chapter twenty-three/twenty-four

Question 1

3 major factors that alter allele frequency

Answer 1

1. natural selection
2. genetic drift
3. gene flow

Question 2

genetic drift

Answer 2

• allele frequencies fluctuate unpredictably/randomly from one gen to next
• reduces genetic variation
• sig in small populations

Question 3

gene flow

Answer 3

• movement of alleles among populations
• transferred through fertile ind. or gametes
• reduces variation
• decrease/increase fitness

Question 4

founder effect

Answer 4

few individuals become isolated from larger population
- allele frequencies can be dif

Question 5

bottleneck effect

Answer 5

sever drop in pop size due to environmental change
- can be affect by genetic drift

Question 6

what does evolution by natural selection involve?

Answer 6

change and sorting
- new genetic variations arise by chance
- beneficial alleles sorted

Question 7

what results in adaptive evolution?

Answer 7

natural selection
- increases frequencies of alleles that provide reproductive advantage
- acts on organism’s phenotype

Question 8

why are the phrases “struggle for existence” and “survival of the fittest” misleading?

Answer 8

• imply direct competition
• reproductive success more subtle

Question 9

relative fitness

Answer 9

contribution an ind makes to the gene pool of the next generation relative to contributions of other ind

Question 10

3 modes of selection

Answer 10

1. directional
2. disruptive
3. stabilizing

Question 11

directional selection

Answer 11

favors one extreme end of phenotypic range

Question 12

disruptive selection

Answer 12

favors individuals at both ends of phenotypic range

Question 13

stabilizing selection

Answer 13

favors intermediate variants and acts against extreme phenotypes

Question 14

what increases the frequencies of alleles that enhance survival and reproduction?

Answer 14

natural selection

Question 15

what occurs as the match between an organism and its environment

Answer 15

adaptive evolution

Question 16

why is adaptive evolution a continuous process?

Answer 16

the environment can change

Question 17

why don’t genetic drift and gene flow lead to adaptive evolution

Answer 17

they can increase/decrease match between organism and its environment

Question 18

sexual selection

Answer 18

natural selection for mating success

Question 19

sexual dimorphism

Answer 19

marked differences between the sexes in secondary sexual characteristics

Question 20

intrasexual selection

Answer 20

competition among ind of one sex (often males) for mates of opposite sex

Question 21

intersexual selection

Answer 21

• mate choice
• occurs when ind of one sex (usually females) are choosing in selecting mates

Question 22

how to female preferences evolve?

Answer 22

good genes hypothesis - if trait is related to male health, both male trait and female preference for trait should increase in frequency

Question 23

neutral variation

Answer 23

genetic variation that doesn’t confer a selective advantage/disadvantage

Question 24

diploidy

Answer 24

maintains genetic variation in form of recessive alleles
- heterozygotes can carry recessive alleles that are hidden from effects of selection

Question 25

balancing selection

Answer 25

occurs when natural selection maintains stable frequencies of 2+ phenotypic forms in a pop - includes heterozygote advantage and frequency-dependent selection

Question 26

heterozygote advantage

Answer 26

occurs when heterozygous have greater fitness than homozygotes - natural selection will maintain 2 alleles at that locus - sickle-cell allele causes mutations in hemoglobin but also confers malaria resistance

Question 27

frequency-dependent selection

Answer 27

fitness of phenotype declines if it becomes to common in pop - selection can favor less common phenotype in pop - equal numbers of right and left mouth fish

Question 28

why can natural selection not fashion perfect organisms?

Answer 28

- can only act on existing variations - evolution limited by historical constraints - adaptations often compromises - chance, natural selection, and environment interact

Question 29

what preserves genetic variation?

Answer 29

diploidy and balancing selection

Question 30

speciation

Answer 30

origin of new species

Question 31

microevolution

Answer 31

changes in allele frequency in pop over time

Question 32

macroevolution

Answer 32

broad patterns of evolutionary change above species level

Question 33

"species" word

Answer 33

Latin word meaning "kind" or "appearance"

Question 34

what is compared when grouping organisms?

Answer 34

morphology, physiology, biochemistry, DNA sequences

Question 35

biological species concept

Answer 35

- states species is a group of populations whose members have the potential to interbreed and produce viable/fertile offspring and don't breed successfully w/ other populations

Question 36

what holds the phenotype of a population together?

Answer 36

gene flow between populations

Question 37

reproductive isolation

Answer 37

existence of biological factors/barriers that impeded 2 species from producing viable/fertile offspring - prezygotic and postzygotic

Question 38

hybrids

Answer 38

offspring of crosses between dif species

Question 39

prezygotic barriers

Answer 39

block fertilization from occurring by: 1. impeding dif species from attempting to mate 2. preventing successfully completion of mating 3. hindering fertilization if mating is successful

Question 40

types of prezygotic barriers

Answer 40

1. habitat 2. temporal 3. behavioral 4. mechanical 5. gametic

Question 41

habitat isolation

Answer 41

2 species encounter each other rarely/not at all because they occupy dif habitats

Question 42

temporal isolation

Answer 42

species that breed at dif times of day, dif seasons, or dif years can't mix gametes

Question 43

behavioral isolation

Answer 43

courtship rituals and other behaviors unique to species are effective barriers

Question 44

mechanical isolation

Answer 44

morphological dif can prevent mating

Question 45

gametic isolation

Answer 45

sperm of one species may not be able to fertilize eggs of another species

Question 46

post zygotic barriers

Answer 46

prevent hybrid zygote from developing into a viable, fertile adult 1. reduced hybrid viability 2. reduced hybrid fertility 3. hybrid breakdown

Question 47

reduced hybrid viability

Answer 47

genes of different parent species may interact and impair hybrid's development and survival

Question 48

reduced hybrid fertility

Answer 48

even if hybrids are vigorous, they may be sterile

Question 49

hybrid breakdown

Answer 49

some first-get hybrids fertile, but when they mate w/ another hybrid or w/ either parent species, offspring of next gen are feeble/sterile

Question 50

limitations of biological species concept

Answer 50

1. can't be applied to fossils/asexual organisms/prokaryotes 2. emphasizes absence of gene flow

Question 51

can gene flow occur between distinct species?

Answer 51

yes, like grizzly and polar bears

Question 52

morphological species concept

Answer 52

species defined by body shape and structural features - applies to sexual/asexual species but relies on subjective criteria

Question 53

ecological species concept

Answer 53

views species in terms of its ecological niche - applies to sexual/asexual, emphasizes role of disruptive selection

Question 54

phylogenetic species concept

Answer 54

defines species as smallest group of ind on phylogenetic tree - applies to sexual/asexual, but difficult to determine degree of difference required for separate species