Lecture 15 notes 10/5/15
Lecture 15 notes 10/5/15 EEOB 3310 - 200
Popular in Evolution
Popular in Ecology
This 3 page Class Notes was uploaded by an elite notetaker on Monday October 5, 2015. The Class Notes belongs to EEOB 3310 - 200 at Ohio State University taught by Joan Herbers,Zakee Sabree in Summer 2015. Since its upload, it has received 34 views. For similar materials see Evolution in Ecology at Ohio State University.
Reviews for Lecture 15 notes 10/5/15
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 10/05/15
10515 Lecture 15 Phylogenies what are they how were they traditionally estimated and how are they now Goal of project is to assemble tree of life Understand how species within groups are related and how groups are related to one another What are phylogenies A history of how things have evolved through time Records information about species events Clade any group that shares a single common ancestor Monophyletic a taxon clade comprised of all of the descendants of a common ancestor Paraphyletic taxa that represent some but not all of the descendants of a common ancestor Phylogenetic trees can be drawn in many different ways Some have info about the inferred evolutionary distance between species these are the same pattern but more info May have a key like 50 changes Can be rooted or unrooted Rooted is better because it is easier to see ancestors vs descendants Same trees can have several orientations Node a part of a tree where one lineage splits into two or more lineages Root most ancestral Base of the tree representing the ancestor of the terminal taxa Outgroup a taxon considered a priori to be sister to the other taxa useful for polarizing characters Lineage branch the portion of the tree intermediate to cladogenic events Refers to lines can be terminal or internal Terminal taxa the extant species at the tips of the tree Sistertaxa sisterclades two species or clades that share a common ancestor exclusively Most closely related species to one another on the tree Synapomorphy a trait or feature exclusively found in the members of a clade Basal the base of the tree the most ancestral taxa Taxa or characters that are more ancestral Evolutionary taxonomy subjective reconstruction of phylogeny based on expert opinion Not very scientific basically an appeal to authority Not always real evidence or proof of data Many scientists had issues with this Want to use algorithms Phenetics no way to infer ancestry in a scientific manner organisms should be grouped on the basis of overall similarity Pheneticists and Cladists hated each other Algorithmic approaches Cladistics Shared and derived features of organisms are primafacia evidence for common ancestry Tree which maximizes these synapomorphies best represents species phylogeny Phylogenies represent a hypothesis of relationships Pheneticists wanted to classify based on overall similarity Cladists said this is not the best was because we know that some animals evolve similarly with no recent common ancestor analogous Statistical phylogenetics phylogenies are estimated by identifying the tree that best fits the data and used to test hypotheses This is the most refined version of phylogenetics which most biologists agree with today Phenetic approaches matrix of pairwise distances sequence DNA DNADNA hybridization algorithmic Characterstate approaches seek to identify the genealogy that optimizes the particular criterion used to evaluate the relative quality of the trees These are termed optimality criteria Based on morphological data and molecular data Maximum parsimony tree with fewest number of changes Maximum likelihood tree that maximizes the probability of the data given the model Patterns of change if octopus eye and vertebrate eye are homologous Origin of camera eye if they evolved from a common ancestor of mollusks and vertebrates Does it just evolve twice or does it evolve once and get lost multiple times The evolution or loss of any feature is a somewhat rare event so the best tree is the tree that minimizes the amount of evolutionary change maximum parsimony Can think about maximum parsimony with DNA sequences as well Find all possible trees find number of steps in all possible trees pick tree with least amount of steps This does not always work Mutations can create synapomorphies and reversals back mutations can remove them Probabilistic models certain types of changes happen much more often than others First and second position changes in an amino acid are much more common than third position nonsynonymous changes Computationally this is difficult For n taxa there are gt 2n3 branches Calculate probabilities of tree and tree length Bayesian methods very common in phylogenetics The key ingredients to a Bayesian analysis are the likelihood function which re ects information about the parameters contained in the data and the prior distribution which quantifies what is known about the parameters before observing data The prior distribution and likelihood can be easily combined to from the posterior distribution which represents total knowledge about the parameters after the data have been observed Simple summaries of this distribution can be used to isolate quantities of interest and ultimately to draw substantive conclusions Glickman ME How are phylogenies used by biologists 1 To understand the evolution of major groups of features To date important events To study interactions among organisms and coevolution To classify organisms taxonomy To test hypothesis To understand trait evolution QMPPP Understand the evolution of major groups How did whales evolve Thought to be close relatives of the ungulates but which group Perissodactyls or artiodactyls Tewissem amp Madar 1999 argued that fossil whales had a pulley shaped astragulus bone in their ankle How should whales be fit into ungulates Some groups argue that they are a basal group others argue that they are very closely related to hippos Gatesy et al 1999 used molecular data to test the WHIPPO hypothesis this clade was supported Morphology is difficult to interpret sometimes especially with fossils they may be warped Molecular data helps con rm which tree is best To date important events transmission of HIV to the human populations 19201940 To study interactions among organisms and coevolution aphids and bacterial endosymbionts Patten of diversification stability Tree of aphids is very similar to that of symbiotic bacteria they evolved together Unresolved nodes and numbers on nodes tell us how well nodes are supported and whether we understand the divergence of these species or not To classify organisms taxonomy To test hypotheses Ramirez et al report the discovery of a fossilized bee in amber The amber dates to the Miocene 1520 mya It has orchid pollen on its back There are two hypotheses about the evolution of the Orchidaceae To understand trait evolution why have certain traits evolved Phylogenies an evolutionary context for comparing adaptations among clades or related species why do mega bats have such large testicles Sperm competition Mega bats are almost always females at the zoo Sperm competition sperm are cheap to produce far more are produced than eggs leads to internal competition among sperm to fertilize the egg Occurs when females have many sexual partners during an estrous cycle Reproductive success may be correlated with the amount of ejaculate Often found in social species Strong correlation between group size and relative testes size adjusted for body size The comparative method and its use in identifying adaptations related species share traits that evolved in a common ancestors take into account amount of shared evolutionary history Phylogeny must be taken into account
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'