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25 Cards in this Set
- Front
- Back
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Speciation
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The origin of new species, is at the focal point of evolutionary theory
-evolutionary theory must explain how new species originate and how populations evolve |
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Microevolution
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consists of changes over time in allele frequency in a population. Manifested in adaptations that evolve within a population, confined to one gene pool
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Macroevolution
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refers to evolutionary change above the species level. Grand scale/ longer time
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Prokaryotes vs Eukaryotes
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Prokaryotes- bacteria, aquatic, 1st organisms
Eukaryotes- Protists(ameoba) - fungi- plants- animals |
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The Biological Species Concept
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states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring- they do not breed successfully with other populations
Gene flow between populations holds the phenotype of a population together(rep. isolation) |
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Reproductive Isolation
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the existence of biological factors(barriers) that impede two species from producing viable, fertile, offspring.
- can be classified by whether factors that stop members of 2 species from producing offspring act before or after fertilization |
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Hybrid
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offspring of crosses between different species
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Prezygotic Barriers
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block fertilization from occurring by
-stopping different species from attempting to mate -preventing the successful completion of mating -hindering fertilization if mating is successful |
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Habitat Isolation
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Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers.
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Temporal Isolation
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Species that breed at different times of the day, different seasons, or different years cannot mix their gametes.
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Behavioral Isolation
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Courtship rituals and other behaviors unique to a species are effective barriers
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Mechanical Isolation
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Morphological differences can prevent successful mating. Snails with shells spiraling in opposite directions
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Gametic isolation
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Sperm of one species may not be able to fertilize eggs of another species
- because proteins on the surfaces of the egg and sperm cannot bind to each other -red / purple sea urchins |
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Postzygotic Barriers
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after fertilization
prevent the hybrid zygote from developed into a viable fertile adult -reduced hybrid viability/fertility -hybrid breakdown |
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Reduced hybrid viability
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Genes of the different parent species may interact and impair the hybrid's development
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Reduced hybrid fertility
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Even if hybrids are vigorous, they may be sterile
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Hybrid breakdown
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Some 1st generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile
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Limitations of the Biological Species Concept
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very hard to define species
cannot be applied to fossils or asexual organisms(including prokaryotes) -only for organisms w sexual reproduction |
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Morphological species concept
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defines species by structural features
- applies to sexual and asexual species but relies on subjective criteria - researchers may disagree on which features distinguish a species (limitation) |
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morphological
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shape/appearance
organisms that are similar belong to same species |
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Ecological Species Concept
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Views a species in terms of its ecological niche( the role it plays & resources it uses in the specific environments in which it is found)
-applies to sexual/asexual species and emphasizes the role of disruptive selection as organisms adapt to different environmental conditions |
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niche
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the role it plays & resources it uses in the specific environments in which it is found
Ecological- niche- Amphibians 2 species may appear similar but eat differently and may survive in different temperatures(have different niches) |
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Phylogenetic species concept
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Defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.
a species is the smallest set of organisms that share an ancestor and can be distinguished from other such sets |
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Phylogeny
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Ancestry- where organisms descend from
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What is distinct about phylogenetic species?
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distinct morphology or molecular sequences
- applies to sexual/asexual species -can be difficult to determine the degree of difference required for separate species |
