Natural Selection II

Question 1

What are the three general forms of selection?

Answer 1

Directional selection
Stabilizing selection
Diversifying selection

Question 2

What is another name for directional selection?

Answer 2

Positive selection

Question 3

What is another name for stabilizing selection?

Answer 3

Purifying/negative selection

Question 4

What is another name for diversifying selection?

Answer 4

Divergent selection

Question 5

What is directional selection?

Answer 5

a. Selection that causes directional changes in the evolution of a trait

Question 6

What is stabilizing selection?

Answer 6

a. Selection that prevents changes to a trait by selecting against variants that deviate from the optimal trait

Question 7

What is diversifying selection?

Answer 7

a. Selection that causes a population to diverge in two directions

Question 8

What type of selection is shown in this graph?

Answer 8

Directional selection

Question 9

What type of selection is depicted in this graph?

Answer 9

Stabilizing selection

Question 10

What type of selection is depicted in this graph?

Answer 10

Divergent selection

Question 11

What is the Breeder’s equation?

Answer 11

Predicts the response to selection over a single generation

Question 12

What is this equation? Define all variables

Answer 12

Breeders equation
z1 = mean trait value of offspring
z0 = mean parental value
h^2 = heritability
S = selection differential

Question 13

What is this equation? Define all variables

Answer 13

Breeder’s equation with selection gradient
Vg = genetic variance
Beta = selection gradient

Question 14

What are phenotypic selection analyses?

Answer 14

Estimates natural selection according to the covariation between relative fitness and traits among individuals.

Question 15

What are genotypic selection analyses?

Answer 15

Estimates natural selection according to the covariation between relative fitness and traits among genotypes or genetic families.

Question 16

Define adaptive traits.

Answer 16

Adaptive traits increase the ability of an individual to survive or reproduce compared with individuals without the trait.

Question 17

By definition, what does evolution by natural selection lead to?

Answer 17

Evolution of adaptations

Question 18

What are the 4 misconceptions of evolution?

Answer 18

Populations evolve to future environments
Adaptive evolution is progressive, leading to the evolution of better and more complex forms
Adaptations evolve by random chance
Evolution cannot lead to complex organs.

Question 19

Correct this misconception: Populations evolve to future environments

Answer 19

o Evolution by natural selection is never forward looking, it is a function of past selection/environments
o Changes in environment might render species maladapted
o Don’t know what’s coming, only respond to what is happening

Question 20

Correct this misconception: Adaptive evolution is progressive, leading to the evolution of better and more complex forms

Answer 20

o Adaptation is not necessarily progressing to better and more complex forms. Populations adapt to previous environmental conditions
o Evolution by natural selection can lead to more complex OR simpler forms, depending on which traits are most fit and given adequate genetic variation

Question 21

Give examples of evolution leading to simpler forms.

Answer 21

 Loss of eye function
 Tapeworms losing digestive capacity
 Loss of photosynthesis in some plants (parasitic)

Question 22

Correct this misconception: Adaptations evolve by random chance

Answer 22

o Mutations are more or less random
o Natural selection is anything but random – it is the antithesis of random
o Natural selection leads to a near inevitable increase of the “best” (fittest) strategy within a population

Question 23

Correct this misconception: Evolution cannot lead to complex organs

Answer 23

o If intermediate steps increase fitness, then natural selection can lead to the evolution of complex adaptive traits.