Population Dynamics J vs. S shaped growth

Principles of Population Growth What is a population? A healthy or stable population will grow and die at a steady rate unless it runs out of food or space, or is attacked in some way by disease or predators. (it encounters a limiting factor of some type)

Scientists study growth in a variety of ways One way involves introducing an organism into a sterile, nutrient rich environment. This is going to be for smaller organisms such as bacteria Another way is through field studies and radio tagging organisms Larger organisms such as elk

Populations do not follow linear growth increase. Instead they start out slowly but once they build up the rate increases dramatically Population Growth of Houseflies 1 million 500,000 Population size 100 One year

This type of growth is called exponential growth. Exponential growth means that as a population size increases the rate of growth also increases. Exponential growth results in a J-shaped graph curve.

If left unchecked exponential growth would continue forever. In reality we know that it doesn’t. At some point growth stops. This is where limiting factors come into play. They are going to prevent the population from exceeding an imaginary line called a carrying capacity. A carrying capacity is the number of organisms that an environment can support indefinitely, without outside assistance.

When looking at a graph illustrating population growth with a carrying capacity the j-shaped curve becomes an s-shaped curve Characteristics of Population Growth Exponential growth PREDA-TORS DISEASE SPACE FOOD Carrying capacity J curve S curve Population Time

Most species follow a set path of population growth They start of with slow growth Then there is a period of rapid growth as it enters exponential growth Next it reaches its carrying capacity and levels off However there are still some fluctuations in the numbers