Sz2- Students will explain the evolutionary history of
animals over the geologic history of Earth.
Geologic History

Geologic time- time that began when earth was
formed until present day
Evolution of the Earth with Time: Continental Drift
50 Million Years Ago
200 Million Years Ago
150 Million Years Ago
100 Million Years Ago
Present
Important Terms
Evolution- gradual change in a species over
time- sci. theory
 Theory-well-tested explanation that
explains a wide range of observations.
 Adaptation- any trait that helps an
organism survive and reproduce

Natural Selection

the process by
which individuals
that are better
adapted to their
environment are
more likely to
survive and
reproduce.
Charles Darwin
Natural Selection cont.
Over a long time, natural
selection can modify a
population enough to
produce a new species
 Helpful variations
accumulate in a species
while unfavorable ones
disappear.

Speciation
 When a group of individuals remain
separated from the rest of the species long
enough to evolve different traits
How Speciation Occurs
 Geographic isolation○ Pangaea /Continental Drift
○ Landform isolation- river, mountain,
water. (ex. Squirrels of N. Grand
Canyon)
 Competition
 Gene flow
 Environmental change- local
adaptation to local environment
Speciation of SquirrelsGrand Canyon

The Kaibab squirrel (Sciurus aberti kaibabensis, left)
became isolated in the Grand Canyon ~ 10,000 years ago.
Features have gradually evolved that separate it from close
relative, the Abert squirrel (S. aberti aberti)
A Problem with Traditional Classification
Example: The Crab, The barnacle, & The limpet
•
The barnacle and the limpet have similarly shaped
shells & look alike
•
The crab has a very different body form
•
Based on anatomy, the barnacle & limpet could be
classified together and the crab in a different
group.
Related
This incorrect because
crabs and barnacles
are actually related
Crustaceans
Gastropods
Molted Exoskeleton
Segmentation
Free swimming Larva
Even though they do
not look a like, crabs &
barnacles are actually
related
A Problem with Traditional Classification

Traditional classification systems relied on
body structure comparisons only

Due to convergent evolution, organisms that
are quite different from each other evolve
similar body structures.
Convergent Evolution:
Process by which
unrelated organisms independently evolve
similarities when adapting to similar environments.
Modern Evolutionary Classification
Evolutionary Classification:
Is the
strategy of grouping organisms together based on
their evolutionary history, instead of physical
features.
Uses DNA and RNA, embryological development,
comparative anatomy to classify species.
Modern Three-Domain System



As scientists further analyzed cell structure and
DNA , a broader category was addedThe domain is the most inclusive taxonomic
category; larger than a kingdom
The three domains are:
 Bacteria : kingdom Eubacteria
 Archaea,: kingdom Archaebacteria;
 Eukarya :Kingdom Protista, Fungi, Plantae, and
Animalia.
Genus species
If these three species belong to the same genus,
they are descended from a common ancestor.
Felis domestica
domestica
Felis
Domestic
Cat
Felis leo
leo
Lion
Felis margarita
margarita
Sand cat`
Classification Using Cladograms
Cladogram:
A diagram that shows the
evolutionary relationships among a group of organisms.
new
traits that show up in
a lineage
ex. jaws, lungs,
mammary glands
Modern Evolutionary Classification

Molecular Clocks
 A model known as a

Comparison reveals
more DNA in common,
the more recent the
common ancestor
molecular clock uses
DNA comparisons to
estimate the length of
time that two species
have been evolving
independently.
19
Terminology

Classification
 Assigning organisms to
different catagories based
on their relationship

Taxonomy
 The science of naming
organisms

Systematics
 Determining evolutionary
relationships of organisms

Phylogeny
 Evolutionary history
20
Phylogenetic Tree
Shows evolutionary
relationships
 More historical than
cladogram

21
Uniramia
Echinodermata
Chordata
Lophophorates Chelicerata
Crustacea
Protochordates
Arthropoda
Annelida
Hemichordata
Other
pseudocoelomates
Nematoda
Mesozoa
Sarcomastigophora
Ciliophora
Apicomplexa
Microspora
Mollusca
Nemertea
Platyhelminthes
Ctenophora
Cnidaria
Placozoa
Porifera
Myxozoa
22
Birds
Mammals
Reptile
Feathers
Amphibian
Fish
Fur
Endothermic
Amniotic Egg
Four Limbs
Vertebrae
23
Monophyletic groups (Clades)
A group of all the
descendants of a
common ancestor
 The common
ancestor is in the
group
 Example: Birds and
Reptiles

 Ancestor was a bird
like reptile
24
Polyphyletic
group that has some
similarities
 Contains organisms that
have not descended from
a common ancestor
 Based on physical
characteristics instead of
evolutionary evidence
 Example: Flying
vertebrates- pterosaurs,
birds, mammals

25
Cladogram
Shows Evolutionary
relationships of a
group of organisms
 Each clad (group)
share something in
common
 Ancestral traits are
the oldest
 Derived traits evolved
later

26
Cladogram for Transportation
Wheels are the most
ancestral
 Wings are the most
derived

27
Construct a Cladogram
28
Gorilla
Four limbs
 Fur
 Lost tail

29
Tiger
Four limbs
 Fur
 Tail

30
Lizard
Four limbs
 Tail

31
Fish

Tail
32
Chimpanzee
Four limbs
 Fur
 Lost tail

33
Clad With 4 Limbs
34
Clad With Fur
35
Clad With No Tail
36
Characteristics for Constructing
Cladogram
Tail is the most ancestral
 Four limbs is the oldest derived trait
 Fur is a later derived trait
 Loss of tail is the most derived trait

37
Gorilla
Chimpanzee
Tiger
Lizard
Fish
Tail Lost
Fur
Four Limbs
38
Gorilla Tail?

How do we know the
gorilla lost its tail?
39
Gorilla’s Vestigial Tail
Gorilla
Human
40
The End.