February 2009 - Biology Issues

Biology Issues

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Biology Issues - February 2009

Why did endothermy evolve?

February 26th 2009 10:41

Many animals are endothermic. That is, they generate internal heat rather than relying upon the energy acquired directly from the ambient environment. This isn't an absolute delineation among animals, since even many animals that are nominally "cold blooded" - like bees and sharks - can raise their internal temperature when they really need to (though they do so in ways that are different to the way we do it, and some of them heat only certain organs) and some nominally "warm blooded" animals can in fact change their internal temperature at times. But ambiguities aside, what benefit is there to constantly maintaining a warm body? Is it actually an adaptation in and of itself, or is it a side-consequence of something else? Maintaining constant warmth expends a lot of energy. While reptiles, for example, need to eat relatively infrequently, relying for their heat by exposing themselves to the sun (and moving out of it to avoid overheating), we wouldn't survive for very long if we stopped eating.

Thermal signatures of a monkey. Image from Linda Hermans-Killam / outreach@ipac.caltech.edu

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Posted By: LuisC - Category: No Category

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Protecting Mars from Earth germs

February 25th 2009 03:08

Mars already has life. But it didn't originate on the planet; it originated on Earth, and hitched a ride on the landers that have been sent there over the past few decades. Scientists are now more acutely aware of the ruggedness of microbes, and they are worried that if Earth microbes are able to survive and multiply, then they might disrupt Martian indigenous life (if it exists). To this end, they are refining some already existing protocols to minimise the risk of contamination (one of these is actually a UN accord that aims to protect celestial bodies from harmful contamination).

Image of the planet Mars. From Federation of American Scientists

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Posted By: LuisC - Category: No Category

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Recovering the Neanderthal genome

February 19th 2009 06:20

In amazing new developments, the initial draft of the genome of a 38,000 year old Neanderthal has been completed (check out this article from Ewen Callaway in New Scientist for some more details). Scientists will be able to compare the genomes of modern Homo sapiens and the extinct human species H. neanderthalensis to see what sorts of changes have accrued since the two shared a common ancestor and what sorts of regions have likely been involved in developmental processes since the divergence. Also, it will give us more clues as to whether the two species engaged in any intermixing. Currently, signs are that they didn't do this to any significant extent if at all, but the newly sequenced genome will allow us to investigate this with considerably more certainty. I should also point out that I also said something apparently contradictory: I alluded to the possibility of two species intermixing. According to the biological species concept, a species is the most inclusive set of all potentially interbreeding individuals, so by that criteria, Neanderthals and H.sapiens should count as members of the same species if they could intermix and produce offspring. But, like so many things in nature, species are rather fluid and there are different ways to define them. Since species formation is typically a gradual process, a continuity must exist from varieties to sub-species to species proper (however defined). It is possible that we did interbreed and that the offspring were less viable but still left some genes behind in the population. Whatever the story, this is certainly a wonderful development and it will address some important questions about human evolution.

An excerpt from the article in New Scientist

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Posted By: LuisC - Category: No Category

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New hints about turtle evolution

February 10th 2009 04:46

Turtles have proven among the most elusive lineages to study from an evolutionary perspective. Their relatedness to other groups has always been rather unclear, but a recent discovery could prove vital for a more definitive resolution. The fossil also provides clues as to how the turtle shell evolved.