Lecture 7 - The Basis of Evolution by Natural Selection

Question 1

What are the three possible theories for the history of life?

Answer 1

Evolution
Transformation
Separate creation

Question 2

What is evolution?

Answer 2

A change in gene frequencies over time

Question 3

What are the 4 kinds of evolution

Answer 3

1. Mutation
2. Natural selection
3. Genetic drift
4. Founder effects

Question 4

What is mutation?

Answer 4

The source of genetic variation

Question 5

What is natural selection?

Answer 5

The sifting of variation to produce adaptions

Question 6

What is genetic drift?

Answer 6

Random sampling of individuals over time

Question 7

What is founder effect?

Answer 7

Small group of individuals “bud off” or survive by chance

Question 8

What do mutations drive and innovate

Answer 8

New alleles in the generation

Question 9

What evidence is there for evolution?

Answer 9

1. The fossil record
2. Observations of similarities and differences BETWEEN living species
3. Evolution in action - Observing changes in real time

Question 10

What are present continuously in the fossil record?

Answer 10

Intermediate forms

Question 11

What does the order of fossils suggest?

Answer 11

Evolutionary relationships
- If you dig into the earth, there is an order of things. In different zones you can find different levels of complexity.

Question 12

What are analogous species?

Answer 12

One that has evolved independently as a solution to a problem

Question 13

What are homologous species?

Answer 13

Evolved through decent with modification

Question 14

Example of an analogous species

Answer 14

Octopus: Inverted retina of vertebrate (left) and non-inverted retina of octopus (right). An example of totally separate evolutionary pathways

Question 15

What are vestigal structures?

Answer 15

They suggest evolutionary descent.
- Pectoral and pelvic articulations are homologous in tetrapods; where the limbs are no longer adaptive, they have been lost but remains can still be seen in the skeleton

Question 16

Example of a vestigal structure

Answer 16

Appendix is not needed anymore. It was a past adaptation from when we had high cellulose diets

Question 17

What are phylogenetic approaches?

Answer 17

Understanding evolution by comparing features if extant species

Question 18

What are two problems with evolutionary classifications based on external features

Answer 18

1. Discriminating features
2. Convergent evolution

Question 19

What is convergent evolution?

Answer 19

Independent evolution of similar features in species. Creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups

Question 20

What are phylogenetic approaches?

Answer 20

the study of the evolutionary relatedness among groups of organisms.

Question 21

What generates variations?

Answer 21

• Random mutations
• Recombinations (via sex)
• Gene flow

Question 22

How many mutations were you born with?

Answer 22

• 300 of which at least 1 or 2 are potentially harmful if they are homozygous
• Over 10000 human genes have been described that in their mutated form cause diseases or defects.
• Variation is the building block for evolution

Question 24

What are recombinations and variations?

Answer 24

• All genetic variation owes its origin ultimately to mutation.
• However in the short term recombination accounts for a great deal of the genetic variation in wild populations.

Question 25

What factors can cause allele substitution in a population?

Answer 25

Natural (sexual) selection and genetic drift.

Question 26

What is genetic drift?

Answer 26

Most populations are a finite size and random fluctuations in allele frequencies can result in the replacement of alleles (non-adaptive evolution)

Question 27

What is effective population size?

Answer 27

The effective size (Ne) of a population is the number of adult individuals in the population that actually reproduce.

Question 28

What are the implication of drift for metapopulations?

Answer 28

- Demes that initially are genetically identical evolve by chance to have different genetic constitutions. - This assumes that the two alleles have identical effects on fitness (i.e. they are neutral).

Question 29

What are founder effects?

Answer 29

- Populations that go through a restricted size are said to have gone through a bottleneck. - This can happen when new populations are founded.

Question 30

How does natural selection variations arise and why are individuals so well adapted to their environment?

Answer 30

Designing agent = Selection - Acts to sift variants of behaviour, favouring those that provide their bearer with greater representation in the next generation

Question 31

Selection for survival steps

Answer 31

1. Huge numbers of individuals are produced 2. Insufficient resources for all, so many die before reproducing 3. Individuals vary in attributes 4. Individuals with attributes better suited to environment are less likely to die 5. These individuals will be over represented in next generation

Question 32

Selection for reproductive share "sexual selection"

Answer 32

1. Individuals differ in their reproductive output 2. May depend on fecundity – number of offspring they can produce themselves 3. May depend on attractiveness – number of mates they can obtain and the sum of THEIR offspring

Question 33

What is the red queen hypothesis?

Answer 33

- Species (or populations) must continually evolve new adaptations in response to evolutionary changes in other organisms to avoid extinction. - The term is derived from Lewis Carroll’s *Through the Looking Glass*, where the Red Queen informs Alice that “here, you see, it takes all the running you can do to keep in the same place.”