lecture 16

Question 1

Speciation

Answer 1

• Process by which one species splits into two or more daughter species

Question 2

What happens during the gradual separation of species? (Speciation)

Answer 2

2 populations at various stages of becoming a new species will exist

Question 3

Reproductive isolation (speciation)

Answer 3

Important component of the process of speciation

Question 4

What happens if individuals within a population mated with one another but not with individuals of other populations? (Speciation)

Answer 4

They are an independent evolutionary unit on separate branches on the tree of life

Question 5

Morphological species concept

Answer 5

• Members of species look alike because they share many alleles
• immature individuals may not look like their parents

Question 6

Sexual dimorphism

Answer 6

Males and females may not look alike

Question 7

Biological species concept

Answer 7

• Species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
• they do not breed successfully with other populations
• gene flow between population holds the phenotype of a population together

Question 8

What happens if 2 populations are isolated, over time?

Answer 8

• Their genetic structure may change enough
• interbreeding is no longer possible
• gene flow must be interrupted

Question 9

Allopatric speciation

Answer 9

• Population forms a new species while geographically isolated from its parent population
• Populations separated by a physical barrier
• thought to be the dominant mode of speciation

Question 10

Sympatric speciation

Answer 10

• Subset of a population forms a new species without geographic separation
• no physical isolation

Question 11

Sympatric speciation can result from:

Answer 11

• Polyploidy
• habitat differentiation
• sexual selection

Question 12

Polyploidy

Answer 12

• Presence of extra sets of chromosomes due to accidents during cell division
• more common in plants than animals

Question 13

2 forms of polyploidy

Answer 13

• Autopolyploid
• allopolyploid

Question 14

Autopolyploid

Answer 14

• Individual with more than two chromosome sets, derived from one species
• non disjunction of gametes by meiosis, results in diploid gametes
• if they self-fertilize the offspring would have four sets of chromosomes, they would be tetraploids

Question 15

Allopolyploid

Answer 15

• Species with multiple sets of chromosomes derived from different species
• more common
• in other generations, various mechanisms may transform a sterile hybrid into a fertile polyploid
• polyploid hybrids are fertile with each other but cannot breed with either parent species

Question 16

Habitat differentiation

Answer 16

• Result of sympatric speciation
• appearance of new ecological niches

Question 17

Hybrid zone

Answer 17

• Region in which members of different species mate and produce hybrids
• distribution can be more complex if parent species are found in patches within the same region

Question 18

Hybrids

Answer 18

• Result of mating between species with incomplete reproductive barriers
• often have reduced fitness compared with parent species

Question 19

What happens (3) when closely related species meet in a hybrid zone?

Answer 19

• Reinforcement
  -Fusion
• stability

Question 20

Reinforcement

Answer 20

• Hybrids are less fit than member of parental species, natural selection strengthens prezygotic reproductive earners
• reduce the formation of unfit hybrids
• strengthens reproductive barriers, especially between sympatric species

Question 21

Fusion

Answer 21

• When barriers to reproduction in the hybrid zone are weak, gene flow may weather the reproductive barriers between species
• process of speciation may reverse ,causing the two hybridizing species to fusion into one

Question 22

Stable

Answer 22

• Many hybrid zones are stable
• hybrids continue to produce

Question 23

Sexual selection

Answer 23

• Can drive sympatric speciation

Question 24

Reproductive isolation

Answer 24

• Existence of biological factors (barrier) that impede 2 species from producing viable fertile offspring
• can be classified by whether factors act before or after fertilization

Question 25

Habitat isolation

Answer 25

2 species encounter each other rarely or not at all, because they occupy different habitats, even if they are not isolated by physical barriers

Question 26

Temporal isolation

Answer 26

Species that breed at different times of the day, different seasons, or different years cannot mix their gametes

Question 27

Behavioral isolation

Answer 27

Courtship rituals and other behaviors unique to a species are effective barriers

Question 28

Mechanical isolation

Answer 28

Morphological differences can prevent successful mating

Question 29

Gametic isolation

Answer 29

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

Question 30

Prezygotic barriers

Answer 30

• Habitat isolation
• temporal isolation
• behavioral isolation
• mechanical isolation
• gametic isolation

Question 31

Postzygotic barriers

Answer 31

• reduced hybrid viability
• reduced hybrid fertility
  -Hybrid breakdown

Question 32

Reduced hybrid viability

Answer 32

• genes of the different parent species may interact and impair the hybrid’s development

Question 33

Reduced hybrid fertility

Answer 33

Even if hybrids are vigorous, they may be sterile

Question 34

Hybrid breakdown

Answer 34

• Some 1st gen hybrids are fertile but when they mate with another species or with either parent species, offspring of the next gun are feeble or sterile

Question 35

Gradualism

Answer 35

• Evolution proceeds continuously over long periods
• species descend from a common ancestor
• through time a gradually change or diverge from the ancestor occurs as they acquire unique adoptions
• fossils records incomplete