Exam 5 chapter 26

Question 1

Hardy-Weinberg principle

Answer 1

a principle of population genetics stating that genotype frequencies in a large population do not change from generation to generation in the absence of evolutionary processes

Question 2

Inbreeding

Answer 2

mating between closely related individuals. Increases homozygosity of a population and often leads to a decline in the average fitness via selection

Question 3

Gene pool

Answer 3

all the alleles of all the genes in a certain population

Question 4

If every plant in a population self-pollinates and produces the same number of offspring, then

Answer 4

Allele frequencies are identical and the population has not evolved

Question 5

Why do we say that evolution is not “goal directed” or “progressive

Answer 5

• Evolution is not goal directed, it’s random. Every once in a while there is a mutation that will be beneficial to the population so natural selection will act on that. Sometimes things will evolve to become more simple, it just depends on the environment they are trying to adapt to. Ex: tapeworms

Question 6

What are some examples of clear constraints to evolution

Answer 6

We have to wait for the right variation of traits to be produced for adaptation to occur.
Traits that evolve are not always best fit for everything

Question 7

What would be an example of a fitness trade-off

Answer 7

• Fewer offspring but increase of change of survival for those offspring

Question 8

Describe directional selection

Answer 8

It changes the average value of a trait in one direction, reducing genetic diversity. Ex: body size increasing and increasing; individuals in population are shifted towards a larger body size

Question 9

What is the difference between direction selection and purifying selection

Answer 9

In purifying selection, the trait will be completely removed from the population. In directional selection we are just moving towards a certain trait.

Question 10

Describe stabilizing selection

Answer 10

Reduces the amount of genetic variation in a trait and reduces extremes. Ex: high fitness individuals will have an intermediate body size and the ones with tiny bodies and big bodies are less fit. Like birth rate – higher death rate of babies with very small birth rate and very large birth weight

Question 11

Describe disruptive selection

Answer 11

• Increases the amount of variation in a trait, favoring extreme phenotypes
• Ex: short and long beak lengths are better fit than intermediate beak length. Small beaks could eat small seeds and large beaks could eat large seeds

Question 12

In disruptive selection, if birds with small beaks and birds with large beaks end up having different niches, what could happen

Answer 12

speciation

Question 13

Describe balancing selection

Answer 13

Maintains variation in a trait and occurs when no allele has an advantage and there is a balancing among alleles in fitness and frequency

Question 14

What is sexual dimorphism

Answer 14

Traits that differ between males and females of the same species.
• Weaponry
• Ornamentation
Body size

Question 15

founder effect

Answer 15

when a few individuals in a population colonize a new location that is separate from the old population

Question 16

genetic bottleneck

Answer 16

, when a population’s size becomes very small very quickly

Question 17

How are deleterious mutations removed

Answer 17

purifying selection

Question 18

What happens when a beneficial allele is produced by mutation

Answer 18

It will increase in frequency in the population because natural selection will act on it

Question 19

An earthquake decimates a ground-squirrel population, randomly killing 98% of the squirrels. The surviving population happens to have broader stripes on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake

Answer 19

genetic bottleneck