Taxonomy & Evolutionary History
I.
II.
III.
IV.
Taxonomic Concepts
Taxonomic Principles
Time Scale
Rate of Evolutionary Change
I. Taxonomic Concepts
A.
B.
C.
D.
Taxonomy – scientific system for classification.
Uses a set of rules to determine relationships
among items (organisms?) in a set.
Today, still based on Linnaeus’ seven level
system: Kingdom, Phylum, Class, Order,
Family, Genus, and Species.
Remember as King Phillip Crossed Over For
Grape Soda
All organisms are referred to by their genus &
species (binomial nomenclature).
II. Taxonomic Principles
A.
B.
Structures that are shared
through descent from a
common ancestor are called
homologies.
Homoplasy is the process
by which similarities can
develop in different
groups of organisms.
Leads to analogous
structures.
II. Taxonomic Principles
C. Structures in organisms
that are used for the
same function, but have
developed
independently and are
not the result of common
descent, are called
analogies.
D. Analogies are often the
result of convergent
evolution.
II. Taxonomic Principles
E.
Cladistic Taxonomy
An approach to taxonomy that groups species
according to shared derived characteristics.
1.
2.
Traits that reflecting the ancestral condition
of an organism are primitive.
Traits shared by all members of a group, but
not present before the group's appearance,
are said to be shared derived
characteristics (e.g nails in primates).
II. Taxonomic Principles
E. Cladistic Taxonomy
3. Related groups are thus in the same clade,
or branch/level (genus, family, or whatever)
4. At the finest levels, determining where one
species starts or stops, however, is
sometimes a problem.
II. Taxonomic Principles
F. Speciation
1.
Groups of organisms capable of breeding to
create fertile offspring that COULD normally be
expected to contact one another.
2.
Species are reproductively isolated from one
another:
i.
Biological – physical or genetic limitations
ii.
Geographic – separation of the organisms on
the landscape
iii. Behavioral – social separation of organisms
(e.g. nocturnal/diurnal)
III. Time Scale: Geological Eras
A.
Paleozoic

B.
Mesozoic


C.
The first vertebrates appeared 500 mya
Reptiles were dominant land vertebrates.
Placental mammals appeared 70 mya
Cenozoic

Divided into two periods: Tertiary and
Quaternary and 7 epochs.
III. Time Scale: Cenozoic Epochs
Draw and leave space to fill this chart:
Epoch
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
Time
65 mya
55 mya
34 mya
23 mya
5 mya
1.8 mya
0.01 mya
Primates
III. Time Scale: Mammal Evolution
A.
B.
C.
The Cenozoic era is known as the Age of
Mammals.
After dinosaurs became extinct at 65 mya,
mammals underwent adaptive radiation,
resulting in rapid expansion and diversification.
One advantage was the larger neocortex,
which controls higher brain functions,
comprised the majority of brain volume in
mammals resulting in greater ability to learn.
III. Time Scale: Mammal Evolution
D.
E.
F.
Another was the variety of diet mammals were
capable of, due to their digestive and dental
differentiation (heterodont – having many
types of teeth)
Yet another was mammals’ endothermy, or
ability to easily self-regulate their body
temperature
Still another was mammals’ emergence of
marsupial and later placental birthing –
keeping the developing embryo inside the
mother for protection and greater development
IV. Rate of Evolution
A.
Punctuated Equilibrium
–
–
–
B.
Long periods of no change
punctuated by rapid evolution
and speciation (@ right)
S. Gould and N. Eldredge
Explains gaps in record
Phyletic Gradualism
Darwin’s idea of slow gradual
change leading to eventual
speciation