BIO151 Lecture Exam 3 - Chapter 25

roles of phylogenetics in systematics

studies evolutionary relationships using phylogenetic trees to show shared ancestry

the roles of taxonomy in systematics

focuses on the naming of species and organizing them into higher level groups (genus, order, class, etc.)

How are species named?

taxonomy, assigns each a binomial name

How are groups of species classified?

taxonomy, hierarchical categories

How do scientists determine which species belong together in groups?

Phylogenetics: groups species by shared traits (synapomorphies)
Phylogenetic trees: show evolutionary relationships

What information is expressed in a phylogenetic tree?

evolutionary relationships, common ancestors, degrees of relatedness, and branching order of species over time

Homology

similarity because of shared ancestry

• building accurate phylogenies

homoplasy

similarity from independent evolution (convergent evolution), not shared ancestry, can mislead analyses

What is convergent evolution?

unrelated species evolve similar traits independently, leads to homoplasy

Example of homology?

Limb bones in humans, birds, and whales, from common ancestor

Example of homoplasy due to convergent evolution?

Wings in birds and bats, evolved flight separately

What is a monophyletic group?

common ancestor and all of its descendants (a complete branch on a phylogenetic tree)

What is a paraphyletic group?

common ancestor but not all of its descendants

Why are protists considered a paraphyletic group?

some descendants of their common ancestor

eukaryotes are excluded

what eon do we live in?

Phanerozoic Eon

What are the major eras of the Phanerozoic Eon (in order)?

1. Paleozoic Era

2. Mesozoic Era

3. Cenozoic Era

What geologic epoch do we live in?

Holocene Epoch

What is an adaptive radiation?

One lineage quickly evolving into many species for different environments

How does adaptive radiation affect species number and morphology?

Increases species and their physical differences as they adapt to niches

What factors can trigger adaptive radiations?

• New resources (ecological opportunity)

• New traits (morphological innovation)

systematics?

field of biology that studies relationships among organisms

a sister group (sister taxa)?

Two taxa that share an immediate common ancestor

a shared ancestral character?

Trait from a common ancestor shared by all group members

How is a scientific name written properly?

The genus is capitalized and the species is lowercase, both italicized

ex: Homo sapiens

monophyletic group (clade)?

includes a common ancestor and all of its descendants

shared derived character (synapomorphy)?

Trait in two or more taxa, shared by recent common ancestor not older ones.

hierarchical classification?

organizing species into nested groups like genus, family, order, etc

ingroup?

group of species being studied in a phylogenetic analysis

outgroup?

species closely related to, but not part of, the ingroup

• ancestral vs. derived traits

parsimony in phylogenetics?

simplest tree, with the fewest evolutionary changes, most likely

taxon (plural: taxa)?

Any named group of organisms in a phylogenetic tree

the most recent common ancestor?

last shared ancestor from which two or more taxa evolved

polytomy?

Node with 3+ branches showing unclear evolutionary relationships