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Biology 121 > Evolution: Speciation > Flashcards

Evolution: Speciation Flashcards

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1
Q

Species

A

an evolutionary independent population or group of populations
- genetically separate enough from other taxa that evolutionary mechanisms that affect one species are not shared by another

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2
Q

4 criteria to identify a species:

A

1) Biological species concept
2) Morphospecies concept
3) ecological species concept
4) phylogenetic species concept

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3
Q

What is the biological species concept?

A

1/4 criteria to identify a species

  • species = member of a population(s) that can interbreed and (potentially) produce fertile offspring
  • species are reproductively isolated due to reproductive barriers
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4
Q

the reproductive barriers of BSC

A

1) prezygotic isolation: prevents individuals from successfully mating or sperm from fertilizing the egg.
5 common barriers…

a) Temporal: Populations are isolated because they breed at different times.
- ie: Bishop pines and Monterey pines release their pollen at different times of the year.

b) Habitat: Populations are isolated because they breed in different habitats (in the same area).
- ie: hawthrorn & apple maggot fly

c) Gametic: Matings fail because eggs and sperm are incompatible.
- ie: Differences in the shape of bindin protein determine whether sea urchin sperm will penetrate eggs

d) Behavioural: Populations do not interbreed because they have different mating rituals.
- ie: fireflies have a sspecies-specific sequene of flashes that attract mates

e) Mechanical: male and female reproductive structures are incompatible.
- ie: spiked penis of a beetle

2) postsygotic isolation: individualds of adifferent species CAN mste but thir offspring dont survive or are infertile
2 common barriers….

a) Hybrid viability: Hybrid offspring do not develop normally and die as embryos.

b) hybrid sterility: Hybrid offspring mature but are infertile as adults.
- ie: A female horse can mate with a male donkey to produce a sturdy and long-lived mule. However, the mule is sterile.

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5
Q

BSC disadvantages

A
  • if nearby populations don’t overlap its hard to tell if they are reproductively isolated or not
  • doesn’t apply to asexual populations
  • cant be tested on fossils
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6
Q

Morphospecies concept

A

1/4 criteria to identify a species

- same species if they have the same/similar morphology/anatomy (look the same).

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7
Q

Benefits and disadvantages to the Morphospecies concept

A

Good: widely applicable (can be used with sexual, asexual species and fossils)

Bad:
1) cannot identify cryptic species (species that can’t be distinguished from similar species by an anatomical trait)

2) naming +1 species when there’s really one polymorphic species (a species where individuals look different at different life stages)

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8
Q

ecological species concept

A

1/4 criteria to identify a species
- organism that have the same ecological niche (share the same habitat, food, predators, have the same range of environmental tolerances, et )

emphasizes natural selection

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9
Q

Benefits and disadvantages of the ecological species concept

A

Good: useful when identifying asexual species (ie bacteria)

Bad:

1) some species change their niche overtime
- ie: caddisfly -> larva(aquatic), adult (terrestrial)

2) some species share the same niche
- ie: purple shore crab and the yellow shore crab

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10
Q

the phylogenetic species concept

A

1/4 criteria to identify a species

  • a species is the smallest non-divisible monophyletic group
  • *if you snip a branch off the tree, everything that falls under it is a monophyletic group.
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11
Q

monophyletic group

A

evolutionary unit that includes an ancestral population and its descents only (no other descendants!)
- aka: clade, lineage

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12
Q

synapomorphy

A

a trait unique to a monophyletic group

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13
Q

Benefits and disadvantages of the phylogenetic species concept

A

Good:
- can be applied to any population (fossil, sexual, asexual)

Bad:
- carefully constructed phylogenies are only available for a few species

  • cost lots of $$, time and analysis to construct new phylogenies
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14
Q

speciation

A

a lineage splitting event that produces 2 or more separate species

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15
Q

3 steps to speciation

A

1) population must be isolated, STOP GENE FLOW
- so mutation, natural selection and/or drift can act on a population independently

2) Populations genetically diverge due to mutation, genetic drift, natural selection)
3) prezygotic/postzygotic barriers to reproduction evolve (in case of recontact – to satisfy the BSC)

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16
Q

two types of speciation

A

1) allopatric speciation: geographic isolation
due to…

a) dispersal - some individuals disperse to a new location (founder effect)
b) vicariance - physical barriers separate a population (ie.canyons, coastal mountains)
2) sympatric speciation: reproductive isolation (live in the same geographic area such that breeding is possible)
a) Disruptive selection: individuals in a population become reproductively isolated by adapting to different ecological niches (habitat preference, food, etc)

17
Q

what happens when isolated population some into contact?

A
  • distinctions may be reinforces if hybrids have low fitness
  • hybrid zones may be established if hybrids have intermediate fitness
  • speciation by hybridization may occur if hybrids have high fitness
  • *FINISH READ THIS SECTION (24.4)
18
Q

paraphyletic group

A
  • not all descendants of a common ancestor are included

INCLDES ancestor, not all descendants

19
Q

polyphyletic group

A

a group composed of a collection of the organisms in which the most recent common ancestor of all the included organisms is NOT included

20
Q

synapomorphies

A

shared derived characteristics (ie, hair in mammals)

- more closely relates species should share more synapomorphies

21
Q

Two categories off homolgous traits

A

1) Ancestral traits: traits that were inherited from a distant ancestor
2) Derived traits: those that appear (via mutation) in the most recent ancestor

**depends which taxa you are referring to.

22
Q

homologous trait

A
  • aka homologs
  • traits shared by two or more species due to a shared ancestry
    therefore used to build a phylogenetic tree
23
Q

analogous trait (aka homoplasies)

A
  • two structures that look the same and have the same function BUT weren’t inherited from a common ancestor
  • arise when different species live in similar ways and/or a similar environment, and so face the same environmental factors => similar problems can lead to similar solutions.
24
Q

convergent evolution

A

when organisms independently evolve similar traits

  • arise when different species live in similar ways and/or a similar environment, and so face the same environmental factors => similar problems can lead to similar solutions.
25
Q

The Principle of Parsimony

A

states that the explanation that is most likely to be true is the simplest.

  • for phylogenetic trees, the one with the fewest characters is most likely
26
Q

phylogenetic relationships (how to identify which taxa are more closely related)

A

more closely related taxa share a MORE RECENT common ancestor

27
Q

TRUE OR FALSE: the proximity of the tips pf a phylogenetic tree indicated relatedness

A

FALSE!

28
Q

TRUE OR FALSE: degree if relatedness is indicated by the # of nodes separating them

A

FALSE!

29
Q

The order of the nodes IS important when determining whether two phylogenetic trees are the same

A

TRUE!

- Trees must display the same monophyletic groups

30
Q

TRUE OR FALSE: Taxa that appear on the top right of a phylogenetic tree have been evolving for longer (and therefore are more advanced) than other organisms on the tree

A

FALSE!

31
Q

TRUE OR FALSE: evolutionary change only occurs at the nodes

A

FALSE!

  • evolution continues to happen along the branches/lineages
  • There can be many species along a branch!***

Biology 121 (5 decks)

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