Origins of Species Flashcards

1
Q

How do complex traits evolve?

A
  • Advantageous intermediates (intermediate step might be advantageous in itself. Trait evolved by natural selection and improves an organisms ability to survive and leave descendants)
  • Exaptation (Process by which features acquire functions for which they were not originally adapted or selected. Structure originally evolves for one purpose and then evolve further for another)
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2
Q

What are the 2 types of speciation?

A
  • Allopatric (vicariant or founder effect)

- Sympatric

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3
Q

What is allopatric speciation?

A
  • ancestral population geographically divided
  • isolated subpopulations evolve reproductive barriers between them
  • can occur two ways (vicariant and founder effect)
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4
Q

What is Vicariant speciation?

A
  • climate or geology causes populations to fragment
  • fragments of the ancestral population are left intact
  • fragmentation can occur in several species simultaneously
  • Isthmus of Panama (land bridge that connects North and South America)
  • Formed approx. 3,5 million years ago
  • 30 species of snapping shrimp; genus Alpheus
    15 sister species on each side of the land bridge
  • Many speciation events due to the same geographic barrier
  • Land bridge caused geographical barriers which led to reproductive barriers
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5
Q

What is the founder effect?

A
  • occurs when a small number of individuals disperse to a distant place and form new populations
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6
Q

What is sympatric speciation?

A
  • diverging lineages co-occupy a geographic area

- different individuals within a species become specialized for occupying different components of the environment

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7
Q

What is the biological species concept?

A
  • characterizes species by their ability to interbreed to produce fertile offspring
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8
Q

What is the morphological species concept?

A

characterizes species by body shape and other morphological features

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9
Q

What is ecological species concept?

A

characterizes species in terms of its ecological niche

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10
Q

Why are not all hybrids infertile?

A
  • Interspecific hybrids (offspring produce by mating of individuals from two different species)
  • Interspecific hybrids can sometimes be fertile and mate with another hybrid or other of their parental species
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11
Q

What is a species?

A
  • Bottom line: not easy to define
  • The designation of species is a human construct
  • No consensus, but most biologists would agree
    individuals descend from a common ancestral population
    reproductive compatibility
    genotypic and phenotypic cohesion
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