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BIOL 103 Lecture Notes Mar 18

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BIOL 103
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March 18 th Beginning on slideshow 6, slide 6-9 Elements and terms used to describe phylogenetic trees:  Node A represents the common ancestor to all taxa in the tree  Extreme polytomy sometimes called ‘star phlogeny’ Monophyletic taxon: common ancestor and all descendants Paraphyletic taxon: common ancestor but not all descendants Polyphyletic taxon: groups of species with different common ancestors  The goal of taxonomy is to place organisms in monophyletic groups Monophyletic taxon  “true” higher grouping (genus/family)  A taxon should be monophyletic  Contains all known descendants of a common ancestor (eg. Mammals)  Reflect true evolutionary relationships  Sometimes called clades Monophyletic (I, III) vs. Paraphyletic (II) taxa Paraphyletic taxon, Reptiles  true monophyletic group would be birds and reptiles together, as birds are the result of dinosaurs  proof being found recently show that most dinosaurs has feathers  whales should be where birds are on tree Polyphyletic taxon  does not share recent common ancestors  shares homoplastic features (features which are derived from another individual of the same species)  misrepresents evolutionary relationships o Protista is being re-examined, but is most likely not a real kingdom; multiple unrelated groups clumped together due to poor measures of shared characteristics (txt p 26) Example: historically, existent dolphins and extinct ichthyosaurs were grouped together Evaluating alternate phylogenetic hypotheses using parsimony  A, B, and C traits (hair, milk, ear bones) evolved separately on two different occasions, which is why dolphins are so similar to dinosaurs (people thought they were directly related) The future of systematics  Molecular systematics o Determines evolutionary relationships by comparing macromolecules o Ribosomal RNAs 5S, 16S, 23S (transcribed from conserved DNA regions) o Mitochondrial DNA o ‘Molecular clocks’ help date trees  Powerful computers for analysis  Shortcuts, eg. DNA barcoding -10 M species (proposed by Paul Hebert @U of G) o There are approximately 10-100 million species, but we recall/recognize 1000 of them o Barcoding is effective in varied geographic settings and varied taxonomic groups o Greater than 99.99% resolution Molecular Clocks: estimate time since divergence from common ancestor by differences in nucleotide/protein sequences; rate of change is assumed constant  Example – (see graph below) number of amino acid change per 100 residues of cytochrome c molecule  Calibration of % sequence change to years requires at least two points on line must be verified by fossil record with associated ecological dating  Change in number of amino acids in cytochrome c vs. time since divergence from common ancestry  Must have fossil evidence from when two points diverged, and then calibration is completed DIY – Build phylogeny from shared, derived traits Population ecology (Lecture note 7) Ecology is the study of how organisms interact and adapt to environment – abiotic and biotic factors  Abiotic – rainfall, soil type, temperature  Biotic factors – competitors, predators Population Ecology is the study of how/why the number of individuals in a population changes over time  This requires knowledge of factors like population size and makeup/composition (ratio of males to females, reproductive success, age structure, etc.) Population Density is the number of individuals of a species per unit area at a given time Population Dispersion is the spacing of individuals within an environment, which directly relates to population process and relations with local environment  Clumped Dispersion: animal groups like wolves to hunt and defend territory from other packs  Uniform Dispersion: birds like king penguins spread themselves out to a distance to where neighbours can’t peck each other; in other cases this prevents competition for resources and moisture  Random Dispersion: plants like dandelions have seeds dispersed in wind and grow wherever they land **Note: Dispersion is a mathematical term meaning spacing – this is DIFFERENT FROM DISPERSAL FINAL EXAM  how to go from one rep of taxon to another  tree representation and chart rep slide – match tree to chart given th March 20 , Lecture 2 Relative Importance of 4 processes that affect population size, growth and composition These four factors may be influences by other factors like age of individual, density, environmental quality, etc:  Natality (birth rate, b)  Morthality (death rate, d)  Immigration (i)  Emmigration (e) **Note: always assume i=e, so they cancel out Growth rate (r), the per capita increase/decrease of population  If r is positive, the rate is incr
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