A Hike Through the Rainforest
Class Set- Do not write on
Background: Ecologist often study and ecosystem’s Feeding Relationships to learn more about the
ecosystem and how it functions. They may first observe each organism in the ecosystem to determine
what it eats. If there are only a few organisms the ecologist might construct a simple Food Chain that
looks like what you see to the right: sunflower – grasshopper – shrew – cat
The feeing relationships in an ecosystem are usually much more complex than what a food chain
illustrates. An ecologist constructs a Food Web to illustrate the complex feeding relationships that are
found in most ecosystems. A food web looks something like what you see below:
As you can see, food webs help you understand how all the organisms in an ecosystem are connected
together in complex relationships. Food webs are useful tools that can help you see how the changes in
one organisms' population numbers can have a dramatic effect on the numbers of a seemingly unrelated
species.
Food Web Rules:
 Arrows in the Food Web point the direction of energy flow
 Write each organism’s name only once
 Some organisms have many arrows associated with them
 Producers are placed at the bottom of the food web. Tertiary consumers are placed at the top.
Procedure:
1. You recently began your new job as a Wildlife Biologist for the Research Center for Tropical
Studies. You are in a remote area of South America on your first assignment. You have
been asked to study the organisms in a section of the rainforest and construct a food web of
their feeding relationships.
2. Take a hike through the rainforest by reading the attached story. Next, construct a food web
that correctly illustrates all the feeding relationships you observe.
3. Answer the questions that follow and turn in for a grade.
A Hike Through the Rainforest
Welcome to the rainforest! You have your binoculars and water bottle, you are wearing your rubber
boots to keep your feet dry and protect you from snakebites, and you have your poncho to keep you dry
when it starts to rain. Let’s go!
The first thing you notice after entering the rainforest is that there are huge, tall trees everywhere.
Their large canopies of leaves create a great deal of shade down where you are walking. One of the most
magnificent trees is the kapok tree, and there is one in front of you now. While admiring the kapok tree
you notice a large, dark, ball-like mass around one of the limbs. On closer inspection you discover that the
mass is a termite nest. The termites eat the kapok’s wood; although you remember from your
environmental science training that a protozoan that lives in the termite’s intestine actually digests the
wood for the termite. A bright red color at the bas of the kapok tree draws your attention. It is a strawberry
poison dart frog feeding on termites as they scurry by. Don’t touch this frog; its skin secretes a very toxic
poison!
Next you see an orange cup fungus growing and feeding on a dead kapok branch. On top of the
fungus is a fungus beetle chewing away at the fungal cells. Before you can get a closer look at the beetle
you are startled by very LOUD, howling-like sounds high up in the kapok’s crown. As you look up, you
catch a glimpse of a large harpy eagle as it flies off with a young howler monkey in its claws or talons. The
troop of howler monkeys must have been feeding quietly on the leaves of the kapok tree when the harpy
eagle swooped down for a meal. You return your attention back to the fungus beetle, but just as you do,
another bird called an antshrike flies in, grabs the fungus beetle in its beak, and then flies away to a
nearby branch to eat its small catch.
You continue walking down the path when you see a beautiful understory plant. It is a heliconia.
You notice the long, green leaves are filled with holes and on closer inspection you find several katydid
grasshoppers feeding on the leaf tissue. The heliconia has a large flower cluster that resembles a
lobster’s claw and a rufous-tailed hummingbird hovers back and forth as it feeds on the flower. Seemingly
out of nowhere, an eyelash viper strikes out and catches the hummingbird just in front of the flower. The
poisonous eyelash viper has been coiled around the heliconia flower all along, its colors blending in so well
that you (or the hummingbird) hadn’t even noticed.
You next stop to admire a cecropia tree. Each leaf of this tree looks like a large hand with its fat
fingers spread out. Hanging upside from one of the branches you see a ball of fir that you identify as a
three-toed sloth. This very slow moving mammal is hanging from the branch using its three, long-curved
claws on each foot and looks like a furry Christmas tree ornament. The sloth hangs out all day happily
munching cecropia leaves. You remember reading that harpy eagles also eat sloths. The sloth certainly
wouldn’t be hard to catch! Near the very top of the cecropia you see several large iguanas resting on
branches as they feed on the crecopia leaves. These iguanas must be at least five feet long. You have
heard that humans in the area commonly eat the iguanas. They call them “tree chickens” because they
say they taste like chicken (and live in trees). You look forward to trying one someday! A green katydid
grasshopper jumps from one of the cecropia leaves where it was feeding and lands on your shoulder. You
brush the green-colored katydid away and continue on.
