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 GKHS? Space Teachers Supplies Student Behavior These resources are our limiting factors Limiting factors limit the number of organisms that can live somewhere

Let’s graph!!!!! I am going to give you a scenario and you have to graph it as we go along… do this at the top of your “Carrying Capacity Notes”

Black and Yellow Wiz Khalifa wants to have a party for the release of his new CD. He rents out the coolest club in all of Pittsburgh. He wants to have the BEST PARTY EVER so he orders enough food and drinks for 400 people. The club can fit 400 people. Step 1: Label the x-axis “Time” and label the y-axis “Number of People”

Black and Yellow Between 10 and 10:30 pm 100 people show up to the party. Wiz is disappointed because he has ordered enough food and drinks for 400 people and the club can fit 400 people. Step 2: Graph the information you were just given (between 10 and 10:30 the party goes from having 0 people to 100 people)

Black and yellow By midnight (12am), the party has really picked up. There are now 500 people there. People say that the party is crowded and hot and they are annoyed because the caterers aren’t serving a lot of food because they say they are running low. Step 3: Graph the new information you have been given (between 10:30pm and 12 am the party has gone from 100 people to 500 people)

Black and Yellow At 1 am the party is down to 200 people so these people start to text their friends to let them know there is a ton of open space at this AWESOME party for Wiz. Step 4: Graph the new information (between 12am and 1am the party has gone from 500 people to 200 people)

Obviously all of these people want to come party with Wiz and by 1:30 am, 450 people are at the party. Step 5: Graph the information you have been given- between 1am and 1:30am the party goes from 200-450 people

The bouncers have had to start turning people away at the door because it is a fire hazard to have that many people in this space that only fits 400 people.

By 2 am, the bouncers have turned away all of the extra people and there are 400 left. Step 6: Graph the new information. Between 1:30am and 2am the party has gone from 450 people to 400 people

The party keeps rocking with 400 people till 5am- everyone had the perfect amount to eat and drink and plenty of space to dance while Wiz performs!!!!!! Graph the new information- from 2am-5am the party remains at a constant 400 people

Uhhhh…. What does this all mean? Why 400 people? What happened when there were more than 400 people? What happened when there were less than 400 people? What happened eventually around 2am?

Carrying Capacity Limiting factors: Food Water Space Predators Key Point #1: The size of every population has certain limiting factors that keep it from growing and growing and growing Limiting factors: Food Water Space Predators

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. 

Carrying Capacity Every species has a different carrying capacity. Key Point #2: The maximum number of organisms that can live somewhere based on the limiting factors is called a population’s carrying capacity Every species has a different carrying capacity.

Carrying Capacity Key Point #3: 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

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

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… but the increases and decreases get smaller and smaller…

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. Until eventually, the population size BECOMES STABLE AT THE CARRYING CAPACITY

Carrying Capacity and population size -If a population is increasing, this means birth rates are higher than death rates -If a population is decreasing that means death rates are higher than birth rates -If a population size remains constant that means birth rates=death rates 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.

THE MAIN POINT… Above carrying capacity  population will decrease (death rate is higher than birth rate) Below carrying capacity  population will increase (birth rate is higher than death rate) Levels off at the carrying capacity  population remains stable (birth rate=death rate)

Quick Class Practice In what three years does population size most exceed carrying capacity? Why does the population decrease after 1850? Why does population size rise again after each big drop? What is this population’s carrying capacity?

Now do a few problems on your own

Now… Biodiversity!!!!

Biodiversity is… Biodiversity is a measure of how many different species live in an ecosystem.

Low Biodiversity

High Biodiversity

Low or High Biodiversity? Series of checks for understanding. Can students identify situations of low vs. high biodiversity? Low or High Biodiversity?

Low or High Biodiversity? Series of checks for understanding. Can students identify situations of low vs. high biodiversity? Low or High Biodiversity?

