Physical Anthropology Ch/wk4 (2/3)

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Linnaeus

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18th cent. First to classify organisms systematically. Modern classification system is based on his ideas.

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taxon (pl: taxa)

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Any group of related organisms (classification term)

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Hollotype

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the type specimen from a species. Displays characteristics that set it apart from other species.

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SYSTEMATICS:

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The science concerned with the diversity of organisms and the relationships among them – provides the basis for determining phylogenetic relationships.

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TAXONOMY:

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Theory and practice of classifying organisms once phylogenetic relationships are known.

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Phylogenetics:

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The study of how genealogical relationships can be determined from HOMOLOGOUS similarities.

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homologous trait

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any characteristic of organisms that is derived from a common ancestor

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analogous traits

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similarities between organisms that were not in the last common ancestor of the taxa being considered but rather evolved separately

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evolutionary reversal

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a trait that is present in one taxon reverts to earlier state not present in last common ancestor. E.g. dolphins becoming water-dwellers.last common ancestor with land mammals lived in water , so reverted to earlier evolutionary state

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evolutionary convergence

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(type of homoplasy) similarity by independent development from different sources. e.g.: dolphins are streamlined like sharks, share many features, but are mammals. Don’t have recent common ancestor, but have adapted to same environment.

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parallel evolution

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(type of homoplasy) similarity by independent development from a single source: descendants have same characteristics but not bc of common ancestor. Usu due to environmental adaptation.

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Primitive/ancestral trait

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a structure found on an ancestral form (as opposed to a specialized/dervied trait).

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plesiomorphic trait

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an ancestral trait not unique to the taxon in question

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symplesiomorphic trait

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ancestral traits that are shared among a number of animal species, inherited from ancestors older than the last common ancestor. homologous within a particular group of organisms but is not unique to members of that group

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specialized/derived trait

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a structure found or developed in an animal and not part of the biology of an ancestral animal.

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apomorphic trait

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A trait which characterizes an ancestral species and its descendants. This is an evolutionary novelty for the group. These are evidence for the existence of a group. Put another way, attributes shared in common are taken to indicate a shared evolutionary history.

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synapomorphic trait

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The possession of apomorphic features by two or more taxa in common (i.e. the features are shared, derived). If the two groups share a character state that is not the primitive one, it is plausible that they are related evolutionarily, and only synapomorphic character states can be used as evidence that taxa are related. Phylogenetic trees are built by discovering groups united by synapomorphies.

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cladistics

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Newer method, ~30 years old
Primary method used in anthropology today
Classifies organisms based on synapomorphies
Trees have no time dimension

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clade

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a branch of a cladogram that includes all, and only, the descendants of a particular ancestor. can be removed from the tree with a single "snip."

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hox genes

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regulate morphogeny (determine shape of animal) by producing a protein that directs the expression of other genes. Are highly conserved between organisms, can be subtsituted between organisms, regulate other genes.

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biological species concept

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classic definition of species (Mayer, 1942): a species possesses a genome that will not function in combination with the genetic materials of other species. either fertilization will not occur, or (if fertilization occurs) zygote will not complete development, or (if completes development) offspring will be infertile.

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exceptions to rules and definitions of speciation

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mules aren't always infertile. one liger reproduced. geladas and baboons, which have had dif. evolutionary trajectories for several million years and totally different social structures, can mate and produce offspring.

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Anagenesis

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classic darwinian view of speciation. Microevolutionary events occur over the course of time. gradual changes in an ancestral species lead to its eventual "replacement" by a novel form (i.e., there is no "splitting" of the phylogenetic tree).

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Cladogenesis

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n evolutionary splitting event in a species in which each branch and its smaller branches forms a "clade", an evolutionary mechanism and a process of adaptive evolution that leads to the development of a greater variety of sister organisms. This event usually occurs when a few organisms end up in new, often distant areas or when environmental changes cause several extinctions, opening up ecological niches for the survivors.

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Ring species

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Group of animals that live in a particular environment with an unlivable barrier in the center. Different species around barrier, with hybrid zones along the way

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ways to identify/define fossil species (since reproductive info is unavailable, there is variation within a species, and morphology changes throughout lifespan)

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-morphology (physical characteristics). This is the best criterion for identifying fossil species.
-time and space. How old are they, and where are they found? How does this compare to other, similar fossil specimens? Do they use materials from other areas, implying travel?
Capacity for symbolic thought: do they use religious or other symbols, etc?
-dna. Recent development, often contested.

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S.J. Gould's theory of adaptive landscape

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?? look up!