Adaptation, Systematics, convergent evolution (L9)

What is a phylogeny

The evolutionary history of a species or group of related species

What is phylogenetic bracketing

A method of inference used to predict the likelihood of unknown traits in organisms based on their position in a phylogenetic tree

What is systematics and what do systematists use?

Systematics classifies organisms and determines their evolutionary relationships

To infer evolutionary relationships systematists use fossils, molecular data, and genetic data

What are the two key features of Linnaean classification that remain useful today

Two part names for species (binomial nomenclature)

Hierarchical classification

List the taxons from most inclusive to least inclusive

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

What's the difference between Linnaean classification and phylogeny?

Linnaean classification focused more on resemblances while phylogeny recognizes only groups that include a common ancestor and all its descendants

Phylogenetic tree, branch point, sister taxa, rooted tree, basal taxon, polytomy

1- represents a hypothesis about evolutionary relationships

2- each branch point represents the divergence of two species… tree branches can be rotated around a branch point without changing the evolutionary relationships

3- sister taxa are groups that share an immediate common ancestor

4- a rooted tree includes a branch to represent the last common ancestor of all taxa in the tree

5- a basal taxon diverges early in the history of a group and originates near the common ancestor of the group

6- a polytomy is a branch from which more than two groups emerge

What do phylogenetic trees not show us?

They show patterns of descent, not phenotypic similarity

They do not indicate when a species evolved or how much change occured in a lineage

It should not be assumed that a taxon evolved from the taxon next to it

Phylogenies are inferred from x and y

Morphological and molecular data

Homology vs analogy . What is convergent evolution?

Homology is a similarity due to shared ancestry

Analogy is similarity due to convergent evolution

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

What are homoplasies? How can homology be distinguished from analogy

Analogous structures or molecular sequences that evolved independently are also called homoplasies

Homoplasy also includes reversals (a trait is present in an ancestor but not its immediate descendants, but appears later in a subsequent descendant)

Homology can be distinguished from analogy by comparing fossil evidence and degree of complexity

The more complex two similar structures are, the more likely they are homologous