Transcript Food Webs and Food Chains

Food Chains and Food
Webs
Science Foundations
Predator and Prey Relationships
One important interaction in the ecosystem is
between predators and their prey.
Predators are organisms which hunt and feed
on other organisms Whereas the living things
that are eaten are referred to as prey.
1. To maintain balance in the ecosystem, the
interaction between predator and prey
should not be disturbed.
Example
In parts of the South, one natural predator of
the white-tailed deer, the mountain lion, has
been reduced in number. Because there are
fewer mountain lions to prey on the deer, the
deer population in some regions has risen
tremendously.
WHY?
Food Chain
A food chain is the relationship of organisms
that depend on each other for energy or food.
It is a straight line relationship such as algae
is food for fish which are food for squid which
are food for sharks.
Food Web
A food web is more complex and is a food
chain with the interrelated chain of organisms
that depend on each other for food.
If one organism is removed, other organisms
may be endangered or possibly die out.
How Come?
Food Web
Carrying Capacity
Carrying capacity is the number of individuals
in a population that the resources can support.
This provides for a balanced ecosystem.
Trophic Levels
The living things in an ecosystem can be
divided into four levels. Each step in a food
chain or food web is called a trophic level.
Producers are the first step.
Consumers are the next steps.
Each step depends on the step below it for
food and to provide its energy.
Producers
Producers are the green plants and some
bacteria and algae that are able to make their
own food from water, the sun, carbon dioxide
in the air, and minerals in the soil.
When plants make their own food, they use
sunlight. This process is called
photosynthesis.
What is Photosynthesis?
The process of photosynthesis is a
chemical reaction.
It is the most important
chemical reaction on our planet.
What is the Equation for the
Chemical Reaction of
Photosynthesis?
What is the equation for the
chemical reaction of
photosynthesis?
What is the equation for the
chemical reaction of
photosynthesis?
Six molecules of carbon dioxide react with
six molecules of water to form 1 molecule of
glucose and six molecules of oxygen.
Describe Photosynthesis
The process of changing light energy to
chemical energy
 Energy stored as sugar
 Occurs in plants and some algae
 Plants need light energy, CO2, and H2O
 Takes place in the chloroplasts, using
chlorophyll, the green pigment in plants

What happens during
photosynthesis?

Plants capture light energy and use that
energy to make glucose

Sunlight provides the energy needed by
chlorophyll to change molecules of carbon
dioxide and water into glucose

Oxygen is also released in this reaction
What happens during
photosynthesis?
Carbon dioxide enters the leaf through holes
called stomata
 CO2 combines with the stored energy in the
chloroplasts through a chemical reaction to
make glucose
 The sugar is moved through tubes in the leaf to
the roots, stems and fruits of the plants
 Some of the sugar is used right away by the
plant for energy; some is stored as starch; and
some is built into plant tissue

Why is this important to us?
We cannot make our own food (glucose,
energy), we must get our food from
plants.
Plants are the first step in the food chain.
Why is this important to us?
The oxygen released during photosynthesis
is necessary for all living things.
Learn more about
photosynthesis at:
http://www.ftexploring.com/me/photosyn1.html
Consumers
Consumers are the animals that rely on other
organisms for food. This group can be further
divided into three groups:
 Primary consumers are herbivores, or plant
eaters. Examples – some insects, deer, or
mice.
 Secondary consumers are carnivores, or
flesh eaters. They feed on herbivores.
Examples – snakes and coyotes
 Tertiary consumers can be carnivores or
omnivores, which eat both plants and
animals. Example – hawks and humans
Scavengers
Scavengers feed on dead organisms. They
include ants and vultures.
Decomposers
Decomposers are organisms that break down
dead organic matter. This decomposition
produces many of the raw materials that are
used by the producers in photosynthesis.
Examples are bacteria, fungi and earthworms.
Symbiotic Relationships
Symbiosis = a beneficial relationship
between 2 organisms that live together.
 3 types of symbiosis

– Commensalism = 1 organisms benefits, the
other neither benefits or is harmed.
– Parasitism = 1 organisms benefits the other is
harmed.
– Mutualism = both organisms benefit.
Commensalism

Commensalism occurs in
a relationship where one
animal benefits and the
other is unaffected.

The dorsal fin of the
Remora is modified into a
sucker. They attach to
sharks during feeding and
eat the scraps. The
sharks do not try to eat
the Remora.
Parasitism
A parasite is an organism
that lives on or in the
body of another organism
(the host)
 from whose tissues it
gets its nourishment, and
 to whom it does some
damage

The flea is
common on
dogs and cats


Animals are parasitized
by viruses, bacteria,
fungi, protozoans,
flatworms (tapeworms
and flukes), nematodes,
insects (fleas, lice), and
arachnids (mites).
Plants are parasitized by
viruses, bacteria, fungi,
nematodes, and a few
other plants.
Mutualism

The clownfish can come
in contact with the
stinging tentacles of the
sea anemone and not be
harmed by them.

At the same time, it
receives protection from
its enemies.

The clownfish feeds the
anemone by gathering
nutrients and also leaving
nutritional waste on the
tentacles.
Ecological Pyramids
Ecological pyramids are diagrams that show
each trophic level in a biome. There are three
types:
 Energy pyramid
 Biomass pyramid
 Numbers pyramid
Energy Pyramid
The energy pyramid shows the transfer of
energy from one level to the next. The bottom
of the food chain shows the largest amount of
energy which comes from the sun then as you
move up energy is used but also lost in the
form of heat energy.
Energy Pyramid
Biomass Pyramid
The biomass pyramid is based on the
mass of organic material at each level.
Numbers Pyramid
The Numbers pyramid shows the relative
numbers of organic material at each level.