Comparative Embryology introduction

Note-taking with instructor

1. Comparative Embryology How do species change over time? & Why might they change?

2. Agenda CLASS: All vertebrates start the same way… Work through slides (3-12) together. Participate in the discussion & complete text boxes. Independently: Review (slide 13) watch the PBS video - for visual evidence. Write a “Big Take Away” idea; 2-3 sentences on (slide 14). How do living things evolve over time - and WHY?

3. WHOA The ones in the first row LOOK almost the SAME!! fish tortoise pig hare s alamander chick sheep human

4. Basics of: Comparative Embryology looks at embryos of different species, to show all animals are related. What could we learn from comparing different types of embryos?

5. All vertebrate embryos have a similar basic body design. As they grow, we can see the traits that tell them apart Studying this process helps us understand evolution. What does this mean? (summarize) Vertebrate embryos have some similar genes.

6. Von Baer Karl Ernst Von Baer, came up with four principles of comparative embryology:

7. Common features can be seen before specialized features. You can see homologous structures in early embryos. What would this mean?

8. 2. Common features slowly develop into more specialized (complex) features. (specialize into body systems) What would this mean? This shows BUT

9. 3. Gill slits are seen in early human embryos, Von Baer believes it is due to a common ancestor between humans and fish. Embryos of more evolved animals diverge away from more primitive animals. Using this theory, since early human embryos have the same structures as adult fish… What changes happened? Why did they happen?

10. 4. Embryos of higher species look similar to primitive embryos. This shows higher animals and primitive animals... What could this prove?

11. Darwin found that differences between species become greater as evolution continues, agreeing with Von Baer’s theories. HERE IS THE SLIDE TITLE! Charles Darwin

12. Darwin had two ways to look at evolution 1. Focus on common descent using embryo similarities. OR 2. Focus on modifications to show how structures developed that helped animals adapt to changing conditions. HERE IS THE SLIDE TITLE! Charles Darwin

13. Similar structure - from having a common ancestral structure. Like, the wing of a bird and the forelimb of a human are homologous structures. More importantly, their parts are homologous. S imilar structure - from doing a similar activity or behavior , NOT a common ancestor . Like, the wing of a moth and wing of a bird are analogous. They have a common function but happened through evolution Homologous Analogous Homologous & Analogous Review PBS VIDEO

14. Comparing embryology ... What is Your Big Take Away Idea?