1. Darwin’s Theory of Evolution

2. What is Theory ?? Most people think of it as a guess
“It’s just a theory.”
In Science a theory is not a guess.
A hypothesis is more like a guess than a theory
In Science a theory is a well tested and well supported explanation

3. What is a Theory?
A well supported testable explanation of phenomena that have occurred in the natural world.
The Theory of Evolution

4. Evolution “Change over Time” Geological Evolution Organic Evolution
Change in non living characteristics of the earth over time
Examples = Climate & Continental Drift
Organic Evolution
Change in species over time
Change (in DNA) over time

5. Evolution: Key Concepts
History: Darwin, Lamarck , Hutton, Lyell
Natural Selection : Survival of the Fittest
Evidence:
Fossils
Geographic Distribution of Species
Homologous Structures
Embryological Development
Evolution and Genetics
History of the Earth : Geologic Time Scale
Classification

6. Can an Individual Evolve?
No!
Individuals are born with a set of chromosomes that determine their characteristics.
This set does not change
Individuals Develop
Populations EVOLVE

7. Charles Darwin Age 22 set sail on the H.M.S beagle (1831)
Chart coast line of South America and some pacific islands
Voyage took 5 years
Most significant observations were made on Galapagos Islands
He returned convinced that species evolve

8. Voyage of the Beagle

9. Survey made by the Beagle

10. Current Survey

11. Galapagos Island Finches

12. Galapagos Island Tortoise

13. Intermediate Shell
Pinta Island
Saddle-backed shell
Hood Island
Dome-shaped shell
Isabela Island

14. What Island does this Tortoise come from?
Isabela

15. Modern Evolution spurred from??
Darwin’s Publications of ……
On the Origin of Species by means of Natural Selection
Published in 1858
Nearly 25 years after the beagle returns home

16. 6 Main Points of Darwin’s Theory
Variation
Overproduction
Competition
Adaptations
Natural Selection
Speciation

17. Earlier Theories of Evolution
James Hutton (1785)
Earth is shaped by geological forces over millions of years not thousands of years
Charles Lyell (1831 )
Writes about how the earth can be shaped (volcanoes , earthquakes)
Influences Darwin’s thinking
If the earth can change why can’t species

18. Lamarck’s Theory of Evolution
Jean-Baptiste Lamarck (1809)
Selective use or disuse of organs, organisms acquired or lost certain traits during their life time.
Traits passed onto offspring
Over time this leads to change in a species
DISPROVEN

19. Jean-Baptiste Lamarck believed…
Was based on the idea that individuals adapt during their own lifetimes and transmit traits they acquire to their offspring.
Offspring then adapt from where individuals left off, enabling evolution to advance.
As a mechanism of adaptation , Lamarck proposed that individuals increased specific capabilities by exercising them, while losing others through disuse.

20. Lamarck’s Giraffe

21. Lamarck vs. Darwin

22. Back to Darwin’s Six Principles
Species tend to overproduce
This leads to competition
There is variation in a population
Some of these variations are positive adaptations
Natural selection means that those best adapted tend to survive and reproduce
This process of natural selection changes the gene pool

23. Variation
Individuals in a species do not have identical characteristics
Darwin observed this fact but he could not explain the mechanisms that caused variability
Darwin did not know about DNA and Genetics

24. Overproduction Habitats have limited resources
Habitats can only support a limited number of individuals
Species tend to produce more offspring than can survive in a given environment

25. Competition Overproduction leads to competition
Members of a species compete for limited resources

26. Adaptations Adaptations are positive traits
That increases an individuals ability to survive in a given environment
Individuals with adaptations have higher fitness
They tend to survive and reproduce most successfully

27. Natural Selection
The environment selects those individuals with the best adaptations to be the parents of the next generation
Those less fit cannot compete and they reproduce less (Survival of the Fittest)
Over many generations natural selection causes changes in the characteristics of species

28. Speciation
New species arise from existing species through the process of natural selection

29. Summary of Darwin’s Theory
Individual organisms differ from one another.
More offspring are produced than can survive.
Members of a species compete for limited resources.
Each unique organism has different advantages and disadvantages in the struggle for existence.
Individuals best suited to their environment survive and reproduce most successfully.
Species change over time. Natural selection causes changes in characteristics of species. New species arise, and other species disappear.
Species alive today have descended with modification from species that lived in the past.
All organisms on Earth are united into a single tree of life by common descent.