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23 Cards in this Set

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evolution
change in allelic frequencies within a population over time
Evolution acts on _______s, not ________s
populations; individuals
descent with modification
changes over time produced modern species from ancestral species
vestigial trait
a reduced or incompletely
developed structure in an organism that has no
function or reduced function, but is clearly similar
to functioning organs or structures in closely
related species
structural homology
similarities in adult morphologies
When does speciation occur?
occurs when populations of the same species become genetically isolated by lack of gene flow and then diverge from each other due to natural selection, genetic drift, or mutation
What constitutes a distinct species?
populations that are reproductively isolated from each other, have
distinct morphological characteristics, or form
independent branches on a phylogenetic tree
biological species concept
populations are evolutionarily independent if they do not interbreed
prezygotic factor
a mechanism that prevents mating or fertilization
postzygotic factor
a mechanism that prevents development or viable or fertile adults (i.e. ligers)
Types of prezygotic factors
1) Habitat Isolation
2)Temporal Isolation (different breeding times)
3) Behavioral
4) Morphological
5) Gametic (sperm-egg incompatibility)
Types of postzygotic factors
1) Hybrid zygote inviability
2) Hybrid sterility
3) Hybrid “breakdown”
•Genetic incompatibility with self or parents
•Behavior inappropiate to be recognized by either
parent
•Is ecologically intermediate between parent species
allopatric speciation
speciation occurs in geographic isolation
sympatric speciation
speciation within a panmictic
population
founder effect
a special kind of allopatric
speciation in a small isolated population on the edge of a species range
parapatric
speciation in adjacent populations with gene flow
polyploid
an organism with multiple sets of chromosomes
autopolyploid
produced because of a mutation that causes a doubling of chromosome number
allopolyploid
individuals created when
parents that belong to different species produce an offspring in which chromosome number
doubles
Aneuploidy
Duplication or loss of an individual chromosome
Paralogues
two genes within an organism that have arisen from the duplication of a single gene in an ancestor
Orthologues
reflects conservation of a single gene from a common ancestor
Horizontal gene transfer (HGT)
Genes hitchhike from other species