Ch 21: Species and Speciation Flashcards
Speciation
The process whereby new species are produced.
Species
A group of individuals that can exchange genetic material through interbreeding to produce fertile offspring.
Biological Species Concept
As described by Ernst Mayr, the concept that “species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups.” The BSC is the most widely used and accepted definition of a species, but cannot be applied to asexual organisms.
Morphospecies Concept
The idea that members of the same species usually look like each other more than like other species.
Hybrid Offspring
The offspring produced by a cross; sometimes applied specifically to interbreeding between two closely related species.
Hybridization
Interbreeding between two different varieties or species.
Niche
The combination of traits and habitat in which a species exists.
Ecological Species Concept
The concept that there is a one-to-one correspondence between a species and its niche.
Phylogenetic Species Concept
The idea that members of a species all share a common ancestry and a common fate.
Pre-zygotic
Describes factors that prevent the fertilization of an egg.
Post-zygotic
Describes factors that cause the failure of the fertilized egg to develop into a fertile individual.
Behaviorally Isolated
Describes individuals that only mate with other individuals on the basis of specific courtship rituals, songs, and other behaviors.
Gametic Isolation
Incompatibility between the gametes of different individuals (typically belonging to different species).
Mechanical Incompatibility
Structural configuration of the genitalia that prevents mating with another individual (typically of another species).
Temporal Isolation
Pre-zygotic isolation between individuals that are reproductively active at different times.
Geographic Isolation
Spatial segregation of individuals.
Ecological Isolation
Pre-zygotic isolation between individuals that specialize ecologically in different ways.
Genetic Incompatability
Genetic dissimilarity between two organisms, such as different numbers of chromosomes, that is sufficient to act as a post-zygotic isolating factor.
Partially Reproductive Isolation
Describes populations that have not yet diverged into separate species but whose genetic differences are extensive enough for the hybrid offspring they produce to have reduced fertility or viability compared with offspring produced by crosses between individuals within each population.
Allopatric Speciation
Describes populations that are geographically separated from each other.
Subspecies
Allopatric populations that have yet to evolve even partial reproductive isolation but which have acquired population-specific traits.
Dispersal
The process in which some individuals colonize a distant place far from the main source population.
Vicariance
The process in which a geographic barrier arises within a single population, separating it into two or more isolated populations that are isolated from each other.
Peripatric Speciation
A specific kind of allopatric speciation in which a few individuals from a mainland population disperse to a new location remote from the original population and evolve separately.
Mainland Population
The central and largest population of a species.
Island Population
An isolated population; may apply to true islands (land surrounded by water) or to ecological islands that similarly isolate their inhabitants (for example ponds, for fish).
Adaptive Radiation
A period of unusually rapid evolutionary diversification in which natural selection accelerates the rate of speciation within a group, with new species adapted for specific niches.
Co-speciation
A process in which two groups of organisms speciate in response to each other and at the same time, producing matching phylogenies.
Sympatric Population
Describes populations that are in the same geographic location.
Instantaneous Speciation
Speciation that occurs in a single generation.
T/F: Given the generation time of certain organisms, the biological species concept can be difficult to test.
True
The reason that lions, which live in Africa, and tigers, which live in Asia, do not produce ligers (infertile offspring of lions and tigers) in the wild is likely the result of:
ecological isolation of lions and tigers.
_____ is the process by which two populations of the same species living in the same habitat diverge into separate species.
Sympatric speciation
T/F: If two populations are reproductively isolated from one another, they must be genetically isolated from each other and, therefore, cannot belong to the same species.
False
In the southwestern desert of the United States there are temporary ponds that form only after heavy summer rains. As a naturalist, you visit these ponds and notice that female frogs mate with males of their own species, which are identified solely by listening to male calls. The lack of mating between species would be an example of _____ and _____.
pre-zygotic isolation; behavioral isolation
In _____ speciation, there is gene flow between populations that are in the process of diverging into two or more species. In _____ speciation, there is no gene flow between populations that are in the process of diverging into two or more species.
sympatric; allopatric
Imagine that a zoo in Sri Lanka has started an elephant-breeding program. Zookeepers have introduced an Indian and Sri Lankan elephant into the same enclosure. What will be the result of this mating?
This mating will demonstrate that these elephants are members of the same species and will produce fertile offspring.
T/F: Natural selection is always the driving force of speciation.
False
A researcher is trying to determine whether different populations of asexually reproducing bacteria belong to the same species. What concept will be most helpful in making this determination?
the ecological species concept
If two individuals from different species attempt to mate, but fertilization fails to occur, this is likely the result of _____. However, if such a mating produces a zygote that fails to form a viable embryo, this is likely the result of _____.
pre-zygotic factors; post-zygotic factors
T/F: Adaptive radiation is more likely to occur in a population produced by a dispersal event than in a long-established population on a continent.
True
While in South America, you come across what you think are two groups of birds in the same location. They are nearly identical aside from their color. After years of observation, you conclude that the birds eat similar diets and share similar behaviors but do not reproduce with each other. These groups of birds appear to be an example of:
two different species on the basis of reproductive behavior.
T/F: Post-zygotic reproductive isolation may be due to temporal or ecological separation.
False
T/F: In general, allopatric species will evolve pre-zygotic isolating mechanisms more rapidly than sympatric species.
False
T/F: You would expect similar species with a different number of chromosomes to be genetically compatible and, therefore, able to reproduce fertile offspring.
False
Ronald Fisher developed a critical idea for the modern synthesis of Darwin and Mendel. What is the basis of this synthesis?
Multiple genes can explain the continuous nature of most observed traits.
Migration tends to _____ genetic differences among populations.
Decrease
Competition among members of one sex for access to the other sex results in _____ selection.
Sexual
You are researching a population of moles. In the course of your research, you identify a nearby population that occasionally comes into contact with your study population. What best describes the evolutionary process at work?
gene flow
If two populations are thought to be diverging from one another, what would you expect to observe?
an accumulation of different mutations in different populations
Individuals that are heterozygous for the sickle-cell anemia allele are more resistant to malaria than those that do not have a sickle-cell allele. Why does the sickle-cell allele not become fixed in the population?
Individuals that are homozygous for the sickle-cell allele have sickle-cell anemia, and are at a fitness disadvantage.
A gene that no longer retains function is called:
a pseudogene.
Is natural selection the same thing as evolution?
No, because forces other than natural selection can also cause evolution.
T/F: A population experiencing genetic drift will be in Hardy-Weinberg equilibrium.
False
T/F: All mutations in a population—both harmful and beneficial—contribute to the evolution of that population.
True
T/F: Migration, genetic drift, and mutation are all mechanisms of evolutionary change.
True
What is the eventual long-term result of different mutations accumulating in different populations?
the evolution of different species
Why is it thought that the majority of natural selection is stabilizing selection?
Most mutations are deleterious and produce an extreme phenotype that is selected against.
Dodos were flightless birds that have been extinct for about 300 years. Imagine that biologists found two surviving dodos on present-day Earth and mated this pair of birds. What would you expect of the resulting dodo population?
Due to a population bottleneck, the frequency of alleles in this new dodo population may be very different from the frequencies expected in larger, now non-existent, populations.
Some proteins have a slower molecular clock due to ______ selection, which eliminates harmful alleles.
negative
Mutation and recombination are the only processes that can increase genetic variation because they are also the only processes that:
can produce new genotypes.
