Chapter 3: Identifying Related Species

EH: 3.3.1 WARM-UPStudents learn that the Mystery Fossil skeleton contained a fetal skeleton and consider

how whales, wolves, and crocodiles give birth (5 min).

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

Students compare body structures of whales and wolves to determine both their shared

structures and structures that differ between them (15 min).

Review the Chapter 3 Question.How can we tell if the Mystery Fossil is more

closely related to wolves or to whales?

Answering this question will help each of

you to choose a claim and explain to Andre

Mosley where in the museum to place the

Mystery Fossil.

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

Review the Chapter 3 Question. How can we tell if the Mystery Fossil is more

closely related to wolves or to whales?

The two key concepts from

Chapter 3 help us to answer our

Ch.3 question.

These two key concepts will be

important to keep in mind during

the next activity.

key concept 1: Among any three species, the two

species that separated most recently are the most

closely related to each other.

key concept 2: When two species share a

structure that is not shared with a third species,

this can be evidence that the first two species

are more closely related to each other than to

the third species.

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

Sorting Information About Whales

and Wolves.

You will receive a set of cards that will provide information about

different body structures that whales

and wolves have.

You will sort these cards in order to

figure out which structures are

unique to the whale and to the wolf,

so that you will know which

structures to look for in the Mystery

Fossil in order to determine if it is

more closely related to whales or to

wolves.

DO NOT annotate on these cards.

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

Some of the cards will give information

about a structure that only one of these

species has.

That structure, or something about it such

as its shape, will be unique to that species.

Other cards will give information about

similarities in structures that both species

have.

You will work with your partner to discuss

each card and place it in the column in the

table that you think it belongs.

When you are finished, you will know which

structures will be important to look for in the

Mystery Fossil to see if it shares these

structures with whales or with wolves.

5 MIN. TO READ,

DISCUSS, and

SORT CARDS ON

TABLE 1

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

Which cards did you place in the

column for shared structures for

both species?

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

What does the presence of these shared structures mean?

Whales and wolves have a common

ancestor population that had these

structures and passed them down.

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

If both species share these structures,

are they useful for figuring out where to place the Mystery Fossil?

No, we need to look for structures that

the Mystery Fossil shares with only

whales or only wolves.

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

We can see clear ways to group these

species together (evidence in Column 3),

and we know that this means they are

related. But, we also found some structures

that show how whales and wolves are

different.

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

When we want to determine which

species are more closely related

among three species that share

many common structures (like

these species do), we need to do

a more careful analysis and look

at the important structures that

they do not share.

These diagnostic structures can

help us determine which species

the Mystery Fossil is more closely

related to.

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

Answer the question at the bottom of your screens.

PLACE ANSWER HERE!

EH: 3.3.2 STUDENT DISCUSSIONCONSIDERING SIMILAR STRUCTURES

Wolves

- Nostrils – front

- Teeth all different shapes

- Skulls with shorter jaws

- Back Limbs

Whales

- Nostrils – top of skull

- Teeth all same shape

- Skulls elongated with long jaws

- No Back Limbs

EH: 3.3.3 STUDENT DISCUSSIONEXAMINING DIAGNOSTIC STRUCTURES

Students focus on the Mystery Fossil to figure out which structures it shares with either wolves or whales, and they use this evidence to decide which species it is more closely related to(20 min).

On the Observing the Mystery Fossil Cards

there are lines for writing on the cards.

Each of the cards is focused on one of the

structures you investigated in the last card

sort: teeth, skull shape, and nostril placement.

Use the Mystery Fossil on your screen to help!

Work with a partner to make careful and

precise observations about each of the

Mystery Fossil’s structures and compare each

to see whether the Mystery Fossil’s structures

look more like the whale’s structures or more

like the wolf’s structures.

8 min. to

complete

cards.

Sorting Shared Structures Among the

Mystery Fossil, Whales, and Wolves.

You will use the cards from the last

activity, as well as the five cards about

the Mystery Fossil you just filled out, to

complete this table.

Your findings from the Comparing Body

Structures Cards can be combined with

evidence about the Mystery Fossil to

decide which structures shared with

whales or wolves belong in each table

column.

