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Bio Questions & Stuff
Terms in this set (25)
A proposed explanation in evolutionary biology stating that new species arise from the result of slight modifications (mutations and resulting phenotypic changes) over many generations.
Punctuated equilibrium (also called punctuated equilibria) is a hypothesis in evolutionary biology which proposes that most species will exhibit little net evolutionary change for most of their geological history, remaining in an extended state called stasis.
Structures in different species that are similar because of common ancestry. ex. The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale
similarities among unrelated species that result from convergent evolution ex. the wings of a fly, a moth, and a bird
Organ that serves no useful function in an organism ex. appendix
form of genetic drift in which a population becomes extremely small; may lead to differences in allele frequencies and a loss in genetic variability ex. Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000—but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.
A founder effect occurs when a new colony is started by a few members of the original population. ex. Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington's disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency. This effect is easy to recognize in genetic diseases, but of course, the frequencies of all sorts of genes are affected by founder events.
Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals. ex. white mice
form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle ex. white mice and black mice
Natural selection that favors intermediate variants by acting against extreme phenotypes ex. brown mice in the middle of white and black
A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates. ex. peacocks (top left) maintain elaborate tails, elephant seals (top right) fight over territories, fruit flies perform dances
A change in the allele frequency of a population as a result of chance events rather than natural selection. ex. Of the two pink monkeys in the world - one male, one female - the female dies, ensuring that there will never be a pure-bred pink monkey again, A random succession of births results in all other hair colors going extinct within a village full of redheaded people.
Discredited theory that evolution proceeds through the inheritance of acquired characteristics. Acquired characteristics arise form use or disuse during an organisms life. THE SILLY ONE
artificial selection supports evolution
Habitat, Temporal: species that mate during different times of day, seasons, or different years, Behavioral: sexual behavioral rituals-mate recognition, mechanical isolation: morphological features prevent, gamete isolation: sperm cannot get into egg
reduced hybrid viability:gene of different parent species may interact and impair the hybrid's development, reduced hybrid fertility-sterile-MULE, Hybrid breakdown: hybrid + hybrid = no baby, The first-generation hybrids are viable and fertile, but when they mate the offspring are feeble and sterile
The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.
The formation of a new species as a result of a genetic change that produces a reproductive barrier between the changed population (mutants) and the parent population. No geographic barrier is present.
The biological species concept is the most widely accepted species concept. It defines species in terms of interbreeding. For instance, Ernst Mayr defined a species as follows:
"species are groups of interbreeding natural populations that are reproductively isolated from other such groups."
The biological species concept explains why the members of a species resemble one another, i.e. form phenetic clusters, and differ from other species.
When two organisms breed within a species, their genes pass into their combined offspring. As this process is repeated, the genes of different organisms are constantly shuffled around the species gene pool. The shared gene pool gives the species its identity. By contrast, genes are not (by definition) transferred to other species, and different species therefore take on a different appearance.
Ecological Species Concept
The ecological species concept is a concept of species in which a species is a set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognize as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters.
Ecological research, particularly with closely related species living in the same area, has abundantly demonstrated that the differences between species in form and behavior are often related to differences in the ecological resources the species exploit.
Morphological Species Concepts
Characterizes a species by body shape and other structural features and is
applied to asexual and sexual organisms and useful when information on gene flow is
unknown. Since it is subjective, researcher may disagree on which features to use to
distinguish a species.
higher relative fitness than homozygous dominant or recessive
sickle cell anemia (homo-recessive), carriers have resistance to malaria
remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species.
hardy weinberg equilibrium
breeding population = large
mating is random
no mutation of alleles
no differential migration occurs
there is no selection
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