Activity 6 : “Sexual reproduction in animals: Hermaphrodites”

Videoclip projection: "Hermaphrodites"

a) Read and translate the text before watching the video.

b) Watch the videoclip with the help of the transcription next to it.

c) Answer the questions.

a) Read and translate this text before watching the video.

Hermaphrodites

So, all these animals having left the sea solved the problem of moving around and breathing air in their own different ways. But there was another difficulty: mating.

What is external fertilization?

In the sea, animals need only release their eggs and sperm, and the water mixes the two together; on dry land that couldn't happen, even for the most moisture-loving of creatures.

How does sexual reproduction occur in hermaphrodites?

An individual slug carries both male and female organs, but even then that was of no help: each had to both give and receive. Somehow or other, pairs of individuals had to get together, and the ways they have evolved in which to do so are quite extraordinary, indeed some of them are almost beyond imagining.

The leopard slug, you might think, has the simplest of habits. Maybe, but not when it comes to mating. When an individual is looking for a partner, it gives its trail of slime a special taste that advertises the fact. Another, if it feels the same way, will detect the invitation and start to follow.

The pursuer, to confirm that it's there, and ready to mate, gives the pursued a nibble. The leader heads upwards - an overhang's what's needed. The underside of a branch will do very nicely. The two start to circle one another more and more closely, until they entwine. For an hour or so they continue to wind themselves around one another.

Then, suddenly, the pair release their hold on the branch and start to slide downwards on a rope of mucus. Now, in mid-air, they move to the next stage in their pairing. Each everts its male organ from just behind its head. These grow longer and longer. Then they, too, begin to entwine. They fan out to form a translucent flower-like globe. And now, at last, sperm passes from one slug to the other.

The transfer is complete. Each has been fertilised.

Finally, their strange relationship comes to an end - with a bump.

b) Watch this videoclip with the help of the transcription next to it:

So, all these animals having left the sea solved the problems of moving around and breathing air in their own different ways. But there was another difficulty: mating.

In the sea, animals need only release their eggs and sperm and the water mixed the two together; on dry land that couldn't happen, even for the most moisture-loving of creatures.

An individual slug carries both male and female organs, but even then that was of no help: each had to both give and receive.

Somehow or other, pairs of individuals had to get together, and the ways they have evolved in which to do so are quite extraordinary, indeed some of them are almost beyond imagining.

The leopard slug, you might think, has the simplest of habits. Maybe, but not when it comes to mating.

When an individual is looking for a partner, it gives its trail of slime a special taste that advertises the fact. Another, if it feels the same way, will detect the invitation and start to follow.

The pursuer, to confirm that it's there, and ready to mate, gives the pursued a nibble.

The leader heads upwards - an overhang's what's needed.

The underside of a branch will do very nicely. The two start to circle one another more and more closely, until they entwine. For an hour or so they continue to wind themselves around one another.

Then, suddenly, the pair release their hold on the branch and start to slide downwards on a rope of mucus.

Now, in mid-air, they move to the next stage in their pairing. Each everts its male organ from just behind its head. These grow longer and longer. Then they, too, begin to entwine. They fan out to form a translucent flower-like globe. And now, at last, sperm passes from one slug to the other.

The transfer is complete. Each has been fertilised.
Finally, their strange paletic relationship comes to an end - with a bump.

c) Answer these questions:

1.- What is the difference between external and internal fertilization? Give some examples.

2.- How does sexual reproduction occur in hermaphrodites?

3.- Complete these sentences:

a) Reproductive organs are called ………………….., and they make reproductive cells called ………………
b) Which are the reproductive organs in a male and a female?............................................
c) Which are the reproductive cells in a male and a female?..................................................

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