Category Zoology

Eagles do not flap their wings often, yet fly for long. How?

            Eagles adopt an energy-saving flight mode called gliding. Their broad wings and broad rounded tail enable them to exploit thermals in the air. (Thermals are upward air currents in the atmosphere caused by the absorption of heat, from the sun or land, by the air.)

            The birds flap their wings slowly and laboriously in the air in wide circles, but once they catch the rising air they begin to soar effortlessly without even a single beat up to a point where the warm air has cooled and stopped rising.

            From this point, they start gliding down to another thermal, which they spot by seeing other groups of rising raptors or perhaps by their delicate sensitivity to even minute changes in air currents. Their primary feathers are spread out to obtain the maximum advantage from the rising air. The wing tips are broadly splayed or ‘fingered’ to reduce turbulence in the air surrounding it. They also assist in gaining speed when the bird glides downwards.

            Sea birds such as albatrosses, fulmars, gannets and Manx shearwater also adopt gliding but a slightly altered version. As thermals do not form over the sea, they take a shallow downward glide across the wind then turn into the wind and climb steeply until they resume gliding in their original directions. They thus use relative wind speeds to power both the climb and control the long, downward glide over the sea. These birds can cover thousands of kilometers without expending much energy.

Why do our arms move to and fro when we walk?

To keep our torsos stable and conserve energy, we swing our arms backwards and forwards while walking. When you swing, say, your right leg forward to take a step, you provide a rotational moment about the central vertical axis of your torso. By the principle of conservation of angular momentum, an opposite reactionary moment is felt by your torso. By swinging your right arm backwards and your left arm forwards, you counterbalance this moment. Just try running without swinging your arms at all. Or worse still, try running while swinging your arms in the opposite directions to normal: that is, swing your left arm forward when you swing your left leg forward and so on. You will find that your torso rotates from side to side in an uncomfortable and unnatural manner.

            Of course, legs are heavier than arms, so as to ensure that the moments are the same; evolution has ensured that our arms are further from the central axis of our bodies than our legs are. This allows the moments from our legs and our arms to be roughly equal.

            Going back a few steps (pun intended), Serge Gracovetsky hypothesized in the 1980’s that the spine, rather than the legs, is the primary source of power for gait, and this is now accepted by most, if not all, researchers in this fields.

            Many bilateral amputees, for example, can walk successfully. The mechanism works because the spine is curved. Any attempt to straighten such a structure will result in a twisting action.

            The lumbar muscles acting on the lumbar spine cause such a twist and provide the main impetus for placing one foot in front of the other.

.swinging one’s arms while walking assists in this twisting motion, increase efficiency, and reduces the physiological cost of walking. Indeed, nearly everything that we do naturally when moving is done purely to reduce the amount of energy that is expended in order to achieve the desired result.

            Other two-legged walking animals balance themselves by synchronizing the movement of the backbone to the side of the leg that stays in contact with the ground.

            This keeps their gravitational centre close to the standing leg. It is seen in chickens and, to better effect, in penguins.

Why does our hair change its colour as we age?

     Hairs are the appendages of the skin generated from the epidermal layer. Hair is a made up of Keratin a highly insoluble and mechanically stable fibrous protein. This Keratin is not only found in hairs but also in the skin. Actually Keratin is produced from the Keratinisation zone of the epidermis, which is the outer most layer of the skin. In the skin it provides water proofing quality.

            The Keratin is generally pigmented. It is intensively pigmented in the hair. The dark black colour of the hair is due to the presence of high concentration of melanin pigments in it. The skin colour is also due to the presence of this pigment in the keratinocytes.

            The Keratin gets its melanin pigments from melanocytes, which are found in the inner layer of the epidermis, which is found just beneath the keratinizing layer. The melanocytes have long progresses which extent between and under the cells of the epidermis. The melanin granules formed in the melanocytes pass along their branches and are secreted at their tips. The granules are subsequently engulfed by the keratinocytes, which make up 90 per cent of the epidermal cells.

            Melanin is a protein like polymer of the amino acid tyrocin. In its biosynthesis tyrocin is converted in to dihydroxy phenyl alanine (DHPA) by oxidative enzymes amongst which tyrocin is particularly important. Then a series of reactions take place during which polymerization occurs to form the final melanoprotein.

            The hair grows only from the keratinocytes of the germinal matrix of the hair follicle. This germinal matrix lies in the proximal enlargement of the rot hair, called the hair bulb. The shaft, which projects from the surface, consists of an inner medulla, an intermediate cortex and an outer cuticle. All these parts are made up of cornified cells.

            The medulla is composed of polyhedral cells; the cortex consists of elongated cells with inner lumen. These cells are united to form flattened fusiform fibers. The lumens of these cells contain pigmented granules in dark hair and air space in white hair.

            The development of white hairs because of the absence of melanin pigments, may be due to the absence of one or more enzymes, necessary for the DHPA path way. It will lead to the failure of melanin accumulation in the keratinocytes, found in the hair bulb, from which hair is growing.

            Usually such physiological disorder occurs in the old age, which results in the growing of gray and white hairs in the body.

How do birds navigate home after long journeys?

         

 

 

 

 

 

 

  There are many theories explaining this capability of birds. According to one of them, the Sun’s rays and the direction of winds help them to navigate. Birds’ extra sensory capabilities assist them in this task and direction them with the help of the Earth’s magnetic field.

            Another theory suggests that these winged wonders understand star-maps so well that it helps them to rack their way. But no one answer has been put down for this as of now.

            Birds have the capability to detect changes in atmospheric pressure, weather and earth’s magnetic field. Based on these they locate specific regions and find their home. But the most important navigational aid is said to be “internal magnetic compass” that they are said to posses in their brain. The compass works in relation to the earth’s magnetic field. The magnetic currents generated here are turned into flight paths.

            As a result, disturbances in Earth’s field can seriously affect bird’s judgment. In July, 1998, 3000 homing pigeons that set off for their return journey from northern France to southern England could not reach their destination because an explosion on the surface of the Sun, a few days prior to their journey, had sent radiations that disrupted the Earth’s magnetic field. As a result their internal magnetic compass picked up confusing signals and the birds lost their way.

Do sheep swim? If so, how do they learn?

            Yes, sheep do swim, said Edward Spevak, assistant curator of mammals at the Bronx Zoo. “It’s basically instinctive, a life-saving device,” he said. They don’t go swimming every day, but in case of flooding, or falling into a river, in essence they know how to swim. Sheep have never been known as big swimmers, and mose of the habitat where they evolved does not have a lot of water resources, but swimming is part of their repertoire of skills, he said.  First of all, like many animals, they float, Spevak explained, “Then, in struggling to keep the head above water and to keep breathing, the method they use is basically fast walking, which constitutes a kind of dog paddle,” he said.

            Other large mammals are swimmers, too. Spevak said. Cattle can swim when herded across a river, as Western movie fans know. Deer can swim, as well, “The moose, the largest deer in the world, actually feeds in water and is a very good swimmer.” Spevak said.

It is true that a red flag agitates a bull?

    It is generally believed that anything red makes a bull angry and causes it to attack. Therefore, the bull fighter has to have a bright red cape and use a red cloth.

            The truth is that if the bull fighter had any other coloured cloth he would be able to accomplish the same reaction from the bull. Bulls are colouring blind.

            Many experiments were conducted where they used white cloth and got the bulls to behave in the same way as with the red cloth.

            The reason is the movement of the cap and not colour of the cloth brings about the reaction in the bull. Anything waved in front of a bull would excite it.