1. Carrying Capacity
3/21/18
Biology
Mrs. Harper

2. March 21, 2018
Begin working on Do Now

3. Do Now 3/21/18 1. Under what conditions do we see exponential growth?
2. What are some limiting factors found in a population?
3. What is a density-dependent limiting factor and give an example?
4. What is a density-independent limiting factor and give an example?
5. Is there more competition in a large or small population?
6. Is parasitism a density-independent or density-dependent factor? Why?
7. Is a hurricane a density-independent or density-dependent factor? Why?

4. Carrying Capacity
An environment can only support as many organisms as there is available resources
Carrying capacity = maximum number of organisms that an environment can support over a long period of time
Every species has a different carrying capacity.
Limiting factors determine carrying capacity.

5. Graph Analysis
We can read a carrying capacity graph to predict changes in population size
Time
Population size
Graph line = Population size at a specific time
Dotted line = Carrying Capacity
A = x-axis = time
C = y-axis = population size
B = graph shows population size at any given time
D = carrying capacity

6. Carrying Capacity
Time
Population size
Remember from math class, exponential increase = constantly doubling. (Makes a curved line on a graph.)
Analogy: each person at the party invites a new friend. Each one of them invites another new friend. Etc.
When a population is BELOW its carrying capacity, it will INCREASE in size
Birth rate exceeds death rates

7. Carrying Capacity
Time
Population size
Analogy: We run out of food at the party, and people start to leave.
Remember over the last few days, when one population in a food web died, so another population that ate it decreased in size? That’s because the carrying capacity decreased!
But if it increases too much and rises ABOVE its carrying capacity, it will DECREASE in size
Death rate exceeds birth rate

8. Carrying Capacity
Time
Population size
Analogy: Once there’s enough food again, more people will come. But we’ll probably be a bit more cautious, and not invite people as quickly. So if we go over carrying capacity, it won’t be by as much.
This happens over and over… until the graph flattens out where it has reached carrying capacity.

9. Carrying Capacity
Time
Population size
Remember from yesterday: stable = does not change
This is the concept that my students last year had the most trouble with. Really harp on this.
Eventually, the population size BECOMES STABLE at carrying capacity.
Birth rate = death rate

10. At which point does birth rate exceed death rate the most?
EXAMPLE 1
What are three
factors that limit
deer population
size?
Why does
population size
decrease in the graph?
At which point does birth rate exceed death rate the most?
What is the carrying capacity of deer on WallaWalla Island?
At which point do deer exceed their carrying capacity?
Food, water, competition
Death, emigration
From year 1 to year 3, because population increases
About 80 deer
Around year 3

11. In what three years does population size
EXAMPLE 2
In what three years does population size
most exceed carrying capacity?
What is the carrying capacity of this population?
Identify a year in which death rate exceeds birth rate.
1850, 1875, 1910
About 1.5 mil
When below capacity like

12. Video How Wolves Impacted Yellowstone National Park
On the back of your notes, answer the questions about the effects that the wolves had on the environment