Tag: natural selection

Natural Selection by Alfred Russel Wallace

Everyone knows about Charles Darwin, but hardly anyone remembers Alfred Russel Wallace, who came up with the idea of natural selection at the same time as Darwin. Darwin’s publication of the On the Origin of Species was spurred on by Wallace. Flora Lichtman and Sharon Shattuck shed a little light on Wallace with this video:

Indeed, from the introduction of On the Origin of Species:

I have more especially been induced to [publish], as Mr. Wallace, who is now studying the natural history of the Malay archipelago, has arrived at almost exactly the same general conclusions that I have on the origin of species. Last year he sent to me a memoir on this subject, with a request that I would forward it to Sir Charles Lyell, who sent it to the Linnean Society, and it is published in the third volume of the Journal of that Society. Sir C. Lyell and Dr. Hooker, who both knew of my work—the latter having read my sketch of 1844—honoured me by thinking it advisable to publish, with Mr. Wallace’s excellent memoir, some brief extracts from my manuscripts.

— Darwin, 1859. On the Origin of Species.

↬ The Dish

Terraforming Earth

Before: Barren, Volcanic. Image by Ben Tullis via Wikimedia Commons.

Charles Darwin and colleagues attempted to vegetate the barren, volcanic Ascension Island with plants from botanical gardens around the world. Essentially, it was an experiment in transforming. And it worked. Howard Falcon-Lang has the details at the BBC.

After: An eclectic, lush mix of vegetation. Image by LordHarris via Wikimedia Commons.

Breeding Drug Resistant Bacteria at Farms

Modern commercial farming uses a lot of antibiotics, and, as a consequence, we’re beginning to see them breeding drug resistant bacteria (see here for exponential growth demo). Jeremy Laurance reports on one bug (MRSA ST398) now being found in milk.

Three classes of antibiotics rated as “critically important to human medicine” by the World Health Organisation – cephalosporins, fluoroquinolones and macrolides – have increased in use in the animal population by eightfold in the last decade.

The more antibiotics are used, the greater the likelihood that antibiotic-resistant bacteria, such as MRSA, will evolve.

…

The MRSA superbug can cause serious infections in humans which are difficult to treat, require stronger antibiotics, and take longer to resolve. Human cases of infection with the new strain have been found in Scotland and northern England

— Laurance (2012): New MRSA superbug strain found in UK milk supply in The Independent.

Note that consumers of milk don’t have to worry because the milk is pasteurized.

Natural Selection and Polar vs. Grizzly Bears

What I end up seeing, in this quintessentially 21st century creature, is a glimpse of the future.

— Gamble (2012): One, two, three, er…many. in The Last Word on Nothing.

The effect of rapid Arctic warming on polar bears has been a theme this year in Environmental Science, so this article on the hybridization of polar bears and grizzly bears caught my eye.

As caribou migration routes have moved North, grizzlies have followed and started mating with polar bears. Not only have they produced hybrid young, but those young are fertile. Polar bears and grizzlies only diverged about 150,000 years ago and haven’t developed many genetic differences, despite quite dramatic visual dissimilarities. Second-generation hybrids have now been confirmed in the wild.

This article is also of note to my Middle School science class because we’ve talked about speciation — the divergent evolution of two populations into separate species — before when we looked at the phylogenetic tree and bison evolution in particular. This seems to be a re-convergence after separation. As the climate warms the grizzly bears are able to range further north, while the polar bears are more restricted to the shores by the melted sea ice, so the two populations encounter each other more and more. Thus polar bears, may eventually disappear as they are re-incorporated into the grizzly population.

The author, Jessa Gamble, thinks this is a glimpse of things to come.

↬ The Dish.

Semi-artificial Selection?

Just like drug resistant germs (we’ve discussed earlier), the rats are evolving.

“They’ve also mutated genetically and are bred to be immune to standard poisons.

“We have had to start using different methods such as trapping and gassing, which can be less effective and more costly.”

–Graham Chappell, from Rapid Pest Control in Newbury in Rowley (2012): Home counties demand stronger poison to deal with mutant ‘super rats’ in The Telegraph.

The requirements of Natural Selection

Drosophila (fruit fly) head. Fruit flies are used extensively in biological and genetic experiments (image from Wikipedia).

Hannah Waters at Culturing Science has nice post on an experiment designed to find out how fast a population of flies could adapt to dryer conditions. Apparently, the flies could not adapt.

We tend to take it for granted that life is robust, and will adapt: “Life will find a way”. This is true to an extent, but obviously not always:

Natural selection itself is based on three assumptions in a population. The first is that there will be variation in traits, such as multiple colors of eyes or hair. The second is that these traits be heritable through the generations, that children will inherit the traits of their parents. The third is that these variable traits have differential fitness, or that some versions of a trait might help you survive better than another. Thus certain trait variants will help its carrier organism survive better, passing that trait to its offspring which will in turn bear this trait. – Waters, 2011: When adaptation doesn’t happen.