4.2

Question 1

What does ‘survival of the fittest’ mean?

Answer 1

Organisms that are best adapted are more likely to survive

Question 2

What is evolution?

Answer 2

a change in allele frequency in a population over time (generations).

Question 3

The Darwin – Wallace theory for natural selection stages

Answer 3

• A population contains natural genetic variation with new alleles created through mutations.
• A change in the environment causes a change in the selection pressures acting on the population.
• An allele now becomes favorable.
• Organisms with this allele are more likely to survive, reproduce and produce offspring.
• The offspring are more likely to have the allele and can pass the allele on. The allele becomes more common in the populati

Question 4

What is stabilizing selection?

Answer 4

When the average / normal is selected for

Question 5

What is a selection pressure?

Answer 5

A factor that determines how well organisms survive

Question 6

What is a gene pool made up of?

Answer 6

ALL the alleles in the population

Question 7

What has to be in place for the Hardy–Weinberg equation to work?

Answer 7

• for genetic drift not to occur
• there are no mutations
• there is random mating with respect to genotype
• there is no natural selection
• there is no movement in or out of the population.

Question 8

The ability of a population to adapt to new conditions depends on what?

Answer 8

• the strength of the selection pressure
• the size of the gene pool
• the reproductive rate of the organism

Question 9

Can an organism be perfect?

Answer 9

• No

- The environment may change, and there will then be a time lag before the organism can adapt by natural selection

Question 10

Why is it good for a species to be highly specialized?

Answer 10

because it helps avoid competition with similar species

Question 11

Why is it bad for a species to be highly specialized?

Answer 11

because it makes the species vulnerable if the environment changes

Question 12

How do new species form?

Answer 12

• For new species to arise there has to be reproductive isolation.
• A group of species must be isolated from the rest of the species, so that they accumulate different allele frequencies.
• The formation of a new species is called speciation.

Question 13

How are new species are made step by step IGNS?

Answer 13

• Reproductive isolation – two populations of a species become separated, e.g. geographically by a river.
• Genetic variation – each population has a wide range of alleles that control their characteristics.– Natural selection – in each population, the alleles that control the characteristics which help the organism to survive are selected and allele frequencies change.
• Speciation – the populations become so different that successful interbreeding is no longer possible.