Food
Webs Trophic Dynamics Producers
Ability to photosynthesize
Algae and plants (some
bacteria)
Usually small in size;
exist in large numbers
Base of food chains
Responsible for primary
productivity
Generate carbohydrates
for respiration
Primary Consumers
(Herbivores)
Organisms that consume
plants or algae
Usually small in size
Examples:
Zooplankton, snails, cows, horses, insects, zebras, ciliated protozoa
Contribute to secondary
productivity
Secondary Consumers
(Carnivores)
Consume herbivores
Usually larger in
size
Examples: wolves,
lions, sharks, reptiles, hawks, shrews, spiders, amoebae
Many layers of carnivores
in an ecosystem
Contribute to secondary
productivity
Omnivores
May act as herbivores
or carnivores
Varied feeding habits
(versatile consumers)
Include humans, pigs
and many insects
Contributed to secondary
productivity
Decomposers
Detritovores (consume
decaying material)
Very important to
detrital food chains; recycle nutrients
Found in large numbers
in forest litter, marine and aquatic benthos
Examples: fungi, some
invertebrates, bacteria, protozoa
Grazing vs. Detrital
Food Chains
Grazing food chains
based on producers (photosynthesis)
Detrital food chains
based on detritovores (breaking down detritus and wastes)
Grazing food chains
important in marine and aquatic ecosystems
Detrital chains important
in forest litter
Trophic Pyramid
Show feeding patterns
Smaller to larger
size
Many to fewer in numbers
Levels vary from one
ecosystem to another
Ecosystem Energetics
Diagram of primary
and secondary productivity (see text)
SUMMARY
Food Webs
Trophic Dynamics
Ecosystem Energetics