Population Growth (Population growth rate of Pakistan)
The simplest case of population growth is that which occurs when there are no limitations on growth within the environment. In such situations two things occur.
1. The population displays its intrinsic rate of increase
2. The population experiences exponential growth
Intrinsic rate of population
The intrinsic rate of population increase is the rate of growth of a population when that population is growing under ideal conditions and without limits, i.e., as fast as it possibly can.
A population with a higher intrinsic rate of increase will grow faster than one with a lower rate of increase. The value of rmax for a population is influenced by life history features, such as age at the beginning of reproduction, the number of young produced, and how well the young survive.
Exponential growth
Exponential growth simply means that a population’s size at a given time is equal to the population’s size at an earlier time, times some greater-than one number.
For example, if a population increased in size per unit time in the following manner: 1, 2, 4, 8, 16, 32, 64, 128, etc. (or, e.g., 1, 3, 9, 27, or 1, 5, 25, 125, etc.) then the population is displaying exponential growth, each unit time the population is increasing by a factor of 2 (or 3 or 5 in the other examples; note that exponential growth is occurring so long as the rate of increase per unit time is greater than a factor of 1, e.g., 2 or 4 or 10 or 1.2 etc.)
Limits on population growth
Exponential growth cannot go on forever; sooner or later any population will run into limits in their environment.
Carrying capacity (K) in Population Growth
Populations subsist on a finite amount of available resources, and as the population becomes more crowded, each individual has access to an increasingly smaller share. Ultimately, there is a limit to the number of individuals that can occupy a habitat.
Property of Environment
Ecologists define carrying capacity as the maximum stable population size that particular environment can support over a relatively long period of time. Carrying capacity, symbolized as K, is a property of the environment, and it varies over space and time with the abundance of limiting resources.
Population Size
Generally, as population size approaches carrying capacity, the amount of some key resource declines per capita to the point where individuals experience either a higher death rate or a lower fecundity; thus, as population size approaches carrying capacity, the rate of population growth declines towards zero.
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