1. Analogous and Vestigial Structures
Catalyst
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?
What are two things all animal embryos have in common? What does this tell us about how animals evolved?
Write in complete sentences!
Don’t talk during the Catalyst!

2. By the end of today, all SWBAT…
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. Agenda Review Structures Guided Practice Independent Practice/Homework
Analogous
Vestigial
Guided Practice
Independent Practice/Homework
Closing
Exit Questions

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?
It is a homologous structure.
This shows that humans and cows evolved from a common ancestor with a four- chambered heart.
If you’re worried about time, skip the homework review and do it on Thursday (review day for unit test)

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.
If you’re worried about time, skip the homework review and do it on Thursday (review day for unit test)

6. Comparative Anatomy
Scientists can compare the anatomy of different organisms to figure out how closely they are related.
Anatomy = body structure
Remember, the theory of evolution tells us that all life branched off from one original species (red circle) and the more closely two organisms are related, the more recently they shared a common ancestor

7. 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.
Unrelated* (with a star) because no organisms are ACTUALLY unrelated, given that we all descended from the same original organism. But it’s easier to say unrelated than it is to say “organisms with no recent common ancestor” over and over.
Introduce definition first (explicitly state that this is satisfying our first objective), KP explains why it’s important (b/c it provides a certain sort of evidence for evolution… hey, our second objective!). Then, CFU: can you explain to me how analogous structures support evolution? (All they have to do is spit KP back out at you… but make sure they can do it.)

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

9. 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!

10. 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

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

12. Blind salamanders have eye sockets!?!?
They live in caves. Siiick.

13. 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
* because, technically, everything is (at least distantly) related. But the point is that they don’t share a recent common ancestor.
If you can’t find the answer…
ADD IT!!!

14. 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
That organisms
If you can’t find the answer…
ADD IT!!!

15. Study!
Guided 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.

16. HOMOLOGOUS Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?
Human embryos and cat embryos both have gill slits.
After revealing the correct answer, ask random students to explain how the structure supports evolution
HOMOLOGOUS

17. ANALOGOUS 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.
After revealing the correct answer, ask random students to explain how the structure supports evolution
ANALOGOUS

18. VESTIGIAL 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.
After revealing the correct answer, ask random students to explain how the structure supports evolution
VESTIGIAL

19. VESTIGIAL 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.
After revealing the correct answer, ask random students to explain how the structure supports evolution
VESTIGIAL

20. HOMOLOGOUS Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?
Cat embryos and human embryos both have tails.
After revealing the correct answer, ask random students to explain how the structure supports evolution
HOMOLOGOUS

21. ANALOGOUS Guided Practice (GP)
Are these structures…
(A) Homologous, (B) Vestigial, (C) Analogous?
Dolphins and sharks both have fins, but they evolved completely differently.
After revealing the correct answer, ask random students to explain how the structure supports evolution
ANALOGOUS

22. HOMOLOGOUS 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).
After revealing the correct answer, ask random students to explain how the structure supports evolution
HOMOLOGOUS

23. VESTIGIAL 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.
After revealing the correct answer, ask random students to explain how the structure supports evolution
VESTIGIAL

24. ANALOGOUS 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.
After revealing the correct answer, ask random students to explain how the structure supports evolution
ANALOGOUS

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

26. 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
Get a volunteer to read KP1, second volunteer to explain how KP1 fulfills the first objective, third volunteer to explain how KP2 fulfills the second objective
Repeat with KP2, KP3

27. Exit Question: Choose one option Write in complete sentences!
What is one thing that human embryos and dolphins embryos both have in common?
What kind of structure is this?
How do these structures provide 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 kind of structure is this?
How do these structures provide evidence for evolution?
Student Choice – there’s a WOW factor!