What are the three processes that affect population size
Answers
The Bureau of Land Management (BLM) asked the committee to address the following questions as part of the discussion of potential rates of horse and burro population growth: Would free-ranging horse and burro populations self-limit if they were not controlled? If so, what indicators (such as rangeland condition, animal condition, and health) would be present at the point of self-limitation? To address those questions, it is necessary to review the factors that limit population growth in an unmanaged population1 and that determine free-ranging horse and burro population growth and dynamics aside from management removals. Population growth and self-limitation are population processes in the sense that they involve a suite of underlying functions that lead to the result. The underlying functions include changes in natality and survival in response to environmental variables that affect forage availability, such as weather and population density.
The committee was also asked to assess whether there is compensatory reproduction as a result of population-size control, such as fertility control or removal from Herd Management Areas (HMAs). Compensatory reproduction is defined as an increase in reproduction as a direct or indirect consequence of management reductions, including removals and contraception. Indirect responses could include increased fertility, foal survival, or adult survival due to reduced competition for forage.
For self-limitation to occur, it is necessary for population processes to respond to population density (Figure 3-1). That is, population processes—such as population growth rates, age-specific survival rates, natality, and age of bearing first offspring (primiparity)—must be density-dependent. As density increases, population growth rate decreases because of increased competition for resources. Population processes are also altered by density-independent factors, particularly climatic conditions and variations. Natality and mortality can be affected by climatic conditions through direct effects on animals. Climatic conditions also affect resource abundance, for example, through effects on forage production.
Answer:
the size of the human population is cause of concern because an expanding population make it difficult to improve the standard of living the rate of birth and death in a given population determine its size the population size increase if the birth rate is higher than the death rate and vice versa