Vocabulary of concepts of chs 17, 18, 19

1. analogous structure

Body parts that once differed in evolutionarily distant lineages but converged in structure and function as responses to similar environmental pressures.

2. asteroid

Rocky, metallic body, a few to 1,000 kilometers across, hurtling through space.

3. comparative morphology

Scientific study of comparable body parts of adults or embryonic stages of major lineages.

4. derived trait

A novel feature that evolved but once and is shared only by the descendants of the ancestral species in which it evolved.

5. fossil

Recognizable, physical evidence of an organism that lived in the distant past.

6. fossilization

How fossils form. An organism or evidence of it gets buried in sediments or volcanic ash; water and dissolved inorganic compounds infiltrate it; then chemical changes and pressure from accumulating sediments above transform it to stony hardness.

7. geologic time scale

Time scale for the Earth's history with major subdivisions corresponding to mass extinctions. Now radiometrically dated.

8. Gondwana

Paleozoic supercontinent; with other land masses, it formed Pangea.

9. half-life

The time it takes for half of a given quantity of any radioisotope to decay into a different, and less unstable, daughter isotope.

10. homologous structure

Of separate lineages, comparable body parts that show underlying similarity even when they may differ in size, shape, or function; outcome of morphological divergence from a shared ancestor.

11. lineage

Line of descent.

12. morphological convergence

Macroevolutionary pattern. In response to similar environmental pressures over time, evolutionarily distant lineages evolve in similar ways and end up being alike in appearance, functions, or both.

13. morphological divergence

Macroevolutionary pattern; genetically diverging lineages undergo change from body form of a common ancestor.

14. Pangea

Paleozoic supercontinent upon which the first terrestrial plants and animals evolved.

15. plate tectonics theory

Theory that great slabs (plates) of the Earth's outer layer float on a hot, plastic mantle. All plates are slowly moving and have rafted continents to new positions over time.

16. stratification

Stacked layers of sedimentary rock, built up by gradual deposition of volcanic ash, silt, and other materials over time.

17. theory of uniformity

Early theory that the earth's surface changes in gradual, uniformly repetitive ways (major floods, earthquakes, and other infrequent catastrophes also occur every year and were not considered unusual). Has since been replaced by plate tectonics theory.

18. adaptive radiation

Macroevolutionary pattern; burst of genetic divergences from a lineage that gives rise to many species, each using a novel resource or a new (or newly vacated) habitat.

19. adaptive zone

Minimum amount of energy required to get a specific reaction going, with or without the help of an enzyme. Reactions differ in the amount required.

20. allopatric speciation

Speciation model. A physical barrier arises, separates populations or subpopulations of a species, ends gene flow, and favors divergences that end in speciation.

21. anagenesis

Speciation pattern; changes in allele frequencies and morphology accumulate within an unbranched line of descent.

22. archipelago

Island chain some distance away from a continent.

23. biological species concept

Defines a species as one or more populations of individuals that are interbreeding under natural conditions, producing fertile offspring, and are isolated reproductively from other such populations. Applies to sexually reproducing species only.

24. cladogenesis

Speciation pattern in which a lineage splits and isolated populations undergo genetic divergence.

25. dosage compensation

Any mechanism that balances gene expression between the sexes during critical early stages of development.

26. evolutionary tree

Treelike diagram; a branch point means divergence from a shared ancestor and branches signify separate lines of descent.

27. extinction

Irrevocable loss of a species.

28. gene flow

Microevolutionary process; alleles enter and leave a population as an outcome of immigration and emigration, respectively.

29. genetic divergence

Gradual accumulation of differences in gene pools of populations or subpopulations of a species after a geographic barrier arises and separates them; thereafter, microevolution occurs independently in each.

30. gradual model of speciation

Idea that species arise by many small morphological changes that accumulate over great spans of time.

31. hybrid zone

Where adjoining populations are interbreeding and producing hybrid offspring.

32. mass extinction

Catastrophic event or phase in geologic time when entire families or other major groups are irrevocably lost.

33. parapatric speciation

Idea that neighboring populations can become distinct species while maintaining contact along a common border.

punctuation model of speciation

Idea that most morphological changes occur in a brief span when populations start to diverge; speciation is rapid, and the daughter species change little for the next 2-6 million years or so.

