Module B3 Life on Earth

IB3.2 Follow the evidence

B3 Life on Earth

• Whales are mammals.

• All mammals share some features.

B3 Life on Earth

• Whales belong to a group of mammals called the

Cetacea.

• Cetacea have two features that other mammals

don’t have.

B3 Life on Earth

• Cetaceans are split into four groups.

• Click if you want to know more about baleen plates

and echo-location.

Cetacean group Baleen plates? Teeth? Echo-location?

Baleen

Sperm

Other toothed

Beaked

Yes

No

No

No

No

Teeth in lower jaw only

Many teeth

Few teeth

No

Yes

Yes

Yes

B3 Life on Earth

• Which of these ways of classifying whales is the

most sensible?

• Use the evidence in the last slide to help you.

B3 Life on Earth

• From the evidence so far, baleen whales are more

different.

• There are 11 species of baleen whale.

• They include blue whales and sperm whales.

• Click if you want to know more about baleen

whales.

B3 Life on Earth

Q5, Q6

• But in the 1990s new

evidence was found.

• Scientists looked at DNA

from 16 species of

cetaceans.

• The DNA showed that:

- Sperm whales were

more closely related

to baleen whales

than other groups.

- Beaked whales are

only distantly related

to any of the other

groups.

• Look back at the your

choice for classifying

whales. Which way of

classifying seems best

now? Do you need to

change your mind?

B3 Life on Earth

Discuss with a colleague

• What is this lesson about?

• Suggest a suitable lesson objective(s) and outcomes for this lesson.

B3 Life on Earth

• Changing your ideas doesn’t mean that you were

wrong the first time. You just didn’t have enough

information.

• It also doesn’t mean that the new ideas are

definitely right. Any conclusion is only as good as

the evidence behind it.

B3 Life on Earth

• You can get up to date information about whale

classification here.

• There’s more background information on whales

here.