Natural Selection

Question 1

When does discontinuous variation in a trait occur?

Answer 1

when the phenotype is controlled by one or only a few genes, there are only a few possible phenotypes that fall into distinct classes

Question 2

When does continuous variation in a trait occur?

Answer 2

when phenotypes do not fall into distinct classes, a continuous distribution of phenotypes (ex. eye colour)

Question 3

What is a more common term for continuous variation?

Answer 3

quantitative variation, trait that has a quantitative value (ex. height, iq)

Question 4

What are multifactorial traits? Example?

Answer 4

traits that are the result of the interactions between one or more environmental factors and two or more genes

ex. height is related to multiple different genes but it can be stunted by malnutrition

Question 5

What type of phenotypic variation is subject to evolutionary change? Why?

Answer 5

genetically based phenotypic variation

it depends on differences in heritable traits

Question 6

What is acclimatization?

Answer 6

adjusting to stress through behaviour or physiology

Question 7

Does acclimatization occur to individuals or a population? Is it evolution? Why or why not?

Answer 7

happens to individuals

no it isn’t

b/c its a short-term, reversible process that happens to individuals

Question 8

What is adaption?

Answer 8

any heritable trait that increases the fitness of an individual with that trait in a particular environment compared to others without that trait

Question 9

Does adaption occur to individuals or a population? Is it evolution? Why or why not?

Answer 9

populations

yes

b/c its a long-term, genetic response of a population caused by natural selection

Question 10

How are traits usually quantified?

Answer 10

measurement

Question 11

What does the mean describe in terms of a characteristic in a population?

Answer 11

the average value of that characteristic in a population

Question 12

What does variance measure?

Answer 12

the variability from the average or mean

Question 13

What are the types of natural selection?

Answer 13

disruptive, directional, stabilizing, balancing

Question 14

What is directional selection?

Answer 14

when natural selection move in one direction, changes the average value of a trait

Question 15

What can directional selection lead to?

Answer 15

fixation of advantageous alleles and the loss of harmful alleles

Question 16

What is stabilizing selection?

Answer 16

reduces the extremes of the population, no change in the average value of the trait being selected

Question 17

What can stabilizing selection lead to?

Answer 17

decrease in genetic variation and a reduction in genetic diversity

Question 18

What is disruptive selection?

Answer 18

favours the extremes of the population, opposite of stabilizing selection

Question 19

What can disruptive selection lead to?

Answer 19

maintains genetic variation, average phenotype is eliminated, can lead to formation of new species

Question 20

What is the difference between directional and disruptive selection?

Answer 20

directional moves towards one extreme in one direction (can be either extreme/direction)

disruptive moves towards both extremes in both directions

Question 21

What is balancing selection? Example?

Answer 21

when multiple alleles are maintained in a population, genetic variation is maintained

heterozygote advantage

Question 22

What is frequency dependent selection? Example?

Answer 22

form of balancing selection, where fitness is dependent upon the frequency of a phenotype/genotype in a population

negative frequency dependent selection: rare phenotypes hae higher fitness because they are eaten less

Question 23

Will natural selection eventually lead to perfection?

Answer 23

no

Question 24

Are adaptions universally good? Why or why not?

Answer 24

no, it increases their fitness in a particular environment so it isn’t universally good (environments can change)

Question 25

What are fitness trade offs? Why does this happen?

Answer 25

compromises between traits in terms of the performance of these traits in a particular environment

selection acts on many traits at once, every adaptation represents a compromise between different selection pressures

Question 26

What are some examples of fitness trade offs?

Answer 26

size of eggs/seeds and the number of offspring, rapid growth and long lifespan, bright colouration and attracting predators

Question 27

Can natural selection eliminate all deleterious traits?

Answer 27

No, because heterozygotes and homozygous dominant organisms have the same phenotype and therefore the same fitness so the recessive deleterious allele will still be passed down