4 Effects of Temperature of Ecological Factors

Temperature has manifold effects on the structure, physiological processes, behaviour and distribution of most of the organisms. Some of these effects are as follows:

1. Effect on Metabolism

Temperature has direct effect on the metabolic activity of the organisms. Most of these activities are under the control of enzymes which in turn are influenced by temperature. Initially with the increase in temperature, enzymatic activities also increase; thereby increase the rate of metabolism. For example, the activity of enzyme liver arginase goes on increasing with the increase in temperature from 17°C to 48°C. But any increase in temperature beyond this limit brings about retardation in the activity of the enzymes. Similarly chirping of crickets is higher in warm weather and lower in cool weather.

2. Effect on Reproductive Behaviour

Reproductive behaviour in a large number of animals has been found to be governed by temperature. Some animals breed uniformly throughout the year, some mainly in summer, others exclusively in winter white still others have two breeding periods, one in spring and the other in the fall.

3. Effect on Reproduction

Temperature is a major controlling factor for reproduction in most of the organisms. The maturation of sex cells and the liberation of gametes takes place at a particular temperature in different species. For example, in blow-fly Calliphora sericate the number of “eggs laid increases with increase in temperature up to 32.5°C. With further increase in temperature there is a decrease in the number of eggs laid.

Temperature plays a critical role in egg production and hatching in grasshopper. The optimum temperature for grasshopper, Melanoplus sanguinips, is 39°C. Below this temperature the egg hatching is reduced and at 22°C it is brought down to 20-30 times below the normal rate of egg production. During excessive cold weather the eggs freeze.

At 23°C these can remain dormant up to one month but at a temperature of 29°C, these are unable to survive. The egg laying and hatching is also associated with drought. The grasshopper outbreaks usually with the extended periods of hot dry weather. But the serve drought also reduces the fecundity of females because of reduction in the succulent food.

4. Effect on Sex-ratio

In certain animals such as rotifers and daphnids, the sex-ratio is considerably affected by the temperature. Under normal conditions of temperature daphnids produce parthenogenetic eggs which develop into females. But with the increase in temperature these give rise to sexual eggs which on fertilization may develop into males or females.

But with the increase in temperature these give rise to sexual eggs which on fertilization may develop into males or females. In the plague flea, Xenopsylla cheopis, males outnumbered females on rats on days when the mean temperature was between 21°C and 25°C. But the position is reversed on cooler days.

5. Effect on Growth and Development

Temperature also affects the growth and development considerably at different stages in the life-cycle of an organism. The optimum temperature for the development of trout eggs is 8°C. The adult trout does not grow in water with a temperature of less than 10°C and the maximum growth takes place between 13-19°C. In cold, egg development starts at -19C. It increases regularly up to a temperature of 14°C and above it the egg does not survive. Sea urchin, Echinus esdulentus, attains the maximum size of warmer waters.

Mackerel egg starts developing at 10°C. Form 10°C to 21°C, the rate of development increases and at the upper value, the egg will hatch in just 50 hrs. At 25°C no development takes place. The effect of temperature on the growth of Mackerel eggs can be best understood.

The time required for the development at various temperatures is also an important feature in the species of malaria parasite in their mosquito host.

Bhatia and Kaul (1966) have made elaborate studies on the effect of temperature on the development and opposition of the red cotton bug Dysdarcus koenegii. According to them the lower and upper limits for the development of eggs seems to be between 12.5 and 1°C; and 32.5°C and 35°C respectively. With the rise of temperature from 15 to 32.5°C, the duration of incubation period decreases and the viability of the eggs is lower at the extremes of temperature.

The nymphs have a narrower range of effective temperature than the eggs (0-35°C) and the duration of the life-cycle at 20, 25, 27.5 and 30°C reduces gradually. With the decrease in the temperature from 35°C to 15°C, there is lengthening of the premating and preoviposition periods.