Obviously you mean male and female homo sapiens, because if you mean male and female in the entire animal kingdom, you've got another thing coming.
Funny you should restrict yourself to biological differences, because sociological differences are much more interesting. If you were dealing with the social aspects, I'd suggest Manwatching by Desmond Morris as a start.
There's an important English lesson (
http://www.bartleby.com/64/C005/010.html) to be had before we continue. Bartleby are putting it gently, but I rather out with it: "Gender" refers to the grammatical categories of masculine, feminine, and neuter, while "sex" refers to the biological categories of male and female. I would deem any other use as incorrect. However, writers try to appeal to the general audience, which doesn't like reading the word "sex".
I'm back to biology. There are plenty of good answers in The Cambridge Encyclopedia of Human Evolution (
http://www.amazon.co.uk/exec/obidos/ASIN/0521467861). This book has all you need at the introductory level. Whether or not you read the book, you should not search online. I could find no good articles about the subject.
I'd like to sit here and type a 60-page work of anything I could think of that relates to biological differences between men and women, but I don't have all the references at hand, and more importantly, I'm not getting anything out of it. Otherwise, I believe sociology will help you understand human behavior much better than evolutionary psychology. They both give the same answers, but sociology is much more straightforward, scientific, and applicable.