Unit 7: Topics 6, 7, 8, and 9

Systematics

Systematics

classification of organisms and determining their evolutionary relationships

Taxonomy

naming and classifying species

Phylogenetics

hypothesis of evolutionary history. Use phylogenetic trees to show evolution

To determine evolutionary relationships, scientists us

• Fossil records

• DNA

• Proteins

• Homologous structures

Phylogenetic trees

diagrams that represent the evolutionary history of a group of organisms

Similar to cladograms

except trees show the amount of change over time measured by fossils

In a cladogram, each line represents

a lineage

In a cladogram, each branching point is

a node

Nodes and branches from a cladogram are called

clades

The root

the common ancestor of all the species

Two classes that emerge from the same node are

sister taxa

A lineage that evolved from the root and remains unbranched is

the basal taxon

Synapomorphy

a derived character shared by clad members

Derived characteristic

similarity inherited from the most recent common ancestor of an entire group

Ancestral characteristic

Similarity that arose prior to the common ancestor

Many cladograms and trees include an

outgroup

Monophyletic group

includes the most recent common ancestor of the group and all of its descendants (clade)

Paraphyletic group

includes the most recent common ancestor of the group, but not all its descendants

Polyphyletic group

does not include the most recent common ancestor of all members of the group

Parsimony

If there are conflicts among characters, use the principle of parsimony. Use the hypothesis that requires the fewest assumptions (DNA changes)

Primary sources of evidence

• the fossil record

• comparative morphology

• biogeography

fossils

remains or traces of past organisms

Fossil record

gives a visual of evolutionary change overtime

Fossils can be dated by examining the rate of

carbon 14 decay and the age of rocks where the fossils are found

Comparative morphology

analysis of the structures of living and extinct organisms

Homology

characteristics is related species that have a similarities even if that have similarities even if the functions differ

Homology

characteristics is related species that have similarities even if the functions differ

Embryonnic homology

many species have similar embryonic development

Vestigial structures

structures that are conserved even though they no longer have use

Molecular homology

many species share similar DNA and amino acid sequence

Homologous structures

characteristics that are similar in two species because they share a common ancestor

Convergent evolution

similar adaptations that have evolved in distantly related organisms due to similar environments

Analogous structures

structures that are similar but have separate evolutionary origins

Structural evidence indicates common ancestry of

all eukaryotes

Cellular examples

• membrane-bound organelles

• linear chromosomes

• introns in genes

Biogeography

the distribution of animals

What types of data provides evidence for evolution?

Fossil data, biogeography and morphology

Populations continue to evolve, genomes change

• antibiotic resistance in bacteria

• insect resistance to pesticides

• pathogens cause emerging (new) diseases