Species which reproduce parthenogenetically and sexually have the best of both worlds - enjoy the advantages of very different things at the same time.

既能单性生殖又能有性生殖的物种两头受益——同时享有截然不同的事物的优势。

So, why do other animals bother with sex?

那么，为什么还需要有性生殖呢？

So for one thing, they work only in sexually reproducing species.

首先只能应用于有性生殖的物种。

It is not involved in sexual mixing, so it changes only by the random process of mutation.

不参与有性生殖中的基因重组，所以只有在随机突变中才会发生变化。

Scientists hypothesize that sex makes up for its shortcomings with long-term gains.

科学家提出，为有性生殖的长期收益能弥不足。

And in the autumn, they switch back to sex.

到了秋，就会回归有性生殖。

So, how does this have to do with sexual reproduction?

那么，这与有性生殖有什么关系呢？

IVF works by mimicking the brilliant design of sexual reproduction.

试管受精通过模仿有性生殖的精妙设计来实现其功能。

The fact that it is nonetheless widespread suggests that sex must have big advantages too.

尽管如此广泛存在，这表明有性生殖肯定也有很大的优势。

And so sexual reproduction does that in three ways.

而且有性生殖通过三种方式实现这一点。

Sexual reproduction with gene exchange is going to make a difference.

通过基因交换的有性生殖将会产生影响。

Along with the sexual reproduction, right, there is something about the renewal process, something about the ability to respond to a changing environment where it just becomes, you know, just killing off the old generation and letting new generations

伴随着有性生殖， 没错，存在着更新过程的某些特性，以及适应变化环境的能力， 在这种环境中，淘汰老一代、让新一代尝试似乎成为适应生态位的最佳途径。

It may be worth notice that when Wagner's remarkable discovery was first announced, I was asked how was it possible to account for the larvae of this fly having acquired the power of a sexual reproduction.

值得注意的是， 当瓦格纳的非凡发现首次被宣布时，有人问我如何解释这种苍蝇的幼虫获得了有性生殖的能力。

And us sexual reproducers, we add some fun twists to natural selection, but as far as we know, it is the basic driver of evolution.

而对于我这些有性生殖的生物来， 我在自然选择中增添了一些有趣的变数，但据我所知， 这仍是进化的基本驱动力。

Also, if environmental conditions are poor, asexual reproduction involves less effort than sexual reproduction because the female doesn't need to waste resources finding a mate.

此外， 如果环境条件较差，无性生殖所需的努力比有性生殖要少， 因为雌性不需要浪费资源寻找配偶。

But just like the human immune system, the reason that we use sexual reproduction is it creates variety in the immune system.

就像人类的免疫系统一样，我使用有性生殖的原因在于能在免疫系统中产生多样性。

In sexual reproduction, genes can flow much more easily through populations, which has a huge evolutionary advantage.

在有性生殖中， 基因可以在种群中更轻易地流动，这具有巨大的进化优势。

So sexual reproduction is the way we maintain genetic variation.

所以有性生殖是我维持遗传多样性的方法。

And while humans, with our experience of plants and animals, are of course most familiar with sexual reproduction, that is absolutely not the only way it can be done.

而虽然人类， 凭借我对植物和动物的经验，当然最熟悉有性生殖，但这绝不是唯一的方式。

We'll also, if we have time, going to look at sexual reproduction, which is probably what you guys are all interested in anyway.

如果有时间的话， 我还会研究有性生殖，这可能也是你都感兴趣的。