By prodigality of nature it is meant that organisms have an enormous potential to reproduce. A carp or salmon is known to lay over a million eggs. A frog may lay Bs many as 12,000 eggs. If all the eggs survive and reproduce, then within a short time the entire earth would be strewn with frogs. Darwin himself worked out the reprodilcti-We rates of elephants which are known as slowest breeders of all known animals.Assuming an elephant during its 100 years of existence gives bjrth to six calves in sixty years of its active reproductive life, in around 750 years there should be at least 19 million elephants living in the world. Several such examples could be quoted to highlight the fact that organisms have an immense potential for reproduction.How is it that in spite of an enormous potential to reproduce, the numbers of most of the species are always maintained at optimal levels? How is it that lakes are not choked with fishes, or fields not strewn with frogs or the earth not crowded with elephants? This is because that various limiting factors in the environment, both biotic and abiotic, keep a check on the increase in numbers.