1. Charles Darwin: Theory of Evolution as a Mechanistic Process
JRMGUCE 2009

2. Charles Darwin: Theory of Evolution as a Mechanistic Process
Darwin’s Idea of Common Descent
Darwin’s Idea of Multiplication of Species
Darwin’s Idea of Gradualism
Darwin’s Idea of Natural Selection

3. Darwin’s Idea of Common Descent
Descent with modification A.K.A EVOLUTION
common ancestor/prototype
Accumulated diverse modifications or adaptations

4. The finches posed questions to Darwin:
Did they descend from one mainland ancestor, did islands allow isolated populations to evolve independently, and could present-day species have resulted from changes occurring in each isolated population???

5. Darwin’s Idea of Common Descent
Life history is like a tree
Common trunk: multiple branching and re-branching
Common ancestor in each fork of branching
lineage of common descent
Extinct species

6. TAXONOMY: Tree of Life Carolus Linnaeus - Species are fixed
Kingdom
Phylum
Class
Order
Family
Genus
Genus species
Carolus Linnaeus
- Species are fixed
- Ordered the great diversity of organisms into “groups subordinate to groups”

7. Reflected the genealogy of the tree of life

8. Darwin’s Idea of Multiplication of Species
species either split into or bud off other species
geographical isolation of a founder species.
Founder effect. The frequency of the a allele is low in the initial population, but a small subset, in which one individual is Aa, is removed from the large population and founds a new population. The frequency of a is markedly higher in this new population, due to its relatively high frequency in the founders

10. Darwin’s Idea of Multiplication of Species
different ecological niches provide different ways of living
different plants and animals come to fill different niches with different shapes and behaviors

12. Darwin’s Idea of Gradualism
changes through the gradual change of population rather than the sudden production of new individuals
species arise:
Through gradual accumulation of adaptations to a different environment

14. e.g. Darwin’s finches  ADAPTIVE RADIATION

15. Rapid evolution may arise:
Isolation of small population
Migration of small group in a new environment
Through mass extinction
Because of geological barriers

16. Darwin’s Idea of Natural Selection
Compared processes in nature with artificial selection
Developed a scientific hypothesis to explain how evolution occurs
Struggle for existence (Malthus)
Members of each species compete regularly to obtain food and living space and other necessities in life
Central to his Theory of Evolution

17. Survival of the Fittest
* key factor in the struggle for existence
* Fitness
-ability to survive and reproduce
-result of adaptation
-central to the process of evolution by natural selection

18. referred to as: NATURAL SELECTION
LOW FITNESS
Either DIE or LEAVE FEW OFFSPRINGS
HIGH FITNESS LEVEL
many OFFSPRINGS
referred to as: NATURAL SELECTION
accumulation of changes that differentiate groups from one another, such that a new species may arise

19. DARWIN’s MISSING INGREDIENT
Darwin did not understand the genetic basis for variation
variations
mutations
genetic recombination
mutation as a raw material for evolution

20. OTHER THINGS TO BE CONSIDERED
Natural vs. Artificial selection
Importance of population in evolution
smallest unit that can evolve
Natural selection acts on individuals but INDIVIDUALS DO NOT EVOLVE

21. DESCENT WITH MODIFICATION FROM ANCESTRAL SPECIES
Darwinian View of LIFE
Diverse forms have arisen
DESCENT WITH MODIFICATION FROM ANCESTRAL SPECIES
Biological diversity
Mechanism of modification
NATURAL SELECTION

22. Patterns of Evolution Mass extinction
99% of the species ever lived are now extinct
wiped out whole ecological systems*
Cretaceous extinction
Large asteroid struck the earth
Can be caused by eruptions of many large volcanoes (Permian and Cretaceous) , changing of positions of continents and changing of sea levels
* Disrupting energy flows and causing food web to collapse

23. Patterns of Evolution Adaptive Radiation
single species or small group of species has evolved into several different forms that live in different ways
Ex. Darwin’s Finches
Dinosaurs
Mammals

25. Patterns of Evolution Convergent Evolution
unrelated organisms come to resemble one another
Natural selection may mold different body structures
structures tend to function the same way and look similar
Analogous structures
same look and function
Different embryonic origin

27. Patterns of Evolution Coevolution
two species evolve in response to the changes in each other over time
Ex. Fig trees and wasps

28. Patterns of Evolution
Developmental Genes and Body Plans
Hox genes

29. Process of Speciation Species
group of organisms that can interbreed and produce a fertile offspring
Share a common gene pool
As new species evolve populations become reproductively isolated from each other
Reproductive isolation
Can be: Behavioral, Geographical and Temporal

30. Process of Speciation Behavioral isolation Geographical isolation
Capable of interbreeeding but has different courtship rituals or behavior
Geographical isolation
Two populations are separated by geographic barriers
Acted by natural selection
Ex. Abert and Kaibab Squirrels

31. Process of Speciation

32. Process of Speciation

33. DIANE DODD’s Experiment