Tuesday, December 20, 2011

Anomalocaris had excellent vision

Anomalocaris is a strange and interesting genus. So strange, in fact, that three separate parts of their fossils were once identified as three separate creatures. It took nearly a century from the discovery of the first piece, for Anomalocaris canadensis to be properly identified and unified into single animal1.

Anomalocaridids, the group in which Anomalocaris belongs, grew to over a meter in length. Although small in comparison to marine animals today, at the time they swam the oceans (see an animation), between 540 and 472 million years ago, they were the biggest predators in the sea by far1,2.

Anomalocaridids had two segmented tentacle-like appendages that were probably used in hunting, perhaps by stabbing or by grasping prey. Their mouth was circular and had ‘teeth’ that closed like a camera shutter. Some of them may have eaten hard-bodied animals like trilobites, but it is thought that soft-bodied animals were their primary prey.

Monday, December 19, 2011

Red Spot, Blue Dot

In September 1977 the Voyager 1 probe was launched. Its primary mission was to study Jupiter and Saturn, which it completed in late 1980. It took some fantastic photos of Jupiter, Saturn and their moons. Like this one of Jupiter's red-spot.

A decade after passing Saturn, Voyager 1 was beyond Pluto and headed for the edge of the Solar System, where it is now. At the request of Carl Sagan, Voyager 1 took this picture:

At first glance it's a boring image of black space with brown bands of sunlight reflecting off dust. But, it is actually an image that I find awe inspiring. If you look about halfway down the right-most band of brown, you'll see a tiny speck of pale-blue. That's Earth. In this image, which contains 640,000 pixels, Earth is little bigger than one tenth of a pixel. In the vastness of the universe our little planet is completely insignificant. But, Carl Sagan saw something in the image that was significant. In his book 'Pale Blue Dot' he wrote:

From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.

Earth appears pale-blue partly because of sunlight reflecting from the surface, which is mostly open ocean. The ocean absorbs more of the longer wavelengths of light (such as red) than it does the shorter wavelengths (such as blue), which is why large bodies of water appear blue. However, Rayleigh scattering of sunlight by the atmosphere, which is what makes the sky blue, also contributes to making Earth appear blue from space. If the Earth had no oceans, Rayleigh scattering alone would give it a blue tinge.

Sunday, December 18, 2011

Hello World

The last paragraph of Charles Darwin's 'On the Origin of Species' is one of my favourite pieces of writing. Some of what Darwin writes in On the Origin of Species is difficult to get through, but the last paragraph is exceptional.
It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

It is, indeed, interesting to contemplate an entangled bank and the animals and plants that live on and within it. Equally, though, it is interesting to contemplate the wave-washed shore and the organisms that associate with it. And then to lift your gaze to the waters behind the breakers and reflect on the elaborately constructed forms that live beneath the surface. The ocean places a whole host of challenges on the life found there that lead to the evolution of strategies not seen in terrestrial habitats. In this blog I'll be writing about the things that interest me. Mostly, that's the open ocean.