For example, backbones are shared

between all three species, so you should

put Cards A and D in the third column.

EH: 3.3.3 STUDENT DISCUSSIONEXAMINING DIAGNOSTIC STRUCTURES

You may think some of the evidence

cards do not fit into any of the columns

in the table, this is OK.

3 min. to sort

cards. Be

ready to share

EH: 3.3.3 STUDENT DISCUSSIONEXAMINING DIAGNOSTIC STRUCTURES

BACKBONE

MAMMAL – LIVE BIRTH

Which cards did you place in the

thirds column for shared

structures for all species?

EH: 3.3.3 STUDENT DISCUSSIONEXAMINING DIAGNOSTIC STRUCTURES

BACKBONE

MAMMAL – LIVE BIRTH

If all vertebrates have a backbone, does that

mean that the Mystery Fossil is part of the vertebrate group? YES

This is a structure that was passed down to all

vertebrates, so we know that all three of these

species are vertebrates. Does this structure help us

decide whether the Mystery Fossil is more closely

related to whales or to wolves? NO WHY?

Because all three

species have that

same structure.

EH: 3.3.3 STUDENT DISCUSSIONEXAMINING DIAGNOSTIC STRUCTURES

BACKBONE

MAMMAL – LIVE BIRTH

If all mammals have live birth and produce milk,

and paleontologists are fairly certain that the

Mystery Fossil did both, does that mean it is part of the mammal group, too? YES

Live birth and milk production are things that all three

species share. So, this structure is also not useful for

deciding where to place the Mystery Fossil.

EH: 3.3.3 STUDENT DISCUSSIONEXAMINING DIAGNOSTIC STRUCTURES

BACKBONE

MAMMAL – LIVE BIRTH

The structures that the Mystery Fossil shares with

both whales and wolves are important because

they confirm that the Mystery Fossil is related to

both whales and wolves. For example, we know

it is more closely related to whales and wolves

than to crocodiles or birds because it has live

birth and crocodiles and birds do not. But, now

we want to know whether it is more closely

related to whales or to wolves.

EH: 3.3.3 STUDENT DISCUSSIONEXAMINING DIAGNOSTIC STRUCTURES

Which claim do you feel is best supported based on the evidence and why?

EH: 3.3.4 PLACING THE MYSTERY FOSSIL ON THE EVOLUTIONARY TREE

Students model one of the claims about where the Mystery Fossil

belongs by placing it on a branch of an evolutionary tree (5 min).

Discuss final arguments for the

museum director.

For homework you will write a final

argument to the museum director,

explaining why you think the Mystery

Fossil should be placed either with the

whales in the Cetacea exhibit or the

wolves in the Carnivora exhibit.

You will make your arguments as a

paleontologist would, using evidence

about bone structures that are shared

between two species (and not the third)

to support the conclusions you draw.

EH: 3.3.4 PLACING THE MYSTERY FOSSIL ON THE EVOLUTIONARY TREE

Let’s look at the evolutionary

tree.

What is this tree showing?

- A branch of an evolutionary tree

that shows three branches, in

which students can indicate

whether the Mystery Fossil’s

branch is closer to the whale

branch or to the wolf branch.

How you place the wolf and whale

species on the tree will represent

the claim that you want to support.

EH: 3.3.4 PLACING THE MYSTERY FOSSIL ON THE EVOLUTIONARY TREE

This tree will be a part of the

argument that you submit to

Dr. Mosley.

It will be a visual way of

showing where you think the

Mystery Fossil should be placed

on an evolutionary tree (when

compared to whales and

wolves), and therefore, where

it should be placed in the

museum.

Complete the Evolutionary Tree.

EH: 3.3.5 HOMEWORK

Students complete a written argument for the museum director explaining

what they know about the Mystery Fossil’s evolutionary history.

Answer Here and Hand In.

Answer Here and Hand In.

EH: 3.3.6 SELF-ASSESSMENT

This optional homework provides a chance for students to reflect

on their learning so far.

Answer Here and Hand In.

COMPLETE

QUESTIONS 1-6