The Theory of Evolution

1. The Theory of Evolution Chapter 13 – Sect. 1: Natural Selection

2. Charles Darwin - 1859 • Published convincing evidence that species evolve • Proposed a reasonable mechanism to explain how evolution occurs

3. Darwin’s Voyage on the HMS Beagle

4. Darwin’s Voyage on the HMS Beagle • 1831-1836 (5 year voyage) • Darwin was 22 years old at the start • Naturalist – someone who studies nature • Ships purpose was to survey the coast of South America

5. Darwin observed that many of the plants and animals of the Galapagos Islands resembled but were not the same as those on the nearby coast of South America Darwin’s Finches Population – all the individuals of a species that live in a specific geographical area and that can interbreed

6. Natural Selection • Individuals that have physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those that do not have such traits • These advantageous traits are adaptations • As a result, the nature of the population will gradually change – evolution!

7. Harsh Criticism • Darwin wrote down his ideas about evolution and natural selection in 1844 • He did not try to publish his work until 1858 • The theory of evolution goes against religious beliefs and was not accepted by the public in general

8. On the Origin of Speciespublished in 1859 (pg. 280 1-4) • Inherited variation exists within the genes of every population or species (the result of random mutation or translation errors) • In a particular environment, some individuals of a population or species are better suited to survive and have more offspring • Over time, the traits that make certain individuals of a population able to survive and reproduce tend to spread in that population • There is overwhelming evidence from fossils and many other sources that living species evolved from organisms that are extinct

9. Reproductive Isolation • Two populations of the same species do not breed with one another because of geographic separation, a difference in mating periods, or other barrier to reproduction • These isolated populations will become more different over time until they are no longer able to breed with one another

10. The Tempo of Evolution

11. The Theory of Evolution Chapter 13 – Sect. 2: Evidence of Evolution

12. Most Scientists Agree on the Following: • Earth is about 4.5 billion years old. • Organisms inhabited Earth for most of its history. • All organisms living today share common ancestry with earlier, simpler life forms.

13. The Fossil Record • The preserved or mineralized remains or imprint of an organism that lived long ago. • Provide a record of Earth’s past life forms • Evidence of evolution can be seen in the fossil record.

14. Formation of Fossils • The fossil record is not complete. • Fossils do not form in all environments • Most fossils form when organisms are rapidly buried in fine sediments • Bodies may decay too quickly or be eaten or scattered • Fossils are most likely to form in: • Wet lowlands, slow-moving streams, lakes, shallow seas, and areas near active volcanoes

15. Anatomy & Development • Comparisons of the anatomy of different types of organisms reveal basic similarities in body structures • The structures may have different functions in different organisms • Ex.) bones may be present in both organisms but are reduced in size and have no use or less important function

16. Vestigial Structures • Reduced in size or function, but may have been complete in an ancestor • Ex.) hind limbs of whales

17. Homologous Structures • Structures that share a common ancestry • ex.) forelimbs of vertebrates

18. Changes in DNA • Mutation – a change in the nucleotide-base sequence of a gene or DNA molecule • If species have changed over time, then the genes that determine the species’ characteristics should also have changed by mutation

19. The Theory of Evolution Chapter 13 – Sect. 3: Examples of Evolution

20. Natural Selection at Work • Environment dictates the direction and amount of change in evolution • If the environment changes in the future, the set of characteristics that most help an individual reproduce successfully may change

21. Factors in Natural Selection(pg. 288 1-4) • All populations have genetic variations. • The environment presents challenges to successful reproduction. • Individuals tend to produce more offspring than the environment can support. • Individuals that are better able to cope with the challenges presented by their environment tend to leave more offspring.

22. Examples of Natural Selection • Strains of lung disease tuberculosis (TB) becoming resistant to certain antibiotics • DNA in each strain is different = evolution & natural selection • Darwin’s finches developed different size and shape beaks based on food sources • Finches with proper beak for food survive = evolution & natural selection

23. Formation of New Species • Divergence – accumulation of differences between groups • Leads to the formation of new species • Subspecies – populations of the same species that differ genetically because of adaptations to different living conditions • Can become so different that can no longer interbreed successfully • Speciation – the process by which new species form