Analogous and Vestigial Structures

1. Analogous and Vestigial Structures Write in complete sentences! Don’t talk during the Catalyst! Catalyst • Cougars eat Bucaneers, which have decreased in population over the past few years. What is the environmental pressure? • Humans and cows both have hearts with four chambers. • What type of structure is this? • Describe what it tells us about how humans and cows evolved. • What are two things ALL animal embryos have in common? What does this tell us about how animals evolved?

2. Objectives By the end of today, all SWBAT… • Explain how analogous structures support the theory of evolution • Explain how vestigial structures support the theory of evolution

3. Catalyst Review • Cougars eat Bucaneers, which have decreased in population over the past few years. What is the environmental pressure? • The environmental pressure is the decrease in population of the Bucaneers. • WHY?

4. Catalyst Review • Humans and cows both have hearts with four chambers. What type of structure is this, and what does it tell us about how humans and cows evolved? • Human and cow hearts are homologous structures. • This shows that humans and cows evolved from a common ancestor with a four-chambered heart.

5. Catalyst Review • What are two things all animal embryos have in common? What does this tell us about how animals evolved? • All animal embryos have gill slits and tails. • This is evidence that all animals evolved from the same common ancestor.

6. Homework Review • What are homologousstructures? Provide two examples of homologous structures. • What is an embryo? • What is a common ancestor? Give an example. • All animal embryos start off looking very _______________. For example, they all have _______________ and _______________. These traits are examples of _______________ structures.

7. Homework Review • Lions and tigers have similarly structured tails. What type of structures are these? EXPLAIN how these structures support the theory of evolution. (Hint: use the phrases “evolve” and “common ancestor”!) • How can we use the appearance of cat and horse embryos to support the theory of evolution? (Hint: use the phrases “evolve” and “common ancestor”!)

8. Comparative Anatomy • Scientists can compare the anatomy of different organisms to figure out how closely they are related. • Anatomy = body structure

9. Analogous Structures • Analogous structure: Parts of different species that have the same function, but EVOLVED SEPARATELY • Key Point #1: Analogous structures show that unrelated* species will evolve similar adaptations in response to similar environmental pressures • Natural selection selects for (keeps around) mutations that increase fitness in the specific environment. • If organisms they live in similar environments, they will evolve similar structures.

10. Insect, bird, and bat wings evolved completely separately. Unrelated organisms will evolve similar adaptations in response to similar environmental pressures! No recent common ancestor!!!

11. Seals and penguins both have streamlined bodies, and store fat to keep them warm in the cold water. Unrelated organisms will evolve similar adaptations in response to similar environmental pressures!

12. Vestigial Structures • Vestigial structure: Part of an organism that is no longer used for anything • Key Point #2: Vestigial structures show that a species used to live in a different environment. • Organism moved into a new environment, where the vestigial structure decreases fitness • No longer needed, waste of energy • Risk of disease

13. Letter “c” = hind legs of a baleen whale skeleton Vestigial = no longer used!!!

14. Blind salamanders have eye sockets!?!?

15. So, what about me?

16. Guided Practice – Notes Reflection • How do analogous structures provide evidence for evolution? • Analogous structures show that unrelated* organisms will evolve similar adaptations in response to similar environmental pressures If you can’t find the answer… ADD IT!!!

17. Guided Practice – Notes Reflection • How do vestigial structures provide evidence for evolution? • Vestigial structures show that the species used to live in a different environment • Organism moved into a new environment where the vestigial structure decreased fitness… so it started to degrade If you can’t find the answer… ADD IT!!!

18. Study! • This practice will cover yesterday’s lesson (homologous structures) as well as today’s (analogous and vestigial structures). • Take three minutes to study your notes from yesterday and refresh your memory before we proceed.

19. Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? • Human embryos and cat embryos both have gill slits. HOMOLOGOUS

20. Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? • Birds and insects both have wings, but they developed in completely different ways. ANALOGOUS

21. Guided Practice (GP) Is this structure… (A) Homologous, (B) Vestigial, (C) Analogous? • Snakes don’t have legs, but they do have hip and leg bones. VESTIGIAL

22. Guided Practice (GP) Is this structure… (A) Homologous, (B) Vestigial, (C) Analogous? • The human appendix – a small organ next to the intestines – doesn’t seem to do anything at all. VESTIGIAL

23. Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? • Cat embryos and human embryos both have tails. HOMOLOGOUS

24. Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? • Dolphins and sharks both have fins, but they evolved completely differently. ANALOGOUS

25. Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? • Alligators and bats have the same bone structure in their forelimbs (front legs for alligators, wings for bats). HOMOLOGOUS

26. Guided Practice (GP) Is this structure… (A) Homologous, (B) Vestigial, (C) Analogous? • Humans have wisdom teeth (third molars), even though they are not needed to chew up food. VESTIGIAL

27. Guided Practice (GP) Are these structures… (A) Homologous, (B) Vestigial, (C) Analogous? • Humans and squids both have eyes, but they evolved in completely different ways. ANALOGOUS

28. Independent Practice (IP) • Get an early start on the homework.

29. Key Point Wrap-Up • Key Point #1: Analogous structures show that unrelated* species will evolve similar adaptations in response to similar environmental pressures • Key Point #2: Vestigial structures show that a species used to live in a different environment. • Organism moved into a new environment, where the vestigial structure decreases fitness

30. All humans have a tail bone, but we don’t have tails. What type of structure is this? EXPLAIN how this structure provides evidence for evolution. Dogs and alligators both have long snouts that allow their jaws to open wide. However, they evolved in completely different ways. What type of structure is this? EXPLAIN how these structures provide evidence for evolution. Exit Question: Choose one optionWrite in complete sentences!