AP Biology Chapter 24: The Origin of Species Flashcards

Terms Definitions
The origin of new species in evolution.
Evolutionary change above the species level, including the appearance of major evolutionary developments, such as flight, that we use to define higher taxa.
Evolutionary change below the species level; change in the genetic makeup of a population from generation to generation.
Phyletic evolution, is the accumulation of changes that gradually transform a given species into a species with different characteristics.
Branching evolution, is the splitting of a gene pool into two or more separate pools, which each give rise to one or more new species. Can promote biological diversity by increasing the number of species.
Biological Species Concept
Definition of a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are not able to produce viable, fertile offspring with members of other populations.
Reproductive Isolation
The existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids.
Prezygotic Barrier
A reproductive barrier that impedes mating between species or hinders fertilization of ova if interspecific mating is attempted.
Postzygotic Barrier
Any of several species-isolating mechanisms that prevent hybrids produced by two different species from developing into viable, fertile adults.
Habitat Isolation
A prezygotic reproductive barrier.
Two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though they are not isolated by obvious physical barriers such as mountain ranges.
Example: Two species of garter snakes in the genus Thamnophis occur in the same geographic areas, but live mainly (a) in water and (b) terrestrially
Temporal Isolation
Prezygotic reproductive barrier.
Two populations reproduce at different times. Species that breed during different times of the day, different seasons, or different years cannot mix their gametes.
Example: In North America, the geographic ranges of the (a) eastern spotted skunk and (b) western spotted skunk overlap, but (a) mates in the late winter and (b) in the late summer
Behavioral Isolation
A prezygotic reproductive barrier.
Courtship rituals that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species.
Example: Blue-footed boobies mate only after a courtship display unique to their species. Part of the "script" calls for the male to high-step, a behavior that calls the female's attention to his bright blue feet.
Mechanical Isolation
A prezygotic reproductive barrier.
Morphological differences between species can prevent successful mating. They are anatomically incompatible and transfer of sperm is not possible.
Example: Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. Two species of monkey flowers differ greatly in the shapes and colors of their blossoms, thus cross-pollination between the plants does not occur.
Gametic Isolation
A prezygotic reproductive barrier.
The sperm of one species may not be able to fertilize the eggs of another species.
Example: Separates certain closely related species of aquatic animals such as sea urchins. The sea urchins release their sperm and eggs into the surrounding water, where they fuse and form zygotes. gametes of different species, like the red and purple urchins, are unable to fuse.
Reduced Hybrid Viability
A postzygotic reproductive barrier.
Genes of different parent species may interact and impair the hybrid's development.
Example: Some salamander subspecies of the genus Ensatina live in the same regions and habitats, where they may occasionally hybridize. But, most of the hybrids do not complete development, and those that do are frail.
Reduced Hybrid Fertility
Postzygotic reproductive barrier.
Even if hybrids are vigorous they may be sterile; meiosis in hybrids may fail to produce normal gametes.
Example: The hybrid of offspring of a donkey and a horse, a mule, is robust but sterile.
Hybrid Breakdown
A postzygotic reproductive barrier.
Some first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species, offspring of the next generation are feeble or sterile.
Example: Strains of cultivated rice have accumulated different mutant recessive alleles at two loci in the course of their divergence from a common ancestor. Hybrids between them are vigorous and fertile, but plants in the next generation that carry too many of these recessive alleles are small and sterile.
Morphological Species Concept
Characterizes a species by its body shape, size, and other structural features. It can be applied to asexual and sexual organisms, and it can be useful even without information on the extent of gene flow.
Paleontological Species Concept
Definition of species based on morphological differences known only from the fossil record.
Ecological Species Concept
Defining species in terms of ecological roles (niches).
Phylogenetic Species Concept
Defines a species as a set of organisms with a unique genetic history
Sibling Species
Species that appear so similar that they cannot be distinguished on morphological grounds
Allopatric Speciation
A mode of speciation induced when an ancestral population becomes segregated by a geographic barrier or is itself divided into two or more geographically isolated subpopulations
Sympatric Speciation
A mode of speciation occurring as a result of a radical change in the genome of a subpopulation, reproductively isolating the subpopulation from the parent population.
A mutational change during cell division that results in extra sets of chromosomes
An individual that has more than two chromosome sets, all derived from a single species
A common type of polyploid species resulting from two different species interbreeding and combining their chromosomes.
Adaptive Radiation
The emergence of numerous species from a common ancestor introduced into an environment that presents a diversity of new opportunities and problems
Punctuated Equilibrium
In evolutionary theory, long periods of apparent stasis (no change) interrupted by relatively brief periods of sudden change.
Structures that evolve in one context but become co-opted for another function
Evolutionary change in the timing or rate of an organism′s development.
Allometric Growth
The variation in the relative growth rates of various parts of the body, which helps shape the organism.
The retention in an adult organism of the juvenile features of its evolutionary ancestors.
Homeotic Genes
Any of the genes that control the overall body plan of animals and plants by controlling the developmental fate of groups of cells.
Species Selection
A theory maintaining that species living the longest and generating the greatest number of species determine the direction of major evolutionary trends.
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