Chapter 5 - Origin of Species Flashcards

1
Q

Speciation

A

the process by which one species splits into two or more species

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2
Q

Microevolution

A

changes in allele frequency in a population over time

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3
Q

Macroevolution

A

refers to broad patterns of evolutionary change above the species level

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4
Q

How do we define a species?

A
  • a group of similar living things that ranks below the genus in scientific classification and is made up of individuals able to produce offspring with one another
  • Used to be based just on physical similarity (morphology).
  • Now use morphology, physiology, DNA, ecology.
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5
Q

Biological Species Concept

A

states that a 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 members of other such groups
i.e., they are reproductively isolated from other species.

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6
Q

Reproductive barriers (isolating mechanisms)

A

Pre-zygotic Barriers
Post-zygotic Barriers

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7
Q

Pre-zygotic Barriers

A

Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
Gametic Isolation

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8
Q

Post-zygotic Barriers

A
  1. Reduced Hybrid Viability
  2. Reduced Hybrid Fertility
  3. Hybrid breakdown
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9
Q

Habitat isolation

A

populations live in different habitats and do not meet

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10
Q

Temporal isolation

A

different breeding times, seasons

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11
Q

Behavioral isolation

A

courtship or mating behaviors

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12
Q

Mechanical isolation

A

sex organs are mechanically incompatible

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13
Q

Gametic Isolation

A

gametes (egg and sperm) are incompatible

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14
Q

Reduced Hybrid Viability

A

Genes of the different parent species may interact and impair the hybrid’s development or survival in its environment

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15
Q

Reduced Hybrid Fertility

A

a common feature of reproductive barriers separating recently diverged species

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16
Q

Hybrid breakdown

A

Some first-generation hybrids are fertile, but when they mate with each other or with either parent species, offspring of the next generation are feeble or sterile

17
Q

Limitations of the Biological Species Concept

A
  • Cannot be applied to fossils or asexual organisms
  • Hybridization sometimes observed in nature
18
Q

Morphological species concept

A

defines a species by structural features
- It applies to both sexual and asexual species but relies on subjective criteria

19
Q

Ecological species concept

A

defines a species in terms of its ecological niche

20
Q

How Does Speciation Occur?

A

Speciation will occur if environmental conditions are different, and populations are separated for long periods and developed their own unique characteristics.

21
Q

Speciation can occur in two ways:

A
  1. Allopatric speciation
  2. Sympatric speciation
22
Q

Allopatric speciation

A

geologic barrier divides a population, leaving each group to follow its own evolutionary path.

23
Q

Sympatric speciation

A

more common in plants, no geographic barrier. Isolation is due to accidents during cell division resulting in polyploid offspring.

24
Q

The Process of Allopatric Speciation

A

Geographical barrier arises
Separated populations may evolve independently through mutation, natural selection, and genetic drift
- Causes genetic divergence
Reproductive isolation may arise as a by-product of genetic divergence
- E.g., geographically isolated populations of mosquitofish have become reproductively isolated as a result of selection under different levels of predation

25
Sympatric Speciation Can occur if gene flow is reduced by factors including:
- Polyploidy - Sexual selection - Habitat differentiation
26
Polyploidy
 involves a spontaneous doubling of chromosomes, also means random  is a condition of having more than 2 complete sets of chromosomes  the presence of extra sets of chromosomes due to accidents during cell division  much more common in plants than in animals  can produce new biological species in sympatry within a single generation
27
Autopolyploid
individual has more than two sets of chromosomes that came from same parent of species
28
Allopolyploid
individual that has more than 2 copies, but these copies come from different type of species.
29
Sexual selection
 members of one sex choose mates of the other sex to mate with and compete with members of the same sex for access to members of the opposite sex.  Sexual selection for mates of different colors has likely contributed to speciation in cichlid fish in Lake Victoria
30
Habitat differentiation
 more types of habitat in the same quantity in geographical zones  Sympatric speciation can also result from the appearance of new ecological niches  E.g., North American maggot fly (Rhagoletis pomonella) can live on native hawthorn trees, as well as more recently introduced apple trees
31
Hybrid Zones
where ranges overlap, and mating occurs
32
Hybrid Zones Three possibilities:
Reinforcement Fusion Stability
33
Reinforcement
strengthens reproductive barriers if hybrids have reduced fitness
34
Fusion
members of the two lineages mate together forming hybrids
35
Stability
each lineage keeps its own range apart of each other save for some areas of overlap.
36
Punctuated Equilibrium
is a theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history
37
Gradualism
is a hypothesis, a theory, or a tenet assuming that change comes about gradually or that variation is gradual in nature and happens over time as opposed to in large steps