19. Evidence of evolution

Question 1

Darwins Postulates

Answer 1

1st … all organisms can reproduce more offspring than can possibly survive.

2nd … Those who win the struggle live to reproduce to pass on the genes.

3rd … there is variation for every trait. The pattern of variation is represented by a bell-shaped curve. That curve tells us that there are some that are “less” than their parents and some that are “more”, but most are in the middle and are just like their parents.” As a result of that variation, some of the organisms at an extreme might be born slightly different and that difference might give them an advantage in the struggle.

4th … The environment determines ‘who’ lives and dies occurs naturally. Thus, it is natural selection.

5th … Those that survive the environment will produce offspring that are more similar to the parents causing small changes that accumulate over time.

Question 2

UNdertsanding natural selection
a. Conditions for natural selection

Answer 2

3 Conditions Must Exist:
Variation must exist in the population

Among individuals this variation must lead to differences in reproductive success.

Among individual’s variation must be genetically transmitted to the next generation

Question 3

UNdertsanding natural selection
b. Types of selection

Answer 3

1. Natural selection - Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time.
2. Artificial selection - occurs when humans actively choose which individuals to breed based on desirable traits.
3. Sexual selection - occurs when individuals choose mates based on certain traits, such as size, color, or song

Question 4

Effect of environment on evolution
a. Divergent/Convergent

Answer 4

Divergent Evolution - One structure evolves into two or more different forms (occurs when environment pushes organisms into a different niche = diverging structure)

Convergent Evolution - two species develop similar features despite not sharing a recent common ancestor (product of natural selection)

Question 5

Effect of selection on a population
a. Stabilizing, directional, disruptive

Answer 5

Stabilizing — Selection favors the average. (heterozygous genotypes)

Directional — one extreme is favored. (homozygous dom or rec genotypes)

Disruptive — both extremes are selected (homozygous dom and rec genotypes)

Question 6

Evidence supporting evolution
a. Evidence showing change in a population
b. Evidence showing common ancestry

Answer 6

Evidence showing change in population
- Fossil Layers
- Vestigial Structures

Evidence showing common ancestry
- Adaptive Radiation
- Homology
- Artificial Selection

Question 7

Distinction between Darwin’s propositions and evidence

Answer 7

Evidence of evolution is a measurable physical change in a species over time. (e.g. number of alleles changes, or fossil records show a change in the size compared to another point in time)

Propositions are ideas that are a form of reasoning which lead to a new way of thinking