The wings of butterflies and moths are covered with small scales. These tiny scales produce the magnificent colours and patterns by optical interference of light. The tiny scales reflect and disperse light producing brilliant colours. When we touch the wings, these tiny scales come out in the form of powder, thereby leaving the surface of the wings colourless.
The direction in which roots and shoots move after germination of a seed is guided by two opposing properties. On germination, the roots emerge first. They are guided downwards by the action of hormones which sense gravity. This property is called geotropism. The shoots, on the other hand, are guided upwards by hormones that sense light. This property is called phototropism. Together these two properties ensure that the roots and shoot grow the right way irrespective of the position of the germinating seed in the soil.
Most birds produce sounds in their throats using a voice organ called the syrinx. But not all birds’ calls can be described as ‘songs’. Males of only about 5000 species of birds are known to produce organized patterns of sounds that can be called melodious and described as songs. Male birds sing to attract females and to warn off other males. Although no two individuals sing alike, the song of each species is distinct. Most birds usually sing in the morning or evening and are quiet at midday. During winter most birds don’t sing, but they burst out into myriads of melodies with the onset of the spring, the time for courtship and breeding.
In animals belonging to the cat family and other nocturnal animals the back of the eye ball – the retina, has a layer called “tapetum lucidum”. This layer is made of special cells which reflect light falling on the retina. It is this layer which makes the eyes of these animals glow in the dark. The tapetum layer also helps the animals in gathering all the available light to see in near darkness
The camel’s hump is filled largely with fat, accumulated at times when food and water are available. This fat is digested to meet the energy needs of the animal. Camels can go for a week or more without water and for 10 days without food. During such periods the accumulated fat is used up. The hydrogen released as a by-product by the breakdown of fat combines with the oxygen the camel breathes in to produce water. By utilizing this metabolic water the camel can keep going for many days. In this process, it may lose up to 100 kg of body weight. But as soon as it arrives at an oasis, it is capable of rapidly drinking some 120 litres of water.
Most of the birds that we see around us are perching birds. They have four toes on each foot, three of which point to the front and one point backwards. This enables the birds to perch on leaf stems, telephone wires and even thick branches. The tendons in the feet of perching birds make the toes flexible and allow the birds to bend their toes to grasp the perch tightly. If any movement disturbs the balance of the birds, even while sleeping, their feet automatically tighten their grip on the perch thus preventing the bird from falling off.
The buzzing sound made by the bees is due to the rapid beating of their wings. The rapid beating of the wings creates ripples in the air which produces the sound. All insects fly by beating their wings. But some insects, like the butterfly whose wings beat slowly- 6 to 10 times every second do not produce a buzzing sound. Other insects such as the mosquitoes with very small wings produce very little sound which can be heard only when it is close to our ears. However, the wings of bees are large and they beat very fast – 300 to 40 times every second. This produces the buzzing sound that is clearly audible.
Snakes are unable to sniff the air through their noses quickly enough to follow the scent of their prey. To do that, they depend on a special organ called Jacobson’s organ located deep inside the upper surface of mouth, which detects odours. By flicking the forked tongue in and out rapidly, the snake picks up odours and puts it on to the Jacobson’s organ. The amount of odour picked up by each tip of the forked tongue also provides information about the direction of the prey.
Bats are flying mammals. However, unlike birds which can fly and walk as well, bats have lost the ability to stand on their feet or walk. Evolution has modified their forelimbs to support them in air. At rest, the easiest posture for them to adopt is the ‘head down’ posture. They hang on to branches by means of special claws at the end of their limbs.
In many parts of the world which experience extreme winter, food and water become scarce during winter. Besides the days also become very short. Most birds would starve if they remained in such places during winter. So they migrate to warmer and moister parts of the globe. Most of them breed during the period as they plenty of food around. With the onset of warmer weather in their original habitat, they return with their offspring.
For any living being to get electrocuted, a current of sufficient voltage has to pass through its body, i.e. there should be completion of the electric circuit. Birds perching on live electric transmission lines are not killed because they are in contact with only on wire and no current passes through them. But if the bird sitting on a live-wire simultaneously comes in contact with the ground or touches another live-wire, the electric circuit would be complete and the bird will be killed by the current flowing through it. Similarly a person hanging on to a single live-wire will not be electrocuted unless he touches the ground or the earth wire.
When someone asks you if you want something, you will usually shake your head up and down if you mean ‘yes’ or from side to side if you mean 'no'. In most places, an up and down movement of the head signifies agreement, and side to side movement means disagreement. But did you know that in some places like Bulgaria, parts of Greece, Yugoslavia, Turkey, Iran, and Bengal, people shake their head from side to side to say ‘yes’ or to show agreement
The breaking-off of the lizard’s tail is a defense mechanism which helps the lizard to run away unharmed from the attacker. There is a pre-set crack in the lizard’s backbone, from where the tail comes off. The broken part continues to turn and twist for a while thus detracting the attacker’s attention. The movement lasts till the energy stored in the tail muscles gets exhausted.
Dreams are a normal part of sleep. In fact, several cycles of dream occur during a single night’s sleep. Dreams can come at any time during sleep, but the stage of sleep known as rapid eye movement (REM) sleep produces most dreams. If one is awakened during REM sleep the dream can usually be vividly recalled.
As yet there is no definite theory to explain why we dream. According to one theory, dreams are an extension of daytime consciousness. It is a process in which ideas, feelings and mental impressions absorbed from a variety of sources during our waking hours are sorted out. According to Sigmund Freud, some dreams are a form of wish fulfillment, closely related to the deep emotional reactions of infancy. They reveal a person’s repressed feelings and thoughts, often in a disguised form.
Sleep is a normal activity of higher organisms. Every human being, on average, spends a third of his or her life sleeping. Babies and children spend more time sleeping than adults while old people sleep less. The sleep-wake cycle is controlled by an internal biological clock which usually coincides with the day-night cycle. We do not know yet what sleep does to our body except that we feel refreshed after a good night’s sleep. But what lack of sleep does to an individual is quite well known. Prolonged lack of sleep leads to irritability, lack of concentration and even hallucinations. Thus sleep certainly has a restorative function which helps the body to face another active day.