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Lecture

LEC 3 - FALL 2013- MACROEVOLUTION - ANTb14.docx

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Department
Anthropology
Course
ANTB14H3
Professor
Michael Schillaci
Semester
Fall

Description
LEC 3 – MACROEVO AND EVO ANTHRO MACROEVO  •Large-scale changes at or above the special level.  •Extends over geologic era.  •Associated with research on the formation of new taxonomic groups. EARLY SPECIES CONCEPTS  Typological species concept:  similar-looking individuals lumped into discrete categories.  Modified typological species concept: similar-looking individuals that can successfully produce fertile offspring lumped into discrete species categories.  (How in early taxonomy – linneaus classification – typological way) MODERN SPECIES CONCEPTS Biological Species Concept  Actually or potentially interbreeding populations (Mayr, 1942).  Must apply all known morphological, behavioural, and ecological data to use as deductive proof of reproductive isolation between species.  But, what about fossil species?  Species concept – all have underlying themes – divided into 2-3 categories –  Bio species concept – species are actually interbreeding pop –  When pop not able to interbreeding – pop is reproductively isolated (most important for bio species concept)  Not geographic iso – but reproductively iso (continuum)  Eg. iso starts w/ recognition of potential mate LEC 3 – MACROEVO AND EVO ANTHRO  Requires a lock and key mech (penis and vagina) Zygote forming? No viable fetus? Dead new born (survival) Reduced fecundity  Selection against (reducd fitness of offspring)  Problems w/ bio species concept: Potentially interbreeding is hard to identify  Fossils? Can’t observe fossil reproduction – don’t know if potentially interbreeding Phylogenetic Species Concept  Smallest aggregation of sexual populations diagnosable by unique combination of character states.  Measure and analyze variation in characters within and between populations.  Can be applied to living and fossil organisms.  Most evo anthro use this phylogenetic species concept  smallest aggreg of sexual pop diagnosable by a unique combo of character states (phenotpic char)  At least 1 trait must be diff b/w 2 pop in order for diff species  Cladistics – way of describing evo rlsps using character states (version of diff morphological traits  focused on indiv traits  Phonetic analysis – looking at morph pattern – use idea that simliar organism will be related  Problems: eg. birds and bats are similar – must share common ancestor. But not the case  When trying to look at evo history – have to look at indiv char – not the overall morphological pattern SPECIATION  •Evolutionary process involving the formation of new species. LEC 3 – MACROEVO AND EVO ANTHRO  •Adaptive or non-adaptive process?  •Are intermediate forms needed in speciation?  Natural sel , mutation, gene drift, gene flow(not important component for speciation)  b/c Gene flow dec var among pop (non random) – inc w/in pop, b/c it breaks down variation among pop – it can’t be a part of speciation  Speciation needs a divergence or inc in genetic difference  Gene drift – inc gene var among pop (random – dec w/in pop  Dones’t take much gene flow to stop process of speciation – influenced by geographic separation  If process only includes NS – adaptive process  Are intermediate forms needed in speciation – phyletic gradualism and punctuated equil  YES – but..  Creationist used to refute the evo th – intermediate forms leading from primitive to more derived form  Use gaps or lack of intermediate forms that evo dones’t exist ALLOPATRIC SPECIATION  •Species formation that occurs following geographic isolation of populations.  •Isolation in terms of limited gene flow.  •Two modes of allopatric speciation: vicariant and peripatric.  Pop A and B – geo distribution – not touching = allopatry  Another scenario – A and B meet but no overlap = peripatry  sympatric – overlap  Geographic separation  Why allopatry interesting in speciation? – reproductively isolation  When isolation – no gene flow – LEC 3 – MACROEVO AND EVO ANTHRO  Two modes of allopatric speciation: vicariant (separate) + peripatric speciation (involves peripatry) VICARIANT SPECIATION  •Occurs when a physical barrier creates large, geographically separated populations.  •In time, populations diverge and can no longer interbreed. PERIPATRIC SPECIATION  •Occurs when small, peripherally isolated colony of main population diverges to become new species. 3 ASSUMPTIONS OF CLADISTICS  1.There are changes in characteristics within lineages over time.  2.All organisms are descended from a common ancestor.  3.When a lineage splits, it divides into exactly two groups. 3. Doesn't necessarily have to be two groups LEC 3 – MACROEVO AND EVO ANTHRO  e.g., result of adaptive radiation  Cladistics --> also referred to as phylogenetics CLADOGRAM OR PHYLOGENY  •A branching diagram used to illustrate phylogenetic relationships.   This examples assumes a constant rate of evolution in all taxa and common ancestors  In other trees, branch lengths vary to reflect differences in evolutionary time --> proportional to evolutionary differences from each other  COMPONENTS OF INTEREST in cladograms:  - Branch Tips --> different taxa/species  - Branch Nodes --> hypothetical common ancestor  -Clades --> branch tips that share a common ancestor  - Nested clades --> share closer evolutionary relationships READING A CLADOGRAM  •Each internal node represents a hypothetical common ancestor.  •Within a cladogram may be a number of clades.  –Clade: A group of organisms that contains an ancestral taxon (hypothetical common ancestor) and all of its descendants. LEC 3 – MACROEVO AND EVO ANTHRO  CLADOGRAMS --> have to be viewed as hypotheses; different data sets produce different trees  •Researchers are specifically interested in tree topology.  –Tree topology: the branching patterns of lines connecting nodes and organisms. (internal branching pattern of nodes)  •Focus on internal branching patterns and not tips of branches. 3 MISCONCEP
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