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Biological species concept |
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Definition
Definition of a species as a population or groups of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such populations.
(Manhattan woman unlikely to meet farmer in Mongolia, but could still produce offspring). |
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Morphological species concept
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Definition
A definition of species in terms of measurable anatomical criteria.
Advantage: can be applied to asexual organisms/fossils
Disadvantage: subjective - researchers may disagree |
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Term
Phylogenetic species concept
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Definition
| A definition of species as the smallest group of individuals that shares a common ancestor and forms one branch on the tree of life. |
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Ecological species concept
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Definition
| A definition of species in terms of ecological roles (niches). |
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Definition
| Evolutionary change on a grand scale, encompassing the origin of new taxonomic groups, evolutionary trends, adaptive radiation, and mass extinction. |
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Definition
| A biological feature of a species that prevents it from interbreeding with other species even when populations of the two species live together. |
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Definition
| A reproductive barrier that impedes mating between species or hinders fertilization if mating between two species is attempted. Includes temporal, habitat, behavorial mechanical, and gametic isolation. |
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Definition
| A reproductive barrier that prevents hybrid zygotes produced by two different species from developing into viable, fertile adults. Includes reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown. |
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Definition
| The offspring of parents of two different species or of two different varieties of one species; the offspring of two parents that differ in one or more inherited traits; and individual that is heterozygous for one or more pairs of genes. |
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Definition
| The formation of new species in populations that are geographically isolated from one another |
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Definition
| The formation of new species in populations that live in the same geographic area. |
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Definition
| An organism that has more than two complete sets of chromosomes as a result of an accident of cell division. |
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Definition
| Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill new or vacant ecological roles in their communities. |
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Gradualism vs. punctuated equilibrium
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Definition
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Term
| Compare and contrast the four different species concepts. |
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Definition
The biological sepcies concept says organisms are considered to belong to the same species if they can potentially reproduce with each other and have offspring that are healthy and fertile. Otherwise, they are considered to belong to different species. The biological species concept can not categorize asexual species.
Morphological species concept defines species based on observable and measurable physical traits. Advantage is that it can be applied to asexual and organisms and fossils, but disadvantage is that it relies on subjective criteria and researchers may disagree.
The ecological species concept focuses on unique adaptations to particular roles in a biologicalcommunity. (2 species of plants in Lake Victoria may be similar in appearance but distinguishable by what they eat).
Phylogenetic species concept defines species as the smallest group of individuals that shares a common ancestor and that forms one branch on the tree of life. |
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Term
Explain the mechanisms (both prezygotic and postzygotic) by which a species can be isolated. Use examples
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Definition
There are 5 different prezyogtic barriers.
Temporal isolation occurs when species breed at different times of day/year or season. Eastern and western spotted skunks breed at different times of the year, while different plants located in the same area may release pollen at different times of the year.
Habitat isolation occurs when two species live in the same area but not in the same kinds of places. For example, related garter snake species may live in the same area, but one lives in water and the other on land.
Behavioral isolation occurs when there is little or no sexual attraction between different species. For example, female fireflies only respond to signals of thir own species and may not respond to male flies.
Mechanical isolation occurs when structural differences in genitalia or flowers prevent copulation or pollen transfer. For example, some snails have different spiral directions in their shells and their genital openings cannot align.
Gametic isolation occurs when male or female gametes die before uniting or fail to unite. Male and female sea urchins of many different species release eggs and sperm into the sea, but fertilization occurs only if species-specific molecules on the surfaces of egg and sperm attach to each other.
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Postzygotic barriers operate after hybrid zygotes are formed.
Reduced hybrid viability occurs when hybrids fail to develop or to reach sexual maturity. Most hybrid offspring do not survive.
Reduced hybrid fertility occurs when hybrids fail to produce functional gametes. (Horse and donkey may produce a sterile offspring).
Hybrid breakdown occurs when offspring of hybrids are weak or infertile. (diff specis of cotton plants can produce fertile hybrids, but the offspring of the hybrids do not survive). |
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