35. reproductive isolating mechanism

Heritable feature of body form, functioning, or behavior that prevents interbreeding between two or more genetically divergent populations.

36. speciation

The formation of a daughter species from a population or subpopulation of a parent species by way of microevolutionary processes. Routes vary in their details and duration.

37. species

One kind of organism. Of sexually reproducing organisms, one or more natural populations in which individuals are interbreeding and are reproductively isolated from other such groups.

38. sympatric speciation

A speciation event within the home range of an existing species, in the absence of a physical barrier. Such species may form instantaneously, as by polyploidy.

Vocabulary of Concepts of Ch. 17: Evidence of Evolution

allele One of two or more molecular forms of a gene that arise by mutation and code for different versions of the same trait. allele frequency For a given gene locus, the relative abundances of each kind of allele among all the individuals of a population.
antibiotic	Metabolic product of soil microbes that kills bacterial competitors for nutrients.
balanced polymorphism	Form of selection in which two or more alleles for a trait are being maintained in a population over time.
biogeography	Scientific study of the world distribution of species.
bottleneck	Severe reduction in the size of a population, brought about by intense selection pressure or a natural calamity.
catastrophism	Idea that abrupt changes in the geologic or fossil record were divinely invoked.
comparative morphology	Scientific study of comparable body parts of adults or embryonic stages of major lineages.
directional selection	Mode of natural selection by which allele frequencies underlying a range of phenotypic variation shift in a consistent direction, in response to directional change or to new conditions in the environment.
disruptive selection	Mode of natural selection by which the different forms of a trait at both ends of the range of variation are favored and intermediate forms are selected against.
evolution	Genetic change in a line of descent. Outcome of microevolutionary events: gene mutation, natural selection, genetic drift, and gene flow.
fitness	Increase in adaptation to environment, as brought about by genetic change.
fixation	Loss of all but one kind of allele at a gene locus for all individuals in a population.
fossil	Recognizable, physical evidence of an organism that lived in the distant past.
founder effect	A form of bottlenecking. By chance alone, a few individuals that establish a new population have allele frequencies that differ from those of the original population.
gene flow	Microevolutionary process; alleles enter and leave a population as an outcome of immigration and emigration, respectively.
gene pool	All genotypes in a population.
genetic drift	Change in allele frequencies over the generations due to chance alone. Its effect is most pronounced in very small populations.
genetic equilibrium	In theory, a state in which a population is not evolving. Compare Hardy-Weinberg rule.
Hardy-Weinberg rule	Allele frequencies stay the same over the generations when there is no mutation, the population is infinitely large and isolated from other populations of the species, mating is random, and all individuals are reproducing equally and randomly.
inbreeding	Nonrandom mating among close relatives that share many identical alleles.
lethal mutation	Mutation with drastic effects on phenotype; usually causes death.
microevolution	Of a population, any change in allele frequencies resulting from mutation, genetic drift, gene flow, natural selection, or some combination of these.
mutation rate	Of a gene locus, the probability that a spontaneous mutation will occur during or between DNA replication cycles.
natural selection	Microevolutionary process; the outcome of differences in survival and reproduction among individuals that differ in details of heritable traits.
neutral mutation	A mutation with little or no effect on phenotype, so natural selection can't change its frequency in a population.
polymorphism	The persistence of two or more qualitatively different forms of a trait (morphs) in a population.
population	All individuals of the same species that are occupying a specified area.
sampling error	Use of a sample or subset of a population, an event, or some other aspect of nature for an experimental group that is not large enough to be representative of the whole.
sexual selection	A microevolutionary process; a type of selection that favors a trait giving an individual a competitive edge in attracting or keeping a mate (favors reproductive success).
stabilizing selection	Mode of natural selection by which intermediate phenotypes in the range of variation are favored and extremes at both ends are eliminated.
theory of uniformity	Early theory that the earth's surface changes in gradual, uniformly repetitive ways (major floods, earthquakes, and other infrequent catastrophes also occur every year and were not considered unusual). Has since been replaced by plate tectonics theory.