10.5- QUANTITATIVE INVESTIGATIONS OF VARIATION

Question 1

What is interspecific variation?

Answer 1

if one species differs from another

Question 2

What is intraspecific variation?

Answer 2

members of same species differing from each other

Question 3

What does sampling involve?

Answer 3

taking measurements of individuals, selected from population of organisms which is being investigated

Question 4

Reasons why measurements may not be representative (2)

Answer 4

sampling bias- selection process may be biased
investigator may be making unrepresentative choices, either deliberately or unwillingly

chance- individuals chosen may by pure chance not be representative

Question 5

What is the best way to prevent sampling bias?

Answer 5

to eliminate, as far as possible, any human involvement in choosing samples

Question 6

How can eliminating human involvement in choosing samples achieved?

Answer 6

random sampling

Question 7

An example of random sampling (3)

Answer 7

divide study area into grid of numbered lines e.g. by stretching two long tape measures at right angles to each other

using random numbers, from table/ generated by computer, obtain series of coordinates

take samples at intersection of each pair of coordinates

Question 8

How to minimise effect of chance from sampling process? (2)

Answer 8

using large sample size

analysis of data collected

Question 9

How can using a large sample size minimise the effect of change from the sampling process?

Answer 9

the more individuals selected, smaller the probability that chance will influence result + less influence anomalies will have
greater the sample size, more reliable data will be

Question 10

How can analysing the data collected minimise the effect of change from the sampling process?

Answer 10

tests allow us to decide whether any variation observed is result of chance or more likely to have some other cause

Question 11

For a normal distribution curve, what shape is typical for a feature that shows continuous variation?

Answer 11

bell-shape

Question 12

Normal distribution curve- what is the standard deviation a measure of?

Answer 12

width of curve

Question 13

Normal distribution curve- what does the SD give an indication of?

Answer 13

range of values either side of mean

Question 14

Normal distribution curve- what is a standard deviation?

Answer 14

distance from mean to point where curve changes from being convex to concave

Question 15

Standard deviation equation meaning?

(sq root) Σ(x - x_)^2 / n - 1

Answer 15

Σ- sum of
x- measured value
x_ - mean value
n - total number of values in sample