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Bird Coloration: Pigments and Structural Colors
Jul 22 2011 5:00:00 pm EST
Topics:The remarkable diversity in color and iridescence of birds is achieved by pigments and structural colors.
Pigments are colored substances that reflect certain wavelengths of light, while absorbing others. It is the reflected light that is identified as the pigment’s color. Pigments are located on the skin or feathers of the bird and are independent of the structure of the feather. Bird pigments come in three different groups: melanins, carotenoids, and porphyrines.
Melanins are the primary determinate in human skin color. They also serve to color the skin and feathers of birds, as well as providing strength and durability to feathers. Melanins produce blacks, reddish browns, and pale yellows.
Interestingly, a feather without any pigmentation is the weakest of all. White birds will often have melanin fortified black feathers on their wings where they are subject to the greatest stress.
Carotenoids are naturally occurring organic pigments in the chloroplasts and chromoplas
Color Range Perception, Evolution of the Eye:
Jul 21 2011 10:15:55 am EST
Topics:From the entire range of the electromagnetic spectrum, most life that can perceive light evolved to perceive a narrow band—the visible light spectrum (400 nm-700 nm). This range of perception is based on hundreds of millions of years of adaptation.
An interesting phenomenon of the visible spectrum is that it penetrates water by about 6 orders of magnitude better than adjacent frequencies. In other words, the visible spectrum penetrates water much better than other frequencies. This phenomena is demonstrated in the graph below (Fernald, 1997).
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Size of Organism and the Eye, Scaling
Jul 18 2011 5:00:00 pm EST
Topics:Many biological systems vary in proportion to the size of the animal. For example, as an animal increases in size, the skeletal system must increase in proportion to handle the added weight. However, the eye has ranges and limitations of magnitude of its own, resulting in less straightforward scaling.
From the simple eyespots of a unicellular organism, to the diverse range of simple and compound eyes of multicellular organisms, the eye has evolved to detect a narrow band of electromagnetic radiation: visible light. In the case of the unicellular organism, it might only be able to detect the presence of light and perhaps its direction. Whereas vertebrates have evolved to differentiate wavelengths of light as color, and determine shape and movement. In all cases, the shape and size of the eye is determined more by what the animal needs to see and less by the animal’s size. As D’Arcy Wentworth Thompson points out, “A big do
Wright Peak, Algonquin Peak, Iroquois Peak from Heart Lake
Jul 7 2011 5:00:00 pm EST
Topics:I published a trail review of Wright Peak, Algonquin Peak, and Iroquois Peak from Heart Lake.
From Heart Lake, the trail to Algonquin Peak, the second highest summit in New York, is a manageable day hike. Along the way, the hiker has an opportunity to summit Wright Peak and Iroquois Peak, both high peak summits. From Heart Lake, the hike to Wright Peak is 3.8 mi, adding in a .4 mi spur from the main Algonquin trail. Not factoring in this spur, the distance to Algonquin peak is 4.3 mi, though some of this is relatively steep with some scrambling.
From the summit of Algonquin, an unmarked, but relatively well established trail leads to another high peak, Iroquois. The distance from the Van Hoevenberg trailhead to Iroquois Peak, not factoring in the Wright spur trail, is a sometimes difficult 5.4 mi.
Overall, this is an excellent warm up day hike for the high peaks. If Algonquin seems out of r
I recently published a photo gallery of the Indian Ladder Trail. The trail is carved within the Helderberg Escarpment, and traverses the Indian Ladder Gulf. The limestone escarpment is replete with fossils and underground streams.
The trail traverses many rock shelters and passes under two impressive waterfalls. The Empire State Plaza in Albany can be seen over ten miles away, as well as much of the surrounding region to a great distance.
I recently visited the Huyck Preserve in Rensselaerville, NY. A network of loop trails traverse Lake Myosotis, Lincoln Pond, Rensselaerville Falls, both natural and man-made dams, and the surrounding watershed within the 2000 acre preserve.
I posted a gallery of photographs from my explorations. Overall, I felt the trails were easy going with pleasant views.
Just posted a gallery of Algonquin Peak photos. The second highest peak in New York State, Algonquin has uninterrupted views of the surrounding Adirondack region, and nearby peaks to explore—all in a day hike.
As of late June, the insects were not bad at all, I found it unnecessary to use bug spray. Overall, the hike was enjoyable, and an excellent warmup to the high peaks of the Adirondacks.
Size of Animal and Vocal Pitch
Jun 9 2011 5:14:35 pm EST
Vocal chords share similar qualities to musical instruments in that pitch rises as string length diminishes. The vibration of vocal chords varies inversely as the square root of the linear dimensions of an organism. The larger animal tends to have a deeper bass, whereas the smaller animal tends to have a higher pitch.
From On Growth and Form (52-53):
The vibration of vocal chords and auditory drums has this in common with the pendulum-like motion of a limb that its rate also tends to vary inversely as the square root of the linear dimensions. We know by common experience of fiddle, drum or organ, that pitch rises, or the frequency of vibration increases, as the dimensions of pipe or membrane or string diminish; and in like manner we expect to hear a bass note from the great beasts and a piping treble from the small. The rate of vibration (N) of a stretched string depends on its tension and its density; these being equal, it varies inversely as its ow
Fairyflies are tiny parasitic wasps whose eggs are laid and larvae reared within the tiny eggs of larger insects. Their size varies to less than half a millimeter, to 4 mm. One genus (Alaptus), parasitic on Psocoptera eggs, approaches the record of 0.18 mm.
The required thrust and lift is so tiny proportional to the body that the wings of some fairyflies are made of tiny hairs or bristles instead of a continuous membrane.
Practical Limits on the Size of an Exoskeleton
Jun 7 2011 9:28:48 am EST
Topics:The perils of molting, the force of gravity, and the percentage of oxygen in the atmosphere play a role in the practical limit on the size of an exoskeleton.
Unlike an endoskeleton, which allows an organism to grow in small increments, an exoskeleton needs to be discarded to allow the organism to grow—the process of molting. In between the shedding of the old exoskeleton, and the hardening of the new, the organism is vulnerable to predation and the forces of gravity. Too large an organism would take too long molting, and risks collapsing under its own weight.
Similarly, a fully hardened exoskeleton needs to be scaled appropriately to the dimensions of the organism to prevent it from collapsing. Since strength is proportional to the square of the linear dimensions, whereas mass is proportional to the cube of the linear dimensions, the skeleton needs to become ever thicker as size increases. At a certain point, the design becomes impractical.
Since an exoskeleton serves as a r
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