Temperature

Animals and plants are sensitive to the changes in temperature. Changes in temperature may bring a positive or negative affect on the life of plants and animals. Temperature affects plants and animals in various ways, which are as follows:

A) Effects on Metabolism: All metabolic processes are affected by temperature. Since temperature regulates the activity of enzymes, all chemical reactions in the body of organisms are controlled by temperature. It affects the rates of transportation, photosynthesis in plants and respiration rates and other metabolic processes in plants as well as animals.

B) Effects on Reproduction: Flowering in plants is affected by temperature through thermoperiodism. In animals, the maturation of gonads or sex cells and the liberation of gametes take place at a particular temperature, which varies from species to species. Breeding in some animals remains unaffected by temperature throughout the year, whereas in some animals breading occurs only in summer or in winter.

C) Effect on Growth and Development: Both extremely low and high temperature brings about such cold injuries as desiccation, chilling injury and freezing injury. Extremely high temperature causes stunting and final death of plants, which is due to adverse effects on a number of physiological processes like respiration, transpiration, protein metabolism, etc. This is called heat injury. In animal also temperature affects growth as well as development. For example in the Oyster, the length of the body increase from 1.5 mm to 10.3 mm with an increase in temperature from 10'C to 20'C. Sea Urchin shows maximum size of body in warmer water, etc.

D) Effect on Crossing Over: In animals like Drospohila species, temperature is shown to affect the crossing over and somatic expression of gene characters. Development of wings, eyes, is affected low or high temperature;wings tend to be longer at high and shorter at low temperature.

E) Effects on sex Ratio: In some animals like rotifers and daphnids, sex ratio is affected by temperature. Under normal condition Daphnids give parthenogenetic eggs that develop into females, whereas with increase in temperature, they give sexual eggs which after fertilization develop either into males or females.

F) Effects on Coloration: Some insects, birds and mammals in warm humid climates bear darker pigment than the races of same species present in cool and dry climates.

G) Effect on Morphology: The temperature also affects the absolute size of an animals and the relative proportions of various body parts. Birds and mammals attain greater body size in cold regions than in warm areas. But poikilotherms are smaller in cold region. The tail, snout, ears and legs of mammals are relatively shorter in colder parts than in the warm areas.