Mechanisms of Evolution

Question 1

Charles Darwin (1809-1892)

Answer 1

H.M.S Beagle Voyage (1831-1836): explored south seas and collected plants & animals; went to Galapagos Islands and noticed uniqued species of finches
- Isolations and natural factors (different climates, food availability & type, caused different finches to evolve)
- Realized all species evolved from common ancestors by means of natural selection

Question 2

Darwin’s Book and Theory

Answer 2

Wrote “On the Origin of Species by Means of Natural Selection” (1859) –> by June 1858, Darwin formulated his theory after receiving a letter from Alfred Wallace, a naturalist working in Malaysia (Wallace had independently arrived to same conclusions in just 2 days, while it took Darwin almost 20 years to get enough evidence)

Question 3

Critical Elements of Natural Selection

Answer 3

Variation in Traits, Survival of the Fittest, Competition, Adaption

Question 4

Critical Elements of Natural Selection: Variation in Traits

Answer 4

Individual members of a species vary in physical characteristics (which can be passed down from generation to generation)

Question 5

Critical Elements of Natural Selection: Survival of the Fittest

Answer 5

Environment can’t support unlimited population and not all individuals reproduce to their full potential

Question 6

Critical Elements of Natural Selection: Competition

Answer 6

Members of all species compete with each other for limited resources –> certain members able to capture resources better than others

Question 7

Critical Elements of Natural Selection: Adaption

Answer 7

Natural selection causes a population, and ultimately a species, to adapt to the environment –> each new generation includes more individuals that are better adapted to the environment

Question 8

Requirements of Natural Selection

Answer 8

The ability to survive and reproduce –>
Natural selection describes the way nature favours the reproductive success of some individuals in a population over others

Question 9

Evidence of Natural Selection

Answer 9

Peppered Moths in England:
Before 1800s, moths were light in colour. During industrial revolution, waste began to darken trees, killing the lichen. Light coloured moths couldn’t adapt to the change, soon dark moths became abundant due to selective predation from birds.

Question 10

Mutations

Answer 10

Source of all new alleles (can be neutral, beneficial, or harmful) –> are rare in individual cells, however are numerous in large populations over many generations

Question 11

Gene Flow (Migration)

Answer 11

Changes in allele frequency between populations results in loss or gain of new alleles –> tends to reduce differences between populations (said to counteract natural selection)

Transfer of genetic material (alleles) from one population to another

Question 12

Genetic Drift

Answer 12

When populations are small, chance can play a significant role in altering allele frequency –> can lead to fixation of alleles, which can increase incidence of homozygous individuals which reduces genetic diversity

Question 13

Effects of Genetic Drift

Answer 13

Bottleneck Effect and Founder Effect

Question 14

Bottleneck Effect

Answer 14

When a severe event (flood, parasite, overhunting, etc.) results in a drastic reduction in numbers, a population may experience a bottleneck effect –> only very small sample of alleles survive to establish new population (which alleles/individuals survive is pure chance)

Question 15

Founder Effect

Answer 15

A small group from a large population leaves and starts a new population –> new population will have a different allele frequency than original population (e.g. finches in Galapagos Islands)