January 2008 - Biology Issues

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Biology Issues - January 2008

Human-engineered genome a reality

January 27th 2008 09:28

J. Craig Venter, the famous geneticist and biotechnology entrepreneur, is a man of vision. What does he, and other scientists of similar vision, want? Organisms that can be programmed - in the same sense as computer software are - to perform a whole suite of functions for us. This is no idle futuristic speculation, for the pace of bioengineering is such that the creation of a fully synthetic life form is expected to come true in the very near future, possibly even in the coming year. There are still some odds and ends to iron out, but you can rest assured that it will be achieved.

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The amazing Ichneumon wasps

January 18th 2008 05:16

Did you know that most wasps are parasites? More accurately, they’re parasitoids, or organisms whose larvae are parasites. Ichneumon wasps (belonging to the superfamily Ichneumonoidea) comprise well over 80,000 species, far outnumbering social wasps. Many use their ovipositor – a sting-like projection extending from the abdomen – to inject their larvae into other organisms. Others paralyse their victim and lay an egg on its abdomen, from which the larva hatches and then consumes the still living but helpless organism. Depending on the species of wasp, hosts can be many different types of invertebrates, including caterpillars, aphids, cockroaches, mature tarantulas, and butterfly larvae.

One of the most utterly amazing feats of animal design I have ever heard about is manifested through one of these wasps, called Ichneumon eumerus. The story begins with another insect, the Alcon Blue butterfly (Maculinea alcon), which lays its eggs on Gentian plants. When the larvae hatch, they drop down into the soil, where passing ants are “fooled” through means of an allomone released by the larvae (an allomone is a chemical produced by an organism to affect the behaviour of an individual of another species), which mimics those released by ant larvae. The M.alcon larvae even make sounds like those of the ants'. Taking the butterfly as one of their own, they carry it back to their nest, where it is fed and groomed. That’s interesting by itself, but here comes the wonderfully sinister side to the story. An I.eumerus wasp in the vicinity can detect the nests, among many others, that harbour the butterflies. Naturally, the ants are not want to accept an intruder into their domain, but the wasp has another ace up its sleave: it releases a chemical that causes the ants to turn on each other, giving it enough time to go off and look for the precious items. And yes, inject them with its future. The wasp then leaves, and things soon return to normal for the warring ants. They continue to feed and groom the M.alcon larvae, oblivious to the intrigue that is about to unfold. During chrysalis, the ants care for the butterfly as one of their own pupae (the next stage in the ant life cycle), scurrying around the casing, still intoxicated by the allomone. But, of course, it is not always an adult butterfly that emerges. In those unfortunate grubs that were injected by I.eumerus, a wasp emerges. And it goes on, of course, to do as its parent did. This wasp is a parasite of a parasite, for it exploits and consumes an organism that is itself an exploiter

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Why creationism must be fought

January 17th 2008 09:43

Creationism - whether it goes by that name, or creation "science", or its most modern incarnation, "intelligent design" - is religion, not science. It has no place in the science classroom. Many people think that it's simply a matter of "fairness", that "students should hear both sides of the story", and therefore that evolution should be taught alongside creationism. The problem is that creationism doesn't qualify as another side to the story, because it's complete bunk. We don't hear calls for witchcraft to be taught alongside the germ theory of disease, or for the flat earth hypothesis to be taught alongside astronomy. Evolution is one of the most well corroborated theories in all of science; it draws upon thousands of independent pieces of evidence that together lead us to think that evolution it is the most satisfactory account for biological complexity and natural history that we have. It matters not one bit whether people find it uncomfortable or contrary to their religious beliefs; it's still true. Despite virtually all scientists accepting this basic tenet, many non-scientists still think that there is a controversy worth speaking of. But there simply isn't; the "controversy" between evolutionary biology and creationism is a purely cultural phenomenon, born of ignorance and misunderstanding (both of which are eagerly sized upon by the creationist propaganda mill to stoke the flames of anti-intellectualism, but neither of which are in and of themselves anything to be ashamed of, for everyone is ignorant about a whole range of things. It does, however, become a problem when it is exploited). Here are just three of the most common misunderstandings of evolution out there, as well as the scientific responses to them:

"Evolution is just a theory, not a fact

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Dinosaur wonders

January 16th 2008 04:59

In the past decade or so, the study of dinosaurs has become so detailed and sophisticated that researchers are now able to tell (of particular dinosaurs) how rapidly they grew, how they breathed, that they had feathers, how fast they could run, how large their brains were (and even how much of their brains were dedicated to smell), whether a fossil is that of a male or female, their likely parenting behaviours, their biting strength, how alike their bone proteins were to those of modern birds, and what their scales and patterning looked like. Of course, given the very real limitations of the fossil record, there is a great deal we still don’t know (and probably never will know, as so much is lost in the turbulence of history), so a good deal of guesswork and speculation must necessarily still go on, but individual discoveries add new understanding to particular dinosaurs, and are suggestive of broader patterns. It is now fairly safe, for example, to say that birds evolved from dinosaurs, because the convergence of several independent pieces of evidence in favour of this hypothesis is pretty strong. Speaking more generally, it's just incredible how human ingenuity and good old-fashioned perseverance (accompanied by a bit of good luck here and there to help us along) has allowed us to peer back in time - over 65 million years ago - and reconstruct such a detailed portrait of a lost world.

Where once dinosaurs were widely thought to be dull-witted, slow and unsuccessful denizens of natural history, they are now seen as active, sophisticated animals that could hold their own. Their affinities to birds are nowadays often depicted with some very birdlike reconstructions in palaeo-art. Where once we thought of them as being greenish-brown, they are now endowed with dazzling colours like modern day lizards and birds. And why not? After all, dinosaurs were living, breathing animals. Their lineages evolved and adapted in accordance to local circumstances, and those circumstances were determined by the biotic and abiotic environments prevailing at the time. Evolution, we can surmise, was working by the same rules back then as it is now. We can also surmise that there were ecological niches being filled in much the same manner as they are today, with predators, grazers, scavengers, fish eaters, insectivores, and omnivores. The Permian-Triassic extinction event that occurred some 251 million years ago – terminating the Palaeozoic era – wiped out about 95 percent of all species living at the time (earning it the apt name, the “Great Dying”), and opening the way for the later prominence of the dinosaurs (of course, it didn’t happen in order for dinosaurs to have their shot. Meteorites and volcanic eruptions have no foresight; they do their business, and that’s that, however much the results matter to us). We call what came afterwards the Mesozoic Era, or the "Age of Reptiles" (pretty misleading, as it gives the impression of a ladder of evolution. Lots of other groups continued to live on, and indeed, as the late palaeontologist Stephen Jay Gould said in his excellent book “Full House”, it has always been the Age of Bacteria. Reptiles – including the dinosaurs, ichthyosaurs, flying reptiles and others - would together only have constituted a small fraction of the total biodiversity; it’s just that we characterise each age from the vantage point of its most exciting inhabitants). This is when the dinosaurs came to prominence (on land, at least). After mass extinctions, the niches filled by the previous fauna come to be occupied by newly evolved species. So it was with the dinosaurs, filling in the niches previously filled by the "mammal-like reptiles” that lived during the Palaeozoic Era. When the dinosaurs met their end in the Cretaceous-Tertiary extinction event (more widely known to the general public than the Permian-Triassic event even though it wasn’t as devastating), the niches they had occupied came to be filled by mammals. There is a recurring, large-scale pattern to life; as someone once said of history, “it rhymes

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July 2008

1 Posts

May 2008