1. Definitions of Biological Disciplines
evolution—change through time
biodiversity—variety of living forms & their habits
anatomy & physiology—structure & function
behavior—how animals do things
ecology—interactions of animals w/ each other & their physical environments

2. Perpetual Change & Geological Time
Perpetual geological & biological change is the rule.
Consider the vastness of geological time.
radiometric dating
age of Earth—4.6 billion years

3. Evidence of Perpetual Change
Banded Iron Formation, Australia
rocks up to 3 billion years old

4. Evidence of Perpetual Change
Big Island, Hawaii
oldest part of island 400,000 years old (7,500 times younger than the old rocks)

5. Fossil Record oldest microscopic fossils—3.5 billion years
oldest macroscopic fossils—650 million years
most animal phyla present 540 million years ago

6. Fossil Record Burgess Shale (580 million years old [Cambrian])
many phyla present that are long extinct
some modern phyla represented
an “experiment of evolution”

7. Fossil Record oldest vertebrates >500 million years old
human agriculture ~10,000 years old
Therefore, human agriculture is about % (two one-hundred thousandths of one per cent) as old as the oldest vertebrates
% of a mile = 1/3 of a millimeter

8. Darwin and Evolution
Charles Darwin served as naturalist on mapping expedition around coastal South America.
Used many observations to develop his ideas
Proposed that evolution occurs by natural selection

9. Influences on Darwin voyage of the H.M.S. Beagle Darwin 23 years old
5-year voyage around the world

10. Influences on Darwin observed & collected fauna & flora found fossils
found seashells in mountains at 4,000 meters
experienced major earthquake in S. America

11. Influences on Darwin
Beagle stopped at the Galapagos Islands (on equator 600 miles off of W coast of S. America)
spent 5 weeks on islands

12. Influences on Darwin
Galapagos visit hugely influential on Darwin’s development of theory of evolution
organisms unique, yet similar to continental forms in S. America (e.g., giant tortoises due to lack of predators)

13. Charles Darwin Evolution: Modification of a species over generations
“descent with modification”
Proposed that evolution occurs by natural selection
Natural Selection: Individuals with superior physical or behavioral characteristics are more likely to survive and reproduce than those without such characteristics

14. Natural Selection proposed by Darwin (and Wallace)
supported by abundant evidence
describes how populations accrue ‘favorable’ characteristics over evolutionary time
evidence from artificial selection
e.g., dog breeds
supported by series of observations & inferences from those observations

15. Darwin’s Evidence Similarity of related species
Darwin noticed variations in related species living in different locations

16. Darwin’s Evidence Population growth vs. availability of resources
Darwin realized that not all members of a population survive and reproduce
Deduced that the organisms best adapted to obtaining resources would survive to reproduce

17. Post-Darwin Evolution Evidence
Comparative anatomy
- Homologous structures have same evolutionary origin, but different structure and function.
- Analogous structures have similar structure and function, but different evolutionary origin.

18. Common Descent
all forms of life ultimately descended from a common ancestor via a branching of lineages
single origin of life

19. Common Descent: Phylogeny
structure of life is like a tree—phylogeny
common ancestor of ratite birds

20. Common Descent: Homology
homologous structures reflect common evolutionary ancestry
e.g., limb skeleton of tetrapods from salamanders to humans share homologous elements

21. Homologous Structures

22. Common Descent: Homology
Whether or not two structures are homologous depends on the “level” being considered.
E.g., bird wing & bat wing grossly homologous
modified forelimb
but specific elements supporting the airfoil of each are not homologous
feathers in bird vs. skin in bat

23. Analogy
similar structures that serve similar function but do not indicate common ancestry
e.g., bird wing vs. butterfly wing

24. What is a species? Biological Species Concept (Mayr 1940)
an interbreeding natural population (or group of populations) that is reproductively isolated from other such groups
Evolutionary Species Concept (Simpson [1961] & Wiley [1981])
a single lineage of ancestral-descendant populations that maintains its identity from other such lineages & that has its own evolutionary tendencies & historical fate
at least 30 other published species concepts

25. How does speciation occur?
evolution of reproductive barriers
can be physical, physiological, ecological, behavioral, etc. (frequently a combination)
generally accepted that the evolution of reproductive barriers b/t populations of animals requires the presence of geographic barriers (e.g., mountain range, isolated island) that physically separate populations

26. How does speciation occur?
allopatric speciation
population separated into two separate groups by geographic barrier
followed by evolution of reproductive barriers
examples of geographic isolating mechanisms
formation of new mountain range separating population of low elevation species
formation of new island (e.g., land in ocean, lake on land) followed by rare immigration of individuals

27. How does speciation occur?
examples of allopatric speciation
marine iguana & land iguana on Galapagos
reptiles on islands in Sea of Cortez
Hawaiian crow
squirrels on N & S rim of Grand Canyon
other speciation mechanisms exist, but allopatric speciation is most pervasive

28. Gradualism
major differences in traits among species evolve by accumulation of many small incremental changes over time
somewhat controversial
phyletic gradualism

29. Alternative to Gradualism: Punctuated Equilibrium
sudden appearance of new species & rapid morphological changes followed by long periods of stasis
some patterns show gradualism & others indicate punctuated equilibrium
reality likely combination of both
punctuated equilibrium

30. What Evolution Is & Is Not
Evolution is not like a ladder. Evolution is like a tree.
The parts of an organism (i.e., its characteristics) can be ancestral or derived, depending on what other organisms it is being compared to.
An organism is the sum of its parts. Therefore, an organism is a composite of ancestral & derived characteristics.
Avoid using the terms primitive & advanced in reference to organisms or taxonomic groups.