Investigating Variation

Question 1

What is variation?

Answer 1

The difference that exists between individuals

this can occur between species and within species

Question 2

What is genetic diversity within a species called?

Answer 2

Introspecific

Question 3

What is genetic diversity between a species?

Answer 3

Interspecific

Question 4

What could be the possible causes of variation?

Answer 4

• Caused by genetic factors
  
  • different species have different genes causing variation between species
  • Individuals of the same species have the same genes, but different alles - causing variation within species
• Environment e.g climate food lifestyle
• Could be combination of genetic and environmental factors e.g genes can determine how tall an organism is but the nutrient available tells how they actually grows

Question 5

What techniques to compare genetic diversity?

Answer 5

• Comparing DNA sequence
• mRNA sequences
• Amino acid sequences

Question 6

What type of sample chosen when investigating variation?

Answer 6

Usually look at a sample of the population not the whole thing

for species it would be too time-consuming or impossible to catch individuals in the group

Sample are used as models for the whole population

Question 7

Why does the sample have to be random?

Answer 7

• Avoid bias
  
  • Divide field into grid and use random number generator to select coordinates
• To analyse results statistically making more confident that results are true to reflect whats going on population rather due to chance

Question 8

Why would you sample a large size?

Answer 8

Data should be representative of the whole population

Enough data to do a statistical test

Question 9

What is the mean?

Answer 9

Average of values collected in sample

Question 10

What does this show?

Answer 10

Most sample will include values on either side of the mean

called normal distribution - symmetrical around the mean

Question 11

What is the standard deviation?

Answer 11

Average variation of data away from the mean

or

measure of spread of values about the mean

Question 12

Analysis of SD

Answer 12

Question 13

Properties of SD

Answer 13

• 9+- 3
  
  • Mean is 9
  • SD is 3
  • Spread between 6 and 12
• Large SD means values in sample vary a lot - small standard SD is most data is around mean value - varies a little

Question 14

What does this show?

Answer 14

If overlap - not significantly different

If not overlap - significantly different

longer the bar, longer the standard deviation more spread out of sample data is from mean

Question 15

Formula of SD

Answer 15

Question 16

List two reasons why a sample may not be representative of the population as a whole

Answer 16

Sampling bias

Chance variation: chosen may be pure chance not representative

Question 17

Explain how sampling bias may be prevented

Answer 17

By using random sampling - efficiently using a computer to generate sampling sites

Question 18

Distinguish between

mode

mean

median

Answer 18

Mean : Sum of set of values divided by number of terms

mode: single value that occurs most often
median: central/middle value when numbers arranged in ascening order