How Many Penguins Does It Take?
Studying carrying capacity and limiting factors
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Author Contact Information
This activity was adapted from a Project Wild K-12 activity called, “How Many Bears Can Live in This Forest?”
The adaptation, explanations, penguin diet calculations, and resources were done by Elissa Elliott.
The students will parcticipate in a hands-on activity, simulating the process of population fluctuation. They will learn the terms limiting factors and carrying capacity. Rather than memorize the terms limiting factors and carrying capacity, the students can “see” the terms come to life in this animated penguin activity. The results clearly show how populations are affected by many things--one of them being food availability. This parcticular activity focuses on a penguin population; however, serious debates regarding the human population have been going on for some time. What is the carrying capacity of the earth?
*Students will predict what the carrying capacity of a penguin population of a certain area will be.
*Students will engage in a hands-on activity, simulating the way carrying capacity works.
*Students will explain what the terms carrying capacity and limiting factors mean for a population
Upper elementary and middle school, but may be adapted to high school level
Populations and Ecosystems, Content Standard C
Populations, Resources, and Environments, Content Standard F
1) For a classroom of 30, you will need the following 3” x 3” colored cards:
190 yellow cards marked F-1
40 red cards marked K-.10
60 green cards marked S-.10
2) You will need a large area to do this activity--a gym or a plot of grass or parking lot outside. The students can
run and cover more territory this way.
3) This activity addresses important ecological concepts. Read the synopsis below.
Populations change over time. Deaths, births, immigrations, and emigrations all affect how many
individuals are left in a population. Other factors--such as food, water, shelter, space, disease--dictate population
numbers. These are called limiting factors. They are limiting because they affect whether or not the population
will increase or decrease.
Carrying capacity is the number of organisms an ecosystem can hold long-term without any damage to
that ecosystem. For example, let’s say that you have 100 acres of woods behind your house. That 100 acres can
only hold a certain number of squirrels. There are only a certain number of nuts to go around. Once those nuts are
gone, the squirrels must either find another home, or they will die of starvation. So, over time, you’ll find that the
squirrel population stays at an average number that the woods can support--no more, no less. And that is carrying
4) You will need to know a little background on Emperor penguins. See the brief explanation below, or explore
the web sites at the end of this lesson.
Penguins are flightless birds that live in subantarctic waters. The exception is the Galapagos penguin
which lives at the equator. The Adelie and Emperor penguins are the only penguins that live on the Antarctica
For this activity, we’ll be using the Emperor penguin. The emperors were once thought to be rare but now
are estimated to number more than a million birds in 25 known colonies. Therefore, we are going to assume, for
this activity, that a penguin colony has approximately 40,000 birds. We know that a large penguin colony can
consume several tons of food a day, so we will assume that our penguin colony eats three tons of food a day. This
means each penguin eats 6.7 lbs. of food/day.
Although the type of food varies with the species, the geographical location, and the time of year, most of
the southern species have a diet of small fish and crustaceans. Again, for the sake of this activity, we will assume
that the Emperor penguin’s diet is 95% small fish, 3% squid and cuttlefish, and 2% small crustaceans (krill and
(picture taken by Elissa Elliott, 1998)
290 colored cards mentioned in the Pre-Activity Setup section
1 baggie for each student (represents their stomach)
a large area where the cards can be spread out (simulating the penguins’ food in the ocean)
1 student activity sheet per student (see Student Reproducible Masters section)
One 45-minute class period--to introduce the concepts, assign roles, do the activity, and wrap-up.
Engagement and Exploration (Student Inquiry Activity)
Introduce the Emperor penguin to your students briefly. (See Resource section). Explain that the Antarctic
coastline can only hold so many penguins. Part of this is based upon how much food is available in the
surrounding waters. The amount of food would be a limiting factor (see discussion above). The amount of
penguins the Antarctic coastline could hold for a long period of time would be the carrying capacity. Give the
example of a 1-gallon ice cream container. How much ice cream can the container hold? One gallon. That’s its
carrying capacity, very much like how many organisms a parcticular ecosystem can hold.
Today they will be doing an activity to show how a parcticular environment can only sustain certain
numbers of a population for a long period of time without hurting the environment.
Hand out the activity sheets.
Each student will be a penguin. Hand out a plastic baggie to each student. This represents their stomach.
[You may want to provide a permanent black marker so they can write their name on the baggie.]
You have a pile of colored cards which represent the different types of food available in the Antarctica
waters. Remind the students that they are not only looking for the most cards they can gather but also a variety of
colors, representing the different types of food.
To make things a little more realistic, ask for 3 volunteers. Have them come to the front of the classroom,
and tell the class that these penguins will have a little more trouble than the rest of them. The first penguin has
had one of his legs bitten off by a leopard seal, therefore he will have to hop during the entire activity. The second
penguin’s flippers were injured in a fight with another penguin. His speed in the water is decreased, and his
balance on land is compromised; therefore, he will have to crawl to get his food (simulating sliding or
tobogganing). A third penguin volunteer will represent a parent penguin who has to gather double the amount of
food for himself and his baby penguin.
Go to the large area. The students will line up behind a designated line, each laying their baggie in a spot
where they feel comfortable. You will spread the cards out in an even pattern over the area. They are only allowed
to pick up one card at a time, and they must take each card back to their baggie. This slows them down and
prevents cheating. Before starting the activity, ask students to predict how many penguins they think will survive.
Once all cards are collected, have the students collect their baggies and head back to the classroom.
Ask them to total the numbers on all of their cards. Make sure they notice the difference between 1 and .10 on
the cards. This number represents the pounds of food they collected.
Write on the board:
K stands for krill (2% of penguin’s diet)
F stands for small fish (95% of penguin’s diet)
S stands for squid (3% of penguin’s diet)
Tell them that an Emperor penguin needs at least 6.7 lbs of food per day to live for an extended period of
time. Did anyone get this much? You should only get a few that collected this much. The number of students
who raise their hands is the carrying capacity for the parcticular area that you did the activity in.
You may use the explanatory paragraphs in the Pre-Activity Setup section to explain that food was the
limiting factor in this case. Every population will build in numbers until its ecosystem can no longer hold or
support them. Then individuals die (or move from the area). Therefore, the ecosystem dictates how many
individuals can live in it.
Elaboration (Polar Applications)
Have the students do further research on penguins and how they survive the Antarctica cold. Use the web sites
listed in the Resource section to get you started.
Extension: Human populations work very much in the same way, although we typically move around a
lot more than an animal would. Using the web sites below, discuss what carrying capacity means when referring
to the human population. What would happen if the earth were at its carrying capacity already?
Exchange (Students Draw Conclusions)
Direct the students’ attention to the questions on their activity sheets. Give them a few minutes to answer the
questions. Group work is all right, but you want to make sure that each student understands what he or she just did
and can apply it to new situations or new questions.
Evaluation (Assessing Student Performance)
After most students have answered the questions, go over the answers with them.
1) Yes, there should have been. The volunteer penguins with extra stresses should have been unable to gather as
much food. They would become weaker over time and eventually die.
2) This is a tough question, even for my ninth grade Biology Honors students. The baby is the most kind and
humane choice, but if the parent gives the food to the baby continuously and does not keep his own energy up, the
parent could die, and then where would the baby get its food? So, in this case, both would die, and how would that
continue the species? The parent penguin would eat the food himself because he can always have more baby
3) K represents the carrying capacity. Notice that the population slowly increased over time, but at a certain point
(K), the population numbers reached a plateau. This is the number that the ecosystem can hold over long periods
4) K is more of an average. The population will not stay at exactly one number.
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