Biotic potential is the ability of each species to produce offspring;
it is directly dependent on the number of individuals, especially females,
of reproductive age.
Characteristics of a population include natality, mortality, sex ratio,
age distribution, growth rate, density, and spatial distribution.
Populations have an inherent tendency to increase in size. Population
growth is determined by the combined effects of birthrate and death rate.
Other factors include emigration, immigration, sex ratio, and age distribution.
A death phase occurs when there is a decline in population size.
This occurs as the result of disease, increased predation, low food
supply, toxins entering the ecosystem, or any other limiting factor.
Four factors determining carrying capacity are availability of raw
materials, availability of energy, accumulation of waste products, and interactions
among organisms.
Birthrate is defined as the number of individuals born into a population,
whereas population growth is the result of birthrate and immigration minus
death rate and emigration, or the total net increase in the population size.
Population growth of bacteria growing in a petri dish begins with
a lag phase, continues through an exponential growth, and then levels off
due to an accumulation of toxic waste. Human population growth has a long
lag phase followed by a sharply rising exponential growth phase that is still
rapidly increasing.
K-strategists are typically large, long-lived organisms that reach
a stable carrying capacity. R-strategists are generally small, short-lived
organisms that reproduce very quickly.
As the human population increases it expands its domain and displaces
other species from their habitat. Eventually, habitat becomes less available
and the organisms become more rare. In order to feed the increased human
population, there is over-harvesting of many species which leads to decreases
and possibly extinction of the food species.
Overproduction is advantageous to ensure population density,
dispersal, and colonization of a habitat. The disadvantage is high mortality
due to environmental resistance factors. In the case of human overproduction,
the physical environment and food animals can be over utilized.
