Ecology of Alien(s)
H...@psuvm.psu.edu
From: HYD at PSUVM
To: wt0b+ at andrew.cmu.edu
Subject: Re: Scene Removed from "Alien"? [was: Ridley, Ridley; ...]
Well, the idea of single-sex organisms isn't so far out as you might belive.
Parthanogensis has evolved independantly many times here on earth, there are
many invertebrates, some fish and even a few reptile species in which males do
not exist. There has been a considerable amount of argument on the part of us
ecologists on why this occurs, the consensis is that parthanogensis is an adapt
tation for dispersal or perhaps in some cases reproductive efficiency. In the
dispersal case, females who do not require males to reproduce have an advantage
since only one founder is needed to colonize a new habitat. The second case is
much more complicated, reproductive efficiency of a population can be increased
in some cases if no allocation of resources to producing males is used, the
major assumption of this is environmental stability. In a stable environment,
sexual recombination of genes is less valuable to a species than speed of repro
duction. The theory is in fact supported by most data, parthanogensis is most
common in species which see few changes in environment. Some species even chang
e reproductive stratiges with changes in environment. Some fish can even change
their sex!
BTW: The life history of the alien was lifted from a diverse group of wasps,
called spider-hunting wasps. I can't remember the family name right now, but
their life-cycle is very simular to the aliens. Adults capture spiders, or
other small animals, "stun" their prey with a sting and then deposite their
eggs on the victim. Eventually, the eggs hatch and the wasp larvae eat the nice
fresh (still living) host. Pretty Neat-o Huh? I used to try to catch a wasp
called the Cicada-hunting wasp when I was a kid. It was lots of scary fun since
these are the largest wasps in america (prehaps the world) and are reputed to
have one hell of e painfull sting! The're about 3 in long and colored orange
and black (warning coloration) and use adult cicadas as prey. Cicadas are call-
ed 17 year locusts by some people. Anyway, Ecologists call this type of predito
r a parasitoid, they capture live prey which are used as a resource but not
killed directly, it's more common than you might think.
For more real life horror from the natural world try "The Panda's Thumb" by
Steven Gould, One of the essays is about the myth of "loving" nature and the
actual moral neutrality of the natural world.
Paul (Just another useless male) Heinrich