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Biology 1114H > Speciation > Flashcards

Speciation Flashcards

1
Q

If gene flow stops, what happens to isolated populations?

A
  1. Allele frequencies can diverge
  2. Populations begin to evolve independently
  3. Divergence may occur due to mutation, natural selection, and genetic drift
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2
Q

What is speciation?

A

When genetic divergence results in two or more distinct species stemming from an ancestral species

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3
Q

What is the Morphological Species Concept?

A

When a species shares more similar characteristics with each other because of shared evolutionary history

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4
Q

What is the Genetic Species Concept?

A

When species share more similar DNA because of shared evolutionary history

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5
Q

What is the Biological Species Concept?

A

A species contains groups of organisms that can interbreed and produce viable offspring and are reproductively isolated from other species

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6
Q

After splitting off from an ancestral population, each new population evolves in what ways?

A

Develop mutations independently

Each population has different selective environments

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7
Q

Members of the same species are linked by what?

A

Shared evolutionary history via the ability to exchange genetic information

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8
Q

What are the limitations to the Biological Species Concept?

A

Hybrids, extinct organisms, and asexually reproducing species

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9
Q

What are the limitations to the Morphological Species Concept?

A

Variation within species is tremendous

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10
Q

What are the limitations to the Genetic Species Concept?

A

Variation within species is tremendous

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11
Q

What is another definition for speciation?

A

The process by which populations attain reproductive isolation

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12
Q

What is reproductive isolation?

A

Biological barriers that impede members of different species from interbreeding and producing viable, fertile offspring

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13
Q

What are the 2 categories of biological barriers?

A

Pre-zygotic and post-zygotic barriers

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14
Q

What are pre-zygotic barriers?

A

Barriers that prevent mating or fertilization if mating does occur

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15
Q

What are post-zygotic barriers?

A

Barriers that prevent hybrid offspring of two species from developing into viable, fertile adults

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16
Q

What are the 5 pre-zygotic isolating mechanisms?

A
  1. Habitat (ecological or spatial) Isolation
  2. Temporal or Seasonal Isolation
  3. Behavioral Isolation
  4. Mechanical Incompatibility
  5. Gametic Isolation
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17
Q

What is Habitat Isolation?

A

When habitat preferences lower the probability of mating between individuals associated with different habitats

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18
Q

What is Temporal or Seasonal Isolation?

A

When species are prevented from interbreeding due to differences in the timing of mating or fertility, such as having different mating seasons

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19
Q

What is Behavioral Isolation?

A

When mating behavioral differences prevent mating

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20
Q

What are 2 examples of mating behavioral differences?

A
  1. Incorrect courtship displays
  2. Can’t recognize mating signals
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21
Q

What is Mechanical Incompatibility?

A

When morphological differences, often in genitals, prevent mating

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22
Q

What is Gametic Isolation?

A

When the sperm does not survive or physically cannot fuse with the egg

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23
Q

What are the 3 post-zygotic isolating mechanisms?

A
  1. Reduced hybrid viability
  2. Hybrid infertility
  3. Hybrid breakdown
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24
Q

What is Reduced Hybrid Viability?

A

The death of a zygote or organism

25
Q

What is Hybrid Infertility?

A

When a hybrid lives, but is sterile

26
Q

What is Hybrid Breakdown?

A

When the viability or fitness of a hybrid decreases with subsequent generations

27
Q

What is Allopatric Speciation?

A

When reproduction is prevented by geographic isolation of a previously continuous population

28
Q

What are the two ways allopatric speciation can occur?

A

Vicariance and dispersal

29
Q

What is vicariance?

A

When a physical barrier splits a population into subgroups that are physically isolated from each other

30
Q

What is dispersal?

A

When a population moves to a new habitat, colonizes it, and founds a new population

31
Q

What is Biogeography?

A

The study of how species and populations are distributed geographically

32
Q

What can Biogeography tell us?

A

How vicariance and dispersal events can occur

33
Q

What can colonization (dispersal) events lead to?

A

Speciation

34
Q

What is parapatric speciation?

A

Geographically continuous populations over extremely vast distances experience divergence

35
Q

Different ends of a parapatric species have two characteristics:

A
  1. Functionally isolated from each other
  2. Experience distinct selective pressures
36
Q

What is a ring species?

A

Continuous populations over large geographic areas form a ring where the populations rejoin

37
Q

What is frequency-dependent selection?

A

When the fitness of a phenotype or genotype depends on the phenotype or genotype composition of the population

38
Q

Populations or species that live in the same area and are close enough to interbreed are called what?

A

Sympatric

39
Q

What is sympatric speciation?

A

When speciation occurs among populations in the same geographic area

40
Q

What are the two events that initiate sympatric speciation?

A
  1. Internal events- chromosomal mutations
  2. External events- disruptive selection (different ecological niches or mate preferences)
41
Q

What is polyploidy?

A

When cells have more than one pair of chromosomes

42
Q

Polyploidy is a mutation important for what?

A

Speciation

43
Q

Where is polyploidy most commonly seen?

A

In plants

44
Q

What is autopolyploidy?

A

A mutation that doubles chromosome number when the chromosomes all come from the same species

45
Q

What is allopolyploidy?

A

When parents of different species mate and an error in mitosis occurs, resulting in viable, nonsterile offspring

46
Q

What is a niche?

A

Range of ecological resources that a species can use and the range of conditions it can tolerate

47
Q

Sympatric species are not geographically isolated, how else can they be isolated?

A

Reproductively isolated due to adapting to different ecological niches via disruptive selection

48
Q

What is a hybrid zone?

A

A geographic area where interbreeding between two populations occurs and hybrid offspring are more common

49
Q

Depending on the hybrid offspring fitness and extent of breeding between parental species, hybrid zones can be (three answers):

A
  1. Narrow or wide
  2. Long or short lived
  3. Stable in one place or move over time
50
Q

Describe how new species form through hybridization

A

Two species may interbreed and produce hybrid offspring that survive, reproduce, and posses a unique combination of traits adaptive to their particular environment, which may result in a new species

51
Q

What are the 5 possible outcomes of secondary contact between species

A
  1. Fusion of the populations
  2. Reinforcement of divergence
  3. Hybrid zone formation
  4. Extinction of one population
  5. Formation of new species
52
Q

Describe fusion of populations as an outcome of secondary contact between species

A

When the two populations freely interbreed

Typically happens when two populations of the same species come in contact with each other

53
Q

Describe reinforcement of divergence as an outcome of secondary contact between species

A

Hybrid offspring have low fitness and natural selection favors the traits that prevent interbreeding between the populations

54
Q

Describe hybrid zone formation as an outcome of secondary contact between species

A

Hybridization occurs in a well-defined geographic area

55
Q

Describe extinction of one population as an outcome of secondary contact between species

A

If one population of species is a better competitor for shared resources, the poorer competitor may be driven to extinction

56
Q

Describe formation of a new species as an outcome of secondary contact between species

A

If the combination of genes in hybrid offspring allows them to occupy distinct habitats or use novel resources, they may form a new species

57
Q

What is negative frequency-dependent selection?

A

When a trait with a higher frequency is selected against (snails)

58
Q
A

Biology 1114H (12 decks)

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