Evolution 2.2

Question 1

what is evolution?

Answer 1

is the change over time in the proportion of individuals in a population differing in one or more inherited traits

Question 2

what happens during evolution?

Answer 2

changes in allele frequency occur through the non-random processes of natural selection and sexual selection, and the random process of genetic drift

Question 3

what does natural selection act on?

Answer 3

it acts on genetic variation in populations

Question 4

what do populations produce?

Answer 4

more offspring than the environment can support

Question 5

how are individuals with variation advantaged?

Answer 5

because they are better suited to their environment and tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation

Question 6

what is sexual selection?

Answer 6

it is the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring

Question 7

what may sexual selection lead to?

Answer 7

sexual dimorphism

Question 8

what can sexual selection be due to?

Answer 8

male-male rivalry and female choice

Question 9

when can genetic drift occur?

Answer 9

when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

Question 10

why is genetic drift more important in small populations?

Answer 10

because alleles are more likely to be lost from the gene pool

Question 11

what is the gene pool altered by and why?

Answer 11

it is altered by genetic drift because certain alleles may be under-represented or over-represented and allele frequencies change

Question 12

what happens when selection pressures are strong?

Answer 12

the rate of evolution can be rapid

Question 13

what does the Hardy-Weinberg (HW) principle state?

Answer 13

in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations

Question 14

what can the HW principle can be used to determine?

Answer 14

whether a change in allele frequency is occurring in a population over time

Question 15

what does change suggest?

Answer 15

evolution is occurring

Question 16

what is fitness an indication of?

Answer 16

an individual’s ability to be successful at surviving and reproducing

Question 17

what does fitness refer to?

Answer 17

the contribution made to the gene pool of the next generation by individual genotypes

Question 18

what can fitness can be defined in?

Answer 18

absolute or relative terms

Question 19

what is absolute fitness?

Answer 19

the ratio between the frequency of individuals of a particular genotype after selection, to those before selection

Question 20

what is relative fitness?

Answer 20

the ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype

Question 21

what is co-evolution?

Answer 21

the process by which two or more species evolve in response to selection pressures imposed by each other

Question 22

what is the bottleneck effect?

Answer 22

an example of genetic drift that can occur when a population size is reduced for at least one generation

Question 23

what is the founders effect?

Answer 23

an example of genetic drift that occur through the isolation of a few members of a population from a larger population and the gene pool of the new population is not representative of that in the original gene pool

Question 24

what are selection pressures?

Answer 24

environmental factors that influence which individuals in a population pass on their alleles

Question 25

what can selection pressures be?

Answer 25

biotic
- competition
- predation
- disease
- parasitism

abiotic
- temperature
- light
- pH
- salinity

Question 26

what are the conditions for maintaining the HW equilibrium?

Answer 26

• no natural selection
• random mating
• no mutation
• large population size
• no gene flow through migration, in or out

Question 27

what is the HW equation and what does each symbol stand for?

Answer 27

p2 + 2pq + q2 = 1

p2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q2 = frequency of homozygous recessive genotype

Question 28

what happens if the absolute fitness is 1?

Answer 28

frequency of that genotype is stable

Question 29

what happens if the absolute fitness has a value greater than 1?

Answer 29

conveys an increase in the genotype

Question 30

what happens if the absolute fitness has a value less than 1?

Answer 30

conveys a decrease in the genotype

Question 31

where is co-evolution frequently seen?

Answer 31

in pairs of species that have symbiotic relationships

Question 32

what is symbiosis and what are the impacts of it?

Answer 32

co-evolved intimate relationship between members of two different species

the impacts can be positive (+), negative (-) or neutral (0) for the individual species involved

Question 33

what is mutualism?

Answer 33

a symbiosis in which the species in the interaction are interdependent on each other for resources or other services and since both species gain the interaction is (+/+)

Question 34

what is commensalism?

Answer 34

a symbiosis in which only one of the species substantially benefits and for the other the relationship is neither substantially positive or negative so it is neural (+/0)

Question 35

what is parasitism?

Answer 35

a symbiosis in which the parasite species benefits in terms of energy or nutrients while the host species is harmed by the loss of resources (+/-)

Question 36

what does the Red Queen Hypothesis state?

Answer 36

in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species, which must adapt to avoid extinction

Question 37

what is each species in a symbiosis relationship called?

Answer 37

a symbiont