Evolution

Question 1

What evidence leads to evolution?

Answer 1

fossil record, biogeography, homologous/analogous/vestigial features, embryonic development, molecular homologies

Question 2

Theories of Lamarck?

Answer 2

1. Theory of Need
2. Theory of Use and Disuse
3. Theory of Inheritance of Acquired Characteristics

Question 3

Theory of Need?

Answer 3

organs appear as the need arises

Question 4

Theory of Use and Disuse?

Answer 4

Used organs get stronger; an organ disappears if not used

Question 5

Theory of Inheritance of Acquired Characteristics?

Answer 5

organism will pass their acquired characteristic down to offspring

Question 6

Theories of Darwin?

Answer 6

1. Overproduction
2. Competition
3. Variation
4. Survival of the fit
5. Hereditary factors

Question 7

Overproduction theory?

Answer 7

all organisms produce more offspring that can survive

Question 8

Competition theory?

Answer 8

struggle for existence

Question 9

Survival of the fit theory?

Answer 9

some organisms are better suited to their environment + survive to have offspring

Question 10

Hereditary factors theory?

Answer 10

The survivors transmit their traits to their offspring

Question 11

Tell me about fossil record

Answer 11

• More complex fossils found in younger rock (shallower)
• Different species in each layer
• Evidence that life evolved from simple to complex

Question 12

What is biogeography?

Answer 12

Study of the geographical distribution of extinct and modern species

Question 13

What’s the difference between homologous/analogous/vestigial features?

Answer 13

Homologous: different traits derived from a common ancestor
Analogous: Similar traits from different lineages
Vestigial: remnants of past structures that are no longer of use (Typically have important function in related species)

Question 14

What is embryonic development?

Answer 14

• Species that differ as adults similar embryonic stages
• The more similar the stages, the more related the organisms

Question 15

What is molecular homology?

Answer 15

• Similarities in cells at the molecular level indicate that living species evolved from a common ancestor
• All living species have DNA that codes for amino acid sequences
• The more similar the sequences for common proteins, the more related the species

Question 16

Natural selection definition

Answer 16

• Alleles for traits that help an organism reproduce are passed down disproportionate to their frequency in the original population
• Over time, the trait being selected for will become more abundant

Question 17

Artificial selection definition

Answer 17

• mate selection based on specific traits
• increases frequency of these traits in future generations
• often not the same trait that would be naturally selected for and only males show the trait

Question 18

Sexual selection definition

Answer 18

members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection).

Question 19

Directional selection definition

Answer 19

• Selection for a rare (extreme) phenotype
• Usually due to environmental changes

Question 20

Stabilizing selection definition

Answer 20

Selection for the average trait and against extreme traits

Question 21

Diversifying/disruptive selection definition

Answer 21

• Selection for extreme traits instead of the average trait
• Usually due to varied environmental conditions

Question 22

What is genetic drift?

Answer 22

Change in the gene pool of a small population due to chance.
- If a population is small, the existing gene pool may not be well represented in the next generation
- Genetic drift is due to chance; not necessarily any adaptive advantage
- Microevolution due to genetic drift usually results in reduced genetic variability due to the fixing of an allele

Question 22

What is the role of mutations?

Answer 22

1. Random mutations/variations can occur and change the DNA of an organism in a way that affects its offspring.
2. Mutation/Variation can be beneficial, harmful or neutral.
   - If harmful, offspring survival & reproduction rates ↓ so the variation dies out.
   - If neutral, it remains in gene pool and increases genetic variation
3. If beneficial, it is naturally selected for.
   - The mutation helps the organism survive and reproduce in its environment

Question 23

Reproductive barriers (postzygotic)

Answer 23

Post-zygotic Barriers – prevent hybrid zygotes from thriving
Ex. A) Zygote Mortality - Gametic incompatibility (different number of chromosomes or big chromosomal differences) may result in abortion of the embryo
Ex. B) Hybrid inviability - If born the zygote will not live to maturity - Ex. Tiger Leopard Hybrid usually miscarried or stillborn. Ex. C) Hybrid Infertility - If offspring are produced they are sterile

Question 23

What is the bottleneck effect?

Answer 23

When a large population is affected by a disaster – fire, flood, earthquake, etc. - Only a few random survivors – not usually representative of the original population - Some alleles over represented, some under represented - Usually results in decreased genetic variation

Question 24

What is the founder effect?

Answer 24

Colonization of a new habitat (isolated island) by individuals of species - The smaller the sample size the less variation in the resulting population - Contributes to evolutionary divergence from the main population.

Question 25

What is allopatric and sympatric speciation?

Answer 25

ALLOPATRIC: Population becomes geographically separated. - Mutations occur until they are reproductively isolated. - Often the result of directional selection SYMPATRIC: Population in same geographical location split into separate gene pools. - Organisms occupy a different niche or undergo non-random mating - Often due to disruptive selection

Question 26

Reproductive barriers (prezygotic)

Answer 26

1) Pre-zygotic Barriers – prevent mating/fertilization of individuals from different species Ex. A) Ecological Isolation - If different similar species are in the same area, they may occupy different niches. Behavioral Isolation - Mating signals differ so that only those of the same species respond. Temporal Isolation - Different breeding times - Different time of day, different season Mechanical Isolation - Anatomically incompatible - Ex. Flowers that have a structure that allows only one type of organism to pollinate it. Thus, a flower designed for a bee may not be able to be pollinated by a flower that is designed for a bird Ex. B) Gametic Isolation - If gametes from different species do meet they will likely not become a zygote. - Due to gamete recognition molecules on the surface of gametes that prevent fusion unless egg and sperm have complimentary molecules If gametes do become zygotes

Question 27

Patterns of evolution (convergent vs. divergent)

Answer 27

CONVERGENT: Similar environments, exhibit the similar selective pressures, thus cause similar traits to evolve in organisms from different lineages DIVERGENT: the evolutionary pattern in which species sharing a common ancestry become more distinct due to differential selection pressure.