ch 24: speciation

Question 1

speciation

Answer 1

splitting event that creates two or more distinct species from an ancestral species

Question 2

what two steps does speciation occur in?

Answer 2

genetic isolation and genetic divergence

Question 3

genetic isolation

Answer 3

barrier to gene flow isolates two populations within species

Question 4

genetic divergence

Answer 4

mutation, natural selection, and genetic drift occur in each of the isolated populations

Question 5

species

Answer 5

evolutionary independent population or group of populations

Question 6

what 3 criteria do biologists use for identifying species?

Answer 6

1. biological species concept
2. morphological species concept
3. phylogenetic species concept

Question 7

biological species concept

Answer 7

main criterion for identifying species is reproductive isolation
- members of populations that cannot or do not interbreed or fail to produce viable, fertile offspring after mating

Question 8

reproductive isolation

Answer 8

mechanisms that prevent gene flow between populations

Question 9

prezygotic isolation

Answer 9

individuals are prevented from successful mating

Question 10

types of prezygotic isolation

Answer 10

temporal
habitat
behavioral
mechanical
gametic barrier

Question 11

temporal prezygotic isolation

Answer 11

populations are isolated because they breed at different times

Question 12

habitat prezygotic isolation

Answer 12

populations are isolated because they breed in different habitats

Question 13

behavioral prezygotic isolation

Answer 13

populations do not interbreed because they have different courtship displats

Question 14

mechanical prezygotic isolation

Answer 14

mating fails because male and female reproductive structures are incompatible

Question 15

gametic barrier prezygotic isolation

Answer 15

mating fails because eggs and sperm are incompatible

Question 16

postzygotic isolation

Answer 16

mating may be successful, but the (hybrid) offspring do not survive or reproduce (inviable or sterile)

Question 17

hybrid inviability postzygotic isolation

Answer 17

hybrid offspring do not develop normally and die at some point during early development

Question 18

hybrid sterility postzygotic isolation

Answer 18

hybrid offspring mature but are sterile as adults

Question 19

advantages of biological species concept

Answer 19

most frequently used by biologists

Question 20

disadvantages of biological species concept

Answer 20

-reproductive isolation in the wild, but viable hybrid offspring can be produced in captivity
-does not apply to fossils or organisms that reproduce asexually

Question 21

morphological species concept

Answer 21

• individual lineages differ in size, shape or some other morphological feature

Question 22

how did distinguishing features arise according to the morphological species concept?

Answer 22

independent populations that are isolated from gene flow

Question 23

advantages of morphological species concept

Answer 23

• useful when there is no data on extent of gene flow
• widely applicable to sexual, asexual, and fossil species

Question 24

disadvantages of morphological species concept

Answer 24

• polymorphic species may be classified as more than 1 speices
• cannot identify cryptic species that differ in non-morphological traits
• features used to distinguish species can be subjective

Question 25

phylogenetic species concept

Answer 25

identifies species based on evolutionary history, based on the theory that all species are related by common ancestry

Question 26

monophyletic group

Answer 26

consists of an ancestral population plus all of its descendents

Question 27

advantages of phylogenetic species concept

Answer 27

- can be applied to sexual, asexual, and fossil populations - different species have unique synapomorphies due to lack of gene flow and independent evolution

Question 28

disadvantages of phylogenetic species concept

Answer 28

- good phylogenies based on DNA are not available for all populations - leads to recognition of many more species - inconsistent with reproductive isolation

Question 29

when does genetic isolation occur?

Answer 29

when populations become geographically separated

Question 30

allopatry

Answer 30

populations that live in different areas

Question 31

allopatric speciation

Answer 31

speciation that begins with geographic isolation

Question 32

what are the two ways allopatric speciation can begin?

Answer 32

dispersal and vicariance

Question 33

dispersal

Answer 33

movement of individuals from one place to another

Question 34

vicariance

Answer 34

physical splitting of a habitat - creates subgroups

Question 35

what occurs where there is a physical barrier?

Answer 35

vicariance can occur when mountain range uplifts or river splits geographic range of species

Question 36

sympatry

Answer 36

populations or species that live in the same geographic area or are close enough to interbreed

Question 37

sympatric speciation

Answer 37

speciation that occurs among populations within the same geographical area

Question 38

what are the two ways sympatric speciation can occur?

Answer 38

external and internal events

Question 39

external (extrinsic) events

Answer 39

disruptive selection based on different ecological niches or mate preferences

Question 40

internal (intrinsic) events

Answer 40

chromosomal mutations

Question 41

disruptive selection

Answer 41

acts on diverse type of traits that include morphology and behaviors - can involve survival of organisms in their environment

Question 42

niche

Answer 42

range of ecological resources that species can use and tolerate

Question 43

polyploidy

Answer 43

possessing more than two complete sets of chromosomes - caused by massive error in meiosis or mitosis

Question 44

autoploidy

Answer 44

individuals when a mutation results in a doubling of the chromosome number - chromosomes from same species

Question 45

allopolyploidy

Answer 45

individuals are created when parents of different species mate and an error in mitosis occurs, resulting in viable and nonsterile offspring - offspring with two different sets of chromosomes produced - usually from self-fertilization

Question 46

is allopolyploidy or autopolyploidy more common?

Answer 46

allopolyploidy

Question 47

how do autopolyploidy and allopolyploidy individuals breed?

Answer 47

with other individuals similar to them - cannot be different otherwise their offspring will be sterile - reproductive isolation

Question 48

what happens without prezygotic and postzygotic reproductive barriers?

Answer 48

gene flow erases distinctions between two previously isolated populations that are fusing together again

Question 49

what happens as pairs of species diverge genetically?

Answer 49

they become increasingly reproductively isolated

Question 50

if two populations have diverged extensively and are genetically distinct, what happens to the fitness of their offspring?

Answer 50

it will be lower than the parent's fitness

Question 50

reinforcement

Answer 50

natural selection for traits that prevent interbreeding among populations

Question 50

what happens when postzygotic isolation occurs?

Answer 50

strong natural selection against interbreeding

Question 51

what does reinforcement cause?

Answer 51

prevents mating between sympatric species but not allopatric species

Question 52

if hybrid offspring of two species are fit and interbreed with both parental populations, what happens?

Answer 52

gene pools are mixed and there is no speciation

Question 53

if hybrid offspring survive or reproduce poorly, what happens?

Answer 53

natural selection will favor prezygotic barriers, which is reinforcement