1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Evolution Evolution is the process of change in the inherited characteristics within populations over generations such that new types of organisms develop from preexisting types. Ideas of Darwin’s Time – Scientific understanding of evolution began to develop in the 17th and 18th centuries as geologists and naturalists compared geologic processes and living and fossil organisms around the world.

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Darwin’s Ideas Descent with Modification – Darwin wrote On the Origin of Species, in which he argued that descent with modification occurs, that all species descended from common ancestors, and that natural selection is the mechanism for evolution.

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Darwin’s Voyage

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Darwin’s Ideas, continued Natural Selection – Organisms in a population adapt to their environment as the proportion of individuals with genes for favorable traits increases. – Those individuals that pass on more genes are considered to have greater fitness.

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Natural Selection

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Ideas About Geology Among geologists, Cuvier promoted the idea of catastrophism, (that catastrophes happen and can explain some extinctions) Lyell promoted uniformitarianism (that the processes of the Earth today are the same as they were in ancient times)

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Fossil Record Evidence of evolution can be found by comparing several kinds of data, including the fossil record, biogeography, anatomy and development, and biological molecules. Evolutionary theories are supported when several kinds of evidence support similar conclusions. The Age of Fossils Geologic evidence supports theories about the age and development of Earth.

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The Fossil Record, continued The Distribution of Fossils – The fossil record shows that the types and distribution of organisms on Earth have changed over time. Transitional Species – Fossils of transitional species show evidence of descent with modification.

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Evidence of Whale Evolution

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Biogeography Biogeography, the study of the locations of organisms around the world, provides evidence of descent with modification. As organisms migrate from place to place they may need to adapt to new climates, predators, foods. They may also need to change their colors to blend in better.

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Anatomy and Physiology In organisms, analogous structures are similar in function but have different evolutionary origins (no common ancestor) – ex: wings on insects and wings on birds both function for flight but no common ancestor with wings Homologous structures have a common evolutionary origin and a common function.

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Homologous structures Analogous Structures

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Vestigial Structure Structures that are “leftover” from an ancestor species. These structures are not needed in the modern organism. These structures are often “on their way out” and in the future may no longer be present.