Transcript Unit 1: Chap 25-26

Classification and
The Tree of Life
Unit 1: Chap 25-26
Classification/Taxonomy
 Carolus Linnaeus
 Swedish botanist and anatomist
 Taxonomy: ordered division of organisms
into categories based on a set of
characteristics used to assess similarities
and differences.
 Not based on evolutionary relationships
but resemblance
Binomial nomenclature
 Common names (monkey, fish) refer to
more than 1 species.
 A 2 part scientific name (binomial) was
created by Linnaeus
1. Genus: to which the species belongs
2. Specific epithet: unique for each species
within the genus
Ex: Leopard = Panthera pardus
Hierarchical Classification
 Species are
placed into
groups
belonging to
more
comprehensive
groups.
Classification+evolutionary
history
 = Phylogeny
 Phylogenic trees: branching
diagram that represents a
•
hypothesis about
evolutionary relationships.
 Constructed from a series of
dichotomies, 2 way branch
points; divergence of 2
species from a common
ancestor.
 • It is a hypothesis.
Phylogeny + Shared
Characteristics
 Cladogram: diagram depicting patterns of
shared characteristics among species.
 Clade: within a tree, a group of species
that includes an ancestral species and all
its descendants
 Cladistics: analysis of how species are
grouped
Cladogram
Cladistics:
1. Monophyletic: single tribe
- Ancestral species and ALL descendants
2. Paraphyletic: result of lack of information on clade members
- Ancestral species and SOME descendants
3. Polyphyletic: several species that lack a common ancestor
Homologous VS Analogous
 Structures in different
species that are
similar because of a
common ancestry.
 Similarity between 2
species due to
convergent evolution
rather than to
descent from a
common ancestor
with the same trait.
Phylograms
 Length of a branch
reflects the number of
changes in a specific DNA
sequence in that lineage.
 Different lengths but all
lineages have survived for
the same number of
years.
 Indicates that a given
gene evolves at slightly
different rates in the
different lineages.
Ultrametric Trees
 Same branching as a phylogram but all
branches are of equal length.
 Branches reflect measurements of
geological time.
History of Taxonomic
Systems
 2 Kingdom: plant (fungi, bacteria) and
animal (protozoans)
 5 Kingdoms: Monera, Protista, Plantae,
Fungi, Animalia (Eukaryotes/Prokaryotes)
Finally:
 3 Domain System: Bacteria, Archaea,
Eukarya (Plants, Animals, Fungi)
- level higher than Kingdom
3 Domain System