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4 Mechanisms of Evolution > 24 The Origin of Species > Flashcards

24 The Origin of Species Flashcards

1
Q

What is macroevolution?

A

The broad patterns of evolution ABOVE the species level.

Therefore it is more about evolutionary history etc. such as the origin of new groups of organism

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2
Q

What are broad patterns of evolution above the species level called?

A

Macroevolution.

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3
Q

What is speciation?

A

The process by which species form.

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4
Q

What are the different definitionS of species?

A

‘Biological species’, ‘morphological species’, ‘ecological species’ and ‘phylogenetic species’

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5
Q

What is the biological species concept

A

A species is a group of populations whose members can interbreed in nature to produce viable, fertile offspring but can not produce fertile, viable offspring with other such groups

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6
Q

What is the most common definition of species?

A

Biological species is most widely used by scientists.

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7
Q

What is required for an organism to become a new biological species?

A

‘Reproductive isolation’

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8
Q

What is the name for the definition based on its ability to interbreed to produce fertile offspring?

A

Biological species concept

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9
Q

What is ‘reproductive isolation’?

A

The existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable, fertile offspring.

Thus it leads to new biological species.

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10
Q

What can ‘reproductive isolation’ be divided into?

A

‘Prezygotic barriers’ and ‘postzygotic barriers’

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11
Q

What are the basic pre zygotic barriers?

A

Before mating attempt:

  • Habitat isolation
  • Temporal isolation
  • Behavioural isolation

After matting attempt:

  • Mechanical isolation
  • Gametic isolation
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12
Q

What is habitat isolation?

A

Two species occupy different habitats with in the same area and thus rarely encounter each other.

Not that they may be close i.e. one in tree, one in bush or far i.e. separated by a mountain range.

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13
Q

What is temporal isolation?

A

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

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14
Q

What is behavioural isolation?

A

Courtship rituals that attract mates and other behaviors unique to a species are often reproductive barriers.

Such behavioral rituals enable mate recognition-a way to identify potential mates of the same species.

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15
Q

What is ‘mate recognition’

A

A way to identify potential mates

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16
Q

What is it called when organisms identify potential mates?

A

‘Mate recognition’

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17
Q

What is mechanical isolation?

A

Mating is attempted by morphological differences prevent its successful completion

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18
Q

What is reduced hybrid viability?

A

The genes of different parent species may interact in ways that impair the hybrid’s development or survival in its environment.

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19
Q

What is reduced hybrid fertility?

A

Even if hybrids are vigorous, they may be sterile. If the chromosomes of the two parent species differ in number or structure, meiosis in the hybrids may fail to produce normal gametes.

Since the infertile hybrids cannot produce offspring when they mate with either parent species, genes cannot flow freely between the species.

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20
Q

What is ‘hybrid breakdown’

A

Some first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species, off- spring of the next generation are feeble or sterile.

(this is typically seen in plants)

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21
Q

What are some limitations of the biological species concept?

A
  • Can’t evaluate speciation in fossils as we do not know reproductive history
  • Doesn’t apply to asexual organisms
  • Ligers etc. show hybrids are possible
22
Q

What is the morphological species concept?

A

Characterizes a species by body shape and other structural features.

23
Q

What are some advantages and disadvantages of the morphological species concept?

A

+:

  • Works on fossils and asexual
  • Easier to identify than observing offspring
  • :
  • Can be subjective - phenotypic variation vs. new species
24
Q

What is the ecological species concept?

A

It views a species in terms of its ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment.

For example, two species of salamanders might be similar in appearance but differ in the foods they eat or in their ability to tolerate dry conditions.

25
Q

What are the characteristics of the ecological species concept?

A

It can accommodate asexual as well as sexual species. It also emphasizes the role of disruptive natural selection as organisms adapt to different environmental conditions.

26
Q

What is the ‘phylogenetic species concept’?

A

The idea that a species is the smallest group of individuals that share a common ancestor, forming one branch in the tree of life.

27
Q

What are the advantages and disadvantages of the phylogenetic species concept?

A
  • Can change as new evidence emerges

- Needs viable samples for genetic analysis

28
Q

What are the basic forms of separation that can lead to new species?

A

‘Allopatric speciation’ and ’sympatric speciation’

29
Q

What is ‘allopatric speciation’?

A

When organisms are separated by a geographic physical barrier i.e. a mountain range.

These independent populations develop into distinct species through genetic drift or natural selection to their new environment.

30
Q

What is an ‘isthmus’

A

A narrow strip of land with sea on both sides. (like a peninsula but goes all the way across and cuts off)

(for example they the Panama Canal cuts through an isthmus)

31
Q

What is ’sympatric speciation’?

A

Speciation that occurs in populations that live in the same geographic area.

32
Q

What is speciation when organisms are separated called?

A

Allopatric speciation

33
Q

What is speciation when organism remain in the same location called?

A

Sympatric speciation

34
Q

What are ’sibling species’?

A

Pairs of species that are most closely related, especially when they diverged from one species to become multiple.

35
Q

What are the basic causes of sympatric speciation?

A

Polyploidy, Habitat differentiation and Sexual selection

36
Q

In what organisms do new species originate through polyploidy?

A

It is extremely common in plants and rarely (but still sometimes) occurs in animals

37
Q

What can speciation through polyploidy be divided into?

A

Autopolyploid and allopolypoid

38
Q

What is autopolyploid speciation?

A

When an organism has more than two sets of chromosomes from the same species and thus it is tetraploid

39
Q

What is allopolyploid speciation?

A

When organisms have chromosomes from multiple species and thus are hybrids.

40
Q

How can autopolyploidy lead to speciation?

A

Imagine a species in which 2n=6. If non-disjucntion occurred a 4n=12 autopolyploid offspring could result.

This 4n=12 would produce n=6 gametes. If these combined with n=3 gametes from the original parents 2n=9 offspring would form.

These would not be able to perform meiosis as it would not be able to halve the number of chromosomes is each cell.

Thus a reproductive barrier is formed where only the new tetraploid individuals can interbreed, thus a new species has arisen.

41
Q

What is ‘habitat differentiation’?

A

A form of spympatric speciation in genetic factors allow a sub-population to exploit a nee habitat.

This separates the old and new populations, possibly to the extent that a new species forms.

42
Q

How can sexual selection lead to sympatric speciation?

A

If a subpopulation of females decides to mate exclusively with only a specific set of males then they exclusivity could lead to separate species forming.

43
Q

What is a region when multiple species interact called? (especially if they have offspring)

A

A ‘hybrid zone’

44
Q

What is a ‘hybrid zone’?

A

A region in which members of different species meet and made.

45
Q

Where are ‘hybrid zones’ typically found?

A

At the boundaries of the ranges of two species.

For example there might be a small overlap between an alpine toad and a toad that lives at the base of the mountain.

Note that they may be large or quite narrow.

46
Q

What are the basic ways that hybrid zones change over time

A

‘Reinforcement’, ‘fusion’ or ‘stability’

47
Q

In terms of how hybrid zones change over time, what is ‘reinforcement’?

A

The reproductive barriers between the species strengthen so that eventually no hybrids are formed.

48
Q

In terms of how hybrid zones change over time, what is ‘fusion’?

A

The reproductive barriers between the species weaken so that eventually the two species fuse into one

49
Q

In terms of how hybrid zones change over time, what is ’stability’?

A

The reproductive barriers remain constant so that hybrids continue to be produced but the species don’t merge.

50
Q

What does ’stasis’ refer to?

A

A period of equilibrium and stability, especially when describing a constant environment.

4 Mechanisms of Evolution (4 decks)

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