The Web of Life
5.9A—Food Webs
The Web of Life
Describe how the flow
of energy derived
from the sun, used by
producers to create
their own food, is
transferred through a
food chain and food
web to consumers
and decomposers.
The Web of Life
I am a spider. Just your average,
run-of-the-mill, garden spider. You
may have seen me 'hanging' around.
I am going to explain the web of life
to you because, you see, I am an
expert on webs. Let’s see, where
shall I start? Uhmm, yes, I’ll start by
doing what I do best: weaving the
web!
The Web of Life
You see, there are all sorts of
creatures in the wild, and they each
play a role in the web of life. There
are lots of different kinds, or
species, of plants and animals. They
come in different sizes, shapes and
colors. They live in different places
and behave in very different ways.
The Web of Life
But for all their differences,
plants and animals need a lot of
the same things to survive. In
fact, they need each other.
That’s what the web of life is all
about! Let me start at the very
beginning with my very own
web.
The Web of Life
You see, as a garden spider, I meet lots of
plants and animals. Some of them are my
friends, some of them are not so friendly, and
some of them are my dinner!
Since I am, after all, a garden spider, let me
show you around my garden. The plants you
see here are my friends. Plants are friends to
everyone in the web of life. To tell you the truth,
none of us could live without them! But don’t
tell them that - they might get swelled heads
over it. Oh, I guess you have a point. Plants
don’t have heads, do they?
The Web of Life
So, there are millions of different
kinds of plants all over the world!
Plants are really quite simple. All
they really need is sunlight and
water!
Plants may not seem very
interesting. I mean, they can’t talk to
you, right? So why am I friends with
them? Well, believe me, none of the
animals you’re about to meet would
be around without plants, so we
should all appreciate them!
The Web of Life
Plants are VERY important
producers. They produce food for
many other organisms!. Let me
introduce you to some animals
that eat plants!
Lots of animals eat plants.
Animals that eat only plants or
plant parts are called herbivores.
As a matter of fact, a whole lot of
animals are herbivores. Let's see,
how many animals can you name
that eat plants? Here, let me help
you.
The Web of Life
Now be very, very quiet. That guy
over there, he's a bird. Some birds
eat seeds, which come from
plants!
Some birds also eat wonderful
little spiders like me, so don't let
him see me! Quick, let's get out of
here!
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Whew, that was close!!!
Let's go talk to a squirrel. They
don't eat spiders. They eat nuts
(which also come from plants).
I bet his friend over there is
hiding nuts for the winter!
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Squirrels eat nuts, and they
also bury them for storage to
eat in the winter time. The
ones they forget about will
grow up to be trees and make
more nuts!
Squirrels and trees are very
good friends.
The Web of Life
Oh dear, here comes a deer!
Deer eat the leaves of plants.
They don't bother me except
when they walk through a
spider web I've worked so
hard to build.
The Web of Life
I better get back to work here, still talking about plants.
You see, plants aren't just a source of food. For many
animals, they're home!
How can an animal live in a plant you ask? Just look at
me! I build my spider webs between branches of trees or
blades of grass. Other animals use grass to hide in, like
baby deer (fawns). Other animals, like mice, use grass to
build homes.
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Trees are homes for many
animals. All kinds of birds,
insects and squirrels can call a
tree home. For large animals
like bears and wolves, the whole
forest is their home. It's what
scientists call "habitat."
The Web of Life
I would introduce you to
habitat, except habitat
isn't a plant or an animal
- it's a whole community
of plants and animals!
It's a lot like the town or
city in which you live. It's
where animals get the
food they eat and the
water they drink - it's just
plain where they call
home. Habitat is just as
important to animals as
animals are to each
other.
The Web of Life
Now, let's get back to the story. Remind me
again, where was I?
Oh my! Now I remember! I completely forgot
to tell you about bugs! Why, bugs are my
favorite animals! I eat them! That makes me
a carnivore, because I only eat meat!
There are many kinds of bugs. And there are
different bugs in different places. What
kinds of bugs live near you?
Have you seen any ants? How about
crickets? Mmm . . . I love crickets. Where did
you see them? I'll have to come visit you!
