Homologous Structures and Embryos

HW on your desk!Catalyst1. Whales evolved from mammals. Do they

have more DNA in common with cows or sharks?

2. Humans share 30% of their DNA with daffodils, and 65% of their DNA with frogs. Which animal are they more closely related to?

3. Land animals evolved from animals that lived in the ocean. Draw a transitional fossil between the two.

Write in complete sentences!

Don’t talk during the Catalyst!

Objectives

By the end of today, all SWBAT…

Explain how homologous structures support the theory of evolution

Compare the development of different animal embryos

Catalyst Review

Whales evolved from mammals. Do they have more DNA in common with cows or sharks? Cows! The more DNA an organism shares with another,

the more closely related they are. Humans share 30% of their DNA with

daffodils, and 65% of their DNA with frogs. Which animal are they more closely related to? Humans are more related to frogs than daffodils. The more DNA an organism shares with another,

the more closely related they are.

Catalyst Review

Land animals evolved from animals that lived in the ocean. Draw a transitional fossil between the two. A transitional fossil is the fossil of an

organism that has traits in between its ancient ancestors and species that came after it.

Homework Review

1. What two classes of mammals does the transition from Pakicetus to Basilosaursus represent?

2. Why do biologists classify at Pakicetus as an early aquatic mammal?

3. What structure does Basilosaurus have that hints at its evolutionary past?

Homework Review

4. What was the largest difference between Australopithecus afarensis and Dryopithecus? The largest difference between…

5. From the picture, what do you think “quadrupedal” and “bipedal” mean? I think quadrupedal means…

6. Which fossil would you most likely find deepest in the rock layer? In the deepest rock layer, you would find the fossil

for…

Human Evolution

Homo habilis H. ergaster H. erectus H. heidelbergensis H. sapiens and H.

neanderthalensis

Side-by-Side

Comparative Anatomy

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

EVOLVE

http://www.5min.com/Video/How-Evolution-Happens-4804307

Homologous Structures

Homologous structure: Part of different species that have the SAME structure and position

Key Point #1: Homologous structures show that two species evolved from a common ancestor Common Ancestor: One organism

that different species evolved from Two species possess a homologous

structure BECAUSE they both inherited it from a common ancestor

Humans, cats, whales, and bats all inherited their forearm from the same common ancestor

Pigs and humans both have pancreases that produce insulin

Pig and human pancreases are _______ structures.

What does this tell us about human/pig evolution?

Embryos

Key Point #2: All animal embryos have gill slits and tails Embryo = organism in the early stages of its development

What type of structures are these? Think-pair-share: What does this

tell us about animal evolution!?

Lookin’ good!

Human embryo Chicken embryo

The fact that all animal embryos have gill slits shows that ALL animals evolved from the SAME common ancestor

The fact that all animal embryos have tails shows that ALL animals evolved from the SAME common ancestor

Which one is the cow embryo?

cat cow horse human

Notes Reflection

How do homologous structures provide evidence for evolution? Homologous structures show that two organisms evolved from a common ancestor

ADD IT!!!

If you can’t find the answer…

Notes Reflection

What parts of animal embryos are homologous? Gill slit Tail

ADD IT!!!

If you can’t find the answer…

Notes Reflection

What do homologous structures in animal embryos tell us about their evolution? All animals evolved from the same common ancestor

ADD IT!!!

If you can’t find the answer…

Test Prep (6 minutes)

What is the definition of a homologous structure? Give one example.

Explain how homologous structures, in general, tell us about how two species evolved.

Dog feet and lizard claws are examples of homologous structures. What do these structures say about how dogs and lizards evolved?

SWITCH!!!

Test Prep (6 minutes)

What is an embryo? What parts of animal embryos are

homologous? What does this imply about

animal evolution? At the beginning, all animal

embryos look very similar. What happens as they each develop?

SWITCH!!!

Test Prep (10 minutes)

Juanita says that frogs cannot be related to bears because adult frogs look so different from adult bears. Explain to her how we can use the appearance of frog and bear embryos to prove that they are related.

Daniel notices that all organisms use the same four bases in their DNA: A, T, G, and C. What does this tell us about how they evolved?

SWITCH!!!

Independent Practice (IP)

Get an early start on the homework.

Tomorrow’s HW is on the back. DO NOT LOSE THIS SHEET.

Key Point Wrap-Up

Key Point #1: Homologous structures show that two species evolved from a common ancestor

Key Point #2: All animal embryos have gill slits and tails These are homologous structures All animals evolved from a common

ancestor!!!

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?

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.

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.

What kind of structure is this?

How do these structures provide evidence for evolution?

A B