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CHAPTER 3.2
Part I
ENERGY FLOW
I.WHERE DOES THE ENERGY COME
FROM FOR EVERY ORGANISM TO
INTERACT
A. SUNLIGHT is the main energy source for LIFE
1. Less than 1% of sunlight is used by living things
2. Photosynthesis – the process of obtaining light energy to
make food.
B. CHEMICALS are another source of energy
1. Chemosynthetic bacteria can convert energy from
chemicals through a process called chemosynthesis
II. WHO MAKES THE ENERGY
A. AUTOTROPHS (PRODUCERS)
1. Plants (Sunlight)
2. Some Algae (sunlight)
3. Some Bacteria (breaking down chemicals – where
no sunlight is found)
B. Without AUTOTROPHS or a constant input
of energy, living things cannot function (live)
III. WHO USES THE ENERGY
MADE FROM AUTOTROPHS
A. CONSUMERS or HETEROTROPHS
1. They rely on other organisms for
food and energy
2. Animals, Fungi, bacteria, protists
B. 5 TYPES of Heterotrophs
1.
2.
3.
4.
5.
HERBIVORE 
CARNIVORE 
OMNIVORE 
DETRITIVORE 
(scavenger)
DECOMPOSER
Eat plants
Eat Animals (meat)
Eat Animals and Plants
Feed on dead matter
(detritus)
Break down organic
matter or dead things
IV. ENERGY FLOW!!!!
A. FOOD CHAIN – energy stored by autotrophs
can be passed on through an ecosystem along
a food chain.
B. FOOD WEB – combination of food chains in
an ecosystem
**Energy flows in ONE direction from
the autotrophs through the
consumers!
Food Chains ,Food Webs,Energy Pyramid in
Ecosystems-Video for Kids – YouTube
Reminder Stop at 3:00
V. TROPHIC LEVELS
1. Each step in a food chain or web is called a
trophic level
2. Producers are always in the first trophic level
3. Herbivores or omnivores are in the second
trophic level
4. Other consumers (omnivore or carnivore) are
in third, fourth,… higher trophic level.
VI. Levels of ConsumerDepends on Food Chain – what was just eaten
1. 1st Order Consumer - eats producer (2nd TL)
2. 2nd Order Consumer – eats 1st order
consumer
3. 3rd Order Consumer – eats 2nd order
consumer
4. 4th order consumer…
Where do the arrows point?
What level of consumer are they?
What are the trophic levels?
Level of Consumer
Trophic
level
Level of
Consumer
Trophic
level
1st TL
1st -Order
2nd - Order
2nd T.L.
3rd T.L
2nd -Order
3rd TL
3rd- Order
4th T.L
1st - Order
2nd TL
1st TL
3rd Trophic Level
1st Trophic Level 2nd Trophic Level
Food Webs
The top of the food chain.
Some animals are said to be at the top of the
food chain. This is because they are not
hunted by other animals.
What are some examples?
LION - Can you think why?
HUMAN – can you think why?
HAWK – Can you think Why?
Breaking the Chain



Organisms living in a habitat depend
on each other.
If one part of a food chain dies out
or is greatly reduced, the
consumers have to find alternative
food, move away, or starve.
This then affects more consumers
in the same way.