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