Zoology ppw 1

phylogeny/phylogenetic tree

branching diagram showing the evolutionary relationships among species (cladogram?)

tips/taxa vs. nodes

singular taxon vs splits defined by presence or absence of some trait

phylogenies can be rotated on any

node

phylogenetic systematics

classifying organisms based on evolutionary relationships

Linnean taxonomy

classifying organisms based on shared characteristics

clade

set of all taxa descended from common ancestor

clades are monophyletic which means

they include ancestor and all of its descendants

why is the red not a clade

it does not include all of the descendants of the common ancestor; so it is paraphyletic

common misconception about phylogenies

the top or most right taxons are the most evolved; in reality no currently living organism is more evolved than another

common misconceptions about outgroups

another misconception is no change in primitive taxa after divergence

common misconception of extant species

they branch off from other extant species, instead they share a common ancestor

representation of extinct organisms on phylogenetic tree

divergence times can be estimated with (FMG)

fossils, molecular clocks, geological events

geological divergence time example

isthmus formation

how do molecular clocks work

on the assumption that genetic differences accumulate at a specific rate and once all those differences are known you can calculate it

chronogram

phylogenetic tree where branch lengths are scaled to represent time

phylogenies are defined using

traits

dots on phylogenies show character states for

character states/inferred ancestral traits are at nodes

how to show changes in character states

tick marks

maximum parsimony

history with fewest number of evolutionary events/most accurate or simplest tree

uncertainty about ancestral traits are also represented with

pie charts (blind is derived)

homology vs homoplasy

when similarity of trait is due to shared ancestry (divergent evolution) vs not due to shared ancestry (convergent evolution=homoplasy)

apomorphy

a trait that has changed from its ancestral form

pleisomorphy

an ancestral trait

synapomorphy

apomorphy shared by two or more taxa and hypothesized to occur in their most recent common ancestor but not any other taxa (hair and mammary glands for humans)