Ecosystems, Food Chains, and Food Webs

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Ecosystems, Food Chains, and Food Webs
Ecosystem A community of living things and the
non-living components of their environment
(things like weather, water, chemicals, etc)
interacting as a system.
Food Web A complex network of living organisms
within an ecosystem whose predator/prey
interactions are connected within an ecosystem.
Food Chain A linear (simple) sequence of
organisms within a food web.
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-The different levels as you move through a food
chain are referred to as trophic levels
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Producers
Photosynthesic mainly algae in the marine
environment. Marine plants are rare due to the
salinity of the water.
Chemosynthesic bacteria in the deepest darkest
areas of the ocean use methane and sulfur dioxide
to create energy.
Phytoplankton small autotrophic organisms who
obtain their energy through photosynthesis.
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Consumers
Primary
Secondary
-Filter feeders heterotrophic organisms which
feed on zooplankton or other smaller filter
feeders. -Can be large (whales/sunfish) or small
(amphipods/small fish)
-Zooplankton small heterotrophic organisms who
feed on phytoplankton or filter nutrients and
minerals out of the water.
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Consumers
-Tertiary, quaternary, etc The larger organisms
that you are most familiar with. -Sharks, squid,
tuna, swordfish, dolphins, seals.
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Decomposers
-Decomposers usually small bacteria (fungi on
land) which break down decaying organic material.
-Can also be scavengers, such as crabs and
some deep water fish. -They are important in
returning nutrients back into ecosystem that
would otherwise be lost in the water
column. -Zooplankton and filter-feeders are the
primary predators of decomposers in marine
environments.
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Affecting one part of a marine food web ends up
impacting the population of every other level.
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-Why are there so few top level predators and so
many zooplankton and phytoplankton?
A Only 10 of an organisms energy is passed on
to the next trophic level.
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Top-down vs. Bottom-up
Organisms higher up in food webs determine the
population size at each level. (ie sharks)
Organisms lower in food webs determine the
population size at each level. (ie kelp)
These are the 2 theories attempting to explain
how ecosystem populations change over time
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Density-dependent factors factors in an
ecosystem that depend on the population size of
the organisms involved.
Density-independent factors factors in an
ecosystem that are not a result of population
size.
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What factors could possibly affect the
populations within an ecosystem?

1. Disease

2) Climate Change (Biggie for marine organisms)
3) Invasive Species
4) Human Impact
5) Death vs. Birth (Carrying Capacity)
6) Predator Prey Interaction
7) Natural Disasters
8) Immigration vs. emmigration
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Carrying Capacity (K) The maximum size a
population can reach before factors force the
population to stop growing.
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Ecosystems from another perspective
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Symbiotic Relationships
Translates to living with in Latin
Close interactions between two different
biological species
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Mutualism both species involved benefit from
the relationship (,)
coral
-Exchange oxygen and carbon dioxide
-Provide a safe place to live
zooxanthellae
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Parasitism the species performing the action
benefits and the other is harmed (,-)
-Juvenile pearl fish swim into anus of sea
cucumber to feed on digestive system and gonads
Sea cucumber
Juvenile pearl fish
Anus
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Commensalism one species benefits, and the
other species is not affected at all (,0)
-The barnacles hitch a free ride on the whale
through nutrient rich waters, while the whale is
unaffected.
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Altruism the species performing the action is
harmed, and the other benefits (-,)
-This goes against typical evolutionary biology
(survival of the fittest) -So why does it happen?
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Identify the type of symbiotic relationship
exhibited in each of the following examples.
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Sea anemone/Hermit crab
commensalism
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Cleaner shrimp/zebra moray eel
mutualism
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Clam/Barnacle
commensalism
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Hermit Crab/egg sacs
parasitism
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Clownfish/sea anemone
mutualism
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Remora/shark, ray, turtle
commensalism