Carrying Capacity 3/21/18 Biology Mrs. Harper

March 21, 2018 Begin working on Do Now

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?

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.

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

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

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

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.

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

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 0 1 2 3 4 5 6 7 8 Death, emigration From year 1 to year 3, because population increases About 80 deer Around year 3

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 1860-1865

Video How Wolves Impacted Yellowstone National Park https://www.youtube.com/watch?v=ysa5OBhXz-Q On the back of your notes, answer the questions about the effects that the wolves had on the environment