環(huán)球英語20160708 Friend or Enemy?
Welcome to Spotlight. I’m Adam Navis.
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And I’m Liz Waid. Spotlight uses a special English method of broadcasting. It is easier for people to understand, no matter where in the world they live.
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Human life is full of friends and enemies. And in a strange way, this is also true in all of nature! Big and small creatures learn their friends very quickly. In nature, this is called a symbiotic relationship. In these relationships, both creatures help each other. Today’s Spotlight is on some of these symbiotic relationships.
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A beautiful winged insect moves through the air. It stops on the leaves of a nearby tree. If you look closely, you can see its wings open and close. This permits you to see the beautiful fine details, and bright fire colours. It is the monarch butterfly. It is so small and light! So how does such a creature defend itself? It does not seem to have any defences - no poisonous bite, or a painful sting. So what does it do?
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Well, nature usually provides some kind of weapon. And, naturally, this is also true for the monarch butterfly. But the monarch’s secret weapon lies in its body. And it begins right at the start of the monarch’s life - as an egg. Adult monarchs stick their eggs under leaves. The leaves are always those of the milkweed plant. This plant is central to the monarch’s defence system.
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Like all butterflies, monarchs begin life as caterpillars. The long, soft caterpillar breaks out of the egg. It does not yet have wings. Immediately, it finds food. It eats the milkweed leaves. The caterpillar fills itself with the milky substance contained in the leaves. And it grows very quickly. When it is about five centimetres long, it stops eating. A kind of shell develops around the caterpillar - a chrysalis. The caterpillar develops inside the green and gold chrysalis. In about two weeks, it changes into a beautiful monarch butterfly.
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The butterfly is still full of the milky substance from the milkweed leaves. And this substance contains a poison. It does not harm the butterfly. But it does make it taste bad to birds and animals. Creatures that eat this butterfly become sick. They do not die. But they do remember that this brightly-coloured insect made them sick. They soon learn to avoid all monarch butterflies. The milkweed plant helps this butterfly to defend itself from harm. The plant is a true friend to the butterfly!
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This is how nature works. It is like having friends and enemies. And each creature and plant knows which is which! All caterpillars have many enemies. They are small, soft creatures. And they are easy to attack. Birds and other animals like to eat caterpillars. And flying insects like wasps like to lay their eggs on caterpillars! But just like the monarch caterpillars have milkweed plants, other kinds of caterpillars have other friends. For the lycaenid caterpillar, this is another insect, the ant. The ant can guard the caterpillar. The ant releases a particular liquid. This liquid smells bad to attackers - so they stay away. In return for this service, the caterpillar produces a sweet liquid for the ant to feed on. What are friends for?
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Under the water, the sea slug uses a similar defence to the monarch. Like the caterpillar, the sea slug has a soft body. And, it also gains its defence weapon from food! Some sea slugs eat sea creatures called hydroids. Hydroids look like plants. And they have special cells that hurt most things that touch them. But these cells do not harm the sea slug. They help it! When the sea slug eats the hydroids it stores the cells. It can then use the cells to protect itself. Some slugs can even shoot out the pain-giving cells at attackers!
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And this is not the sea slug’s only defence! The other is its colour! Many people consider sea slugs beautiful creatures. They have so many different colours! The sea slug takes the colour from the food it eats. So, if the slug eats something red, it turns red. If it eats something brown, it turns brown. The perfect way to hide from enemies! The sea slug’s food is its greatest friend!
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The hermit crab carries its ‘friends’ on its shell! Living under the sea can be dangerous. So the small hermit crab needs more than its protective shell. It needs a way to fight! Sea anemones provide this. Sea anemones look like beautiful plants. But they are really a kind of animal. These small creatures contain powerful cells that hurt if touched. The hermit crab covers itself with sea anemones for extra protection. Its enemies know how painful sea anemones can be.
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In the world of sea creatures, who would befriend the keyhole limpet? You cannot even see the small creature under its huge flat shell! The limpet is safely hidden, and so is any creature that hides with it! This is what the sea worm does. It lives in the ‘keyhole’ on the top of the limpet’s shell. This provides a safe home for the sea worm. And in return, the sea worm defends the limpet from enemies like starfish. If a starfish attacks, the sea worm bites its feet!
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The keyhole limpet and the sea worm. The hermit crab and anemones. The sea slug and its food. The caterpillar and the ant. The monarch butterfly and the milkweed plant. These seem like unusual combinations. But, their successful symbiotic relationships help them survive a dangerous world!
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In the world of nature, a creature defends the life of its ‘friend.’ It does so naturally, without question. It is following the laws of nature. The Bible says this is how God made them to be. But it says that God gave humans freedom to choose. And then he asked them to choose to love each other. This is not always easy. But just like in nature, choosing to care for other people brings many important good things.
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The writer of this program was Marina Santee. The producer was Luke Haley. You can listen to this program again, and read it, on the internet at www.radioenglish.net. This program is called, ‘Friend or Enemy?’.
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You can also leave your comments on our website. Or you can email us at [email protected]. You can also find us on Facebook - just search for spotlightradio. We hope you can join us again for the next Spotlight program. Goodbye.
