18.3: Natural Selection

Question 1

What are selection pressures

Answer 1

Environmental factors that limit the population of a species

Question 2

What are examples of selection pressures

Answer 2

Predation
Speciation
Competition

Question 3

What do selection pressures determine

Answer 3

Selection pressures determine allelic frequency

Question 4

How do selection pressures vary

Answer 4

Selection pressure vary from time to time and place to place

Question 5

What factors does evolution by natural selection depend on

Answer 5

1. Organisms producing more offspring than can be supported by the available supply of food, light and space
2. There is genetic variety within the populations of all species
3. A variety of phenotypes that selections operates against

Question 6

What is the death rate of even the slowest breeding individuals

Answer 6

Very high

Question 7

What has evolved to counteract high death rates

Answer 7

High reproductive rates

Low reproductive rates but a high degree of parental care

Question 8

How do high reproductive rates counteract high death rates

Answer 8

High reproductive rates ensure a sufficiently large population survives to breed and produce the next generation

Question 9

What do high reproductive rates compensate for

Answer 9

High deaths rates as a result of predation, disease and competition for food.

Also natural disasters e.g. Flooding, fires, earthquakes etc

Question 10

How does a high level of parental care maintain the size of a population

Answer 10

High parental care results in a lower death rate of a population of a species, maintaining their population size as they can successfully breed

Question 11

What is the link between over-production and natural selection

Answer 11

When there are too many offspring for the available resources, there is competition between the individuals - Intraspecific competition

Question 12

What can cause greater intraspecific competition

Answer 12

An increase in the number of a population

Question 13

Which individuals will be most likely to survive

Answer 13

The individuals of a population that are best suited to prevailing conditions, this is because they are better adapted

Question 14

What is the consequence of better suited individuals surviving

Answer 14

They will be more likely to breed and therefore pass on their more favourable allele combinations to the next generation

Question 15

What is the result of large genetic variation within a population

Answer 15

There is a greater chance of individuals having the combination of genes needed to survive any new set of circumstances

Question 16

What is the result of small genetic variation within a population

Answer 16

Populations showing little genetic variation are often more vulnerable to new disease and climate change, considering they have a smaller gene pool and are therefore less likely to produce favourable combinations of alleles

Question 17

What is the link between population size and genetic variation

Answer 17

The larger the size of a population, the larger the genetic variation within it.

This offers a greater chance of producing a combination of alleles that leads to a phenotype which is more advantageous for survival