 All
living systems require energy
 No energy = no life
 PRIMARY PRODUCERS are
AUTOTROPHS that make their own
food from either SOLAR energy (most
of them) or from CHEMICAL energy
 This energy is meant for themselves
but other organisms eat their energy
stores
 PHOTOSYNTHESIS
– is the most
common form of harnessing
energy for living things
 Plants on the land
 Algae in the water
 Cyanobacteria – photosynthetic
bacteria are also important
 How
do you get energy deep in the ocean
where the sun can’t shine?
 CHEMOSYNTHESIS
 HETEROTROPHS
–get their energy from eating
other organisms – they are called CONSUMERS
 Consumers are categorized by what and how
they eat
 Carnivores
 Herbivores
 Omnivores
 Scavengers
 Detritivores
 Decomposers
 Carnivores

– kill and eat other animals
Lion, otter
 Herbivores
– eat plants: leaves, seeds or
fruits

Macaw, zebra
 Omnivores

– eat plants and animals
Pigs, humans
These organisms eat dead organisms and
waste products – recycling the nutrients
 Scavengers – animals that consume
carcasses



Decomposers – bacteria and fungi break
down organic matter into detritus (dead
and decaying animal and plant remains)


vultures
mushrooms
Detritivores – feed on detritus particles

Earthworms, crabs
 Energy
FLOWS through the community in a oneway direction by feeding
 ABCD etc.
 All begin with
 primary producer  primary consumer
secondary consumer  tertiary consumer 
quaternary consumer etc.
 Feeding
relationships are usually much more
complicated and interconnected – forming
FOOD WEBS
 Food
Web site
 Extremely
important in food webs
 Decomposers break down organic
matter – dead or decaying plant and
animal matter into DETRITUS that is
eaten by detritivores
 Nutrients are released – these can be
used by plants and other primary
producers
 They are the biosphere’s recyclers!
 Without them dead stuff would just
pile up
 So thank your cockroaches today
 Begins
with algae or PHYTOPLANKTON
 These are eaten by krill or ZOOPLANKTON
 What happens if sea ice melt causes less
krill??
 Each
step in a food web or chain is called a
TROPHIC LEVEL
 Primary producers make up FIRST trophic
level
 ECOLOGICAL PYRAMIDS are diagrams that
illustrate the ecosystems’ relative amount of



energy,
mass or
numbers
 At
each trophic level
 Only
10% of energy goes on to the next level
(10% rule) 90% is released as HEAT.
 Mass
of living matter at
each trophic level
 Grams per unit of area
 Example: g/m2
 Numbers
of
organisms in each
trophic level
 Not always a
pyramid shape!!
 One tree can
support hundreds
of catepillars