Written Answers

Question 1

Describe the genetic and ecological conditions that are necessary for the process of natural selection to operate

Answer 1

1. Variation in the trait
2. Heritability of the trait
3. Differential survival and reproductive success that is predictable by variation in the trait (i.e. the differential success is not random)

Question 2

What are the major forms of selection acting at (a) the level of a single gene?

Answer 2

Purifying : remove deleterious alleles from the population by driving down the frequencies of what are usually harmful recessives

Balancing : genetic variation is maintained and has reached a steady state (via overdominance and frequency-dependent selection)

Directional: one advantageous allele increases in frequency in the population until it reaches fixation

Question 3

What are the major forms of selection acting on the phenotypic level (i.e., on “continuous” or “quantitative” traits)?

Answer 3

directional: when the fitness of the individual consistently increases or decreases with the value of the trait, and the variation in the trait generally stays the same or reduces over time
stabilizing: the intermediate value traits have the highest fitness

disruptive: when individuals with extreme trait values on both sides of the mean trait in the distribution
have better survival or reproductive outcomes. This form of selection disfavors intermediate trait values, and increases the variance of trait.

Question 4

Discuss one example where Darwin’s thinking about evolution by natural selection has subsequently been found to be incorrect

Answer 4

Darwin thought that genes blended together, didn’t know about the rules of inheritance.

Question 5

What is a species?

Answer 5

The three most prominent species concepts are biological,

morphological and phylogenetic.

Question 6

How are they formed?

Answer 6

Reproductive isolation>genetic divergence>maintenance of separation.

Question 7

Criticize the following statements commonly expressed with people unfamiliar with the operation of natural selection. Provide examples to support your arguments wherever possible.

(a) Natural selection is the “survival of the fittest”.
(b) Evolution by natural selection is a matter of chance.
(c) Natural selection is a tautology because it is survival of the fittest, and we identify the fittest by seeing who survives.

Answer 7

a. ‘survival of the fittest’ ignores the key reproductive component of natural selection
b. the process of selection is specifically non-random
c. can only be a tautology if reproduction and inheritance is ignored

Question 8

Describe the chemical makeup of biological membranes

Answer 8

A phospholipid bilayer with a hydrophilic phosphate head and a hydrophobic fatty acid tail that form into a bilayer when in water

Question 9

Describe the physical organization of biological membranes

Answer 9

DRAW

Question 10

Describe the primary functions of biological membranes

Answer 10

Passive and active transport of gases, ions and other molecules, as well as cell signaling and adhesion

Question 11

Summarize the various ways by which molecules can move, or pass through, biological membranes emphasizing the roles played by different proteins

Answer 11

.

Question 12

What is overdominance?

Answer 12

When the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents.

Overdominance can also be described as heterozygote advantage, wherein heterozygous individuals have a higher fitness than homozygous individuals.