AMAZING BIOLOGICAL STRUCTURES

                                     [1] THE BLUBBER OF MARINE MAMMALS

         For decades, scientists could not understand how dolphins could swim at the speed of nearly 40 kilometers an hour. The animals simply did not have enough muscle, the scientists thought. But dolphins have a secret, part of which lies in their blubber, a complex substance also found under the skin of porpoises, whales, and other marine animals

          Blubber is a thick, dense layer of highly organized connective tissue with a lot of fat cells. It covers practically the whole creature, and it is strongly attached to the musculature and skeleton by highly organized, fan-shaped networks of tendons and ligament. These networks, in turns, are composed of elastic fibers and collagen, a protein that is also found in skin and bones. Blubber, therefore, is much more than a layer of insulating fat. It is a highly sophisticated combination of various living tissues.

        How, though, does blubber help dolphins and porpoises to swim so fast –Dall’s porpoises at speeds of up to 56 kilometers an hour? For one thing, blubber gives the animals a more streamlined shape. For another, the blubber between their tail flukes and dorsal fin is crosshatched with an especially dense array of collagen and elastic fibers –a design that gives the tail elasticity and stores mechanical energy. Hence, when muscles move the tail in one direction, the blubber, like a spring, helps to pull it back, thus both adding thrust and conserving energy.

       Blubber also aids buoyancy and provides thermal insulation. Its fat content stores energy for lean times. Understandably, this versatile composite has attracted the interest of those who are trying to improve the efficiency of marine craft and their means of propulsion.

                 [2]                    THE SQUID’S BEAK

             

          The beak of the squid baffles scientists. They wonder: How can something that is so hard be attached to a body that has no bones? Should not the combination of materials cause abrasion and hurt the squid.

         The tip of the squid’s beak is hard, whereas the base of the beak is soft. The composition of the beak –which is made up of chitin, water, and protein –changes in density so gradually from soft to hard that the squid can use its beak without causing any harmful abrasion.

         Professor Frank Zok, at the University of California, says that studying the squid’s beak could revolutionize the way engineers think about attaching materials together in all sorts of applications. One potential application is in the making of prosthetic limbs. Ali Miserez, a researcher at the same University, imagines creating a full prosthesis that mimics the chemistry of the beak, so that it matches the elasticity of cartilage on one side and, on the other side, is made of a material which is very stiff and abrasion resistant.

                         [3]                  THE GLOWIMG BEETLE

            On a quiet evening in rural Brazil, a tiny train emerges from beneath the forest litter. Two red headlights light its path, and 11 pairs of yellow-green lanterns illuminate its sides. To be sure, this is no ordinary train. Rather, it is a 70-millimeter-long larva of the Phengodidae family of beetles, found in North and South America. Because females, which retain their larval form, resemble internally illuminated railway cars, they are often called railroad worms. Brazilian country folk call them little trains.

       During the day the dull-brown larva is hard to spot. But at night it advertises its presence with its amazing array of lights. These are energized by the organic substance luciferin, which, aided by enzyme luciferase, oxidizes to produce cold light. Colors of the light include red, orange, yellow, and green.

       The red headlights glows almost constantly –but the yellow-green lateral lights. Research suggests that the headlights help the larva to find millipedes, its favorite prey, whereas the sidelights seem to discourage predators, such as ants, frogs, and spiders. In effect, the glow says “I am unpalatable. Go away. Accordingly, the sidelamps luminescence when the larva senses a potential predator. They also shine when its attacks millipedes and when the female is curled around her eggs. Under normal circumstances, the sidelights build up to peak intensity and then darken –all within a few seconds –repeating the cycle as often as necessary.    

                            [4]     YOUR SENSE OF TASTE

          Bite into your favorite food, and immediately your sense of taste is activated.  But just how does this amazing process work?

          Your tongue –as well as other parts of your mouth and throat –includes clusters of skin cells called taste buds. Many are located within papillae on the surface of the tongue. A taste bud contains up to a hundred receptor cells, each of which can detect one of four types of taste –sour, salty, sweet, or bitter. Spicy is in a different category altogether. Spices stimulate pain receptors –not taste buds. In any event, taste-receptor cells are connected to sensory nerves that, when stimulated by chemicals in food, instantly transmit signals to the lower brain stem.

      Taste, however, involves more than your mouth. The five million odor receptors in your nose –which allow you to detect some 10,000 unique odors –play a vital role in the tasting process. It has been estimated that about 75 percent of what we call taste is actually the result of what we smell.

     Scientists have developed an electrochemical nose that uses chemicals gas sensors as an artificial olfaction device. Nevertheless, neurophysiologist John Kauer, quoted in Research/Penn State, notes: Any artificial device is going to be extremely simplistic in comparison to the biology, which is wonderfully elegant and sophisticated.

        No one would deny that the sense of taste adds pleasure to a meal. Researchers are still baffled, though, by what causes people to favor one type of taste over another. Science may have many of the basics of the human body down, “says Science Daily, “but our sense of taste and smell are still somewhat of a misery