Carrying Capacity  Catalyst  Humans cut down 2.4 acres of rainforest (about the size of two football fields) EVERY SECOND. We estimate that 137 species go extinct every day as a result. How does deforestation affect biodiversity? Are rainforest ecosystems more or less stable due to deforestation?  There are two forests, “A” and “B.” The same disease spreads through both forests, but Forest A changes more than Forest B. What does this tell us about biodiversity of Forest A compared to Forest B?

Objectives By the end of today, all SWBAT…  Ace the quiz!  Predict if population size will grow or decay based upon limiting factors and carrying capacity

Agenda  Yesterday’s exit question review  Catalyst review  Quiz  How many in a population?  Analyzing graphs  Carrying capacity game  Closing  Exit Question

Yesterday’s Exit Question Read the passage at right to answer the questions below:  How does trawling affect coral reef biodiversity?  Would the coral reef be more or less stable after trawling? Explain why, and be SPECIFIC.  (Hint: describe what happens to all the organisms in the coral reef ecosystem, and use the word “biodiversity.”) Read the passage at right to answer the questions below:  How does trawling affect coral reef biodiversity?  Would the coral reef be more or less stable after trawling? Explain why, and be SPECIFIC.  (Hint: describe what happens to all the organisms in the coral reef ecosystem, and use the word “biodiversity.”) Many organisms live in coral reefs, such as plankton and algae, hundreds of species of fish, sea urchins, and eels. All of these organisms depend on the coral to survive: they live inside of it, use it for shelter, eat it, etc. Trawling is the process of dragging a gigantic rake across the bottom of the ocean floor to scoop up organisms. This is a very good way to catch fish, but has the unfortunate side effect of destroying nearly all the coral in the trawler’s path. Many organisms live in coral reefs, such as plankton and algae, hundreds of species of fish, sea urchins, and eels. All of these organisms depend on the coral to survive: they live inside of it, use it for shelter, eat it, etc. Trawling is the process of dragging a gigantic rake across the bottom of the ocean floor to scoop up organisms. This is a very good way to catch fish, but has the unfortunate side effect of destroying nearly all the coral in the trawler’s path.

Catalyst Review  Humans cut down 2.4 acres of rainforest (about the size of two football fields) EVERY SECOND. We estimate that 137 species go extinct every day as a result.  How does deforestation affect biodiversity?  Are rainforest ecosystems more or less stable due to deforestation?

Catalyst Review  There are two forests, “A” and “B.” The same disease spreads through both forests, but Forest A changes more than Forest B. What does this tell us about biodiversity of Forest A compared to Forest B?

Quiz!  Put away your binders…  Turn your desks into rows… And let’s ace that quiz! You have 15 minutes

How Many?  We’ve been talking about populations of organisms increasing or decreasing in size…  When new predators come  When organisms leave the food web  But what controls how many organisms exist in a population in the first place?

What determines population?  Why can’t we have…1,000,000 students here at L.W. Higgins?  Space  Teachers  Supplies  Student Behavior These resources are our limiting factors

 Key Point #1: An environment can only support as many organisms as there is available food, water, and free space  Carrying capacity = maximum number of organisms that can live somewhere, based on the food, water, and free space there  Every species has a different carrying capacity. Food, water, and free space are the LIMITING FACTORS that determine carrying capacity Carrying Capacity

Your fridge is like all of the resources (food, water, free space) in an ecosystem. What if we want to throw a party? Imagine Your Fridge

We can keep inviting people, as long as there’s enough food in the fridge. But with each new guest, there’s less to go around. Imagine Your Fridge

The fridge won’t replenish magically, and I don’t have the money to keep putting food in the fridge forever. So too many guests means that… So too many animals means that… Someone goes hungry… Not enough food/water/free space… And leaves the party.  And organisms die.  Imagine Your Fridge

Carrying Capacity  Key Point #2: We can read a carrying capacity graph to predict changes in population size Time Population size A B C D

Carrying Capacity  When a population is BELOW its carrying capacity, it will INCREASE EXPONENTIALLY in size Time Population size A B C D

Carrying Capacity  But if it increases too much and rises ABOVE its carrying capacity, it will DECREASE in size Time Population size A B C D

Carrying Capacity  This happens over and over… but the increases and decreases get smaller and smaller… Time Population size A B C D

Carrying Capacity  Until eventually, the population size BECOMES STABLE AT THE CARRYING CAPACITY Time Population size A B C D

Carrying Capacity Time Population size A B C D

Closing  An environment can only support as many organisms as there is available food, water, and free space  Carrying capacity = maximum number of organisms that can live somewhere based on these limiting factors  We can read a carrying capacity graph to predict changes in population size  Below carrying capacity = exponential growth  Above carrying capacity = decease  Over time, population stabilizes at carrying capacity

Time Population size A B C D Exit Questions  In the highlighted section of the graph, the population is about to decline. Why? BE SPECIFIC!