Temperature
Animals and plants are sensitive to the changes in
temperature. Changes in temperature may bring a positive or negative effect on
the life of plants and animals. Temperature affects plants and animals in
various ways, which are as follows:
A)
Effects
on Metabolism: All metabolism 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 thermo periodic. 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 has negative effect on the growth of plants.
Low 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 animals also temperature affects growth as well as
development. For example in the Oyster, the length of the body increases 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 Drosophila species temperature is shown to affect the crossing over and
somatic expression of gene characters. Development of wings, eyes etc 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 Daphnis sex ratio is affected by temperature. Under normal
condition Daphnis give parthenogenesis eggs that develop onto females, whereas
with increase in temperature, they give sexual eggs which after fertilization
develop either into males or females.Effect 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 animal 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 parts than in the warm
areas.