Essay/Term paper: Reproduction

Essay, term paper, research paper:  Science

For some time she had watched his movements,
appearing coyly in his haunts. And now, had it
paid off? Doubtless, he was in love. His muscles
were taut; he swooped through the air more like
an eagle than a Greylag gander. The only problem
was, it was not for her that he then landed in a
flurry of quacks and wingbeats, or for her that he
dashed off surprise attacks on his fellows. It was,
rather, for another - for her preening rival across
the Bavarian lake. Poor goose. Will she mate with
the gander of her dreams? Or will she trail him for
years, laying infertile egg clutches as proof of her
faithfulness? Either outcome is possible in an
animal world marked daily by scenes of courtship,
spurning and love triumphant. And take note: these
are not the imaginings of some Disney screen-16
writer. Decades ago Konrad Lorenz, a famed
Austrian naturalist, made detailed studies of
Greylags and afterwards showed no hesitation in
using words like love, grief and even
embarrassment to describe the behavior of these
large, social birds. At the same time he did not
forget that all romance - animal and human - is tied
intimately to natural selection. Natural selection
brought on the evolution of males and females
during prehistoric epochs when environmental
change was making life difficult for single-sex
species such as bacteria and algae. Generally,
these reproduced by splitting into identical copies
of themselves. New generations were thus no
better than old ones at surviving in an altered
world. With the emergence of the sexes, however,
youngsters acquired the qualities of two parents.
This meant that they were different from both -
different and perhaps better at coping with tough
problems of survival. At the same time, nature had
to furnish a new set of instincts which would make
"parents" out of such unreflective entities as
mollusks and jellyfish.. The peacock's splendid
feathers, the firefly's flash, the humpback whale's
resounding bellow - all are means these animals
have evolved to obey nature's command: "Find a
mate. Transmit your characteristics through time!"
But while most males would accept indiscriminate
mating, females generally have more on their
minds. In most species, after all, they take on
reproduction's hardest chores such as carrying
young, incubating eggs and tending newborns.
Often they can produce only a few young in a
lifetime. (Given half a chance, most males would
spawn thousands.) So it's no surprising that the
ladies are choosy. They want to match their
characteristics with those of a successful mate. He
may flap his wings or join a hockey team, but
somehow he must show that his offspring will not
likely be last to eat or first in predatory jaws.
Strolling through the Australian underbrush that
morning, she had seen nothing that might catch a
female bowerbird's eye. True, several males along
the way had built avenue bowers - twin rows of
twigs lined up north and south. True, they had
decorated their constructions with plant juices and
charcoal. Yet they displayed nothing out front!
Not a beetle's wing. Not a piece of flower. Then
she saw him. He stood before the largest bower
and in his mouth held a most beautiful object. It
was a powder blue cigarette package, and
beneath it there glinted a pair of pilfered car keys.
Without hesitation she hopped forward to watch
his ritual dance. Males have found many ways to
prove their worth. Some, like bowerbirds, flaunt
possessions and territory, defending these
aggressively against the intrusion of fellow males.
Others, like many birds and meat-eating mammals,
pantomime nest building or otherwise demonstrate
their capacity as dads. Still others, however, do
nothing. Gentlemen may bring flowers, but most
male fish just fertilize an egg pile some unknown
female has left in underwater sand. For a fish,
survival itself is a romantic feat. For other species,
though, love demands supreme sacrifices. Shortly
after alighting on the back of his mate, the male
praying mantis probably had no idea what was in
store. This would have been a good thing too,
because as he continued to fertilize his partner's
eggs, she twisted slowly around and bit off his
head. She continued to put away his body parts
until well nourished and thus more able to sustain
her developing young. Luckily for most species,
the urge to mate come on only occasionally,
usually in springtime. For love can hurt, particularly
if you intended has difficulty telling a mate from a
meal. Pity the poor male of the spider species,
Xysticus Cristatus, for instance. His only hope of
survival is to tie a much larger female to the ground
with silk thread, and keep her there. Every time a
moth releases its attracting scent, or a bullfrog
sings out its mating call, these animals are risking a
blind date with some predator. Such alluring traits
have long puzzled scientists, particularly those
which seem not only risky but useless as well.
Why, after all, should a frigate bird mate more if
he puffs out an extra large red throat sac? How
does ownership of such a thing indicate a superior
individual? Until recently, the question stymied
biologists, but then researchers in the U.S. and
Sweden announced a possible answer. While
studying widowbirds, among whom extravagant
tail feathers are hip, they discovered that the
longest-tailed males also carried a lower number
of blood parasites. Sexual ornamentation seemed
to be a means by which males could show of
superfluous health and energy. All of which may
bring us to fast sports cars, flashy clothes and
other accessories of the human suitor. After all, if
he can afford dinner at the city's most expensive
restaurant, chances are he could finance a baby
too.