Transcript 13.4-Food Chains and Food Webs

Notes: Food Chains and Food
Webs
FOOD CHAIN
•
•
•
Single sequence that links species
by their feeding relationships.
Traces the transfer of energy
Simplest way to look at energy flow
in an ecosystem
Trophic Levels
level in a food chain
1. Producers always first level
2. Primary consumers next level
(herbivore)
3. Secondary consumer- eat
herbivores (small carnivore or
omnivore)
4. Tertiary consumer-carnivores
that eat secondary consumers.
Large Carnivore
• 3˚ Consumer (tertiary)
• Killer Whale
Small Carnivore
• 2˚Consumer (secondary)
• Ex: Sea Otter
Herbivore
• 1˚ Consumer (primary)
• Ex: Sea Urchin
Producer
• Ex: Kelp
FOOD WEB
• Interconnected
food chains
• Organisms usually
have multiple
feeding
relationships
FOOD WEB
• More realistic
display of feeding
relationships
• Arrows show
transfer of
ENERGY
ENERGY TRANSFER
• trophic level: position in a series of
energy transfers
• Only 10% of the total energy is passed
onto the next trophic level
• Only 10% of the total energy is passed
onto the next trophic level
1. lost to biological processes
(digestion, growth and repair, running,
walking etc.)
2. lost as heat
90 % Energy
Lost
90 % Energy
Lost
90 % Energy
Lost
Large
Carnivore
Small
Carnivore
Herbivore
Producer
• 3˚ Consumer
• Ex: killer whale
• 2˚Consumer
• Ex: sea otter
• 1˚ Consumer
• Ex: sea urchin
• Ex: Kelp
• Why is a Pyramid used to display
Energy transfer between trophic
levels? Hint: Why not a square?
Video
KEYSTONE SPECIES
• Has a disproportionately large effect
on the ecosystem
KEYSTONE SPECIES
• Has a disproportionately large effect
on the ecosystem
• Dictates community structure
KEYSTONE SPECIES
• Has a disproportionately large effect
on the ecosystem
• Dictates community structure
• Demonstrated by removal of
keystone species from community
EX. sea stars in tidepools
Sea star feeds on all
bivalves. When the
sea star is removed
from the tide pools
one bivalve (mussel)
out competes the rest
for resources and
becomes the
dominant species.