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.
The group OK Go set up an excellent Rube Goldberg machine for their music video, This Too Shall Pass. Thanks to Sage B. for pointing this one out to me. She’ll probably get to see it again next year when we get into physics and electricity and they need a little inspiration for their own machines.
Last year I used Honda’s The Cog advertisement, which is much simpler (and shorter) than OK Go’s.
Punnet square for a gender conferred recessive trait.
Two X chromosomes (XX) makes women female. Men have an X and a Y, the latter of which is responsible for all the things that make them male. What we teach is that one of the X’s in the women’s XX’s dominates the other so that women’s physical characteristics (phenotype) is only determined by the dominant X. Recent research shows that’s not necessarily the case.
“Our study shows that the inactive X in women is not as silent as we thought,” said Laura Carrel, Ph.D., assistant professor of biochemistry and molecular biology, Penn State College of Medicine, Penn State Milton S. Hershey Medical Center. “The effects of these genes from the inactive X chromosome could explain some of the differences between men and women that aren’t attributable to sex hormones.” – From Penn State University, edited by Science Daily.
It’s a fascinating finding, but I don’t think I’ll go into it with the students except, in the very unlikely event, that a direct question comes up. At this point, simpler is better.
Wired has a brief but excellent article on the voyage of the Beagle.
Its goal was to survey the South American coastline. The captain invited along a young man named Charles Darwin, whose father thought the voyage would just be another excuse for him to slack off. The trip ended up taking five years.
This article would be a wonderful addition to our work on exploration of the Americas next time it comes around; however, it’ll also be a neat little footnote because we’ll be delving into evolution next cycle.
Wikipedia’s entry on the ship produced this wonderful cross-section. I particularly like the sketches of people and casks showing the use of of different cabins and spaces.
In the binomial classification, modern humans are Homo sapiens (Genus and species). But you’ll frequently see us described as Homo sapiens sapiens, indicating that we’re a subspecies of Homo sapiens. One of the reasons for this is the still unresolved question of the neanderthals.
Some recent research suggests that 1-4% of our genes came from neanderthals. If true, this would mean that humans interbred, successfully, with neanderthals. Since one of the key parts of the definition of a species is that its members can produce fertile offspring, neanderthals would then be a subspecies of human. Thus we would be Homo sapiens sapiens and neanderthals would be Homo sapiens neanderthalensis, as opposed to being Homo neanderthalensis, a separate species in the same genus.
Skull differences between sapiens and neanderthalensis. Image by hairymuseummatt.
Perhaps even more interesting, the same researchers who did the gene work on neanderthal bones also sequenced some bones from Siberia, and found what may well be another subspecies of humans (the original article is at Krause et al., 2010). The genes are different from what’s been found before, but are in an area, and from a time period, shared both by modern humans and neanderthals. And, modern Melanesians (from the islands north and east of Australia) may share some of the genes of the new group. So this could even be another sapiens subspecies.
There are a number of caveats to this research, which is based primarily on gene sequencing and statistics. One key assumption that I’ve always been skeptical about is that DNA mutates at a fixed rate. However, this type of science ties very closely in to our discussions of evolution and themes of what it means to be human.
There are two great novels that address these two things, but I’ll only be using one of them. The one I’ll use is The Chrysalids by John Wyndham, which I’ve mentioned before (here and here). The other is War Games by Brian Stableford (aka Optiman). While the Chrysalids deals with accelerated mutation resulting from nuclear fallout, War Games considers the effects and moral implications of intentional genetic optimization (hence the other title for the book).
Last Wednesday’s lunar eclipse was nicely captured in the stop-motion video below. What a wonderful way to celebrate getting past the longest night of the year. And, because the question does come up, we’re seeing the shadow of the Earth cross over the moon.
Global temperature difference (anomoly) of 2000-2009 compared to 1950-1980.
NASA’s Earth Observatory is not only a great place for pictures from space, it also posts regular scientific updates, including the most recent map of the change in temperature since 1980.
The most obvious observation from the map is that the poles are warming faster than the rest of the planet, especially the North Pole. This is a pattern that has been predicted since at least the 90’s, so the temperature observations tend to show that the scientists and computer modelers who do this research may just know what they’re doing.
Blood Falls, Antarctica. Note the tent in the lower left for scale. From the U.S. Antarctic Program.
It’s also important to note that the Antarctic is not warming nearly as fast as the Arctic. The continental glaciers that would most significantly raise sea level (think 10’s of meters) are in Antarctica.
The northern hemisphere warming will likely be difficult for a number of species to deal with. Polar bears, the charismatic megafauna (I love that term) most associated with the effects of the melting Arctic sea-ice, are still in big trouble. Recent research, however, suggests that if something can be done to reduce global warming in the coming century, there will remain places with enough ice that the species may survive.
Update: Interesting article on global warming science and politics in the NY Times. It starts off talking about David Keeling, the scientist who came up with a reliable way to measure atmospheric carbon dioxide.
It starts with evidence that the mitochondria in our cells were once separate organisms and goes on to explain things like how the change from quadrupedal to bipedal, upright walking resulted in our S-shaped spine (and frequent backaches) and our unsupported intestines. It’s quite the interesting read.
