Unit 3 Ecosystems
Chapter 6 & 7
Part 1
The Web Of Life p. 92
&
Food Relationships p. 93
Questions #3-9 in the book
Define Ecosystem
Ecosystem = the network of relationships
(interactions) among living (plants, animals) and
the non-living parts (soil, climate, water etc.) in an
environment.
Differentiate the terms producers, consumers
decomposers. P. 93
Other examples:
Grasses
Trees shrubs
Water lilies
Flowers
Vegetables
Fruits
Producer = a plant which can synthesize carbohydrates
using carbon dioxide and the sun’s energy.
Actually “produce” their own food and food for the rest of
the ecosystem
Differentiate the terms producers, consumers,
decomposers. P. 93
Consumers = All those organisms that have
to eat (consume) plants or animals to obtain
their food.
Types of consumers
Primary Consumers: Animals that eat
producers. Also called 1st. order consumers.
(Ex. Rabbit, squirrels, grouse, insects)
Secondary Consumers: Animals that eat
primary consumers. Also called 2nd. order
consumers. (fox, owl, mink )
Tertiary Consumers: Animals that eat secondary
consumers. Also called 3rd. order consumers.
(Wolf, coyote, hawk)
Differentiate the terms producers, consumers,
decomposers. P. 94
Examples:
Worms
Bacteria
Fungi
Protozoa
• Decomposers = Simple organisms that obtain
their food from dead/decaying organisms and
wastes.
Differentiate the terms food chain & food
web. P. 94
Food chain = linear
sequence
representing the
nutrition of various
species
from the simplest
plant to the top
carnivore.
Food web = a series
of interconnecting
food chains in an
ecosystem.
Food web is more
complex and is
composed of several
food chains
Food web is a more
realistic picture of an
ecosystem.
Food Chain
vs
Food Web
Identify ALL examples of each trophic level.
Producers
Shrubs, grass, trees
Primary Consumers
Grasshopper, rabbit, deer,
squirrel
Secondary Consumers
Mountain lion, snake, shrew,
insect-eating bird, hawk
Tertiary Consumers
Hawk, snake, mountain lion
Decomposers
Bacteria, fungi
Give an example
of a food chain
from fig. 6.4. P.
95
Tree
insect
→
Producer
→
Primary
consumer
insect eating
hawk
bird
→
2nd order
consumer
3rd order
consumer
Note: The arrows indicate the flow of energy & nutrients from
one level to the next
Sample Food Chain
Draw an example of a food web
containing humans. P. 94
Mosquito
Hawk
Cow
Grass
Man
Decomposer
Phytoplankton
Fish
Draw an example of a food web containing
humans. P. 94
Hawk
Mosquito
Cow
Grass
Man
Decomposer
fish
Phytoplankton
What happens to energy?
(Handout)
What happens to energy?
85-90% is LOST
or USED up:
maintaining
the organism
(Ex.
metabolism,
reproduction
etc.)
10-15% is
stored:
Available or
transferred to
other animals
when it is
eaten.
And as heat!!!
IF NOT EATEN:
Energy is
transferred to
the
decomposers
.
What happens to the energy at the
decomposer level?
Same thing….ALMOST !?
Most is lost or used up through heat and maintaining
the organism.
If eaten (Ex. A mushroom) energy gets passed on.
HOWEVER, once a decomposer dies….
The energy is LOST FOREVER!!!
Summary – Energy & Food Webs
The ultimate source of energy (for most ecosystems) is the
sun
The ultimate fate of energy in ecosystems is for it to be lost
as heat, metabolism, reproduction, etc..
Energy and nutrients are passed from organism to
organism through the food chain as one organism eats
another.
Decomposers remove the last energy from the remains of
organisms.
Inorganic nutrients are cycled, energy is not.
Summary – Energy & Food Webs
Question #14, 15 & #16 p. 98 make perfect review
questions for the test.