Biology Speciation/paa L3

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Genetic Drift

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Change in allele frequency and gene pool due to accumulated effects of chance, not natural selection. Reduces genetic diversity. Only significant in small populations. Elimination of alleles due to this is pure chance. Can cause one allele to become common in a population at the expense of another allele.

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K-Selected

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Bring up young. Few young. Energy into bringing up young. Less energy in production of low amount of gametes.

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R-Selected

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Many young. Do not bring up young. Low energy in young. Energy used for other things ie. Mating. High energy in production of a large number of gametes.

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Taxis

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Directional response of movement or orientation of animal/cell/organism in response to an external stimulus.

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Kinesis

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Non-directional movement or activity of a cell/organism in response and proportion to external stimuli.

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Orthokinesis

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Non-directional response: speed of movement is proportional to stimulus intensity.

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Klinokinesis

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Non directional response: frequency/rate of turning is proportional to stimulus intensity.

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Directional Selection

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One extreme trait survive better than the other. Increases adaptedness of organisms. ie. faster wolves better at hunting deer.

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Disruptive Selection

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Natural selection acting against the middle range of variation. Two extremes rather than any intermediate traits. Drives a population apart. Causes organisms with intermediate traits to reproduce less, and those with extremes: more. ie. Large and short beaked galapagos finches selected for rather than intermediate medium beaked.

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Stabilizing Selection

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Natural selection acting against the extremes of a range of variation, resulting in resistance to change in allele frequencies. Push a population towards the average/median trait. Stabilizing sleected traits are common among the entire groups of species. ie. Dark and light lemurs selected against, easily seen by predators, brown lemurs selected for.

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Increased Survival Chance of a Mate

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Is favourable in seeking a mate.

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Sexual Dimorphism

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Differences between different sexes of a species.

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Innate

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In the genetic code, passed on, not learnt.

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Intraspecific

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Same species.

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Interspecific

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Two or more species.

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Natural Selection

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The process that brings about new species by the elimination of the less adapted individuals and the survival of the organisms which are better adapted. Main process that brings evolution. Kills the weak, what's left is the strong.

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Allele Frequency

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Allele pattern in a population. Often different in populations that have undergone different selection pressures. Increases in response to increased gene flow. Beneficial alleles increase in frequency, disadvantagous ones decrease in frequency.

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Founder Effect

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Form of genetic drift. A chance change in allele frequency which occurs when a small group of individuals become detached from the main population. In-breeding, reduces genetic variation, more affected by genetic drift, alleles can become fixated and removed entirely. Chance of differing from original population is increased.

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Bottleneck Effect

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Form of genetic drift. After the bottlenecking event, kills off most of the population, what's left is a smaller population. Small group in-breeds, reduces genetic variation, more affected by genetic drift, alleles can become fixated and removed entirely. Chance of differing from original population is increased due to chance of genetic drift occuring increased in a small population.

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Serial Founder Effect

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Founder Effect over large distance migration. Involving relatively rapid movements followed by periods of settlement. Genetic differentiations tend to increase with geographic distance following the "isolation by distance" model.

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Endemic

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Found only in that country.

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Gradualism

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Evolution proceeds slowly but continuously. Eventually the accumulated changes result in speciation.

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Micro-evolution

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The accumulation of (through mutation) new characteristics in a species.

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Polyploidy

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Mutation producing more than twice the normal haploid number of chromosomes.

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Haploid

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Cell that contains a single set of chromosomes. Haploid and chromosome number are the same.

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Vestigial organ

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Any part of an organism that has diminished in size during it's evolution because the function it serves has decreased in importance ie. Appendix in humans

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Macro-evolution

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The formation of a completely new species, genera etc.

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Geological record

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Fossils preserved in sedimentary rock layers that can be used to trace the evolutionary history of a species.

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Hybrid breakdown

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The hybrid offspring are fertile but produce infertile or non-viable offspring.

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Punctuated equilibrium

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There are long periods of little evolutionary change (stasis) interrupted by short bursts of rapid speciation.

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Instant speciation

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Formation of a new species through autopolyploidy or allopolyploidy, because the chromosome numbers of new "instant" species do not match that of the original species.

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Hybrid inviability

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A zygote forms but does not develop properly.

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Ring species

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Two apparently distinct species that are connected by a series of intermediate geographical and structural subspecies between which interbreeding can occur.

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Parallel evolution

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The development of related organisms along similar evolutionary paths due to strong selective pressure acting on all of them in the same way.

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Hybrid sterility

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A hybrid forms but is sterile ie. Mule

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Cline

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A gradual variation in the characteristic of a species or population over it's geographical range.

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Adaptive radiation

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This is a form of divergent evolution in which there is a rapid proliferation of forms from an ancestral type because of the sudden availability of niches.

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Allopolyploidy

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Chromosome complement consisting of more than two copies of chromosomes derived from different species. Occurs when two species mate to produce a hybrid species. Hybrid can be infertile.

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Autopolyploidy

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Chromosome complement consisting of two copies of homologous chromosomes. Occurs by fusion of gametes of the same parenr. Arises by doubling if the chromosome number of the diploid species. 3+ copies of same genome. Containment of multiple copies of chromosomes in the same parent.

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Proliferate

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Reproduce rapidly

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Carrying capacity

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Max habitat population. Predator vs prey relationships keep it intact