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  • Hello. This is 6 Minute English from BBC Learning English.

  • I'm Neil.

  • And I'm Rob.

  • Do you think there are big differences between men and women, Neil?

  • Apart from the old stereotypes we sometimes hear

  • like, that men can't express emotions...

  • I suppose biologically

  • there are differences, Rob.

  • I mean, men and women's bodies are different.

  • Right, and it takes both a man and a woman to make a baby.

  • Well, that's true, in humans anyway.

  • But in this programme

  • we'll be hearing about creatures in the wild,

  • where the classic 'boy meets girl' love story doesn't apply.

  • Yes, we'll be meeting some female animals who don't need a male to make babies.

  • These creatures reproduce by parthenogenesis,

  • also called virgin birth.

  • This is the process where the female can reproduce without a mate,

  • a term used for an animal's sexual partner.

  • All animal species survive by making babies,

  • reproducing to make copies of themselves.

  • But amazingly,

  • the female of some species can do it all by herself!

  • But before that, it's time for my quiz question.

  • In Britain's Chester Zoo in 2006,

  • Flora laid eleven eggs that developed into healthy babies.

  • Her zookeepers were mystified

  • because Flora had only been kept with other females and had never been near a male.

  • What type of animal was Flora?

  • Was she a) a python, b) a zebra shark,

  • or c) a Komodo dragon?

  • Pythons are pretty unusual creatures,

  • so I'll say Flora was a python.

  • OK, Rob, we'll find out later if you're right.

  • Actually, it's not only reptiles who behave this way.

  • The females of many animal species are able to reproduce without sex.

  • By doing this they gain several advantages:

  • they can rapidly spread, colonize and control large areas,

  • and they don't waste time and energy looking for a mate.

  • But if a world without sex is so much better,

  • why bother with males at all?

  • Good question, Neil,

  • and one which BBC World Service programme, Discovery, asked evolutionary biologist, Chris Wilson.

  • Well, absolutely!

  • And there are other advantages,

  • I mean, if you're an all-female population,

  • you don't have to waste time searching and competing for mates,

  • there are no more sexually-transmitted diseases

  • and so it seems like the easiest decision

  • and yet,

  • less than one percent of all animal species are completely celibate,

  • and that's a huge fundamental puzzle in evolutionary biology

  • that we're still not entirely sure we understand

  • it's called sometimes the paradox of sex.

  • Despite the advantages of going without sex,

  • in reality fewer than one percent of all animals are celibate - live without having sex.

  • This begs the question,

  • why is sex so common when it seems so inefficient?

  • Chris calls this the paradox of sex.

  • A paradox is a situation which seems contradictory because it contains two opposite facts.

  • For example, the existence of males if we can reproduce without them.

  • As a male myself,

  • I have to say I'm feeling a little underappreciated right now, Rob!

  • Well, don't worry, Neil,

  • because it turns out there might be a use for males after all!

  • It seems the sex paradox has been solved by one of nature's most ingenious insects - aphids.

  • Here's ecologist, Amber Wright,

  • explaining how to the BBC World Service's Discovery programme.

  • See if you can hear the strategy American aphids use to reproduce.

  • The aphids we have in the US,

  • when spring comes around,

  • the eggs hatch and they'll be all female for several generations,

  • and then at the end of the summer,

  • they will hatch out males and females and mate,

  • and then create eggs that wait for next year,

  • kind of the best of both worlds.

  • Hedging their bets basically,

  • using cloning to rapidly colonize

  • and then using sex to mix up the genes.

  • In the spring, female aphids lay eggs which hatch,

  • break open, allowing the young to come out.

  • The young aphids that hatch are all female.

  • But later, at the end of the summer,

  • both female and male aphids hatch out

  • and start to reproduce by mating.

  • So, the aphids have the best of both worlds,

  • they enjoy the advantages of very different things at the same time.

  • Or to put it another way,

  • the aphids hedge their bets.

  • They follow two courses of action

  • instead of choosing between them.

  • By cloning themselves with 'virgin births' and reproducing sexually,

  • aphids maximize their chances of survival.

  • Gardeners around the world will be upset to hear that

  • those young aphids just love eating tomato plants!

  • But on the plus side,

  • it seems being male can be useful after all.

  • But not if you're Flora,

  • the female you asked about in your quiz question.

  • So, what type of animal was she?

  • Right, I asked whether the virgin Flora was...

  • a) a python, b) a shark

  • or c) a Komodo dragon.

  • I guessed a python.

  • Well, Rob, you're right that some female pythons can reproduce by themselves,

  • and sharks too.

  • But the correct answer is that

  • Flora was c) a Komodo dragon.

  • OK, let's recap the vocabulary,

  • starting with mate, an animal's sexual partner,

  • something you don't have if you're celibate - living without sex.

  • Animal eggs hatch or break open to let the young out.

  • And a paradox is a situation which seems contradictory

  • because it contains two opposite facts.

  • Species which reproduce parthenogenetically and sexually have the best of both worlds -

  • enjoy the advantages of very different things at the same time.

  • And if you hedge your bets,

  • you follow two courses of action instead of choosing between them so you don't miss out.

  • Well, that's all there's time for. Bye for now! Goodbye!

Hello. This is 6 Minute English from BBC Learning English.

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B2 flora female reproduce hatch paradox rob

When males are not needed - 6 Minute English

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    林宜悉 posted on 2021/06/03
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