Zoology Chapter 12

Taxonomy

the naming and classifying of organisms

taxon (pl. taxa)

each level of taxonomy is called a …

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

hierarchical organization of organisms

Genus + species

binomial nomenclature

bacteria, archaea, eukarya

the broadest modern classification divides organisms into three domains…

bacteria and archaea

which of the three domains consist of prokaryotic organisms

phylogeny

the evolutionary history and relationships among organisms

the relationships/history

systematics

the study of the evolutionary relationships among organisms

phylogenetic tree

Show relationships and evolutionary change over time

Relatedness depends on the most recent common ancestor, not how close organisms may appear

sister taxa

two groups that share most recent ancestor

B & C

terminal taxa

H

node (the dots)

where there is a split of an ancestral lineage into two or more descendent lineages

root

branches

homologous characteristics

similarity due to common ancestry → useful for phylogeny

examples: human arm, whale flipper, bat forelimb, and cat foreleg

analogous characteristics

similarity due to convergent evolution → can be misleading for phylogeny

examples: wings in birds and insects, streamlined bodies in sharks and dolphins, camera-like eyes in vertebrates and cephalopods (octopus)

shared ancestral characteristic

present in all

characteristic that originated before the group being examined

shared derived characteristic

differentiates

characteristic that evolved in a particular group and is shared by its descendants

cladistics

method of grouping organisms based on common ancestry and shared derived traits

a way to determine/represent those relationships

clade

a common ancestor and all of its descendants

a group on the tree

monophyletic group

cladogram

shows relationships based on shared traits

molecular systematics

use of molecular data to determine evolutionary relationships

• DNA sequences

• RNA sequences

• amino acid sequences of proteins

more sequence similarity generally supports a more recent common ancestor

molecular clock

method for estimating when lineages diverges

uses rate of mutation to estimate when two or more species diverged from a common ancestor

molecular changes accumulate over time and can be used to estimate divergence time

maximum parsimony

favors the hypothesis requiring the fewest evolutionary changes

simplest explanation requiring the fewest evolutionary changes

smallest possible number of changes

multiple polygenetic trees can often be constructed to fit the available evidence