Cool Reading - CK4P10

If you look at a map of the Atlantic Ocean, you notice that the continents of Africa and South America fit together like a jigsaw puzzle. Is that just coincidence?

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Humbold

Alexander von Humboldt was a German geographer. He was the first person to notice similarities between South America and Africa. Von Humboldt traveled throughout South America, Africa, and other parts of the world, collecting plants and animals, and studying geography and geology. He also found plant and animal fossils in India that were very similar to fossils he found in Australia.

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Continental Drift Another German scientist called Alfred Wegener studied the continents in the 1920s.

Wegener studied fossils of an extinct crocodile called mesosaurus in southern Africa and South America.

But the Atlantic Ocean divides Africa and South America, and mesosaurus was a freshwater crocodile and was only one meter long. Mesosaurus could not swim the Atlantic Ocean.

Wegener also studied plant fossils from the frozen north of Norway.

But the fossils were of tropical plants, from a warmer, more humid climate.

The fossils suggested that Norway had a tropical climate in the past.

He also discovered that the Appalachian Mountains of the eastern United States were made of the same rock as the Caledonian Mountains of Scotland.

Wegener had a theory. He thought that a long time ago the continents were part of one enormous continent

called Pangaea. And he believed that the continents could move.

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Tectonics Plate About 200 million years ago, the supercontinent, Pangaea, started to break up. Over millions of years, Pangaea separated into pieces and became the continents we recognize now.

Today, we know that the continents are on massive pieces of rock called tectonic plates. Tectonic plates are always moving. The North American and Eurasian tectonic plates are moving away from each other at about 2.5 centimeters per year. Africa has two tectonic plates, and will eventually divide into two continents. The Himalaya Mountains are slowly growing because the Indian and Eurasian tectonic plates are pushing against each other.

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Evolution

Monkeys are a good example of how evolution works. There are monkeys in Africa and in the Americas because the continents were connected in the past. But African and American monkeys are different because they evolved in different places. Only monkeys in the Americas have prehensile tails. Prehensile means that they can use them to hold on to things—like an extra hand.

Charles Darwin, 1809-1882

We can understand the different flora and fauna on the continents using the idea of plate tectonics and the theory of evolution. Charles Darwin proposed the theory of evolution in 1859.

Darwin traveled around the world and he studied animals and plants.

When there was one continent (Pangaea), plants and animals moved around easily. After continents moved apart, animals and plants were isolated and evolved in different ways.

evolution, n - the differences between modern plants and animals are because of changes that happened by a natural process over a very long time

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New Species

Isolated Australia

Some animals are quite new species, and they only live in one region. For example, polar bears only live near the North Pole, and penguins only live near the South Pole. This is because they evolved after the continents divided.

Australia has been completely isolated from the rest of the world for 40 million years. This is the reason it has some strange animals. The platypus is a mammal that lays eggs! Marsupials, like kangaroos, have a pouch where they keep their babies. There are large cats, wolves, and bears on most of the continents, but they did not evolve in Australia.

Sloths are unique to the Americas— nothing like them exists in Asia or Africa. And Africa and Asia have elephants, which do not exist in the Americas.

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Similar, But Different

Land Bridges

The Americas have a solitary (not living in a group) carnivorous cat called the jaguar. The equivalent in Africa is the leopard. In Asia it is the tiger. These are three members of the cat family that developed a long way from each other and have evolved differently.

Millions of years ago, camels lived in North America. A land bridge connected North America to Asia about eight million years ago, and camels crossed to Asia. Today, there are two types of camels in Asia—the Bactrian Camel (two humps) and the Dromedary Camel (one hump). Three million years ago, camels crossed another land bridge into South America. Their modern descendants are the llama and the alpaca. North American camels only became extinct in the last few thousand years.

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Worksheet 10 How Our World Was Made 1 Make a mind map.

Evolution

2 Complete the sentences.

Pangaea Appalachian land bridge South America continents platypus Africa Caledonian tectonic plates Charles Darwin 1. Alexander von Humboldt found many similarities between and

.

2. Wegener discovered that the

mountains in

the USA were made of the same rock as the mountains in Scotland.

3.

separated into pieces and became the we know now.

4.

are always moving.

5.

proposed the theory of evolution.

6. The 7. Camels crossed a

is a mammal that lays eggs. between North America

and Asia.

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3 Draw an animal to represent each continent.

The Americas

Australia

Asia

Africa

4 Color the map. Then, answer the questions.

North America: red South America: green Eurasia: yellow Africa: orange Australia: purple Antarctica: pink India: brown Oceans: blue India

1. How do continents move?

2. What is evolution?

3. Give an example of evolution.

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