The Web of Life
Bugs do a lot of different things. Bees visit
the flowers of plants and take nectar and
use it to make honey. While the bee is
collecting nectar, it usually gets a powder
on it called pollen. This is sort of like when
you walk in the woods and seeds get
stuck to your pants. Bees fly from one
flower to the next, carrying this pollen.
Some of the pollen falls off into the
flowers, and the plants use that to
reproduce! The plant is helping the bees,
and the bees are helping the plants! That
works out pretty well, don't you think?
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Some bugs eat plants. Now
I'm sure you've seen
caterpillars before!
Caterpillars eat lots and lots
of leaves before they grow up
and turn into moths or
butterflies. But not every
caterpillar grows up. Why
not?
Because birds eat them!
Some birds are herbivores
while other birds are
carnivores. I'd introduce
you to a caterpillar, but you
see, I ate the last one I met.
Well, don't look at me like
that, I was hungry!
The Web of Life
Now that I'm full, I guess we can stop
talking about what I eat and go meet
some other animals.
Follow me! Ah! Allow me to introduce
you to Red, the fox, and Wiley, the
coyote. Now gentlemen, would you
describe each other as friends?
"GRRR!"
Oh my! Clearly not!
The Web of Life
Perhaps I can shed some light on the situation.
You see, most animals eat lots of different
things. Some animals are predators, which
means they hunt and eat other animals. The
animals they eat are called prey. And then
there are some animals that scavenge for food.
Scavengers eat other animals too, but, unlike
predators, they don't do the hunting. They eat
what other predators have killed or animals
that have died of natural causes. Sometimes a
hungry predator will scavenge for food when
there's nothing else to eat.
What does all that have to do with Red, the fox
and Wiley, the coyote?
Plenty, believe me!
The Web of Life
You see, even though Red the fox is a carnivore
and a predator of rabbits and mice, sometimes
the fox is the prey of the coyote! Keep that in
mind, because the web of life is about to get very
twisted - so hold on!
The fox and the coyote are also competitors!
Why? Because animals usually eat more than
just one thing - they have to in order to survive!
When two animals eat the same food, they're
called competitors, because they are competing
for a limited amount of the same food. Get it?
You see, the fox and the coyote compete to eat
mice and rabbits.
The Web of Life
I bet you're thinking that as a top predator, the
carnivorous wolf is at the top of the food chain, right?
Well, not exactly. You see, describing the web of life as
a food chain isn't very accurate. . .
The Web of Life
Let me just climb up onto this wolf. Huh, huh, oh my,
this is a long climb for me. There, made it! So here I
am, standing in the fur on the back of a wolf. I don't
usually do this sort of thing, but for you, I've made an
exception.
The Web of Life
Let's see who we can meet up here.
Hey, look! It's a family reunion! This is
my distant cousin, the tick! Ticks feed
off of the blood of other animals. You
may have met one before, perhaps on
your dog. They are called parasites.
Mosquitoes and fleas - those wacky
bugs - also feed off the blood of
animals. I'm sure you've met a few of
them in your time!
The Web of Life
So you see, even predators and carnivores are food for
other animals. That's why there really isn't a "top" to a
food chain or a food web.
The Web of Life
Even predators die sooner or
later. Sometimes they die
from old age or from injury.
Other times they die when
there's not enough food
around.
The Web of Life
When a predator or its prey
dies, some of it is usually
eaten by scavengers. What
they don't eat, bugs will eat,
and so its body is broken
down. What's left over
eventually becomes part of the
soil - providing nutrients to the
soil and food for - you guessed
it - plants!
The Web of Life
Carnivores
(Tertiary
Consumers)
Carnivores
(Secondary
Consumers)
Herbivores
(Primary
Consumers)
Producers
Decomposers
The Web of Life
So you see, in the web of life, every animal and
every plant relies on other plants and animals to
survive. The web of life isn't a chain, and it's not
quite a circle. It's an important connection
between all life, and no one part of it is more
important than another. All animals and plants
in a sense work together to survive.
The Web of Life
That's why preserving habitats and protecting
endangered species is very important! So
make sure you do your part.
Be a Defender of Wildlife!