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BIOL 108 Lecture > Topic 8: Speciation > Flashcards

Topic 8: Speciation Flashcards

1
Q

what is meant by the term “species”?

A

populations that can interbreed with members of the same group in nature and produce viable, fertile offspring

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2
Q

what is meant by the term “speciation”?

A

evolutionary process in which one species splits into 2+ species

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3
Q

what is meant by the term “macroevolution”?

A

evolutionary change at or above species level

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4
Q

what is meant by the term “microevolution”?

A
  • evolutionary change at or below species level
  • characterized by changes in the allele frequencies in a population over generations
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5
Q

what is the “biological species concept (BSC)”?

A

populations can interbreed or have potential to interbreed with members of the same group in nature, and produce viable, fertile offspring

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6
Q

what are key characteristics of the biological species concept (BSC)?

A
  • focus on breeding over generation
  • species are distinguished by reproductive isolation
  • relies on actual or potential breeding
  • gene flow between population of the same species contributes to unity of species
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7
Q

how is reproductive isolation caused?

A

by reproductive barriers

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8
Q

what is a reproductive barrier?

A

existence of biological factors that impede members of two species from producing viable, fertile offspring

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9
Q

what are the two main categories of reproductive barriers?

A
  • prezygotic barrier
  • postzygotic barrier
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10
Q

what is the prezygotic barrier?

A
  • reproductive barrier that impedes mating between species or hinders fertilization if interspecies mating in attempted
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11
Q

what are the main types of prezygotic barrier?

A
  • habitat isolation
  • temporal isolation
  • behaviour isolation
  • mechanical isolation
  • gametic isolation
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12
Q

what is meant by “habitat isolation”?

A

two species that live different habitats within the same location encounter each other rarely or not at all (gap in space)

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13
Q

what is meant by “temporal isolation”?

A

two species that breed at different times, leading to rare or no encounters (gap in time)

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14
Q

what is meant by “behaviour isolation”?

A

species use unique courtship rituals and other behaviours to attract mates (like the don’t speak the same language)

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15
Q

what is meant by “mechanical isolation”?

A

anatomical differences prevent successful mating (ducks corkscrew dicks)

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16
Q

what is meant by “gametic isolation”?

A

sperms of one species cannot fertilize the eggs of another species

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17
Q

what is the postzygotic barrier?

A

a reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults

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18
Q

what are the main categories of postzygotic barrier?

A
  • reduced hybrid viability
  • reduced hybrid fertility
    -hybrid breakdown
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19
Q

what is meant by “reduced hybrid viability”?

A

genes from parents of different species may interact to impair the hybrid’s development or survival

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20
Q

what is meant by “reduced hybrid fertility”?

A

hybrids may even be sterile and could not reproduce further, even if the hybrids survive

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21
Q

what is meant by “hybrid breakdown”? what is a possible cause?

A
  • reproductive failure that appears after the F2 generation of crosses between different species
  • possible cause is accumulation of deleterious genetic traits (alleles)
22
Q

what does the term”zygote” mean?

A

fertilized eggs from union of reproductive cells

23
Q

what does the term “hybrids” mean?

A

offspring from the mating of two different species

24
Q

what are the limitations of BSC?

A
  • cannot be applied to asexually reproducing organisms
  • cannot be examined in most fossil species
  • strong emphasis on the absence of gene flow between species (BSC implies that different species would not mate and produce viable offsprings, surviving offsprings do exist in nature)
25
what is the morphological species concept?
- defines species in terms of measurable anatomical features
26
what are the key features of the morphological species concept?
- observable and measurable features of a given species are distinct from other species - applicable to both extant and extinct organisms - applicable to both sexually and asexually reproducing organisms
27
what is the ecological species concept?
defines species by ecological niches, which encompass how organisms of the same species interact with biological and abiotic aspects of their environment
28
what are the key features of the ecological species concept?
- individual of the same species share similar preferences/tolerances to habitat conditions - species are grouped/separated by partitioning of ecological niches - applicable to both sexually and asexually reproducing organisms
29
what is the phylogenetic species concept?
define a species as the smallest group of individuals on a phylogeny
30
what are the key features of the phylogenetic species concept?
- based on evolutionary history and shared ancestry - species can be one of the tips/terminal taxa on phylogeny - applicable to sexually and asexually reproducing organisms
31
why can describing phylogenetic species be difficult?
- phylogenies are update frequently - tips can be expanded into a monophyletic group
32
what are the two categories of speciations based on whether or not geographic separation is present?
- allopatric speciation (geographically separated populations) - sympatric speciation
33
what is allopatric speciation?
- involves two geographically separated populations - formation of new species in populations that are geographically isolated from one another, and gene flow is interrupted
34
what is supporting evidence for allopatric speciation?
number of species is higher in regions with many geographic barriers
35
whether a geographic construct is geographic barrier depends on what?
how the population migrates
36
what are the two ways that lead to geographic isolation ?
- dispersal - vicariance
37
what is meant by the term "dispersal"?
- movement of individuals away from the rest of the population - the movement sometimes expands the geographic range of a population or species
38
what is meant by the term "vicariance"?
- range of a species is split by change in the environment, creating two subpopulations - subpopulations may be subjected to different selective agents and pressures
39
what is sympatric speciation? key characteristics and the general process?
- formation of new species in populations that live in the same geographic area - new species are established only when reproductive isolation is fully established - general process: geographic barrier is absent but some individuals stop interbreeding with others in population (stopping gene flow on a local level)
40
what are the types of mechanisms for sympatric speciation?
- habitat differentiation (under disruptive selection) - sexual selection
41
what is "habitat differentiation (under disruptive selection)"?
- subpopulations of the same species adapt to different environments, leading to reproductive isolation (reproductive barriers can be either prezygotic or postzygotic)
42
what is "sexual selection"?
- individuals with certain inherited characteristics are more likely than others to obtain mates (this selection for traits leads to increased mating, can lead to sexual dimorphism, traits can be deleterious to survival of the individuals) - can be seen as a form of natural selection for mating success & can drive sympatric speciation
43
what are "hybrid zones"?
- a geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry
44
can hybrid zones be partial overlap in ranges of two species?
yes
45
true or false: hybrids are often less fit, but can sometimes lead to speciation
true
46
what are the three possible outcomes of hybrid zones?
(1) reinforcement (2) fusion (3) stability
47
what is meant by the term "reinforcement"? what does this lead to?
- hybrid offsprings are less fit than the parents, and natural selection removed hybrids - leads to the strengthening of reproductive barriers (prezygotic)
48
what is meant by the term "fusion"? what does this lead to?
- hybrid offsprings are as fit as the parents, and gene flow can be maintained between hybrids and parent populations in substantial and stable ways - reproductive barrier is weakened and eventually removed
49
what is meant by the term "stability"? what does this lead to?
- hybrid offspring are continuously formed by the parents, and gene flow can be maintained between the parent populations in substantial and stable ways -stability may lead to fusion
50
can speciation occur with and without natural selection?
- yes - accumulation of genotypic difference leads to speciation - natural selection acts on traits of the new species - new species deemed unfit would be removed

BIOL 108 Lecture (9 decks)

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