Interactions and
Relationships in an
Ecosystem
How Energy Flows
Nutritional Relationships
 Involve the transfer of nutrients
from on organisms to another
within an ecosystem
AUTOTROPHS
 Organisms that can make organic
molecules from inorganic
molecules (using sun—usually)
 Aka producers
 Can be photosynthetic or
chemosynthetic
HETEROTROPHS
 Cannot make organic molecules
 Aka consumers
 Five types





Herbivores
Carnivores
Omnivores
Scavengers
Decomposers
HETEROTROPHS cont.
Types of heterotrophs
 Herbivores
Only eat producers

Aka primary (1st level) consumer
 Carnivores

Only eat other animals

Aka secondary or tertiary (2nd or 3rd
level) consumer

HETEROTROPHS cont.
Types of heterotrophs
 Omnivores
Eat anything

Can be 1st, 2nd or 3rd level consumer
 Scavengers

Eat only other animals after they are
already killed

Usually 2nd or 3rd level consumer

HETEROTROPHS cont.
 Decomposers



Live on dead matter
Aka saprophytes
Include plants, fungi and bacteria
Food Chains
 Food Chain: shows the pathway of energy
from one organism to the next in a direct
line
 Always starts with producers
 Autotroph  herbivore  carnivores
 Algae  krill  cod  leopard seal
 Arrow goes into the mouth! (you put
your food into your mouth)
5th trophic level
4th trophic level
3rd trophic level
2nd trophic level
1st trophic level
Food Web
 Shows the
interactions and
interconnections
among the
different food
chains of a
community
Energy Pyramids
 At each step of the food web/chain, energy
is transferred to the next higher level
 Sun  plant  rabbit  snake  hawk
 This energy transfer is NOT EFFICIENT
 Only 10% of the energy passed to the next
generation is usable; most energy is lost
maintaining homeostasis and as heat
 The amount of usable energy decreases at
each higher feeding level