Natural Selection

Question 1

Selection pressure definition?

Answer 1

the environmental factors that limit the population of a species, such as predation, disease and competition.

Question 2

Definition of evolution?

Answer 2

The formation of new species from pre-existing species over time, as a result of changes to gene pools and allele frequencies from generation to generation

Question 3

What are the 3 types of selection?

Answer 3

Stabilising selection
Directional selection
Disruptive selection

Question 4

What is stabilising selection?

Answer 4

Favours the average phenotype and removes extremes, maintaining average values

Question 5

Example of stabilising selection?

Answer 5

Human birth weight

Question 6

Directional selection?

Answer 6

Favours individuals with a phenotype at one extreme, causing a shift in a populations traits over time e.g. antibiotic resistance

Question 7

Disruptive selection?

Answer 7

Natural selection which maintains high frequencies of 2 different sets of alleles

Question 8

What does disruptive selection cause?

Answer 8

Polymorphism- the continued existence of 2 or more distinct phenotypes in a species
Occurs in an environment which shows variation

Question 9

Example of disruptive selection?

Answer 9

Birds that live on the Galápagos Islands- use their beaks to forage for differnt sized seeds
Size of the beak is either small or large