Episode Three, Internal Affairs, reveals the extraordinary array of strategies creatures use to give life to their offspring. From conception through to birth, the program reveals how numbers, timing and the environment can make all the difference between life and death for many species. There's the amazing survival kit of the kangaroo, which can switch its reproductive system on and off to survive the elements, and a tiny animal that doesn't need a male at all to reproduce. For some, the most enviable control of timing would have to be the strategy of queen bees and bulldog ants to have 'babies on demand'. They can fertilise their eggs at will from a store of sperm - depending on how many workers they want. They only need to have sex once - they've almost done away with males. Almost... But when it comes to completely doing away with males... all hail Bynoe's gecko! They are all female. They do not need males at all to reproduce. They're all virgins and they all give birth. Speaking of fathers... in nature they have 'birth control' too. Seahorse males fertilise and incubate eggs in their stomach - even going into labour to give birth - proving that some fathers are mothers too. And they do it all naturally. By comparison, human reproduction looks boring.