1. Evolution

2. Evolution Change over time
Process by which modern organisms have descended from ancient organisms

3. Charles Darwin Born in England 1809
Set sail on H.M.S. Beagle in 1831 for voyage around the world
Made numerous observations and collected evidence that led him to propose the theory of evolution – how life changes over time

4. Darwin’s Voyage

5. Darwin’s Observations
Observed a tremendous amount of diversity in plants and animals
68 different beetle species in one day in a Brazilian forest
Plants and animals well suited to whatever environment they inhabited

6. Darwin’s Observations
Intrigued by which organisms survived and produced offspring
Collected fossils that resembled organisms that were still alive
Most influenced by Galapagos Islands

7. Galapagos Islands Very different climates on each island
Paid particular attention to giant tortoises, marine iguanas, and finches
Organisms varied in predictable ways from one island to another
ie. Tortoise shells

8. Galapagos Islands
Darwin proposed that animals living on different islands had once been members of the same species
Species would have evolved from an original South American ancestor species after becoming isolated from one another

9. Galapagos Tortoises Pinta Island Intermediate shell Hood Island
Saddle-backed shell
Isabela Island
Dome-shaped shell

10. Darwin’s Influences
Society was not receptive to Darwin’s “radical” ideas
Certain scientists who preceded Darwin helped to shape his views

11. Hutton’s Theory Hutton’s Theory of Geological Change
James Hutton (1795) a geologist
Rocks, mountains, and valleys are shaped by a variety of natural forces
i.e. Rain, heat, & cold temperatures
Geological processes operate extremely slowly therefore Earth had to be much older than a few thousand years old

12. Lyell’s Principles Lyell’s Principles of Geology
Charles Lyell (1833) geologist
The Processes that changed Earth in the past are the same processes that operate in the present
Scientists recognize that Earth is many millions of years old

13. Movement of Earth’s Crust
Sea level
Sea level
Sedimentary rocks form in horizontal layers.
When part of Earth’s crust is compressed, a bend in a rock forms, tilting the rock layers.
As the surface erodes due to water, wind, waves, or glaciers, the older rock surface is exposed.
New sediment is then deposited above the exposed older rock surface.

14. Lamarck’s Theory of Evolution
Jean Baptiste Lamarck French naturalist (1809)
proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime.
These traits could be passed on to their offspring.
Led to changes in species

15. Tendency Toward Perfection
All organisms have a innate tendency toward perfection
Ancestors of birds acquired an urge to fly,
Birds kept trying to fly,
Their wings increased in size,
Birds are now suited to flying

16. Use and Disuse
Organisms could alter the size or shape of particular organs by using their bodies in new ways
Birds try to use front limbs to fly, they grew wings
If a winged animal did not use its wings they would decrease in size and disappear

17. Inheritance of Acquired Traits
Lamarck thought acquired characteristics could be inherited.
If you spent your life lifting weights to build muscles then your children would inherit big muscles, too.

18. Crab Claws

19. Evaluating Lamarck Lamarck’s theory of evolution is incorrect because:
He did not know how traits are inherited.
Behavior has no effect on genetics
He was the first:
to develop a theory of evolution
First to realize that groups of organisms do adapt to their environment

20. Population Growth Thomas Malthus (1798) – English Economist
Observed that babies were being born faster than people were dying.
Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.
Proposed that war, famine, and disease limit the growth of human populations.

21. When is a Fin a Wing? Animal Group Example Legs Fins Tail Mammal Bird
Fish
Amphibian
Reptile
Insect

22. Darwin Presents His Case
Publication of On the Origin of Species
* Darwin’s discoveries went totally against the scientific ideas of the 1800’s
* He did not publish his research until he read Alfred Russel Wallace’s essay, which summarized Darwin’s thoughts on evolution.
* Published 25 years after his trip

23. Natural variation and artificial selection
Darwin’s critics believed that all species were perfect and unchanging
Natural variation: differences among individuals of a species, found in all types of organisms.
Darwin proposed that much of the variation in populations can be inherited, or passed on to the next generation

24. Artificial Selection
Darwin actually made some of his greatest progress studying English farmers and breeders
Artificial selection: nature provides variation among different organisms, humans select and breed for those variations that they find useful.

25. Artificial Selection

26. Evolution by Natural Selection
* The struggle for existence
* Competition for resources
* Food, water, shelter, mates, etc.

27. Survival of the Fittest
The better suited an organism is to its environment, the better chance it has at surviving
The ability of an individual to survive and reproduce in its specific environment – fitness
The inherited characteristics that increase an organism’s chance of survival - adaptation

28. Descent With Modification
Over time, natural selection has produced species that are different than their ancestors
Looking backwards in time you should find the common ancestor of all living things – common descent

29. Darwin’s Tree of Life

30. Tree of Life

31. Evidence of Evolution Fossil Record
Darwin believed that life on Earth has been evolving for millions of years
Darwin saw the fossil record as a detailed record of life on Earth

32. Evidence of Evolution Geographic Distribution of Living Species
Darwin found that organisms living under similar ecological conditions end up evolving similarities without being related – Convergent Evolution
Ex – Fish and whales

33. Evidence of Evolution Homologous Body structures
* The limbs of birds, reptiles, and mammals may have different looks but they form from the same embryonic tissue – Divergent Evolution
* Similarities of Early Development
* Animals have similar embryological development

34. Homologous Structures
Turtle
Alligator
Bird
Mammals
Typical primitive fish

35. Embryonic Development

36. Summary of Darwin’s Theory
Variations are inherited
2. In nature, tendency towards overpopulation
3. Not all organisms survive – compete for resources
4. Natural Selection – struggle for existence

37. Summary of Darwin’s Theory
5. Individuals best suited to their environment survive and reproduce most successfully
6. Species change over time
7. Populations today come from modifications of species of the past
8. All organisms are united into a single tree of life by common decent