How do Igloos keep occupants warm?
Seeds sprout when favourable temperature (15.38°C), enough oxygen and moisture are available. They absorb large amounts of water and swell. The moisture content of cells rises from 10 per cent to 90 per cent or more. The plant growth hormone, indole acetic acid which controls and promotes various stages of growth, sets into action the various life processes. Cells at the growing tips of the embryo within the seed divide rapidly and the primary root emerges through the soft seed coat. Further changes follow leading to emergence of the shoot Soil is not always necessary for the sprouting of seeds. Seeds will sprout in moist sand; saw dust, peat mosses, cloth or even paper if favourable conditions are available.
Other nocturnal animals like owl and loris have very large pupils which allow more light to enter the eyes. In addition, the retinas of these animals have a layer called ‘tapetum lucidum’. This reflects inwards the light falling on retina and thus helps in gathering all the light available in dark surroundings.
The feet of lizards are adapted for walking on rough as well as smooth surfaces. The lizards have slits on their toes and these functions like suction disks helping them to cling to smooth areas such as a glass pane.
The claws present on toes help the lizard to hold on to and walk on a rough surface. In this way a lizard can even walk upside down across a plastered ceiling or on a glass roof without trouble.
Bats navigate by making use of sounds that they emit. The way these sounds bounce off from nearby objects and obstacles and return to the bats’ ears enables it to gauge distances and avoid obstacles. Being in the range of 100,000 Hertz, these sounds are inaudible to human ears which can hear only upto 20,000 Hertz. Bats can discriminate between faint echoes of their own sound in the presence of other sounds.
Interestingly, large bats such as the flying fox do not use sound for navigating but rely on vision instead. They fly and feed by day and become disoriented if forced to fly in the dark.
The quick-change ability of the chameleon is due to the pigment containing cells located just under the skin surface. When the pigments in the cells are concentrated at the centre, the skin is light in colour. When the pigments disperse throughout the cells, the skin colour darkens. This ability to change colour possibly helps the chameleon to regulate body temperature as well as to camouflage themselves as a protective measure.
Dogs can ‘read’ these individual odour signatures and distinguish between different individuals and follow the scent-trail for long distances even in the absence of other clues.
Breeds such as the Blood hound, German shepherd and Beagle are famous for their tracking skills.
Many methods, not all fail-safe seem to be used by the animals in identifying their young. Some animals lick their babies at birth, anointing them with a chemical tag they can identify. Others rely on voice identification with the chicks learning to respond to parental calls. Still others rely on visual identification, with the babies responding to the first large moving object (usually the mother) they see and following it everywhere.
Many animals, especially the social ones, do not discriminate between babies in the herd.