Reproductive capacity

The number of offspring produced differs between organisms according to the conditions around them, hardships, mode of life, life span and size:

• Aquatic organisms produce far more offspring than their land relatives (eggs and larvae are exposed to predators, current and external fertilisation). A cod lays millions of eggs; a land mammal produces few young.
• Parasites produce many more offspring than free-living organisms, to compensate for the great loss of young that never reach a suitable host (e.g. Ascaris and tapeworms produce hundreds of thousands of eggs).
• Primitive and short-lived organisms produce more offspring than higher and long-lived ones, because the young of higher animals are less in danger due to parental care and protection (birds, mammals).
• Small organisms usually reproduce in greater numbers than large ones.