Question

How is population size regulated by biotic and abiotic factors?

Answer 1

Hint: Population size is the number of people in a population. It is very easy to conclude by looking at a population size whether species will survive or there is any chance of extinction. To maintain a stable population biotic and abiotic factors are important which are also called limiting factors.

Complete answer:
Abiotic factors-
• The chemical and physical entities constitute the abiotic factors.
• The abiotic factors include: sunlight, air, water, oxygen availability, pH, temperature, salinity, inorganic nutrients etc.
• There is always a lower limit as well as upper limit within which species or population survives effectively, below or above this range there is a lesser chance of survival of species.
• If a species can survive above the upper limit they have widespread existence and have broad range whereas species which exist within or below a lower limit are narrow ranged.
• For e.g. there is an optimum temperature range for survival ,some survives in colder climates and some in higher temperature but if the temperature changes in both conditions the chances of survival decreases.

Biotic factors-
• Interspecific competition - competition between different species for food. The species which out-compete the other survives better.
• Intraspecific competition - it is competition between members of the same species for the same resource. It aids in maintaining proper population size. If population size increases species compete more and population decreases/stabilizes. If population size decreases then competition also decreases and population increases and regains optimum size.
• Parasitism disease- the symbiosis between pathogen and host or parasite and host is a cyclic phenomenon, wherein if the population of one decreases the size of other increases. For e.g. if the population of parasites increases it will kill more hosts and when host population decreases even parasites die of starvation and by the time host population recovers and gradually again parasites feed on it and increases in population.
•Predation – this is also the same as takes place in parasitism, the only difference is there is a relation between prey and predator here.

Note: Biotic and abiotic factors limit the population size meaning, they keep the size at an optimum level. Sometimes abiotic factors fluctuate from one species to another.
For e.g. abiotic factors in the aquatic ecosystem involve salt concentration, oxygen concentration and sunlight.
Plants are affected by sunlight, temperature and soil. That is how the biotic and abiotic factors keep population level at an optimum range.