SNC 1D
Food Chains, Webs, Pyramids, & Energy
(2.4 & 2.5)
Read pp. 28-47
THE ROLE OF ORGANISMS IN THEIR ENVIRONMENT
The ___________ of an organism is its role in the ecosystem. For example, the
____________ of a deer is to feed on grass and other plants, become food for wolves, to
provide blood for blackflies and mosquitoes, to fertilize the soil with nutrients, and so on.
One key feature is the ___________ role of each species.
PRODUCERS & PHOTOSYNTHESIS
_______________ are organisms (such as plants) that make their own energy-storing
food molecules using molecules from the abiotic environment and the Sun’s energy. This
process of changing light energy into chemical energy is called ______________.
In photosynthesis, plants use light energy and the atoms of __________ and
_____________________ to form __________ molecules and ___________ gas. The
energy from the Sun is now stored as chemical energy in the ___________ molecules.
The photosynthesis reaction can be represented as a word equation:
+
+
CONSUMERS & CELLULAR RESPIRATION
_______________ are organisms that cannot make their own energy-storing food
molecules. They must get their food by consuming or eating other organisms (living or
dead). The food contains the __________ they need to live. To release the energy from
the food, the food must be broken down by the process called
____________________________________. In cellular respiration, ______________
molecules are broken down in the presence of ______________ gas. This produces
______________ and ________________________.
The cellular respiration reaction can be represented as a word equation:
+
+
+
Show the relationship between producers & consumers, and photosynthesis & cellular
respiration by filling in the boxes in the following diagram.
Photosynthesis
(Producers)
Cellular Respiration
(Consumers)
TYPES OF CONSUMERS
____________________ Animals that feed on plants only.
ex. deer, mice, cows, rabbits
____________________ Animals that feed on other animals only.
ex. wolves, eagles, lions, sharks
Carnivores that feed on live animals are called predators.
____________________ Animals that feed on both plants and other animals.
ex. black bear, humans
____________________ Animals that feed on dead plants or animals
Scavengers do not usually kill their own food
ex. vultures, snails, crayfish, crows
____________________ A special group of consumers that feeds on dead plants and
animals, and animals wastes. They differ from scavengers in that they do not actually eat
the dead material; they give off digestive juices that break down the dead matter into
simple molecules. Some molecules (nutrients) are absorbed by the decomposers, while
other molecules are returned to the environment for producers to use (decomposers
recycle dead matter). ex. bacteria, fungi (mushrooms, mould)
FOOD CHAINS
Food chains show the feeding relationships between species. A food chain describes a
feeding sequence in which an organism is eaten by the next organism in the chain. All
food chains begin with a _______________ and include one or more
__________________. A food chain also shows a flow of _____________.
TROPHIC LEVELS
The consumers in a food chain are often classified according to their diet (i.e. herbivore,
carnivore, and omnivore). To classify consumers more precisely, ecologists use trophic
levels or ______________ levels. A trophic level tells how directly a consumer interacts
with the producers.
Food Chain
Organism
Trophic Level
Other Classifications
hawk
carnivore
3rd order consumer
snake
carnivore
2nd order consumer
mouse
herbivore
1st order consumer
grass
producer
FOOD WEBS
In most ecosystems, food chains do not exist on their own because the organisms in the
food chain usually eat more than one kind of food. What results is an arrangement of
interconnecting food chains called a _________________.
For the food web above;
1.
Identify the producers by placing the letter “P” by their picture.
2.
Place the number “1” beside the 1st order consumers (herbivores).
3.
Place the number “2” beside the 2nd order consumers (carnivores).
4.
Place the number “3” beside the 3rd order consumers (carnivores).
5.
Place the number “4” beside the 4th order consumers (carnivores).
6.
How many food chains make up this food web? __________
ENERGY FLOW IN ECOSYSTEMS
The sun is the source of energy for almost all ecosystems. Producers capture some of
this energy in photosynthesis to form food. Only _____% of the sun’s energy is absorbed
by plants for photosynthesis (_____% is absorbed by the Earth’s atmosphere, land, and
water, and the remaining 30% is ____________ by the Earth). Not all of the captured
energy is stored in plant tissue; some of this energy is used by plants for growth, cell
reactions, flowering etc.
Herbivores (i.e. rabbits) that eat plants do not store all the energy in their tissues. Some
energy is used for movement, growth, cell activities etc. Much of the energy is lost as
____________.
Thus, energy is gradually ____________ along a food chain. With each transfer, more
energy escapes into the environment, never to be reused or recycled.
ECOLOGICAL PYRAMIDS
Since food chains only show transfer of energy through an ecosystem, food pyramids are
used to study different aspects of ecosystems. There are 3 types of food pyramids.
Pyramid of ___________________
- based on the # of organisms at each trophic level
- usually, the most numerous organisms are the producers
and the least numerous are the top-order consumers
Pyramid of ___________________
- based on the total mass of organisms at each trophic level
- usually, the producer trophic level has the greatest mass
and the top-order consumers have the lowest mass
Pyramid of ___________________
- based on the total amount of food energy available at each trophic level
- in all cases, the producer trophic level has the greatest amount of energy and the toporder consumers have the least amount of energy
QUESTIONS from textbook:
p. 41 # 1, 2, 3, 5, 6, 7, 10
p. 47 # 3-8
Words for blanks:
carbon dioxide (5)
carnivores
cellular respiration
consumers (2)
decomposers
energy (3)
feeding (2)
food web
heat
herbivores
light energy (2)
lost
niche (2)
omnivores
oxygen (5)
photosynthesis
producers (2)
reflected
scavengers
sugar (5)
water (5)