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Ch. 26: Classification &
Phylogenetics
The Major Lineages of Life
Characteristic
Bacteria
Archaea
Eukarya
Nuclear Envelope
No
No
Yes
Membraneenclosed
organelles
No
No
Yes
Introns
No
Yes
Yes
Histones
associated w/DNA
No
Yes
Yes
Circular
chromosome
Yes
Yes
No
Taxonomy



The tracing of
evolutionary
relationships
(phylogenetic tree)
Linnaeus
Binomial nomenclature:
– Genus, species epithet
– Homo sapiens

Taxon (taxa): a group of
organisms in the same
clade (ancestor + all
descendants)
Phylogenetic Trees


Systematics: classifying organisms according to their
evolutionary relationships
Fossils, morphology, molecular evidence
Protista:
(not “true” kingdom)
Bacteria:
(not “true” kingdom)
The only “true” clade
Constructing a Cladogram

Homology vs. Analogy...

Homology: likenesses
attributed to common
ancestry (inheritance)

Analogy: functional
similarities; not indicative of
close evolutionary
relationships

Convergent evolution:
species from different
evolutionary branches that
resemble one another due to
similar ecological roles
Homologous Structures
Human
Cat
Whale
Bat
A Cladogram:
the basis of a phylogenetic tree
Cladograms are based on shared characters
Classification

3 Domains
– Archaea
– Bacteria
– Eukarya
Prokaryotes:
•1/10 the length & 1/1000
the volume
•Asexual reproduction
•No nucleus or organelles
•Circular DNA instead of
chromosomes, smaller
genome