CHAPTER 22

Question 1

speciation

Answer 1

the process by which one species splits into two or more species. it leads to tremendous diversity in life, repeatedly yielding new species that differ from existing ones. when a species splits, the species that result sure many characteristics because they descended from this common ancestor

Question 2

macroevolution

Answer 2

the broad patter of evolution above the species level.

Question 3

microevolution

Answer 3

changes over time in allele frequencies in a population

Question 4

biological species concept

Answer 4

according to this concept, a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring – but do not produce viable, fertile offspring with member of other such groups. members are united by being reproductively compatible

Question 5

reproductive isolation

Answer 5

existence of biological barriers that impede members of two species from interbreeding and producing viable, fertile offspring

Question 6

hybrids

Answer 6

offspring that result from an interspecific mating

Question 7

prezygotic barriers

Answer 7

block fertilization from occurring

Question 8

prezygotic barriers typically act in one of three ways

Answer 8

1. impeding members of different species from attempting to mate
2. preventing an attempted mating from being completed successfully
3. hindering fertilization if mating is completed successfully

Question 9

postzygotic barriers

Answer 9

if a sperm cell from one species overcome pre zygotic carriers and fertilizes an ovum from another species, a variety of post zygotic barriers may contribute to reproductive isolation after the hybrid zygote is formed

Question 10

prezygotic barriers include:

Answer 10

habitat, temporal, behavioral, mechanical and gametic isolation

Question 11

habitat isolation

Answer 11

two species that occupy different habitats within the same area ma encounter each other early, if at all, even though they are not isolated by obvious physical barriers, such as mountain range

Question 12

temporal isolation

Answer 12

species that breed during different times of the day, different seasons, or different years cannot mix their gametes

Question 13

behavioral isolation

Answer 13

courshup rituals that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species. such behavioral rituals enable mate recognition, a way to identify potential mates of the same species

Question 14

mechanical isolation

Answer 14

1. mating is attempted, but morphological differences prevent its successful completion

Question 15

gametic isolation

Answer 15

sperm of one species may not be able to fertilize the eggs of another species. for instance, sperm may not be able to survive in the reproductive tract of females of the other species, or biochemical mechanisms may prevent the sperm from penetrating the membranes surrounding the other species eggs

Question 16

postzygotic barriers include:

Answer 16

reduced hybrid vitality, reduced hybrid fertility and hybrid breakdown

Question 17

reduced hybrid vitality

Answer 17

the genes of different parent species may interact in ways that impair the hybrid’s development or survival in it environment

Question 18

reduced hybrid fertility

Answer 18

the genes of different parent species may interact in ways that impair the hybrid’s development or survival in it environment

Question 19

hybrid breakdown

Answer 19

some first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species, offspring of the next generation are feeble or sterile

Question 20

morphological species concept

Answer 20

characterizes a species by body shape and other structural features

Question 21

ecological species concept

Answer 21

views a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment

Question 22

phylogenetic species concept

Answer 22

define a species as the smallest group of individuals tat share a common ancestor, forming one branch on the tree of life

Question 23

allopatric speciation

Answer 23

gene flow is interrupted when a population is decided into geographically isolated subpopulations

Question 24

sympatric speciation

Answer 24

speciation occurs in populations that live in the same geographic are

Question 25

polyploidy

Answer 25

a species may originate from an accident during cell division that results in extra sets of chromosomes

Question 26

autopoly-ploid

Answer 26

is an individual that has more than two chromosome sets that are all derived from a single species

Question 27

allopolyploid

Answer 27

the allopolyploids are fertile when mating with each other but cannot interbreed with either parent species = new biological species

Question 28

hybrid zone

Answer 28

A region in which members of different species meet and mate, producing at least some offspring of mixed ancestry.

Question 29

reinforcement

Answer 29

when hybrids are less fit than members of their parent species, natural selection tends to strengthen prezygotic carriers to reproduction, thus reducing the formation of unfit hybrids. because this process is involves reinforcing reproductive barriers, it is called reinforcement. fi reinforcement is occurring, a logical prediction is that barriers to reproduction between species should be stronger for sympatric populations than for allopatric populations

Question 30

fusion

Answer 30

barriers to reproduction may be weak when two species meet in a hybrid zone. indeed, so much of the gene flow may occur that reproductive barriers weakened further and the gene pools of the two species become increasingly alike. in effect, the speciation process reverses, eventually causing the two hybridizing species to fuse into a single species. LEADS TO A LOSS OF SPECIES

Question 31

stability

Answer 31

many hybrid zones are stable int he sense that hybrids continue to be produced. in some cases, this occurs because the hybrids survive or reproduce better than members of either parent species, at least in certain habitats or years. but stable hybrid zones have also been observed in cases where the hybrids are selected against an unexpected result.

Question 32

punctuated equilibria

Answer 32

describers these patterns in the fossil record: periods of apparent stasis punctuated by sudden change