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Comparative Embryology introduction
- 1. Comparative Embryology How do species change over time? & Why might they change?
- 2. Agenda CLASS: All vertebrates start the same way… 1. Work through slides (3-12) together. 2.Participate in the discussion & complete text boxes. Independently: 1. Review (slide 13) watch the PBS video - for visual evidence. 2.Write a “Big Take Away” idea; 2-3 sentences 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
- 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. 1. 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. Similar 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?
Editor's Notes
- Since all vertebrates have a similar embryo - we could see how things evolve. They start as a single cell, go to multi-cells, to clumps of cells, to a hollow ball of cells - then they differentiate. We could see why/how they change
- All vertebrates start out looking very similar. We could learn how some species have evolved into others
- This could show how vertebrate organisms had a common ancestor.
- This shows embryos of similar groups started in a similar way BUT the similar structures differentiated, so they must have a common ancestor.
- Embryos of more evolved animals diverge away from more primitive animals. We evolved into more complex beings.
- Embryos of higher species look similar to primitive embryos. This shows higher animals and primitive animals must have had a common ancestor and just evolved different ways.
- https://illinois.pbslearningmedia.org/asset/tdc02_vid_embryo/