Exponential and Logistic Growth Flashcards
Why don’t population continue to increase exponentially?
- Environments rarely have no environmental resistance
- Population would exceed carrying capacity
What is an established population?
The population tends to fluctuate around equilibrium level. The fluctuations are caused by variations in the birth rate and death rate as a result of population density exceeding or falling below carrying capacity.
Logistic (s) curve
As a population grows, the rate of a population increase slows, reaching an equilibrium level around the carrying capacity.
What is happening when population growth slows down?
The population encounters resistance to exponential growth as it begins to fill up the environment. This is called environmental resistance.
What is happening when the population exceeds carrying capacity?
Environmental resistance increases as the population overshoots carrying capacity (has trouble with resources).
What is carrying capacity?
The population that can be supported by the environment.
What is a colonising population?
- Grows exponentially
What is the lag phase?
When the population is fairly low.
What is happening at the flat part of the (j) curve?
The number being added to the population per unit time is small.
Exponential (J) curve
Exponential growth is sustained only when there is no environmental resistance (No shortage of food/water/ habitat).
- Nothing slowing it down
What is happening at the steep part of the (j) curve?
The number being added to the population per unit time is large.
Why would a newly introduced consumer (rabbit) exhibit a period of exponential or near exponential growth when invading a new area?
When they are first introduced there is little environmental resistance (lots of food and water)
- Unexploited niche
- Under carrying capacity
Describe a likely outcome for rabbit population after initial rapid increase has slowed?
- Will fluctuate and reach equilibrium around carrying capacity.
- Density dependent factors will increase
What would happening to competing native species in a habitat if the rabbits invaded the area?
- There would be a loss in habitat and food supply and an increase of environmental resistance.
- The population may reach carrying capacity.
- The native specifies population would decrease significantly.
