Analogous and Vestigial Structures Catalyst 1. Cougars eat Bucaneers, which have decreased in population over the past few years. What is the environmental

Analogous and Vestigial Structures

Catalyst1. Cougars eat Bucaneers, which have decreased

in population over the past few years. What is the environmental pressure?

2. 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.

3. 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!

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

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?

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.

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.

Homework Review

1. What are homologous structures? Provide two examples of homologous structures.

2. What is an embryo?3. What is a common ancestor? Give an

example. 4. All animal embryos start off looking very

_______________. For example, they all have _______________ and _______________. These traits are examples of _______________ structures.

Homework Review

5. 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”!)

6. 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”!)

Comparative Anatomy

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

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.

Insect, bird, and bat wings evolved completely separately. Unrelated organisms will evolve similar adaptations in response to similar environmental pressures!

No recent common ancestor!!!

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!

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

Letter “c” = hind legs of a baleen whale skeleton

Vestigial = no longer used!!!

Blind salamanders have eye sockets!?!?

So, what about me?

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

ADD IT!!!

If you can’t find the answer…

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

ADD IT!!!

If you can’t find the answer…

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.

Guided Practice (GP)

Human embryos and cat embryos both have gill slits.

Are these structures…

(A) Homologous, (B) Vestigial, (C) Analogous?

HOMOLOGOUS


Birds and insects both have wings, but they developed in completely different ways.



ANALOGOUS


Snakes don’t have legs, but they do have hip and leg bones.

Is this structure…


VESTIGIAL


The human appendix – a small organ next to the intestines – doesn’t seem to do anything at all.



VESTIGIAL


Cat embryos and human embryos both have tails.



HOMOLOGOUS


Dolphins and sharks both have fins, but they evolved completely differently.



ANALOGOUS


Alligators and bats have the same bone structure in their forelimbs (front legs for alligators, wings for bats).



HOMOLOGOUS


Humans have wisdom teeth (third molars), even though they are not needed to chew up food.



VESTIGIAL


Humans and squids both have eyes, but they evolved in completely different ways.



ANALOGOUS

Independent Practice (IP)

Get an early start on the homework.

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

Exit Question: Choose one option

Write in complete sentences! 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.

All humans have a tail bone, but we don’t have tails.


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.


EXPLAIN how 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.


EXPLAIN how these structures provide evidence for evolution.

A B

Documents

Analogous and Vestigial Structures Catalyst 1. Cougars eat Bucaneers, which have decreased in population over the past few years. What is the environmental