biology 113

homologus
structure that were inherited from common ancestor
vestigial
stunted wings in ostrich and remnants of pelvis in whale and snakes
Biogeography
the study of the distribution of plants and animals
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ontogeny
development of a species
phylogney
evolutionary history of a species
genetic drift
involves chance
decreases genetic diversity in a small population
bottleneck effect
a large population reduced in size by a disaster, the remaining individuals are unlikely to have the genetic diversity of the original large population
founder effect
genetic drift in a new isolated colony
gene flow
flow of genes between populations by migrating individuals
Biological Species Concept
Based on reproductive isolation
Populations of a species can interbreed or are interbreeding
Members of a species are reproductively isolated from other species
This species concept hold up well for animals, not so well for many plants or bacteria
Morphological species concept
based on anatomical differences between species
Similar to phylogenetic species concept
Similar to paleontological species concept utilized to identify fossil species
Recognition species concept
Distinct mating adaptations by species – molecular, form, behavior
Example – peacocks tail
Cohesion (pluralistic) species concept
Emphasizes factors that maintain the distinct form and behavior of a species. Factors include such things as reproductive barriers
Ecological species concept
Species are identified by where they live and how they behave, not what they look like.
Evolutionary species concept
Emphasizes the evolutionary history of a species and the species’ unique role in the environment
Similar to the evolutionary lineage concept
speciation
the origin of species
allopatric speciation
involves geographical isolation
lakes,ocean, rivers,deserts
sympatric speciation
genetically divergent
ring species
species arranged in a ring around a geographical barrier- allopatric speciation in progress
Polyploidy
extra sets of chromosomes
Autopolyploid
polyploidy in an individual
allopolyploid
formation of a polypoid offspring from two different species
Exaptations
Structures that have evolved under one context can later take on other functions
Example – stress sensors have evolved into hearing organs in some insects
Allopatric speciation is more likely if:
The environment is different for the isolated populations
If an isolated population comes from a peripheral area
If the isolated population is small

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