Ch 26 Phylogenetic Trees

Warning about trees

1. evolutionary relatedness and physical similarity are not necessarily linked 2. tree provide information about relatedness, not specific ancestry 3. trees do not provide information on complexity

What are three key points about phylogenetic trees

1. they show patterns of descent, NOT phenotypic similarity --they usually look alike, but may ot if lineages evolved at different rates or faced different environmental conditions 2. The sequence of branching in a tree does not necessarily indicate the actual (absolute) ages of the particular species 3. do not assume that a taxon on a phulogenetic tree evolved from the taxon next to it

first investigate the simplest explanation consistent with the facts

Occam's razor

a branch point from which more than two descendant groups emergy

Polytomy

a bat's wing is more similar to the forelimbs of cats than to a bird's wing

a bat's wing is analogous to a bird's wing

similarity between organisms that is due to convergent evolution

analogy

a lineage that diverges early in the history of a group and hence lies on a branch that originates near the common ancestor of the group

basal taxin

refers to a lineage that diverges early in the history of a group

basal taxon

examples of homologous structures

bones in the bat wing and bones in the human forlimb

an ancestral species and all of its descendants

clade

ancestral species and all of its descendants

clades

occurs when similar environmental pressures adn natural seleection produce similar adaptations

convergent evolution; analogous structures

What did Carolus Linnaeus do

created binomial nomenclature, Genus, specis

Systematics is meant to reflect

evolutionary history

Animals that possess homologous structures probably

evolved from the same ancestor

Animals that possess homologous structures probably -------

evolved from the same ancestor

the most parisomoius trees requres the

fewest evolutionary evens

Characteristics used to build phylogenetic trees

homologies

phenotypic and genetic similarities due to shared ancestry are called

homologies

if genes in two organisms share many portions of their nucleotide sequences, it is likely the genes are waht

homologous

underlies similarities possible even if functions different

homology

The four chambered hearts of birds and mammals are best described as

homoplasies

analogous structures that arose independently are also

homoplasies

analogous structures that arose independently are called

homoplasies (to mold the same way)

a process in which genes are transferred from one genome to another through mechanisms

horizontal gene transfer

in a paraphyletic group, the recent common ancestor and all member of the group is or is not part of the group

is

in a polyphyletic group the most recent common ancestor is or is not part of the group

is not

identifies the tree most likely to have produced a given set of DNA data, based on cerain probability rules about how DNA sequences change over time

maximum likelihood

what traits produces a good estimate a phylogeny

molecular traits, biochemical traits, gross morphological traits, and behavioral traits

a clade is what

monophyletic

what group consists of an ancestral species and all of its descendants

monophyletic grou

the similarity in the number and arrangement of bones in the forelimbs of mammals is due to their descent from a common ancestor with the same bone structure

morphological homology

species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes the species we are studying

outgroup

species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes the species we are studyting; a basis for comparison

outgroup

what group consists of an ancestral species and some but not all of its descendants

paraphyletic group

evolutionary history of a group of organisms

phylogeny

the evolutionary history of a species or group of species

phylogeny

class includes all categories except what?

phylum, kingdom and domain

group includes distantly related species but does not include their most common ancestor

polyphyletic

branch point from which two descendant groups emerge and signifies what

polytomy; that evolutionary relationships among the taxa are not yet clear

When a branch point within the tree represent the most recent common ancestor of all taxa in the tree

rooted tree

character that orgininated in an ancestor of the axon

shared ancestral character ex: the backnone predates the branching of mammals from other vertebrates

character that originated in the ancestor of the taxon

shared ancestral trait

an evolutionary novelty unique to a clade

shared derived character ex: hair is a character y all mammals but not found in their ancestor

an evolutionary novelty unique to a clade

shared derived trait

groups of organisms that share an immediate common ancestor

sister taxa

When a single line branches into two or more lines what does that mean

speciation events; multiple lineages came from one common ancestor

branch of biology that focuses on the classification of organism

systematics

What does a phylogenetic tree NOT do

tells nothing about these groups' evolutionary relationships to one another

What does each brand point of a tree represent

the divergence of two evolutionary lineages form a common ancestor

What does the x axis represent on a phylogenetic tree

time; left oldest, right present day

homoplasies in greek means

to mold the same way

dichotomies are

two way branch points

when does convergent evolution occure

when similar environmental pressures and natural selection produce similary (analogous) adaptations in organisms from different evolutionary lineages