"Why do we only have two sexes and are there any anomalies in the animal kingdom?" asks Robert Turner from Leeds.

From reptilian virgin births to hermaphrodite sea slugs, over the next two episodes Drs Rutherford and Fry examine the weird ways other creatures reproduce.

In this first instalment, they tackle what's been called 'the hardest problem in evolutionary biology' - why does sex exist?

Why aren't we all one single sex that clone ourselves to produce offspring? It makes perfect evolutionary sense - you could pass on all of your genes and don't need to bother finding a partner.

Hannah visits London Zoo to meet a fierce komodo dragon named Ganas, the result of a virgin birth. And Adam meets some tiny bdelloid rotifers, microscopic worm-like females who have survived for 50 million years by cloning themselves.

You can send your questions in to curiouscases@bbc.co.uk

Presenters: Hannah Fry, Adam Rutherford
Producer: Michelle Martin.