1. Natural Selection

2. Slide # 2
Important Vocabulary
1. Species: A group of organisms whose individuals can breed together to produce fertile offspring.
2. Population: A localized group of individuals belonging to the same species.
3. Evolution: A slow change in a population over time.

3. Slide # 3
Charles Darwin explained how Natural Selection could cause a population to adapt and change over time. (note he states- a “population” will change -not an “individual”)

4. Old Theories of Evolution: Lamarck’s Theory of Use and Disuse
Slide # 4
Old Theories of Evolution: Lamarck’s Theory of Use and Disuse
1801: Theory of Inheritance of Acquired Characteristics
“Theory of inheritance of acquired characteristics” & “Use and disuse”
If an organism changes in order to adapt to its environment, those changes are passed on to offspring.
Said that changes in organisms occur to help an organism reach perfection.
Problem: No organism is perfect
Lamarck

5. Example of Lamarck’s Hypothesis
Slide # 5
Example of Lamarck’s Hypothesis
Example of Lamarck’s hypothesis:
Male crab uses small front claw to ward off other males
Because it has been used a lot, front claw becomes larger.
Larger claw trait is passed on to offspring.
Even though his hypothesis is flawed, he was the first to address the fact that organisms adapt to their environment

6. The Work of Lyell Influenced Darwin’s Ideas
Slide # 6
The Work of Lyell Influenced Darwin’s Ideas
Charles Lyell – English geologist
1830: On the Principles of Geology
Natural forces & processes that shaped ancient Earth are the same forces acting on Earth today.
Earth’s geologic features formed as a result of gradual processes.
Must take millions of years to change geography
2. Darwin read Lyell’s work while on his voyage & agreed with Lyell’s conclusions
Charles Lyell

7. The Work of Malthus Influenced Darwin’s Ideas
Slide # 7
The Work of Malthus Influenced Darwin’s Ideas
1798: Thomas Malthus --Economist
Essay on the Principle of Population
Said that humans tend to have more offspring than nature can support
Food production increased at a slower rate than population
Darwin read Malthus’s essay after he returned from his voyage
Darwin concluded that all organisms produce more offspring than the population can support
Thomas Malthus

8. Charles Darwin: An Unlikely Evolutionist
Slide # 8
Who was Charles Darwin?
1809: English naturalist
Went on a 5 year voyage on the HMS Beagle as an unpaid scholar
Collected plants & animals during journey
Darwin did not set out to develop a theory of evolution
Observations and specimens collected helped Darwin formulate his theory of evolution
Charles Darwin

9. Route of Darwin’s 5 Year Trip
Slide # 9
Route of Darwin’s 5 Year Trip
Galapagos Islands
Darwin spent a lot of time and collected a lot of specimens from the Galapagos Islands.

10. Darwin’s Observations
Slide # 10
In Argentina, Darwin saw earthquakes raising the earth several feet
Shells of marine animals found far inland & at great heights in Andes Mts
Fossils of huge sloths & armadillo-like animals (both extinct) – similar to modern forms
Animals on Galapagos were similar but not same as those on mainland S. America & Antarctica
Galapagos penguin
14 inches tall
5 lbs
Eat small fish & sardines
Nests in burrows
Chinstrap penguin
28 inches tall
9-14 pounds
Eat small fish & krill
Build nests out of small stones

11. Darwin’s Observations on the Galapagos Islands
Slide # 11
Darwin’s Observations on the Galapagos Islands
Fewer types of organisms on the islands
Island species differ from mainland species & from island to island
Finches on Galapagos resemble mainland finch, but there were more types on the islands

12. Darwin explained Evolution by Natural Selection
Slide # 12
Darwin explained Evolution by Natural Selection
1859: Darwin published On the Origin of Species
Proposed that natural selection was the mechanism for evolution.
Individuals vary in one or more traits & there can be slight differences in their ability to survive & reproduce.
Nature selects those individuals w/ favorable traits to leave more offspring that are better suited (FIT) for their environment.
Published 25 years after Darwin wrote it!

13. Evidence that Supports Evolution: Fossil Record
Slide # 13
Evidence that Supports Evolution: Fossil Record
1. Fossil: preserved remains (bones, teeth, shells) or evidence (imprint or footprint) of ancient organisms.
Fossils found in sedimentary rock
Younger sediments deposited on top of older sediments
Older sediments contain older, simpler fossils
Younger sediments contain younger, more complex fossils
Fossils found in sediments of organisms that are extinct.
Trilobites are extinct!

14. Slide # 14
Evidence that Supports Evolution: Geographic Distribution of Living Species
Similar animals on each continent live in similar ecological conditions
They were exposed to similar pressures of natural selection.
Because of similar selection pressures, different animals ended up evolving similar characteristics
Beaver
NORTH AMERICA
Beaver
Muskrat
Beaver and Muskrat
Coypu
Capybara
Coypu and Capybara
Muskrat
SOUTH AMERICA
Capybara
Coypu

15. Evidence that Supports Evolution: Homologous Structures
Slide # 15
Evidence that Supports Evolution: Homologous Structures
1. Homologous structures: similar structures but different functions
Structures develop from same clump of embryonic cells
Provides evidence that four-limbed vertebrates descended from a common ancestor.
2. Vestigial structures: structures or organs that are reduced in size; do not seem to serve a useful function
3. Homologous & vestigial structures imply that common genes are involved.
Homologous structures: forelimbs of vertebrates
Pelvis & femur bones are vestigial in whales

16. Evidence that Supports Evolution: Similarities in Embryology
Slide # 16
Evidence that Supports Evolution: Similarities in Embryology
The embryos of vertebrates are very similar during early development.
The same groups of embryonic cells develop in the same order and in similar patterns to produce tissues & organs.
Common cells & tissues growing in similar ways produce homologous structures.
Implies that common genes are involved.
Embryos of vertebrates develop gill slits and tails.