J and S CurvesJ and S Curves

J and S CurvesJ and S Curves

• If things were perfect for a population and all the individuals survived and reproduced at the maximum rate, that growth rate is called the biotic potential.

• It is certainly not common for a population to grow at its biotic potential.

• When fish are introduced into a lake where there is plenty of food and space and there are no predators, the fish can reproduce at their biotic potential, but not for a long time.

J and S CurvesJ and S Curves

• The graph of a population growing at its biotic potential, which is called exponential, can be very steep.

• The graph of a population that grows exponentially is called a J-shaped curve.

J and S CurvesJ and S Curves

Carrying Capacity of an Ecosystem

• The area occupied by a population can’t provide unlimited resources such as food and water.

• These factors limit the population growth and many times bring about death rates that equal the birth rates.

• When this happens, the population size reaches a stable balance.

J and S CurvesJ and S Curves

• The graph of a population that grows until it reaches a stable size based on the carrying capacity is called an S-shaped curve.

J and S CurvesJ and S Curves

• A.Begins with a slow rate of growth.

• E. As the number of mates increase, the growth rate speeds up.

• C. When the population reaches a certain level, growth rate slows down and population reaches a steady state.

J and S CurvesJ and S Curves

• At this point, if environmental conditions remain stable, population will continue to exhibit minor fluctuations.