BioScience Dictionary

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Found Population 154 times.

Displaying results 1 to 10.

1. Adaptive radiation
The development of a variety of species from a single ancestral form; occurs when a new habitat becomes available to a population . Evolutionary pattern of divergence of a great many taxa from a common ancestral species as a result of novel adaptations or a recent mass extinction . Examples: mammals during the Cenozoic Era after the extinction of dinosaurs at the close of the Mesozoic Era flowering plants during the Cretaceous Period diversified because of their reproductive advantages over gymnosperm and non-seed plants that dominated the floras of the world at that time.

2. Age structure
The relative proportion of individuals in each age group in a population.

3. Allopatric
Relating to or involving two populations of the same species which cannot interbreed because they are separated by a geographic barrier (such as a mountain range or wide river).

4. Allopatric speciation (geographic speciation)
The evolutionary process through which two geographically separated (and therefore non-interbreeding) population s of the same species become less and less similar to each other over time (via mutation or the success of different traits in each environment) and eventually become distinctly different species.

5. Allopatrically
An adverb refering to a specific mechanism of evolutionary divergence. A species which arose allopatrically from another diverged from the other because of evolutionary changes occurring in two different geographically separated populations. Also see allopatric and speciation .

6. Allopatry
The condition of two population s of the same species being separated by a geographic barrier that prevents them from interbreeding.

7. Alpha1-antitrypsin
This is a protease inhibitor (Pi). Low serum levels of this antienzyme predisposes patients to early onset of emphysema and chronic liver disease. Ten percent of the adult population has the heterozygote genotype MZ in which intermediate levels of alpha1-antitrypsin is present. The incidence of liver disease in MZ is only mildly higher than the general population. (Normal ranges by genotype: normal MM: more than 250mg/deciliter, heterozygous MZ: 50 - 250 mg/dL, homogygous ZZ: less than 50 mg/dL)

8. Amensalism
A symbiotic relationship in which members of one population inhibit the growth of another population without being affected.

9. Aminoglycoside-3'-phosphotransferase (APH)
A bacterial enzyme which confers resistance to the antibiotic neomycin .The APH gene is used as a selectable marker in genetic experiments, whereby bacterial cells which do not have the gene are eliminated from a population and thus selected against when exposed to neomycin.

10. Backcross (back cross)
A population created by crossing an individual back to one of its parents. This mating design enables the comparison of the effect of the allele s contributed by one parent against the genetic background of the recurrent parent.

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