Final answer:
Population size can be limited by biotic factors such as food availability, predation, and disease, and abiotic factors like water, temperature, space, and minerals. Human activities like habitat destruction and the use of pesticides also play a significant role in limiting population sizes.
Step-by-step explanation:
Factors that could limit the size of a population without intervention can be categorized into biotic and abiotic factors.
Biotic factors are living components that affect the population such as availability of food, predation, disease, and competition for resources. For example, if a population of deer in a forest suffers from a lack of food due to overgrazing, this would limit their growth due to increased competition for the limited food sources.
Abiotic factors include non-living environmental aspects like water, temperature, space, and availability of oxygen and minerals. For instance, a draught significantly reducing water availability can greatly decrease a population's size by creating a hostile environment for survival and reproduction.
Additional limits come from human activities, such as habitat destruction, use of pesticides and herbicides, all of which profoundly impact population sizes by altering the environment in which organisms live.