8.1 - Natural Selection

Question 1

Directional selection

Answer 1

Selection that favours a more extreme variation of a trait

Ex. Longer-billed birds are favoured in long-flower environments

Question 2

Stabilizing selection

Answer 2

Selection that favours the average phenotype (favoured by the environment; extreme variations are not favoured)

Ex. Average-length billed birds are favoured

Question 3

Disruptive selection

Answer 3

Selection that favours opposite extremes of a trait

Ex. Small & large billed birds favoured where there are small & large flowers, both not well-suited for medium-length billed birds

Question 4

Sexual selection

Answer 4

Selection that favours the reproductive success of individuals with certain traits over others

Question 5

Genetic drift

Answer 5

Random shifting of genetic makeup of next generation (chance). Can result in an allele becoming very common or disappearing entirely.

Question 6

Genetic bottleneck

Answer 6

Dramatic (often temporary) reduction in population size, usually resulting in genetic drift.

• Usually the population is all genetically similar

Question 7

Founder effect

Answer 7

Genetic drift that happens when a small number of individuals establish a new population

Question 8

Human influence on natural selection?

Answer 8

Hunting can make animals extinct, lose size (fish), lose tusks (elephants), make bedbugs more resistant to pesticides