Transcript Trophic Structure Ch.41 2016

Trophic Structure
Food Chain & Food
Web
What’s the
difference?
Food Chain
More than one??
• Some organisms, like the Kookaburra, can
be at different levels within the same food
web.
• When the Kookaburra eats the centipede,
then it is a secondary consumer
• However, when it eats a frog it is a
quarternary consumer.
Levels of Consumers
• Those that feed
directly on producers
are called Primary
consumers.
• Consumers are also
classified based on
what they eat:
– Herbivore
– Omnivore
– Carnivore
Decomposers
• Fungi
• Bacteria
• Earthworms
Foundation vs. Keystone
• Ex. Sea star, Pisaster ochraceus
– Feeds on mussels
– Allows barnacles, limpets, anemones and
others to colonize.
Foundation or Keystone
Keystone or Foundation?
• Removing three species
of kangaroo rats
changed a desert plain
into an arid grassland.
In areas without
kangaroo rats, grasses
filled in between the
shrubs, stems and other
plant litter accumulated,
large-seeded plants
replaced those with
smaller seeds, snow
melted more slowly and
the numbers of other
rodents increased
significantly.
Effects of losing a “Keystone”
Predator
• Trophic
Cascade: The
cascading effect
that a change in
the population
size ( usually the
keystone
species or apex
predator) in the
web has on the
populations
below it.