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BIO1M03 > Evolution - Ch 24 - Speciation > Flashcards

Evolution - Ch 24 - Speciation Flashcards

1
Q

What is speciation?

A

the evolution of two new lineages (species) from a single ancestral species

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2
Q

What can cause speciation?

A

genetic isolation (NO gene flow) and genetic divergence (caused by natural selection, genetic drift, mutations, and sexual selection)

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3
Q

What is a species? What are four different sets of criteria used to identify species?

A

an evolutionarily independent population or group of populations

  • biological species concept
  • morpho-species concept
  • ecological species concept
  • phylogenetic species concept
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4
Q

What factors cause prezyogtic (reproductive) isolation?

A

temporal, habitat, behavioural, gametic barrier, and mechanical (and genetic)

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5
Q

What factors cause postzyogtic (reproductive) isolation?

A

hybrid viability and hybrid sterility

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6
Q

What is temporal isolation?

A

when populations breed at different times

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7
Q

What is behavioural isolation?

A

when populations have different courtship displays

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8
Q

What is habitat isolation?

A

when populations live in different habitats

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9
Q

What is a gametic barrier?

A

when sex cells are incompatible between mates

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10
Q

What is mechanical isolation?

A

when male and female reproductive structures are incompatible

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11
Q

What is hybrid viability? Hybrid sterility?

A
  • hybrid viability: hybrid offspring die as embryos

- hybrid sterility: hybrid offspring cannot reproduce

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12
Q

What is the biological species concept?

Advantages? Disadvantages?

A

(given NO gene flow) populations that can produce viable offspring are the same species

  • advantage: clear
  • disadvantage: fossil and asexual species; hard to assess if populations do not overlap geographically
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13
Q

What is the morpho-species concept?

Advantages? Disadvantages?

A

based on differences in size, shape or other morphologies

  • advantage: widely applicable
  • disadvantage: “cryptic” species; can lead to too many names for one polymorph; subjective
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14
Q

What is the ecological species concept?

Advantages? Disadvantages?

A

the same species have the same niche (range of resources, and tolerances)

  • advantage: applies to asexual species
  • disadvantage: different species can have similar ecological roles
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15
Q

What is the phylogenetic species concept?

Advantages? Disadvantages?

A

smallest monophyletic group on a phylogenetic tree

  • advantage: widely applicable, can be tested for
  • disadvantage: our data on the tree of life is small; possibly leads to naming of “too many” species
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16
Q

What is allopatry?

A

when populations are living in different geographical areas

17
Q

What is allopatric speciation, and what are its two modes?

A

the divergence and creation of new species by physical isolation
-vicariance and dispersal

18
Q

What is vicariance?

A

the physical separation of a population into components via a chance event that splits a habitat (ex. by glaciation)

19
Q

What is dispersal?

A

when some individuals migrate to a new habitat, and colonize it to found a new, physically isolated population

20
Q

What is sympatry?

A

when populations live close enough together so that interbreeding is possible

21
Q

What is an ecological niche? What type of selection can lead to speciation?

A

the range of environmental resources that a species can use, and the range of conditions it can tolerate
-disruptive selection, which can lead to reproductive isolation in a population as individuals adapt to different niches

22
Q

What is sympatric speciation? What events can cause it?

A

the formation of new species even though populations live in the same geographical area

  • can happen through
    (1) external events (ex. disruptive selection) and
    (2) internal events (ex. chromosonal mutations)
23
Q

What specific type of mutation can be very important in speciation?

A

polyploidism

24
Q

What is a polyploid?

A

a condition when mutant individuals have more than two sets of chromosomes
-leads to reduced gene flow between mutant and wild-type individuals

25
Q

What two ways are polyploid individuals formed?

A

alloploidy (more common) and autoploidy

26
Q

What kind of polyploid is produced when the chromosome doubling and chromosomes come from the same species?

A

autopolyploid

27
Q

What kind of polyploid is produced when the chromosome doubling and chromosomes come from the different species?

A

allopolyploid

28
Q

Compared to other forms of speciation, what is special about polyploidism (in terms of rate)?

A

it creates species instantaneously!

29
Q

Why have polyploids been so successful (especially plants)?

A
  1. Polyploids suffer less from inbreeding depression
  2. Polyploids have more heterozygosity
  3. Genes on duplicated chromosomes can also undergo change, so genetic variation increases in polyploids
30
Q

Suppose two isolated populations come back together. What are the four possibilities?

A
  1. fusion
  2. reinforcement
  3. hybrid zones
  4. speciation by hybridization
  5. extinction of one population
31
Q

How does fusion of two once previously isolated populations happen?

A

if two populations can freely interbreed, populations become more similar to each other

32
Q

Suppose two isolated populations come back together. How does reinforcement happen?

A

hybrids have low fitness (N.S. selects against hybrids, preventing interbreeding)
-solidifies the trait differences between populations which happened because of separate evolutions

33
Q

Suppose two isolated populations come back together. How do hybrid zones happen?

A

hybrids have medium fitness

34
Q

Suppose two isolated populations come back together. How does speciation by hybridization happen?
(ex. sunflowers: H. annus and H. petiolaris produce a hybrid called H. anomalus)

A

hybrids have high fitness because of unique combination of traits

35
Q

What is a hybrid zone?

A

a geographical area in which interbreeding happens between populations and (viable) hybrids are common
-it can move over time, and it depends on hybrid fitness and extent of interbreeding

36
Q

Suppose two isolated populations come back together. How does extinction of one population happen?

A

if one population outcompetes the other for resources

BIO1M03 (14 decks)

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