Unit 7: Phylogeny and the Tree of Life

What is phylogeny?

The evolutionary history of a species or a group of related species.

What evidence is used to determine phylogeny?

Fossils, morphology, DNA, and molecular data.

What is taxonomy?

The classification of organisms based on characteristics.

What is binomial nomenclature?

A two-part naming system: genus + species (e.g., Canis familiaris).

Who developed binomial nomenclature?

Carolus Linnaeus.

What are the levels of classification in order?

Domain, kingdom, phylum, class, order, family, genus, species.

What is a taxon?

A level or group in the classification system.

What do phylogenetic trees show?

Hypotheses about evolutionary relationships.

What do the branches in a phylogenetic tree represent?

Groups nested within more inclusive groups.

What is an outgroup?

The least closely related group used for comparison.

What are homologous structures?

Similar structures from shared ancestry (e.g., whale flipper, tiger leg).

What are analogous structures?

Similar structures from convergent evolution (e.g., dolphin and tuna body).

What is convergent evolution?

Evolution of similar traits in unrelated species due to environment.

Do analogous traits show relatedness?

No, they show similar adaptations, not shared ancestry.

What is molecular systematics?

Uses DNA/molecular data to determine evolutionary relationships.

What does similar DNA mean in evolution?

More similar DNA = more closely related.

What do phylogenetic trees show that cladograms don’t?

Amount of evolutionary change and time.

What does a cladogram show?

Patterns of shared characteristics among taxa.

What is a clade?

A group including a common ancestor and all its descendants.

What is another name for a clade?

Monophyletic group.

What is a shared derived character?

A trait unique to a particular clade (e.g., hair in mammals).

What is a shared ancestral character?

A trait shared by all in a group, inherited from a common ancestor (e.g., backbone).

What is the goal of cladograms?

To reflect true monophyletic groups.

What is a molecular clock?

A tool estimating the time of evolutionary change based on DNA mutations.

What does a molecular clock assume?

More mutations = more time since divergence.

What are highly conserved genes?

Genes that mutate very slowly due to their importance (e.g., glycolysis genes).

How has taxonomy changed over time?

From 2 to 5 kingdoms, now to 3 domains.

What are the three domains?

Bacteria, Archaea, Eukarya.

Which domains are prokaryotic?

Bacteria and Archaea.

Which domain contains eukaryotic organisms?

Eukarya.

What is horizontal gene transfer?

Movement of genes between genomes, not through reproduction.

What are methods of horizontal gene transfer?

Plasmids, viruses, transposons, and cell fusion.

What problem does horizontal gene transfer cause in phylogeny?

It can make trees inconsistent when using different genes.

What is vertical gene transfer?

Gene transfer from parent to offspring.