Lion lion lion Tiger lion lion Hippo hippo hippo Grass lion lion Lion lion lion

Low or High Biodiversity? Series of checks for understanding. Can students identify situations of low vs. high biodiversity? Low or High Biodiversity?

Low or High Biodiversity? Series of checks for understanding. Can students identify situations of low vs. high biodiversity? Low or High Biodiversity?

Low or High Biodiversity? Series of checks for understanding. Can students identify situations of low vs. high biodiversity? Low or High Biodiversity?

Ecosystem stability… What that is!? Stable = things stay the same Key Point #B1: An ecosystem is stable if it does not change easily when disturbed When an ecosystem is resistant to change, it is stable When an ecosystem can be easily changed, it is unstable In this class, we will measure “change” by the number of species that live somewhere Change causes lots of species to die  ecosystem is unstable Change does not cause number of species to change  ecosystem is stable

This food web has low biodiversity Rabbits eat grass. Foxes eat rabbits Foxes Rabbit Grass

This food web has low biodiversity A disturbance hits… A drought happens and kills all the grass. Foxes Rabbit Grass

This food web has low biodiversity What happens to the foxes? Foxes How many species do we have left? 0! Rabbit BIG change? Grass

Biodiversity and stability The food web started with low biodiversity Low biodiversity = unstable ecosystem What this means: just one change can have a HUGE effect on all the species!

This food web has high biodiversity Let’s add a few more species to our original ecosystem Foxes Carrots Rabbit Chickens Grass

This food web has high biodiversity A disturbance hits… A drought happens and kills all the grass. Foxes Carrots Rabbit Chickens Grass

This food web has high biodiversity The food web started with high biodiversity High biodiversity = stable ecosystem What this means: One change… didn’t really do anything! What happens to the foxes? Population size decreases… a little Foxes carrots Rabbit BIG change? Chickens Grass

Comparing Multiple Ecosystems Key Point #B2: We can figure out which of two ecosystems has higher biodiversity based on how stable each one is

The main point: Ecosystems with high biodiversity change less than ecosystems with low biodiversity after a disturbance. If ecosystem “A” changes less than ecosystem “B” in response to the same disturbance, “A” must have higher biodiversity than “B.”

Quick Class Practice In a forest ecosystem, wolves eat rabbits. Rabbits eat grass. High or low bio-d? WHY? A brushfire hits! All the grass is wiped out! What is going to happen to all of the rabbits? What is going to happen to all of the wolves? 3. Is this a stable or unstable ecosystem? WHY?

Do Level 1 by yourself!!!

LEVEL 2 Ecosystem 1 There are many animals that live in the grassland ecosystem. Grass and small shrubs are the producers in this biome. Rabbits, squirrels and mice and are the primary consumers. Rabbits and mice and eat only small shrubs from the grassland. The squirrels eat both grass and small shrubs. Foxes eat the rabbits and mice.

Ecosystem 2 Tropical rainforests are the most diverse biome in the world and there are many connections in between species. There are many producers that live in the rainforest, including orchids(flowers), banana trees, the coconut tree and bamboo. The primary consumers are the macaw (bird), fruit bats, monkeys and insects. The macaw and the fruit bats eat orchids and banana trees. The monkeys and insects eat bamboo, banana trees and coconut trees. Pythons and jaguars are secondary consumers. Pythons eat macaws and fruit bats. Jaguars eat macaws, monkeys and insects.

1. How many species are in the grassland ecosystem BEFORE the brush fire? 2. How many species are in the grassland ecosystem AFTER the brush fire? 3. How many species were lost in the grassland ecosystem because of the brush fire? 4. How many species are in the rainforest ecosystem BEFORE the disease? 5. How many species are in the rainforest ecosystem AFTER the disease?

6. How many species were lost in the rainforest ecosystem because the disease hit? 7. Which ecosystem started with the largest biodiversity? 8. Which ecosystem ended with the largest biodiversity? 9. Which ecosystem is more stable?

End of Class In your folders: Homework: Worksheet Gradesheet Stations Packet Exit Slip Homework: Worksheet