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Evolution, Phylogen.
USC FSH BISC121 Midterm 2 - Evolution & Phylogenetics
| Term | Definition |
|---|---|
| Phylogenetics | The study of evolutionary relationships between organisms |
| Phylogeny | Evolutionary history of a group of related species or populations |
| Systematics | Science of classifying organisms based on relationships |
| Taxonomy | Scheme of classification used to name organisms in systematics |
| Cladistics | Classification of organisms based on their order of branching on an evolutionary tree, emphasizes only monophyletic groups in taxonomy |
| Cladogram | A branched diagram representing the cladistic relationship between a number of species |
| Polytomy | A branch point from which more than two descendant groups emerge |
| Basal taxon (or outgroup) | A group that diverges early in the history of a group and originates near the common ancestor of the group |
| Monophyletic group | A group that consists of a single ancestral species and all its descendants and excludes any organisms that are not descended from that common ancestor |
| Paraphyletic group | A group that consists of the last common ancestor and most of its descendants, but excludes one or more of the descendants. Example: class Reptilia |
| Polyphyletic group | A group that consists of several species that lack a common ancestor. Example: "Warm-blooded animals". Often more work is needed to uncover species that tie them together into a monophyletic clade, therefore these are avoided in modern taxonomy |
| Morphological homology | Similarity in structures resulting from common ancestry |
| Molecular homology | Similarity in DNA (amino acid sequences) among different species from a common ancestor |
| Linnean taxonomy | A taxonomic system that consists of a hierarchy of groups known as taxa that are divided into kingdoms and species |
| Inventor of binomial nomenclature and hierarchical classification system | Linnaeus (18th century) |
| Taxon (pl. taxa) | A taxonomic group of one or more population(s) of an organism, forms a unit in evolutionary biology |
| Genus (pl. genera) | A classification that ranks in between family and species, containing related species and named by a capitalized noun in Latin |
| Species (both sg. & pl.) | The largest group of organisms that can reproduce with one another in nature and produce fertile offspring. |
| Homology | Similarities either in development, structure, or genetics (genetic expression) due to similar ancestry |
| Sister taxa | Pairs of terminal taxa that branched from a common node |
| Node | Represents a branch point from ancestral population |
| Hard polytomy | A speciation event that resulted in >3 new species |
| Homoplasy | Similar, analogous traits that evolved independently in separate lineages, eg. Marsupial mole (Australia) and Golden mole (Africa) |
| Analogous traits | Similar traits due to separate evolutionary events (no common ancestor), eg. similar environment or random chance |
| Homologous traits | Similar traits due to inheritance from a common ancestor |
| Convergent evolution | Lead to analogous homoplastic traits, brought on by natural selection due to similar environment rather than shared ancestry, eg. Howler monkeys and Colobus monkeys |
| Molecular homology tools | Statistical tools have been developed to determine whether DNA sequences share a certain fraction of their bases do so due to homology or homoplasy |
| Parsimony | A theory that states that the phylogenetic tree that assumes the fewest steps is more likely to be correct |
| Occam's Razor | When there are two competing hypotheses that make the same predictions, the simpler hypothesis is more likely to be correct |
| Primitive traits | Traits inherited from distant common ancestors |
| Derived traits | Traits that appeared (by mutation) in the most recent ancestor and gave rise to a newly formed branch. |
| Plesiomorphy | Homologous within a particular group of organisms but is not unique to members of that group, therefore cannot be used as a defining or diagnostic character |
| Synapomorphy | Homologous between a common ancestor and all its descendants, can be used as evidence of common ancestry |
| Example for Synapomorphy | Gorillas and humans share a larger brain and lack of a tail, but these traits are lacking in velvet monkeys -> shows that gorillas and humans are more closely related |
| Ingroup | Taxa that are not outgroups |
| Branch point | Node where lineage diverges, indicating speciation events |
| Maximum parsimony | The best phylogenetic tree requires the fewest changes |
| Parametric statistical methods | Give clade supports values such as maximum likelihood and Bayesian inference |
| Maximum likelihood | Infers probability distributions to assign probabilities to particular possible phylogenetic trees. |
| Bayesian inference | Probability analysis for more complex phylogenetic trees |
| Macroevolution | The evolution of whole taxonomic groups over long periods of time |
| Gradualism | A theory that evolution occurs slowly but steadily |
| Supporters of Gradualism | Charles Darwin & Ernst Mayr |
| Punctuated equilibrium | A theory that species evolve with stasis punctuated by short bursts of rapid change |
| Supporters of punctuated equilibrium | Stephen Jay Gould & Niles Eldredge |
| Molecular clock | A technique that uses the mutation rate of DNA to deduce phylogeny, using both fossil and molecular data |
| Microevolution | Evolutionary change within a species or small group of organisms, over a short period of time |
| How is the molecular clock calibrated? | Using the fossil record or the accumulation of mutations over generations |
| Example of molecular clock with Ape phylogenetic tree | With age of orangutan split & orangutan DNA -> know rate of mutations in certain parts of the ape genome -> count known differences in DNA between humans and chimps -> data indicates a date of the split between Pan and Homo at about 6-8 mya |
| Paleontology | Scientific study of fossil organisms |
| Fossil record | Evidence provided by fossils about the history of organisms in Earth's past, including evolution and adaptation of organisms to their environments |
| Indirect fossil evidence | Trace fossils left by organisms |
| Coprolites | Preserved fecal material providing evidence of the diet and health of past organisms. |
| Stratigraphy | The study of rock layers to date fossils |
| Relative dating | Method of comparing a fossil's placement with fossils in other layers to determine the order of occurrence |
| Absolute dating (chronometric) | Methods used to determine the actual age of a fossil |
| Principle of superposition | When fossils are found in layered rock, the deeper layers hold the older artifacts. |
| Radiometric dating | Method used to measure the absolute age of fossils by measuring the concentrations of radioactive isotopes and their decay products |
| Strata | the many layers of sedimentary rock |
| Uranium series dating | Dating method based on the radioactive decay of uranium with a series of half lives |
| Argon dating | Dating method based on the radioactive decay of radioactive potassium to stable argon gas, used on volcanic rocks with 1.25 bill. yr half-life |
| Carbon-14 dating | Dating method based on the radioactive decay of carbon-14, which has a half life of 5730 years |
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elephantmonkey66
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