BIO 212 Q5

Phylogeny/Cladogram

Phylogeny

Phylogeny

the evolutionary history of a species or group of related species

systematics

classifies organisms and determines their evolutionary relationships

Systematists use ___ to infer evolutionary relationships

fossil, morphological, and molecular data

Taxonomy

the ordered division and naming of organisms

Carolus Linnaeus published a system of taxonomy based on

resemblances

binomial

The two-part scientific name of a species

genus

the first part of the name

specific epithet [i.e., species]

the second part of the name, unique for each kind within the genus

the taxonomic groups from broad to narrow

domain, kingdom, phylum, class, order, family, genus, and species

taxon

A taxonomic unit at any level of hierarchy

Systematists depict evolutionary relationships in branching

phylogenetic trees

A phylogenetic tree represents a

hypothesis about evolutionary relationships

each branch point represents

the divergence of two species

Sister taxa

groups that share an immediate common ancestor

a rooted tree includes

a branch to represent the last common ancestor of all taxa in the tree

basal taxon [outgroup]

diverges early in the history of a group and originates near the common ancestor of the group

polytomy

a branch from which more than two groups emerge

Phylogenetic trees show ____ not ____

patterns of descent, phenotypic similarity

Phylogenetic trees typically do not indicate

when species evolved or how much change occurred in a lineage

To infer phylogenies, systematists gather information about

morphologies, genes, and biochemistry of living organisms

homologies

Phenotypic and genetic similarities due to shared ancestry

When constructing a phylogeny, systematists need to distinguish whether a similarity is the result of

homology or analogy

Homology

similarity due to shared ancestry

analogy

similarity due to convergent evolution

bat and bird wings are homologous as

forelimbs

bat and bird wings are analogous as

functional wings

Convergent evolution occurs when

similar environmental pressures and natural selection produce similar [analogous] adaptations in organisms from different evolutionary lineages

Molecular systematics

uses DNA and other molecular data to determine evolutionary relationships

Cladistics

groups organisms by common descent

clade

includes an ancestral species and all its descendants

monophyletic grouping

a valid clade, consists of the ancestor species and all its descendants

paraphyletic grouping

consists of an ancestral species and some, but not all, of the descendants

polyphyletic grouping

consists of various species with different ancestors

What type of grouping is this?

monophyletic

What type of grouping is this?

Paraphyletic

What type of grouping is this?

Polyphyletic

shared ancestral character

a character that originated in an ancestor of the taxon

ex. vertebratal column

shared derived character

an evolutionary novelty unique to a particular clade

ex. hair

outgroup

species or group of species that is closely related to the ingroup

ingroup

the various species being studied

Systematists compare each ingroup species with the outgroup to differentiate between

shared ancestral and shared derived characteristics

In some trees, the length of a branch can reflect the

number of genetic changes that have taken place

Methods of narrowing the possibilities of the best phylogenetic tree

maximum parsimony and maximum likelihood

Maximum parsimony assumes that

the tree that requires the fewest evolutionary events [appearances of shared derived characters] is the most likely

maximum likelihood states that

given certain rules about how DNA changes over time, a tree can be found that reflects the most likely sequence of evolutionary events

Phylogenetic bracketing

allows us to predict features of an ancestor from features of its descendents

What are some shared features of birds and crocodiles?

four-chambered hearts, vocalization, nest building, and brooding

The shared features of birds and crocodiles likely evolved in a

common ancestor

The shared features of birds and crocodiles were

shared by all of its descendants, including dinosaurs

What is a valuable approach for tracing organisms’ evolutionary history?

Comparing nucleic acids or other molecules to infer relatedness

Ribosomal RNA changes

relatively slowly

Ribosomal RNA is useful for investigating

branching points hundreds of millions of years ago

mtDNA evolves

rapidly

mtDNA can be used to

explore recent evolutionary events

-nae

sub family

-dae

family

What are the three domains?

the Archaea, the Bacteria, and the Eukarya