate human involvement in choosing samples

1) divide the area of study into a grid
2) use a random number generator to chose coordinates
3) take samples from the intersection of coordinates

Question 7

Removing chance

Answer 7

• large sample size > 20
• smaller propability of chance influencing result, less anomalies -> increasing reliability
• use statistical tests to analyse data, determining extent of chance’s influence

Question 8

Continuous variation

Answer 8

• the full range of variables between 2 extreme values
• data is normally distributed in a Normal Distrubution
• mean, mode, median are equal
• e.g. height, weight, length, size
• phenotype either polygenic, causes by environmental factors, or both

Question 9

Normal Distribution

Answer 9

Bell shaped curve

Question 10

Discontinuous variation

Answer 10

• aka discrete
• unaffected by environment, controlled by few genes
• variables assigned to clearly defined categories/distinct groups
• data usually represented as a bar graph
• e.g. sex, blood group, colour

Question 11

Standard deviation

Answer 11

• the distance from the mean to the point where the curve changes from concave to convex
• 68.2% of measurements lie within +-1 standard deviation
• 95% lies within +-1.96
• gives an indication of the range of values either side of the mean