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Evolution - bizarre adaptations

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156146.  Tue Mar 13, 2007 10:49 am Reply with quote

We talked about the possibility of having a 'Call my Bluff' style round where we give each pannelist a description, or a picture (or whatever) of a peculiar biological adaptation, and they have to either guess which is real, or match it with the animal in question.

However we do it, there's no shortage of material. Almost every kind of useful adaptation has already been 'thought of' by nature. As Orgel's Second Rule puts it: Evolution is cleverer than you are.

Duplex chastity belt
Some spiders (and honey bees, Mitch informs us) leave part of their palps in the reproductive tract of the female after insemination, preventing other males access.

Cloaking device to avoid predators
Many marine animals fall prey to predators from beneath because their silhouette stands out against the bright blue water's surface above them.
Also known as 'crypsis' or 'ventral counter-illumination', several species of squid can emit light of exactly the right wavelength from beneath their bodies to counter the shadow effect, becoming effectively invisible from below.
(This paper is by Haddock, Widder and Herring - known as the 'fish sandwich' paper...)

Refrigeration units
Beavers change nearly all of their environment by making dams out of trees, branches and mud. Before the winter months, when food is scarce and the snow lies deeply on the ground, they build very deep, shaded pools which get very cold at the bottom, and then stock it with freshly cut branches of leaves. They then visit this refrigerated larder, where the leaves don't decompose, throughout the winter.
Source: Attenborough, Life of Mammals

Auto-cryogenic hibernation
Currently only possible in Hollywood films, suspended animation happens quite regularly amongst invertebrates, but there are also a few frogs than can pull it off, most notably the American wood frog. Freezing organic tissue is very difficult, as the ice crystals tend to rupture the cell walls and cause irreperable damage. The wood frog manages to grow 'smooth' crystals, and also change its blood to a kind of antifreeze. The heart stops, and the body starts to slowly eat its fat reserves anaerobically for a few months.

Predator early warning system for plants
Some species of acacia tree release a pheremone when they are under attack by giraffes. This pheremone wafts on the wind and is detected by any other acacias downwind, which then start to secrete chemicals into their leaves to make them taste very bitter. The giraffes have learned, in some cases, to beat this trick by only eating this particular species while walking between trees in an upwind direction, whence than cannot communicate the warning.
Attenborough, Life of Plants

Parasitic worm that programs ant brains
The lancet fluke needs certain chemicals to reproduce that are only found in the intestinal tract of sheep. The problem is that the larva get shat out (technical term there) and have to find a way to get back in to reproduce again.

They can get into snails shells, but the snails get rid of them by encasing them in slime. However, ants come across these trails and exploit them for food, unwittingly taking on the larval worms, which work their way up to a specific region of the ant's brain, making it climb up to the top of tall grass and 'wait' for a passing sheep to eat it.

156302.  Tue Mar 13, 2007 5:15 pm Reply with quote

It seems that cheetahs have specialized to the point of putting themselves out of business. Running at such high speeds causes oxygen depletion to the brain, so after they catch something they're knackered and their catch is often stolen by some bastard hyena or lion while they're catching their breath. Even if they can muster the energy to protest, they can't put up much of a fight because they're runners, not fighters.

Until about 100,000 years ago they lived in North America, and this is thought to be the reason why the Pronghorn Antelope can run so damn fast (the 2nd-fastest land animal at 58mph - not really antelopes, but more numerous than people in Wyoming) - there would have been no point in a prey animal evolving such a turn of speed in the absence of cheetahs.

Apparently they have a very limited amount of genetic diversity within the species because they went through an evolutionary bottleneck in the late pleistocene (10,000 years ago), during which the species nearly died out, so all modern cheetahs are descended from a very small community which survived at that time. This has made it difficult for them to evolve their way round their various problems.

156373.  Wed Mar 14, 2007 5:04 am Reply with quote

Cheetahs are very cautious when faced with any other predator of their size - they're not fighters, as you say, simply because any injury at all to them will stop them from being able to catch anything, so they'll starve to death - with their cubs, if they have any.

Pronghorn antelope are incredible in that they can keep up their sprint for far longer than any other animal - around half an hour. There are wolves there, too, which are also very capable of long-stamina pursuit, and in packs to herd the antelope around in circles, chasing them in shifts.

156381.  Wed Mar 14, 2007 5:46 am Reply with quote

Some experts argue that the spotted hyena is a better hunter than the big cats; see
post 140723


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