Populations: Crater Lions

Populations: Crater Lions

Let's use a real-life event and actual scientists' data to help us review and understand types of growth and limiting factors!

Ngorongoro Crater, Tanzania

1. This crater in Tanzania, Africa is home to a diverse community including lions, wildebeests, and rhinos! Ecologists study populations, a specific type of animal in a particular place. Ecologists study how populations interact with each other and with the abiotic factors in the ecosystem.

Multiple Choice

2. Which of the following is a population?

• all the zebras in the world

• all the lions in the crater

• all the lions, zebra, and rhinos in the crater

• all the lions, zebra, and rhinos in the world

Multiple Choice

3. Which of the following is an example of an abiotic factor in the environment?

• Amount of zebras to eat

• The hyenas competing with the lions

• The bacteria that can cause disease

• The availability of water for the lions

The Crater Lions

4. In 1962, heavy rains caused a large build-up of blood-sucking flies. These flies drained blood and caused skin sores, which infected lions and made them sick. By the end of the following year, the population of lions had crashed from 75-100 lions to just 12! We are going to explore different population models to learn about the lion population.

Populations Change over Time pt. 1

5.Populations increase when more organisms enter (immigration) than organisms leave it (emigration) or when more organisms are born than die.

Populations decrease when more organisms leave than enter or more organisms die than are born.

Multiple Choice

6. Which of the following describes the movement of animals out of an area?

• emigration

• immigration

• birth rate

• death rate

Populations Change over time pt. 2

7. From 1960-1963, the population of the lions in the crater decreased, Which of the following is most likely to have been true from 1960-1963?

Multiple Choice

8. From 1960-1963, the population of the lions in the crater decreased. Which of the following is most likely to have been true from 1960-1963?

• more lions are immigrating that emigrating

• more lions died every year than were born

• no lions have died

Populations Change over Time pt. 2

9. Since the lions are isolated in the Crater, we can assume that birth and death rates have a greater influence on the population than emigration or immigration.

What would have to be true, on average, from 1952-1956?

Multiple Choice

10. What would have to be true, on average, from 1952-1956?

• birth rate is greater than death rate

• death rate is greater that birth rate

• birth rate and death rate is the same

Using Models

11. We are going to use a growth model to figure out what happened to the lions after 1963. Let's use the growth of bacteria as a simple model.

Bacteria reproduce quickly. Let's say we put a single bacteria in a petri dish. It will reproduce once every hour, giving rise to two new cells.

Can you predict what the growth might look like after 12 hours?

Draw

Can you predict what the bacteria grow will look like from 0-12 hours?

Growing Bacteria

13. Here is the actual graph compared to your prediction.

As you can see, the population starts growing slowly, but then starts to grow faster and faster, Between 4-6 hours, the population went from 16-32, while between 11-12 hours, the population went from 2048-4096. This type of growth is called exponential growth.

Exponential Growth

14. Exponential growth curves are J-shaped. This type of growth occurs only when there is enough food, space, and other resources for every single bacterium.

Exponential Growth

15. In which hour are the bacteria growing the fastest?

Multiple Choice

16. In which hour are the bacteria growing the fastest?

• 0-2

• 4-6

• 10-12

17. The bacteria doubles every hour! The fastest growth is at hour 10-12. AT hour 24, the bacteria population actually reaches over 16 million!!

Exponential Growth & Lions

18. Unlike bacteria, lions do not reproduce every hour, but their population can undergo exponential growth, Here is the lion population from the crater, with the data from 1963-1980 in orange.

Look at the lion population from 1963-1975. Do you think this type of growth will continue to increase?

Open Ended

19. Do you think the Crater lions will continue to experience exponential growth?

Limiting Factors

20. The previous graph showed exponential growth in the crater lions from 1963-1980. However exponential growth is not sustainable for a long time in a population.

Limiting Factors

21. A more realistic population model recognizes the factors that limit population growth. For example, the bacteria in our petri dish would eventually run out of food, preventing them from growing uncontrollably. Therefore, food is a limiting factor.

22. Using the picture to get started, brainstorm a list of at least three limiting factors that might affect the lion population in the crater.

Open Ended

23. What were the three limiting factors you thought of that might affect the lion population in the crater?

Logistic Growth

24. The resources in the crater can support a certain number of lions, just like the petri dish can support a certain number of bacteria. When limiting factors affect population growth, we describe it as logistic growth, or an S-shaped curve. For example, the lions' population growth would be affected if they ran out of zebra to eat or if there was a natural disaster like drought.

Limiting Factors

25. Food is a good example of a limiting factor that can slow down population growth. What do you think will happen to the rate of lions population growth after 1980? Will it grow faster and faster, or will it start to slow down?

Multiple Choice

26. What do you think will happen to the rate of lions population growth after 1980? Will it grow faster and faster, or will it start to slow down?

• It will grow faster and faster

• it will start to slow down

Carrying Capacity

27. The number of individuals an environment can support is called the carrying capacity. Populations grow quickly and then stabilize at carrying capacity.

Limiting factors in the ecosystem determine the carrying capacity of populations. Competition for resources is highest when the population is near carrying capacity.

28. What do you think is the carrying capacity of the bacteria in the petri dish?

Draw

use an arrow or circle to show where you think the carrying capacity of the bacteria is:

Multiple Choice

30. Which of the following is the carrying capacity of the bacteria population?

• about 1000

• about 3000

• about 6000

• about 9000

Lions and Carrying Capacity

31. Here are the two data sets about the lion population.

Where would you draw a line to estimate the average carrying capacity of the environment prior to the disease outbreak?

Multiple Choice

32. Where would you draw a line to estimate the average carrying capacity of the environment prior to the disease outbreak?

Using the data

33.Ecologists continue using population data to help take care of the crater lion population. Here you see a lioness with a collar. This collar helps the ecologists keep track of the lions, and continue learning about them to help protect the lion populations.