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From land to sea
Whales are mammals, like you, and their ancestors once lived on land. So how did they come to be in the sea?
This astounding transition came shortly after the rise of modern mammal groups, around fifty-five million years ago, during a hot period in the Earth's history. Dinosaurs and large marine reptiles had disappeared some millions of years previously.
One group of hoofed mammals spent more and more time in the water, living on the abundant food there. Eventually they left the land altogether - to become whales.
At the exhibition
Introduce students to this section about the evolution of whales.
Explore the immediate area.
Gather the students back to discuss the following questions and topics.
Questions for 5 to 10 year olds
- Introduce the concept of evolution to students.
- Discuss how change can occur over many generations.
- Play “spot the difference.” What are the differences between Pakicetus and Dorudon?
- Why did these changes occur?
Questions for 10 years old and over
Introduce the concept of evolution to students.
- Discuss how change (or mutations) can occur over many generations or simply in one generation.
- What are the differences between Pakicetus and Dorudon?
- Is it possible that future changes will occur in whales? If so what might these changes be?
- How might future climate change affect the lives of whales?
- Discuss adaptation. How have whales adapted to their changing evironments?
Scientific evidence shows us that whales were once land mammals. They moved into the water in part because of environmental factors – a hot period on Earth. These early whales are known collectively as Archeocetes, or ancient whales. Recent molecular and fossil discoveries shows the relationship of whales to even-toed ungulates (the artiodactyls) , that include cows, sheep, hippopotamus etc.
Features of it’s ear bones, that are unique to the Order cetacea, sugests that Pakicetus is the earliest known ancestor of modern whales.
The Ambulocetus lived in water but would have come ashore to breed..
The Kutchicetus had greatly reduced hind legs, and a large flattened tail that was probably used for swimming. These whales would have swum in much the same way as modern otters.
The basilosaurids were fully aquatic with paddle-like flippers, and only rudimentary hind limbs. The shape of the bones at the tips of their tails show evidence that they possessed tail flukes.
The earliest filter feeding baleen whales (Mysticeti) and the Echolocating toothed whales (Odontoceti), the groups of whales that we see today, appear at about 35million years ago at ime when great cooling happened on earth that saw the development of the oceanic current systems we see today and the formation of polar ice, the creatures that evolved into whales moved into the water during a period when the Earth’s climate was very hot. They took to the sea to feed on the abundant resources there.
Challenge for the students
Study changes in the environment that may cause adaptations and predict how whales are going to adapt to the changes in the future.
Before visiting the exhibition
Discuss the adaptations that whales have made to suit their environment
Study how the adaptations have come about eg mutation
Discuss the changes to the environment over the last 1 million years, 100,000 years, 1000 years and 100 years. Are there treads in the various periods if so what are they?
Discuss the directions that the earths’ environment may be moving in.
From your discussions predict what will happen to the environment in the future 1000 years from now, 100,000 years from now, and 1 million years from now.
During the visit to the exhibition
Visit the segment about the evolution of whales and revisit some of the topics discussed in the classroom such as; changes to the environment, changes in the climate, adaptations, and the trends that are happening today.
Discuss some of the adaptations that whales have to help them survive in their environment.
Discuss the future and the changes that may occur.
Discuss the changes that whales have gone through in the last 55 million years and perhaps some of the changes that will occur in the future.
Make notes on the trends.
Make notes and sketches on the physical changes that whales have gone though over time.
After the visit to the exhibition
Collate the notes and sketches to make predictions as to what changes whales will go though in the future. Create a story to illustrate the changes over time.
Create class artworks to show what whales may look like in the future. This could be in a model form or as drawings.
If you have the resources you may be able to create 2D graphics of the changes and then animate them on your PC.
Other suggested learning experiences
- Time capsule your predictions
- Explore the beliefs of other people as to the origin of whales, make posters and discuss the many different beliefs through out the world.
- Explore how these ancient stories are told in different cultures eg song, dance, carving, etc.
- Create model parts of a whale that you consider to be an adaptation and discuss how these benefit the species.
- Find evidence of change that has occurred to a species in a relatively short period of time and discuss how this change occurred and if it benefited the species or not