Chapter 32 Theories of Evolution

1. Chapter 32 Theories of Evolution

2. Introduction • Biologists have classified more than 1.5million species of organisms for far. • Many scientists estimate that there may be 10million species of organisms living on earth. ***Review Classification • What does a Scientific name consist of? • Kingdom order • Class species • Phylum Genus • Genus species

3. Classification Review • What is the correct way of writing the scientific name for a Lion? • pantheraleo • Pantheraleo • Pantheraleo • panthera Leo

4. Introduction cont. • As we know there are differences between organisms of different species. • In addition, there are also differences among organisms of the same species (variations).

5. Why are there so many variations among organisms? • Evolution is responsible for this great diversity! • Evolution: the process by which organisms change over time.

6. Evolution • Until the 19th century, most scientists believed that organisms existed as they had first appeared on earth. • However, by the 1800’s geologists were finding and studying many fossils. • What do you think these fossils showed? • Scientists began wondering how and why living things may have changed?

7. Evolution cont. During this time 2 biologists proposed a theory on evolution:

8. Lamarck's Theory • Proposed his theories in 1809 • 1st hypothesis: • Organisms develop traits, or characteristics by the use or disuse of body parts. • Ex: If the body part is used, it becomes larger and stronger. If the body part is not used, it becomes smaller and weaker.

9. Lamarck's Theory cont. • 2nd hypothesis: • Acquired characteristics, or the traits that organisms develop during their lifetimes, are passed from parents to their offspring • Ex: Giraffe • He didn’t have any observations or evidence to support his theory. • Therefore most scientists did not support his theory.

10. Lamarck's Theory cont.

11. Investigations of Charles Darwin • British Naturalist born in 1809. • At the age of 22 Darwin voyaged on the HMS Beagle. • HMS Beagle went on a mapping and collecting expedition to South America and the South Pacific.

12. What did Darwin observe during his 5 year voyage? • How earthquakes and other geological processes change the land. • He observed thousands of species of plants and animals • Collected fossils • Notes on all his observations

13. Darwin’s Finches

14. Darwin’s Theory of Evolution • 20 years after his voyage, he published a book called On the Origin of Species by Means of Natural Selection. • What are Darwin’s main ideas about evolution? • Overproduction • Competition • Variations • Survival of the Fit

15. Darwin’s Theory of Evolution cont. • Overproduction: Each species produces many more organisms than can survive and reproduce. • Ex: Crabs, codfish, salmon, sea turtles

16. Darwin’s Theory of Evolution cont. 2. Competition: due to overproduction of offspring, organisms must compete for limited resources (food, water, & a place to live)

17. Darwin’s Theory of Evolution cont. 3. Variation: differences among traits, occur among members of the same species.

18. Darwin’s Theory of Evolution cont. 4. Survival of the Fit: Organisms with traits that make them well adapted to their environment have a better chance to surviving and reproducing (natural selection).

19. Darwin’s Theory of Evolution cont. • Organisms that survive and reproduce pass on their traits to their offspring. • As the process of natural selection continues through many generations, species change and become better adapted to their environment. • As a result, evolution occurs by natural selection.