SF Bay Estuary Ecology Notes
I. What is Ecology?
A. Definitions:
1. Ecology- The study of the interactions of organisms
with one another and their environment.
2. Ecosystem-a self-sustaining collection of
organisms and their environment.
3. Estuary-a partially enclosed body of water where
fresh river water mixes with salty ocean water.
http://www.niot.res.in/
The Ecology of the SF Bay
A.  Abiotic (Non-Living) Factors
1. Factors in SF Bay include:
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Temperature
Water
Sunlight
Wind
Salinity:
•  varies from 0 to 33 parts salt per 1000 parts water
depending on the location in the estuary.
•  0 is typically for freshwater rivers
•  33 is for the saltiest parts of the ocean
Rocks and soil
Natural Catastrophes: fires, floods, earthquakes
B. Biotic (living) Factors
1. Normal biotic factors, including in the SF Bay, fall into
the five kingdoms:
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Plants, Animals, Protists, Fungi, Bacteria (Monera)
B.  Biotic (living) Factors - Continued
2. Organisms are classified as follows:
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Producers- organisms that make their own food
using photosynthesis (Ex: plants and phytoplankton)
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Consumers-organisms that receive their energy from
consuming other organisms (Ex: animals and
zooplankton)
herbivores-eat plants (Ex: Deer)
carnivores-eat herbivores and each other (Ex: Mountain Lion)
omnivores-eat both plants and animals (Ex: Raccoons)
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Decomposers -organisms that obtain their energy
from non-living organic matter (Ex: earthworms and
bacteria)
C. Human Impacts
1. Factors in SF Bay include:
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Endangered or threatened
plants and animals
•  97 species of endangered or
threatened plants and animals use
the Estuary during at least a part of
their lives.
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Diversion of Fresh Water
•  approximately 50% annual flow of
fresh water is diverted for
agriculture.
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Waste and Run-Off
•  From local industry (waste and trace
metals)
•  From urban runoff (roadways and
gutters)
Destruction of Tidal Marshes
•  85% of the tidal marshes have been
destroyed for construction of homes,
etc.
III. Energy in the Ecosystem
A. The Sun is the Source of Energy for Every Ecosystem
1. Producers convert the sun’s energy into chemical
energy through a process called photosynthesis.
2. Equation
Carbon Dioxide + Water !
Glucose
+
Oxygen
(from the air)
(plant sugar/food) (plant waste)
III. Energy in the Ecosystem
B.  Food Chains and Food Webs
1. Consumers receive energy by eating producers or other
consumers.
2. A food chain is a diagram showing the flow of energy
through individual organisms.
3. Example:
diatoms
Energy
Source
shrimp
salmon
sea lion
Trophic level
Producers
Primary
Consumers
Secondary
Consumers
Top consumers
III. Energy in the Ecosystem
B.  Food Chains and Food Webs
4. A food web is a diagram illustrating the flow of energy
through an entire ecosystem.
5. Example:
*Arrows show direction of energy flow
III. Energy in the Ecosystem
C.  Ecological Pyramids -An ecological pyramid represents
energy relationships among trophic levels.
1.  Pyramid of Energy
Ten Percent Rule:
• A consumer gets energy from a producer, but only 10% of the energy in the producer
that was consumed gets stored as energy in the body of the animal that eats it
• 90% of energy in the producer is lost as heat or is used up by the body as it processes
the organism that was eaten
III. Energy in the Ecosystem
C.  Ecological Pyramids
2. Pyramid of Biomass and Numbers
Biomass: The total mass
of all the living organisms
in an ecosystem
IV. Questions to Consider
1. Suggest an explanation why there are fewer lions than
zebras on the African plains.
*90% of energy is lost at each level so there
isn’t as much energy available for top consumers.
Also, it is easier to get food as a producer so population
numbers are higher.
2.  More agricultural land would be available to provide food
for the growing human population if humans did not eat
meat. Explain why.
A person gets the same amount of
Person
1
Grain
10
or
Cow
10
Grain
100
energy from eating the same amount
of either meat (cow) or grain. But due
to the 10% rule, much more grain will
be used if the person eats the cow for
energy. Making more grain uses land
and resources that could be available
to feed more people.