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27 Cards in this Set
- Front
- Back
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What are the 2 ways we recognize and define species?
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1) anagenesis
2) cladogenesis |
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What is anagenesis?
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genetic changes through time WITHIN a population (no speciation)
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What is cladogenesis?
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diversification among populations (such as speciation or "branching evolution")
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What is a clade?
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the complete set of species (evolutionary lineages) descended from a particular common ancestor (aka monophyletic group).
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What do all biological evolutionists agree that a species is?
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the smallest evolutionarily independent unit (isolated by lack of gene flow)
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What does the Greek Species concept state?
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species are unstable and highly variable
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What does the typological (or Essentialist) Species concept state?
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species have a perfect "type" or "essence"...species are static..nonvariable
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Who recognized variation within species? Expand.
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Darwin: Individuals vary within species; species often overlap in characteristics and common descent is the important feature
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What are the 3 Modern concepts of species?
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1) species consist of groups of interbreeding populations
2) Species are a fundamental unit of evolution 3) Species have a distinguishing characteristic: lack of gene flow b/w them a) Species form boundaries for the possible spread of alleles b) evolutionary agents operate on each species seperately c) different species follow independent GENE FLOWS (look up) |
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What's the definition of species based on the Biological Species Concept?
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Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
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What type of organism does this concept apply to?
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sexually-reproducing organisms. This concept emphasizes the importance of genetic barriers b/w species.
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In general, if gene flow is present or possible, two populations __________.
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are not seperate species
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What are the two cases applying BSC to identifying when 2 populations are different species.
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1) Sibling species appear similar but don't interbreed:
cryptic species: species that are indistinguishable morphologically but divergent in songs, calls, odor, or other traits. 2) Populations look different but can interbreed (ex: geographical races)..same species according to BSC. |
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What 2 situations can't be applied to the BSC?
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1) asexual populations
2) plant groups where hybridization b/w strongly divergent populations is routine THE BIOLOGICAL SPECIES CONCEPT IS SOMETIMES DIFFICULT TO APPLY IN PRACTICE ex: allopatric populations (species that live in different geographic areas) |
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The biological species concept is only testable for ________ populations. (define the word in the blank)
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sympatric- 2 species living in the same geographic area.
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Why is the Biological Species Concept not testable for the majority of populations?
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b/c the majority of populations occur in allopatry.
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What's another limitation to the biological species concept? (hint: genetic barriers)
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genetic "barriers" are not always absolute--some "species" hybridize
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What are 2 ways we infer potential reproductive isolation in the usual absence of direct evidence?
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1) distributions of traits across populations: bimodality for multiple (including some neutral) traits would suggest 2 species
2) Morphospecies |
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What are morphospecies?
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populations designated as seperate based on morphological differences.
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What's the definition of species according to the Evolutionary Species Concept?
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a single lineage (an ancestral-descendent sequesnce) of populations or organisms that maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate
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A lineage is the same species until it...
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branches (gets synapomorphies)
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What are the problems with the Evolutionary Species Concept?
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1) Chronospecies: Different names for the same lineage through time
2) Naming daughter species following cladogenesis |
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What are 2 common misconceptions of reproductive isolation?
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1) Different species sometimes DO interbreed
2) Hybrids are NOT always sterile |
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What are extrinsic barriers?
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allopatry
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What are intrinsic barriers?
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prezygotic and postzygotic isolation
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What are examples of prezygotic isolation?
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temporal
microhabitat ethological mechanical gametic |
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Post-zygotic barriers:
What are the 3 possible hybrid fitnesses? |
1) high
2) lower than parental types, but not sterile or inviable 3) sterile or inviable |
