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34 Cards in this Set
- Front
- Back
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Macroevolution |
Evolutionary changes that create new species and groups of species |
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Species |
A group of organisms that maintains a distinctive set of attributes in nature |
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How many species are identified? |
About 1.75 million species |
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Estimates of total number of species range from |
5-50 million |
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Identification of Species |
Characteristics that a biologist uses to identify a species will depend, in large part, on the species in question Mostcommonly used characteristics are morphological traits abilityto interbreed molecularfeatures ecologicalfactorsevolutionaryrelationships |
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Morphological Traits |
Physical characteristics of an organism |
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Reproductive Isolation |
Prevents one species from successfully interbreeding with other species |
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Main Four Problems for determining species |
May be difficult to determine in nature Can interbreed and yet do not Does not apply to asexual species Cannot be applied to extinct species |
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Molecular Features |
Compare features to identify similarities and differences among different populations May be difficult to draw the line when separating groups |
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Ecological Factors |
Variety of factors related to an organism's habitat can be used to distinguish one species from another |
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Biological Species Concept |
–Species is a group of individuals whosemembers have the potential to interbreed with one another in nature to produceviable, fertile offspring –But cannot successfully interbreed withmembers of other species |
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Evolutionary Lineage Concept |
–Species should be defined based on theseparate evolution of lineages |
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Ecological Species Concept |
–Each species occupies an ecologicalniche –the unique set of habitat resources that a species requires, as well as itsinfluence on the environment and other species |
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Reproductive isolating mechanisms |
Mechanisms that prevent interbreeding between different species |
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Interspecies Hybrid |
When two species do produce offspring |
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Prezygotic |
Before fertilization- refers to a time before the sperm and egg fuse |
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Postzygotic |
After fertilization- refers to a time after the sperm and egg have fused |
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Prezygotic Barrier |
Prevent formation of zygote Habitat Isolation- geographic barrier prevents contact Temporal Isolation- reproduce at different times of the day or year Behavioral Isolation- behaviors important in mate choice Mechanical Isolation- size or incompatible genitalia prevents mating |
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Postzygotic Barrier |
Block development of viable, fertile individuals Hybrid Inviability- fertilized egg cannot progress past an early embryo Hybrid Sterility- interspecies hybrid viable but sterile Hybrid Breakdown- hybrids viable and fertile but subsequent generations have genetic abnormalities |
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Gametic Isolation |
Gametes fail to unite successfully |
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Mechanisms of Speciation |
Underlying cause of speciation is the accumulation of genetic changes that ultimately promote enough differences so that we judge a population to constitute a unique species |
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Speciation |
Formation of a new species |
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Cladogenesis |
Division of a species into two or more species |
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Allopatric Speciation |
Most prevalent method for cladogenesis Occurs when some members of a species become geographically separated Canalso occur when a small population moves to a new location that isgeographically separated |
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Natural Selection |
May rapidly alter the genetic composition of the population, leading to adaptation to the new environment |
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Adaptive Radiation |
single species evolves into array of descendents that differ greatly in habitat, form or behavior |
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Hybrid Zones |
Zones where two populations can interbreed |
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Sympatric Speciation |
Occurs when members of a species that are within the same range diverge into two or more different species even though there are no physical barriers to interbreeding |
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Polyploidy |
Organism has two or more sets of chromosomes Can occur through nondisjunciton |
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Alloploids |
contain chromosomes from two or more different species |
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Adaptation to local environments |
Geographic area may have variation so that some members of a population may diverge and occupy different local environments that are continuous with each other |
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The Pace of Speciation |
Gradualism Punctuated Equilibrium |
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Gradualism |
Each new species evolves continuously over long spans of time |
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Punctuated Equilibrium |
Tempo more sporadic Species in equilibrium for long periods and then short rapid bursts of changes |
