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Wednesday, April 29, 2009

sex, sex, sex, part 1

I remember when I had sex-ed in the sixth grade, and someone wrote on an anonymous-note-question for the teacher: Is sex fun?
Our teacher, a sweet older lady named Mrs. Love, replied: Of course! If not, none of you would be here!

And now that I´m studying biology, I´m becoming increasingly aware of all the weird ways sexual reproduction happens. Some seem quite absurd to me, and not very fun at all. I´ve wondered about organisms with external fertilization. Is it as much fun for them without all the "interaction" that internal fertilizers get?

This is the first of a series of posts on the weirdness of sex.

The reason sexes exist in the first place is sometimes considered a bit of a quandary for biologists, seeing as how it reduces the number of possible mates by a factor of two. Also, with completely asexual reproduction, each individual bearing two children gives exponential growth, whereas when each individual combined with an individual of the other sex gives rise to two children, this results in a static population. Also, sex creates novel genotypes, more rapidly, in addition to a few other good things, such as it being fun. (It also helps in removing deleterious mutations by homologous recombination).

NEW DISCOVERY
Earlier this year, paleontologists made a big discovery regarding sex. In english, sex (as in the act) and sex (as in gender) are often referred by the same word. It currently seems that sex (as in gender) is extremely old. Early eukaryotes seem to have been reproducing with distinct variants, and most multicellular creatures reproduce sexually. However, sex as in copulation is much more rare.

Paleontologists discovered a Placoderm (really old fish with massive armor, one of the earliest jawed fish) fossil with a tiny skeleton lodged inside. They thought it was the placoderms last meal. Upon furher investigation, they realized it was an embryo of the same species. And you know what that means. Babies on the inside, means the sperm needed to get inside. Internal fertilization!

The fossils are about 365 million years old, and demonstrate that internal fertilization was probably a lot more common earlier than previously thought.
Pharyngula as usual covers the story thoroughly and with comments on what this means for the evolution of our own ways of sex.

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