ENERGY FLOW &
ECOLOGICAL PYRAMIDS
NOTES
ECOLOGY DEFINITIONS
Ecology – study of
organisms and their
interactions with the
environment
ECOLOGY DEFINITIONS
 Biosphere – region of
the Earth that
supports life (includes
all the land, water and
air in which
organisms live)
ECOLOGY DEFINITIONS
 Ecosystem – all the
organisms that live in
a particular place,
together with their
physical environment
 Both biotic and abiotic
factors interacting
 Abiotic Factors
(nonliving)
Ex: air, temp, water,
rocks
 Biotic factors
(Living)
Ex: all plants and
animals, bacteria,
algae, fungi
Ecosystems
Biotic
Factors:
Moose, Bird,
Rabbit,
Tree
grass
Abiotic Factors:
Water, clouds, rocks
POPULATION DEFINITIONS
Species – a group of organisms so similar
to one another that they can breed and
produce fertile offspring (smallest level)
Population – all the members of a single
species that live in one area
Niche – a particular role a population plays
in the community (“its job”); ex. Honeybee
pollinates flowers; hawks prey on mice
Community – all the populations that live
and interact in one environment
Energy
The main source of energy for life on earth
is sunlight
Autotrophs (like plants) go through
photosynthesis to produce usable energy
(ATP).
ENERGY FLOW DEFINITIONS
Producer (Autotroph) – organism that
makes its own food (ex. Plants)
Consumer (Heterotroph) – organism that
gets its energy directly or indirectly from
producers (ex. Animals)
Decomposer – organism that breaks down
and obtains energy from dead, organic
matter (ex. Fungi and Bacteria)
FOOD CHAINS
Food Chain – a series of organisms through
which food energy is passed in an
ecosystem
Example of a Food Chain:
Sunflower  Caterpillar  Robin  Fox
(producer)
(primary
consumer)
(secondary (tertiary
consumer) consumer)
FOOD WEBS
 Food web –
interconnecting
and overlapping
food chains
Name
Oak Trees
Producer
Primary
Consumer
Secondary
Consumer
Tertiary
Consumer
X
Moths
X
Voles
X
X
Weasels
X
X
Shrews
X
X
Energy Flow
 Energy & nutrients
are recycled by
decomposers.
Definitions
 A trophic level is the
position occupied by an
organism in a food
chain.
Trophic levels can be
analyzed on an energy
pyramid.
 Biomass is the total
mass (amount of living
tissue) of all the
organisms within a given
trophic level
Biomass
Total mass (amount of
living tissue) of all the
organisms within a given
trophic level
Only a small fraction of the biomass
from one trophic level moves to the next
2 Reasons for this:
Many organisms are not consumed
by organisms at the next trophic level
– energy is not available for transfer
Some of the biomass at each level
consists of materials consumers won’t
eat – bones, teeth, beaks, claws,
shells, wood
ECOLOGICAL PYRAMID
Shows the relationships between
producers and consumers at the trophic
levels in an ecosystem
3rd consumers
Owls
2nd consumers
1st consumers
Producers
Snakes
Rabbits, mice
Plants (grass & flowers)
10 PERCENT LAW
Energy available at each trophic level is
about 1/10 the energy available from the
level below
20 kJ
200 kJ
2,000 kJ
20,000 kJ
3rd
consumers
2nd consumers
1st consumers
producers
WHY A PYRAMID SHAPE?
 In most food chains fewer organisms occupy
each higher trophic level (lots of producers,
many primary (1st) consumers, fewer secondary
(2nd) consumers and very few tertiary (3rd) or
quaternary (4th) consumers)
WHY A PYRAMID SHAPE?
The greatest amount of energy is
found at the base of the pyramid.
The least amount of energy is found
at top of the pyramid.
BIOLOGICAL MAGNIFICATION
 The buildup of a
pollutant in organisms
at higher tropic levels
in a food chain
 The concentration of
a pollutant (like DDT)
multiplies as it passes
up the food chain
from producers to
consumers, so the
amount of DDT in toplevel consumers can
be magnified nearly
10 million times
Biological Magnification
Most toxin
Least toxin
 The tertiary consumers
eat many of the 2nd
consumers so they eat
even more of the toxin
 The secondary
consumers eat many of
the 1st consumers so they
eat more of the toxin
 The tiny primary
consumers eat a little bit
of the toxin.
 At every level the amount
of toxin increases!