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| Formation of new species from pre-existing ones |
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| Branching evolution, one new species splits from an existing one, contrary to anagenesis, which is evolutionary change in one lineage |
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Morphological species concept - Linnaeus, distinguishes species by differences in appearance
Biological species concept - uses a common gene pool to define species and discontinuities between gene pools. Emphasizes reproductive isolation and interbreeding
Phylogenetic species concept - Identifies species in the smallest monophyletic groups - the end branches in a tree, A single independent lineage, most species recognized under this grouping. Does not offer a reason for why groups are distinct. |
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Term
| Reproductive isolating mechanisms |
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Definition
Maintains lack of gene flow among different species
Pre-zygotic isolation: Habitat, temporal, mechanical (parts), behavioral (rituals), gametic (egg/sperm)
Post-zygotic: Hybrid inviability (hybrids die during development), hybrid sterility (sterile hybrid offspring) |
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Term
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Definition
Geographic isolation of populations. While separated, genetic divergence occurs due to frequencies, mutations, and environmental pressures.
Secondary sympatry is the completion of reproductive isolation. Possible outcomes: re-merge into a single species, reproductive isolation, intermediate.
Adaptive radiation: Repeated speciation and diversification from a common ancestral species. Results from exploitation |
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Term
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Definition
Speciation without geographic isolation
Polyploidy - when there are more than two sets of chromosomes, and the species is reproductively isolated from parent species. Important for plants. Two different types:
Autopolyploidy - mutation results in doubling of chromosome number
Allopolyploidy - Multiple chromosome sets from hybridization between closely related species. More important in plant speciation. Most animal species arose from allopatric speciation |
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| Occurs in eukaryotes, accomplishes recombination, produces genetically variable offspring |
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| No fusion of gametes, occurs in many organisms, obligate, or only asexual, in some species. Examples include vegetative reproduction, budding, parthenogenesis(development of unfertilized eggs), binary fission in prokaryotes |
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Definition
| Mating - time and energy, recombination - successful genes are broken up, production of males - half genetic material disposed of into a non-reproductive organism |
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Definition
| More rapid evolution, elimination of bad mutations, red queen - must keep evolving to stay ahead of rapidly evolving pathogens |
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Term
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Definition
Males and females are dimorphic in some species. Males differs in physical characteristics, may lower survival.
Difference in gamete size - large egg with cytoplasm, tiny sperm with little.
Parental investment is when an individual contributes to raising its offspring, different evolutionary strategies of genders
Intrasexual - Usually male/male competition with fighting and displays
Intersexual - Involves female choice of male characters, can result in male secondary sex traits (peafowl tails)
Includes good resources, good genes, and runaway selection where female favor a particular trait |
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Term
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Definition
Monogamy - one male with one female. Rare in mammals
Polygny - One male with several females, substnatial difference between sexes, disparity among males in reproductive success, there is sexual dimorphism where males are larger than females, and leks where there are tight clusters of small territories with no resources
Polyandry - one female mates with many males, occurs in some shorebirds, males take over duties of raising young |
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Definition
| Study of medical problems in an evolutionary context. |
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Term
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Definition
| Infectious, non-cellular particles, virtually all kinds of organisms, not considered living. Consist of a genome (1 or 2 strands of DNA or RNA) surrounded by protein. Cannot reproduce indenependently, but mutate and evolve. They take over the host cell and use cell's machinery to reproduce, very abundant in nature |
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Term
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Definition
| Causes AIDS, discovered in the early 1980s, killed over 35 million people, 1 million are infected, killed over 25 million people, common in sub-sahran Africa with an infection rate of 8%, spreads through unprotected sex, exposure to contaminated blood, not spread by contact. Destroys immune system cells, disrupting individual's immune system. Death results usually after 10 years |
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Term
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Definition
Retrovirus with two single strands of RNA. Reverse transcription(directed by reverse transcriptase enzyme), turns viral RNA into DNA
Infects specific white blood cells with receptor protein CD4 on cell surface (infects helper T lymphcytes and macrophages usually)
Viral DNA is spliced into host DNA, and becomes integrated into genome, host cell uses machinery to transcribe the proviral genome to viral RNA, translated into HIV proteins |
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Term
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Definition
| HIV genome has a very high mutation rate and produces a lot of genetic variation in the HIV population within an individual. Some variants are more successful (differential reproductive success), and favored variants prevail. This high mutation rate is a part of the inaccuracy of reverse transcriptase (error-prone) |
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Term
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Definition
| Helper T lymphocytes with macrophages play in with immune response. Helper T cells activate specific B cells with certain chemicals, and these produce antibodies against the HIV phenotype. Also, they activate cytotoxic T cells that destroy cells infected with the same HIV phenotype. HIV evades this with a high mutation rate and innacuracy of reverse transcriptaste, escape mutants are eventually recognized, but natural selection continues in HIV, and overwhelms the immune response by destroying helper T lymphocytes faster than they can be replaced |
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Term
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Definition
Anti-HIV drugs developed block the action of reverse transcriptase, block the action of the enzyme protease (which prevents new viral particles from being formed), HIV eventually evolves ressitance to both kinds.
AZT - One of the first anti-HIV drugs that fools the enzyme and stops transcription.
Resistance to protesase occurs in the same way
Highly active antiretroviral therapy involves a combination of several drugs taken simultaneously. Costly, with large side effects. |
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Term
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Definition
| Arose from SIV in Africa, within the last 100 years. Made trans-species jumps, chimp to human. May have come from capturing/eating chimps |
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Term
| Natural resistance to HIV |
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Definition
| IN humans, there is a mutant allele delta-32, that involves the deletion of 32 base pairs from the human gene that codes for surface co-receptor protein on helper T-cells, resulting in non-functional protein. Highly resistant, and about 10% in European Caucasians. May have evolved in response to black plague. CCR5 delta-32 homozygotes indicate protein is redundant, and anti-HIV drugs may block the CCR5 receptor protein |
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Term
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Definition
| One allele replaces another over time. When there is only one allele at the gene locus in the population, that allele is said to be fixed (gene fixation). |
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Term
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Definition
| Both alleles remain in the population at relatively stable frequencies. Can result from changing selection pressures over time, frequency-dependent selection, heterozygote advantage, |
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Term
| Selection on polygenic characters |
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Definition
Involves multiple gene loci with two or more alleles that produce the phenotype, results in a bell-shaped frequency
Directional selection - Against individuals of one extreme and favors the other, changes the mean and the distribution of the character over time.
Stabilizing selection - selection against extremes, favoring intermididates, unimodal distribution
Disruptive selection - Selection against intermidiates, favoring the extremes, with a bimodal distribution |
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| Examples of Natural Selection |
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Definition
Sickle-cell anemia occurs in homozygous individuals
Geospiza finches shows directional selection with increased beak size from severe drought
Industrial melanism - Moths became darker because they blended in better, but assumed to be because of polution
Lactose intolerance - All humans are lactor tolerant, adult tolerance evolved in populations associated with livestock herding
Herbicide resistance - in weeds, some weed species evolved resistance with gene amplification |
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