Ch22 and Ch23

Question 1

adaptations

Answer 1

inherited characteristics of that enhance their survival and reproduction in specific environments

Question 2

natural selection

Answer 2

a process in which individuals that have certain inherited traits tend to survive and reproduce at higher than other individuals because of those traits

Question 3

artificial selection

Answer 3

human selection of organisms

Question 4

Darwin’s observations and inferences

Answer 4

• members of a population vary
• all species can produce more offspring than their environment can support and many die
• better suited individuals produce more offspring
• this leads to an accumulation of favorable traits

Question 5

homology

Answer 5

similarity resulting from common ancestry

Question 6

homologous structures

Answer 6

similar structures due to common ancestry

Question 7

vestigial structures

Answer 7

remnants of features that served a function in the organisms ancestors

Question 8

convergent evolution

Answer 8

the independent evolution of similar features in different lineages

Question 9

analogous features

Answer 9

shared features due to convergent evolution

Question 10

endemic

Answer 10

found nowhere else in the world

Question 11

microevolution

Answer 11

evolutionary change in populations, smallest scale of evolution, change in allele frequency over generation

Question 12

genetic variation

Answer 12

differences among individuals in the composition of their genes or other DNA segments

Question 13

discrete character

Answer 13

either -or trait;normally single gene locus

Question 14

quantitative character

Answer 14

trait that varies along a continuum; normally two or more genes

Question 15

average heterozygosity

Answer 15

the average percentage of loci that are heterozygous: quantification of gene variability

Question 16

geographic variation

Answer 16

differences in the genetic composition of separate poppulations

Question 17

cline

Answer 17

graded change in a character along a geographic axis

Question 18

poppulation

Answer 18

a group of individuals of the same species that live in the same area and reproduce

Question 19

gene pool

Answer 19

all copies of all alleles in a poppulation

Question 20

Hardy-Weinberg principle

Answer 20

the frequencies of alleles and genotypes in a population will remain constant from generation to generation, provided that only Mendelian Segregation and recombination of alleles are at work: the resulting gene pool is a Hardy-Weinberg equilibrium

Question 21

conditions for Hardy-Weinberg

Answer 21

• no mutations
• random mating
• no natural selection
• extremely large population size
• no gene flow

Question 22

genetic drift

Answer 22

chance events that cause alleles to fluctuate unpredictably, especially in small populations

Question 23

founder effect

Answer 23

a new population separate and different from the original population

Question 24

bottleneck effect

Answer 24

severe drop in population that causes certain alleles to survive by chance

Question 25

genetic drift key points

Answer 25

• significant in small populations
• can cause allele frequencies to change at random
• leads to a loss of genetic variation
• can cause harmful alleles to become fixed

Question 26

gene flow

Answer 26

the transfer of alleles into or out of a population

Question 27

relative fitness

Answer 27

the contribution an individual makes to the gene pool of the next generation relative to the contributions of others

Question 28

directional selection

Answer 28

conditions favor one extreme; directional shift; mice getting darker

Question 29

disruptive selection

Answer 29

favor individuals at both extremes; white and black mice

Question 30

stabilizing selection

Answer 30

favors intermediate variants;all brown mice

Question 31

sexual selections

Answer 31

traits passed on by acquiring mates

Question 32

sexual dimorphism

Answer 32

gender difference

Question 33

intrasexual selection

Answer 33

selection within a gender (normally male)

Question 34

intersexual selection

Answer 34

select from other gender (normally female)

Question 35

neutral variation

Answer 35

differences that do not give advantage or disadvantage

Question 36

balancing selection

Answer 36

when selection maintains two or more forms

Question 37

heterozygote advantage

Answer 37

when being heterozygous is advantageous

Question 38

frequency-dependent selection

Answer 38

when fitness is dependent on commonality

Question 39

4 reasons perfect organisms are not formed

Answer 39

• selection can only act on existing variations
• evolution is limited by historical constraints
• adaptations are often compromises
• chance,natural selection, and the environment interact.