1. Common Ancestry

2. What are some possible causes of a species evolving to become a new species?
Environmental change
Soft-shelled and hard-shelled crab populations
Isolation of groups
Darwin’s finches
Leads to speciation
This objective will be developed further in L.8.2.C.1 The purpose here

3. Speciation
Speciation occurs when populations of the same species evolve to become so different genetically that they can no longer breed with one another to produce fertile offspring.
Takes place over many years
How can speciation occur?
Geographic Isolation

4. Geographical Isolation
Occurs when populations become divided by physical barriers that keep populations from mating
Rivers
Mountains
Islands

5. Speciation of Darwin’s Finches

6. Amoeba Sister’s Speciation
7:33

7. Biological Evidence of Evolution
What evidence do we have from characteristics of both living and fossil remains to support that different species could have common ancestors?
Biological Evidence of Evolution
Similarities in body structure
Vestigial structures
Similarities in early development
Fossil record
This objective will be developed further in L.8.2.C.1 The purpose here

8. Similarities in Body Structure
Comparative anatomy is the study of similarities and differences among structures of living species.
If the two organisms have body structures that are similar, they may have had a common ancestor.
Homologous structures are body parts of organisms that are similar in structure and position but different in function.
Came form common ancestors

9. Similarities in Body Structure
Analogous structures are body parts that perform a similar function but differ in structure.
Did not come from common ancestors

10. Homologous vs. Analogous Structures

11. Vestigial Structures
Vestigial structures are structures found in an organism that have lost their original function through evolution.
Whales possess a femur and pelvis, but these bones are no longer useful to the mammals.

12. Similarities in Early Development
Embryology is the science of the development of embryos from fertilization to birth.
Scientists look at embryos of different organisms and find that many embryos resemble one another.

13. Fossil Record How fossils form
An organism dies and becomes buried in sediment.
Minerals gradually replace the bones and more sediment covers the fossil.
Pterodactyl
Trilobite

14. Fossil Record in the Strata
Fossils from organisms that died longer ago are buried deeper in the sediment/rock than fossils from organisms that died more recently.