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27 Cards in this Set

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What are the 2 ways we recognize and define species?
1) anagenesis
2) cladogenesis
What is anagenesis?
genetic changes through time WITHIN a population (no speciation)
What is cladogenesis?
diversification among populations (such as speciation or "branching evolution")
What is a clade?
the complete set of species (evolutionary lineages) descended from a particular common ancestor (aka monophyletic group).
What do all biological evolutionists agree that a species is?
the smallest evolutionarily independent unit (isolated by lack of gene flow)
What does the Greek Species concept state?
species are unstable and highly variable
What does the typological (or Essentialist) Species concept state?
species have a perfect "type" or "essence"...species are static..nonvariable
Who recognized variation within species? Expand.
Darwin: Individuals vary within species; species often overlap in characteristics and common descent is the important feature
What are the 3 Modern concepts of species?
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)
What's the definition of species based on the Biological Species Concept?
Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups
What type of organism does this concept apply to?
sexually-reproducing organisms. This concept emphasizes the importance of genetic barriers b/w species.
In general, if gene flow is present or possible, two populations __________.
are not seperate species
What are the two cases applying BSC to identifying when 2 populations are different species.
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.
What 2 situations can't be applied to the BSC?
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)
The biological species concept is only testable for ________ populations. (define the word in the blank)
sympatric- 2 species living in the same geographic area.
Why is the Biological Species Concept not testable for the majority of populations?
b/c the majority of populations occur in allopatry.
What's another limitation to the biological species concept? (hint: genetic barriers)
genetic "barriers" are not always absolute--some "species" hybridize
What are 2 ways we infer potential reproductive isolation in the usual absence of direct evidence?
1) distributions of traits across populations: bimodality for multiple (including some neutral) traits would suggest 2 species

2) Morphospecies
What are morphospecies?
populations designated as seperate based on morphological differences.
What's the definition of species according to the Evolutionary Species Concept?
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
A lineage is the same species until it...
branches (gets synapomorphies)
What are the problems with the Evolutionary Species Concept?
1) Chronospecies: Different names for the same lineage through time
2) Naming daughter species following cladogenesis
What are 2 common misconceptions of reproductive isolation?
1) Different species sometimes DO interbreed
2) Hybrids are NOT always sterile
What are extrinsic barriers?
allopatry
What are intrinsic barriers?
prezygotic and postzygotic isolation
What are examples of prezygotic isolation?
temporal
microhabitat
ethological
mechanical
gametic
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