There is a commotion in some grass just up the trail. You find that a small boa constrictor has just
caught a grass mouse and is coiling around the mouse to kill it before eating it whole. The boa constrictor
must have been waiting here all day for an unsuspecting grass mouse to come feed on the grass seeds it
eats. A little further along the trail you surprise a coatimundi family. These raccoon-like mammals have
long, pointy nosed and long, striped tails. One coatimundi has caught a grass mouse for lunch, while
another crunches on a katydid grasshopper it has caught on the ground. As the coatimundis go on their
way, you feel a slight sting on your arm. A mosquito gets a short meal of blood from your arm (human)
before you give it a swat. Mosquitoes in this area can carry the one-celled organism called Plasmodium
from one human to another. When Plasmodium carrying mosquito bites you, the Plasmodium enters your
body and feeds on human red blood cells, causing the disease known as malaria. You’re not worried,
however, because the malaria pills you are taking should prevent you form getting the disease.
Rain begins to fall through the thick forest canopy and quickly turns into a downpour as you
continue your trek. This type of rain is a normal daily event in the rainforest. The trail begins to travel
along a river and you can see several dog-sized animals feeding on water plants near the shore. They are
capybara, the largest rodents in the world. One of the capybara is swimming across the river and you
can’t believe what happens next. A school of piranha attacks the capybara in a feeding frenzy. In a matter
of minutes the capybara is devoured. Very impressive! You think back to yesterday when a friend
(human) showed you a piranha they had just caught for their dinner. You were surprised to see a large
leech stuck to the side of the fish, still sucking blood. Across the river, on the shore, you can see a seven
foot long caiman crocodile. The caiman is waiting for its chance to catch a capybara, one of its favorite
meals. You also notice a tamandua anteater across the river. It is using its strong claws to tear through a
termite nest, then using it long, sticky tongue to “lick up” all the termites it can.
The rain finally stops, the sun pops out and the humidity rises even higher than it was before. You
stop for a drink and notice a large mass of army ants moving along the ground. The ants quickly kill a
katydid grasshopper in their path and carry it off to eat later. A pair of ant shrikes flies around the ant
colony as it moves along. The ant shrikes catch insects as they fly up to get away from the ants. Another
katydid grasshopper flies away just in time to escape the army ants, however, an ant shrike quickly
catches it and eats it.
As you near the end of your hike you are excited to see a mango tree filled with ripe, succulent
fruits. You scare away an agouti (cat-sized rodent) that was feeding on some of the mango’s fruits that
had dropped from the tree. Just when the agouti is about out of sight, you see a flash of fur come out of
nowhere and catch it. A beautiful ocelot cat looks up at you, then grabs the now dead agouti and walks off
to in private. You (human) pluck a ripe fruit from the mango tree and eat it. Delicious! The leaves high in
the mango tree shake violently and you look up to see several white-faced capuchin monkeys staring
down at you. They keep shaking the branches trying to scare you away. You decide to move on so the
white-faced capuchin monkeys can eat their mango fruits in peace. Not far from the tree you find the
remains of a white-faced capuchin monkey. The tracks that are present tell you that a monkey was an
earlier meal of the ocelot.
As you step out of the rainforest ecosystem, you realize what a special experience you have had.
You now have a better understanding of why ecosystems are often referred to as a “complex web of life.”
6. Give an example of an organism you observed that fits each
category below.
5. Did you observe any examples of mimicry in your hike? If so,
describe one.
4. Did you observe any examples of camouflage? If so, describe
one.
3. Did you observe and commensalistic relationships in your hike?
If so, describe one.
2. Did you observe any parasitic relationships in your hike? If so,
describe one.
1. Did you observe any mutualistic relationships in your hike? If
so, describe one.
Your supervisor back in the States is please with your food
web and has faxed back several questions they would like for you
to answer.
Questions – Food Webs
Name: __________________ Period: _____Date: ____________
6. Give an example of an organism you observed that fits each
category below.
5. Did you observe any examples of mimicry in your hike? If so,
describe one.
4. Did you observe any examples of camouflage? If so, describe
one.
3. Did you observe and commensalistic relationships in your hike?
If so, describe one.
2. Did you observe any parasitic relationships in your hike? If so,
describe one.
1. Did you observe any mutualistic relationships in your hike? If
so, describe one.
Your supervisor back in the States is please with your food
web and has faxed back several questions they would like for you
to answer.
Questions – Food Webs
Name: __________________ Period: _____Date: ____________
___________
___________
___________
___________
___________
__
___________
Primary consumer
Decomposer
_______
Secondary consumer
Autotroph
Tertiary consumer
Herbivore
Carnivore
Omnivore
__
___________
Primary consumer
Decomposer
_______
Secondary consumer
Autotroph
Tertiary consumer
Herbivore
Carnivore
Omnivore
7. Carefully follow all the food web connections to help answer
this question.
A disease has destroyed all the mango trees in a large
area of the rainforest. Explain how this would affect the
population of the three-toed sloths in the same area.
Answer on back.
___________
7. Carefully follow all the food web connections to help answer
this question.
A disease has destroyed all the mango trees in a large
area of the rainforest. Explain how this would affect the
population of the three-toed sloths in the same area.
Answer on back.