Chapter 22: The Nature of Species
We will also cover some selected topics from
Chapters 23
-- intro to claudistics
Chapter 26
-- Biological classification
-- Domains vs kingdoms
-- Intro to history of life
Evolution II
1
What is a species?
Scientific naming of species
Scientific binomial – Carolus Linnaeus
Genus + Species
Homo sapiens vs
“humans”
Acer rubrum
“red maple”
vs
Biological classification system:
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Writing Conventions
Question
Definition
“A group of interbreeding organisms that
are reproductively isolated”
What is ‘reproductive isolation’?
Which of these is Acer rubrum?
Evolution II
2
What are some mechanisms
of reproductive isolation?
Pre-zygotic
Ecological (habitat)
e.g., mountain ranges
Mechanical
e.g. reproductive anatomy
Temporal
e.g. mating seasons
Behavioral
e.g., mating rituals
Gametic
gametes incompatible
(many plants)
e.g., frogs of Sierra Nevada foothills
e.g., bowerbirds of Australia
Evolution II
3
Mechanisms of
reproductive isolation, con’t.
Post-zygotic
Hybrid inviability
-- embryo / fetus does not develop
e.g., cattle and water buffalo
Hybrid infertility
-- offspring is infertile
e.g., colored and pied flycatchers
Question
Evolution II
Meet and hybridize in
central and northern Europe
4
The biological
species concept
has limitations
If two species can hybridize,
are they separate species?
-- plants
-- animals
Native: California Tiger Salamander
Invasive: Adult Barred Tiger Salamander
Hybrid: Appears to be
more fit then native
Should all dogs be
classified in the same
species?
http://sciencemode.co
m/2007/09/20/californ
ia-barred-tigersalamandersinterbreed-producehybrids/
Evolution II
5
How does geographic distribution
relate to speciation?
Allopatric speciation: geographic isolation
mountains, rivers, islands
What evolutionary mechanisms
can operate?
Can Sympatric speciation occur?
e.g., “blackbellied seedcracker”
Less fit hybrids -‘reinforcement’
Reinforcement among
European flycatchers
Question
Evolution II
6
How can we explain the origin of the apple maggot?
Apple
Maggot
Hawthorn
Apple
Visit Martin G. Kelly’s site at
http://www.sciencecases.org/maggot_fly/maggot_fly.asp
Evolution II
7
Under what conditions does
‘Adaptive Radiation’ occur?
-A special case of
disruptive evolution
Darwin’s Finches -- classic example
Can occur regionally or globally
-- rise of mammals
Adaptations reinforced by
“Character Displacement’
Question
Evolution II
8
Plotting macroevolution
What are some characteristics
of evolution that can be diagrammed?
Gradualism vs ‘punctuated equilibrium’
Stephen J Gould & Niles Eldredge
What are possible mechanisms of
rapid speciation?
-- polyploidy
-- mutations to developmental genes
-- geologic time vs ‘human’ time
Evolution II
9
Plotting evolutionary relationships
(from Chapter 23)
The traditional “evolutionary tree”
vs Claudistics
Clade= all organisms with
“Shared derived characteristics”
Evolution II
10
Revisiting Classification…
(from Chapter 26)
Domains and Kingdoms
Biological classification system:
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Question
Evolution II
11
Highlights of the History of Life
(from Chapter 26)
Advanced life forms have appeared
Late in earth’s geologic history
Origin of life ~ 3.8 bya
Eukaryotic cells ~ 1.7 bya
Multicellular organisms ~ 1.2 bya
Origin of life
Multicellular
organisms
Humans only ~ 1 mya
Evolution II
12
The origin of major groups
of animals
The ‘eras’
The Cambrian explosion
Vertebrates
Invertebrates
Age of reptiles
Age of mammals
Insects most successful
of them all
Evolution II
13
There have been many mass extinctions!
Some small,
Some BIG!
Question
Evolution II
14