selection and evolution

Question 1

Selection

Answer 1

• -Process that results in the survival and propagation of some individuals or organisms but not of others
• -doesn’t include heritability
• -change in mean or variance in phenotypic distribution within a generation
• -primary mechanism of evolution

Question 2

Natural selection

Answer 2

Natural process in which forces of nature decide which genetic qualities are best suited to a particular environment

Question 3

Artificial selection

Answer 3

Breeding of plants and animals for particular traits

Question 4

Fitness

Answer 4

Survival and reproduction of offspring - not just number of progeny produced but how many genes passed to offspring

Question 5

Selection coefficient

Answer 5

Measures strength of selection; more favored = lower selection coefficient

Question 6

Evolution

Answer 6

• -Change in population gene frequency over time

- -primary mechanism: selection; other mechanism: immigration, mutations, genetic drift, non random mating

Question 7

Microevolution

Answer 7

Evolution on a small scale - within the species level, over a short time that results in the for action of new subspecies

Question 8

Macroevolution

Answer 8

Evolution on a large scale - at or above the level of species, over geologic time resulting in the formation of new taxonomic groups

Question 9

3 criteria necessary for selection to result in evolution

Answer 9

• -variation must exist
• -variation must be gene based
• -variation must correlate with fitness

Question 10

Directional selection

Answer 10

• -discrimination against one extreme in a phenotypic distribution
• -result: change in phenotypic mean/mode within a generation

Question 11

Stabilizing selection

Answer 11

• -discrimination against both extremes in phenotypic distribution
• -result: population is more uniform, less variation

Question 12

Disruptive selection

Answer 12

• -discrimination against mean population, extremes favored

- -result: two or more types, bimodal distribution

Question 13

Selection vs evolution

Answer 13

All phenotypic variation is subject to selection. Selection is independent of heritability. Selection does not always result in evolution.

Ex. Snapping turtle hatchlings. Bigger hatchlings are more likely to survive but size is due to moisture in soil not a heritable trait.

Question 14

Clinal variation

Answer 14

Gradual phenotypic change over a large distance

Question 15

Allen’s rule of clinal variation

Answer 15

Clinal change in extremities of endotherms with extensive distance: cold = short –> warm = long

Surface Area/Volume ratio and the conservation of body heat
Short extremities: less SA, less heat loss
Long extremities: more SA, more heat loss

Question 16

Bergmann’s rule of clinal variation

Answer 16

ENDOTHERMS larger in colder regions, smaller in warmer regions
Less SA , more vol = conservation of body heat
SA increases, but vol increases faster–> SA is proportional to the square of the linear dimension while vol is proportional the cube of the linear dimension

Opposite in ECTOTHERMS– smaller size in colder regions

Question 17

Gloger’s rule of clinal variation

Answer 17

Endotherms in arid regions usually lighter in color than in humid regions

Arid: less humidity, less vegetation, less humus in soil, lighter color

Offset by natural selection in localized situations… Ex. El Mapais lava flows in NM

Question 18

Concordant variation

Answer 18

Expression of one trait is associated with the expression of another

Question 19

Discordant variation

Answer 19

Expression of one trait doesn’t predict a particular expression of another; no consistent pattern

Question 20

calculations

Answer 20

absolute fitness (W) = x/T
relative fitness (w) = W/highest W
selection coefficient (1-rfv) = 1 - w