Topic 6: Natural Selection

Question 1

natural selection

Answer 1

differences in the survival and reproduction of phenotypes, leading to differences in their contribution to the next generation, resulting in a change in the frequency of heritable phenotypic variations in populations over time

Question 2

requirements for natural selection
(Darwin’s 4 postulates)

Answer 2

1. individuals within species are variable
2. some of these variations are heritable
3. in every generation, more offspring are produced than survive. Some are more successful at survival and reproduction than others
4. the survival and reproduction of individuals is not random. Most favourable variations are naturally selected.

Question 3

fitness is affected by 3 different elements of natural selection:

Answer 3

• viability/mortality selection
• sexual selection
• fecundity selection

Question 4

what is it called when viability/mortality, sexual, or fecundity selection oppose each other?

Answer 4

antagonistic

Question 5

T/F natural selection is the only way a population can evolve

Answer 5

False - drift, mutation, gene flow!

Question 6

natural selection is the primary means of ____ ____, meaning?

Answer 6

adaptive evolution:

the avg individual becomes better adapted to their environments (avg pop fitness goes up)

Question 7

adaptation meaning

Answer 7

characteristic or trait that increases an individual’s fitness relative to individuals that do not possess it

Question 8

if phenotypes have a GENETIC BASIS, and have different fitnesses, what will happen?

Answer 8

selection will act on these phenotypes
-> genotype and allele freq changes in next gen

Question 9

what does absolute fitness actually mean?

Answer 9

avg # offspring (zygotes) contributed to gen t+1 by an individual (zygote) in gen t

Question 10

how is relative fitness different from absolute fitness?

Answer 10

relative fitness measures a genotype’s contribution to next gen RELATIVE to other genotypes (in pop)

(scaled to genotype with largest absolute fitness)

Question 11

what is the single locus model of selection measuring? (what element of fitness selection)

Answer 11

viability selection

Question 12

what is balancing selection?

Answer 12

any type of selection that acts to maintain genetic variation
ex. het superiority, inverse frequency dependent selection

Question 13

adaptive radiation
- punctuated equilibrium = ?

Answer 13

diversification of multiple descendent lineages from a single ancestral lineage

punctuated equilibrium:
- RAPID ecological and morphological innovation
- then long periods of STASIS

Question 14

T/F when phenotypic traits are controlled by a single locus, selection alone will often not result in noticeable HW disequil

Answer 14

TRUE - differences in genotype fitnesses tend to be subtle, and one round of random mating restores HW equil each gen

Question 15

Hitchhiking meaning

Answer 15

due to linkage disequil, another connected locus is affected because of one locus’s fitness

Question 16

epistasis

Answer 16

an effect of the interaction of two or more gene loci on phenotypes and/or fitness, where joint effect is diff from sum of ind loci taken separately (synergistic effect of loci)

Question 17

Pleiotropy

Answer 17

a phenotypic effect of a single gene on more than one characteristic