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Biology Raven 9th Edition Chapters 20, 21, 23 and 26 (Not Finished, but pieces from all chapters are present) For 1st Exam Biology 1082


In systematics, a derived character that is shared by clade members.


Principle stating that scientists should favor the hypothesis that requires the fewest assumptions.


Scientist who came up with method of naming organisms with a 2 part scientific name called binomial nomenclature. Father of taxonomy


All members have a single common ancestor


grouping of several species that lack a common ancestor

homologous structures

having the same evolutionary origin but serving different functions


corresponding in function but not in evolutionary origin


referring to a functionless structure that was functional in an ancestral species


the scientific study of how living things are classified


Genetic change in a population of organisms; in general, evolution leads to progressive change from simple to complex.

Natural Selection

The principle that, among the range of inherited trait variations, those that lead to increased reproduction and survival will most likely be passed on to succeeding generations

Artificial Selection

The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits.

Genetic Variation

the number and frequency of alleles that are present in a particular population


The presence in a population of more than one allele of a gene at a frequency greater than that of newly arising mutations.

Hardy-Weinberg principle

No mutation takes place.

No genes are transferred to or from other sources (no immigration or emigration takes place).

Random mating is occurring.

The population size is very large.

No selection occurs.

Hardy-Weinberg equilibrium

A mathematical description of the fact that allele and genotype frequencies remain constant in a random-mating population in the absence of inbreeding

Gene flow

movement of alleles from one population to another

assortative mating

A type of nonrandom mating in which phenotypically similar individuals mate more frequently.

disassortative mating

A type of nonrandom mating in which phenotypically different individuals mate more frequently.

Genetic Drift

Random fluctuation in allele frequencies over time by chance.

founder effect

The effect by which rare alleles and combinations of alleles may be enhanced in new populations.

bottleneck effect

A loss of genetic variability that occurs when a population is reduced drastically in size.


The process by which some organisms leave more offspring than competing ones, and their genetic traits tend to appear in greater proportions among members of succeeding generations

convergent evolution

The independent development of similar structures in organisms that are not directly related; often found in organisms living in similar environments.


The reconstruction and study of evolutionary relationships.


The evolutionary history of an organism, including which species are closely related and in what order related species evolved; often represented in the form


A taxonomic technique used for creating hierarchies of organisms that represent true phylogenetic relationship and descent.

shared derived character

In cladistics, character states that are shared by species and that are different from the ancestral character state.


In cladistics, to determine whether character states are ancestral or derived.


A taxonomic group composed of an ancestor and all its descendents.


In cladistics, another term for an ancestral character state.


In cladistics, another term for a shared ancestral character state.


In cladistics, a shared character state that has not been inherited from a common ancestor exhibiting that state; may result from convergent evolution or evolutionary reversal. The wings of birds and of bats, which are convergent structures, are examples.


In phylogenetic classification, a group that includes the most recent common ancestor of the group, but not all its descendants.

The Linnaean hierarchy



An archaean organism that lives in extreme environments; different archaean species may live in hot springs (thermophiles), highly saline environments (halophiles), highly acidic or basic environments, or under high pressure at the bottom of oceans.

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