Mechanisms of evolution

Question 1

What are mutations?

Answer 1

Mutations are the source of all new alleles. can be beneficial or harmful. they are the source of variation, essential for evolution via natural selection

Question 2

What does the direction of change in natural selection depend on?

Answer 2

• selection pressure:

Question 3

what is stabilising selection?

Answer 3

reduces the variation by selecting against the extremes at each end of the phenotypic range

Question 4

Directional selection

Answer 4

the reduction in variation at one extreme of a range while the favored variants survive

Question 5

Give an example of a directional selection.

Answer 5

Peppered moths:

• two forms of peppered moths : light and dark
• dark- survive more bc it can camouflage well against the lichen-covered bark of trees in unpolluted regions.
• the industrial revolution caused the increase in soot and so2
• this increases the frequency of dark moths
• directional selection favored melanic forms
• industrial melanism

Question 6

What causes random changes in the gene frequencies?

Answer 6

• not all individuals in a gene pool pass on their genes to the descendants.
• alleles may become lost or fixed

Question 7

Give an example of stabilising selection.

Answer 7

human birth weight

Question 8

How did melanic morph change overtime?

Answer 8

• decline of coal burning factories and the air quality is improved between 1960 and 1980.
• this reduces the levels of sulfur dioxide and smoke levels
• with cleaner air, selection is increasingly in favor of the gray form

Question 9

When does disruptive selection occur?

Answer 9

When environmental conditions are varied or when the environmental range of an organism is large. This leads to speciation.

Question 10

Is survival more related to fitness and selection pressure or to a change in gene pool?

Answer 10

Both. but more or less.

Question 11

What is a founder population?

Answer 11

A colonizing population that may migrate away or become isolated from their original population.

Question 12

True or False:

the colonizing population evolves in the same way as the parents population.

Answer 12

False. The colonizing population may evolve in a different direction than the parent population

Question 13

When does a population bottleneck occurs?

Answer 13

It occurs when the breeding population is reduced by 50% or more.

Question 14

Why does a population bottleneck increase genetic drift?

Answer 14

B/c the rate of drift is inversely proportional to the population size.

Question 15

Give an example of a population bottle neck.

Answer 15

All the modern cheetahs may have arisen from a single surviving litter. the lack of genetic variation has led to :

• decreased female fertility
• sensitivity to disease
• sperm abnormalities
• high cub mortality

Question 16

What are species?

Answer 16

A species is a group of organisms able to interbreed and produce fertile offspring.

Question 17

What is meant by budding?

Answer 17

A small part of the species population budding off from the main part and evolve rapidly to form a new species.

Question 18

What is meant by splitting?

Answer 18

A species could split equally into two populations that evolve differently until they become separate species.

Question 19

What are the three types of isolation?

Answer 19

• geological: features such as rivers or mountains
• ecological: different habitats and breeding areas
• reproductive: breeding between groups is impossible due to differences in courtship behavior, physical differences that prevent mating or failure of gametes to fuse

Question 20

What is gradual rate of evolution?

Answer 20

if the environment is stable, organisms undergo very little change over time and evolution is slow and gradual

Question 21

What is punctuated rate of evolution?

Answer 21

Within a different gene pool or a burst of mutations, the isolated group rapidly evolves into separate species.

Question 22

Give an example of a punctuated evolution.

Answer 22

the explosion of birds, mammals after the dino extinction

Question 23

What is meant by divergent evolution?

Answer 23

A common ancestor evolves into a number of species. these species have adaptations allowing them to occupy different niches.

Question 24

What is meant by convergent evolution?

Answer 24

Due to similar environmental conditions, different organisms evolve to have similar physical characteristics to suit the same environment.