1. DARWIN’S THEORY ON EVOLUTION
UNIT #5 EVOLUTION

2. Charles Darwin (1809 – 1882) Born in Shrewsbury, Western England
He always had a consuming interest in nature
His father saw no future for him as a naturalist and sent him to medical school
He quit medical school to become a clergyman at Cambridge University
Became the protégé of John Henslow, a botany professor
After he graduated, he worked with Captain Fitzroy on the HMS Beagle for a long voyage around the world.

3. HMS Beagle

4. Darwin’s Voyage
The mission was to chart the unknown stretches of the S. American coastline.

6. Darwin’s Voyage
Spent most of his time on shore collecting plants and animals
Described how different features of organisms made them well suited to their environment
Spent most of his time reading Lyell’s Principles of Geology
After experiencing earthquake, he observed that rocks and fossils along the coast had been raised by several feet

7. The Galapagos Islands
A group of volcanic islands near located near the equator
Noticed several kinds of finches.
Most of Galapagos species were not known anywhere else in the world
However, the animals on Galapagos were similar to species living on the South American mainland
Darwin hypothesized that the Galapagos Islands had been colonized by organisms coming from South America

8. Darwin’s Views on Adaptation
Adaptations – inherited characteristics of organisms that help their survival and reproduction in specific environments.
Chameleons – camouflage
Snakes – Fangs to attack on prey
Bats – Night hearing
An organisms’ body and behavior adapts to the specific foods located on their home land

10. Natural Selection
Natural Selection – A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits
Lizards – the ability to climb tall trees to avoid floods
“Survival of the Fittest”

11. Darwin’s Publications
By 1840s, Darwin wrote out the major features of his hypothesis and set these ideas on paper
Wrote about descent with modification and natural selection
Darwin published it immediately before anyone could come to the same conclusion and publish it first.

12. Alfred Russel Wallace (1823 – 1913)
By 1858, Darwin’s fear came true
Darwin received a paper from Wallace
Wallace had developed a paper on natural selection similar to Darwin’s
Wallace asked Darwin to evaluate his paper and send it to Lyell for publication
In 1858, Lyell and a colleague presented both Wallace’s paper and Darwin’s unpublished essay to the Linnean Society of London

13. Darwin’s Publications
Meanwhile, Darwin quickly finished his book, titled On the Origin of Species by Means of Natural Selection and published it the next year
Although Wallace had submitted first, Wallace thought that Darwin developed and explained the idea of natural selection much better
Wallace thought that Darwin should be credited for this new theory
Darwin’s book convinced most scientists at the time that life’s diversity is the product of evolution.

14. The Basics of Darwin’s Theory
In his book, Darwin made three broad observations about nature
Unity of Life
Diversity of Life
Relationship between Organisms and their Environment .

15. Descent with Modification
In the 1st Edition of The Origin of Species, Darwin never used the word “evolution”
The final word in the book is “evolved”
Instead, he wrote about descent with modification, a phrase that showed his point of view of life
Due to organisms sharing many characteristics, he perceived a unity in life
He attributed the unity of life to the descent of all organisms from a common ancestor in the past
Darwin reasoned that descent with modification eventually led to the diversity of life that we see today

16. Darwin’s Tree Darwin viewed the history of life as a tree
Multiple branching's from a common trunk out to the tips of the youngest twigs

17. Artificial Selection
Darwin proposed the idea of natural selection to explain patterns of evolution
He created his argument carefully to persuade readers
First he discussed selective breeding of domesticated plants and animals.
Artificial Selection – the process in which humans have modified other species over time by selective breeding of individuals containing desired traits.

18. Observations and Inferences
“Members of a population often vary in their inherited traits”
Inference #1
“Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals”
Observation #2
“All species can produce more offspring than their environment can support and many of these offspring fail to survive and reproduce”
Inference #2
“This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over genetics”

19. Thomas Malthus ( )
Wrote about human suffering – disease, famine and war
He believed that human suffering resulted from human population’s potential to increase faster than food supplies and other resources
Darwin realized that the ability to over reproduce was a characteristic of all species. .

20. Heritable Traits
Heritable Traits – traits that can be passed down to offspring
An organism’s heritable traits not only affects its own performance, but it can also affect how well its offspring copes with environmental challenges .

21. How rapid does change occur?
Darwin believed that if artificial selection can create a dramatic change in such a short period of time, then natural selection can cause change over hundreds of generations.

22. Natural Selection Recap
Natural Selection – a process in which individuals with certain heritable traits tend to survive and reproduce at higher rates because of those traits.
If an environment changes or if an organism moves to a new environment, natural selection can result in adaptations to those new conditions – giving a rise to new species

23. Natural Selection Recap
Even though natural selection occurs through interactions between organisms and their environment
It is NOT the individuals that evolve but the POPULATION that evolves
Favored traits can vary from place to place over time
These traits depend on the context in which a species lives and mates in