The Ecosystem
An Introduction
S4L1b iCan demonstrate the flow of energy through a flood web/good
chain, beginning with sunlight and including producerss, consumers, and
decomposers
.
Ecosystem

A community of interdependent organisms and
the interactions with the physical environment
in which they live.
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It can also be defined as the abiotic and biotic
factors and the interactions between them.
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The interaction between organisms and the
environment is the key!
Differentiate between the
following terms:
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Organism
Species
Population
Community
Niche
Habitat
In your notebook, draw a picture
of a bunch of little organisms
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Label: The organisms of the same type
(species)
Circle: individuals of the same species
(Population)
Draw interactions between the populations
(Community)
Compare the terms habitat and
niche
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Sometimes people confuse these terms.
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Figure out the differences between the terms.
Niche vs habitat

A habitat is wear an organism lives. The
habitat must provide a source of food, water
and shelter for the organism.

Niche: The role of the organism. This is
largely to do with the trophic level of the
organism.
For example: plants produce food for the rest
of the food chain. Tigers keep herbivore
populations under control.
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Abiotic and Biotic factors
Biotic Factor: A living, biological factor that
may influence an organism or a system.
Example: predation, disease, competition

Abiotic factor: A non-living, physical factor that
may influence an organism or a system
Examples: Temperature, salinity, pH, light
Which factors are biotic?
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Rabbits
Cacti
Daylight hours
Precipitation
Moss
Soil composition
Bacteria
Limiting factors
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An abiotic factor can limit the population size if there
is too much or too little of it. Even if there is the
right amount of other factors
Examples to consider:
Sunlight
Precipitation
Salinity
Nutrients in the soil
Trophic levels
Ecostems are often broken up and described
according to feeding relationships.
Trophic level:
 The position of an organism in a food chain

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A group of organisms that occupy the same
place in a food chain
Trophic levels in food chains
Be able to give an example of each!
 Primary producers (autotrophs)
 Primary consumers (herbivores)
 Secondary consumers(carnivores)
 Tertiary consumers (top carnivores)
 Decomposers
 Detrivores
 Scavengers
Energy flow and material cycling
Producer
Autotroph - “self” + “feed”
lAn organism that obtains organic food
l
molecules without eating other organisms
but by using energy from the sun or
inorganic molecules to make organic
molecules
l
Remember: This trophic level supports all
of the others
The role of producers is to convert energy
into a form useable for other organisms
l
Producers
Most producers are photosynthetic
(e.g. algae, mosses, diatoms, some
l
bacteria, plants etc.) but some are
chemosynthetic (e.g. hydrothermal vent
bacteria)
(H2)
Decomposer
lAn organism that obtains energy by breaking
down dead organic matter, including dead plants,
dead animals and animal waste, into more simple
substances
lExamples include: bacteria and fungi
L Interconnects all trophic levels since the
organic material making up all living
organisms is eventually broken down
lRole of decomposers is to return valuable
nutrients to the system so they can be used
again
Compare detritus feeders to
decomposers:
Consumer
lHeterotroph - “other” + “feed”
lAn organism that obtains its nutrition by
eating other organisms
lPrimary consumer (herbivore) - eats producers
e.g. sea urchin, copepod
lSecondary consumer (carnivore) - eats
primary consumers e.g. wolf eel, herring
lTertiary consumer - eats secondary
consumers e.g. sea otter, seal
lQuaternary consumer - eats tertiary
consumers e.g. killer whale
Consumers
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The role of the consumer is to transfer energy
from one trophic level to the next.
Notice that consumers have different names,
depending on what they eat:
Herbivores: plant eaters
Carnivores: meat eaters
Omnivores: eat plants and animals
Food Chains
Food webs
Show energy flow through an
ecosystem
An ecosystem’s trophic structure
determines energy flow and nutrient
cycling
L
Food
webs
Trophic levels
Pyramid of biomass
Second Law of Thermodynamics
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There is a tendency for numbers and quantities of
biomass and energy to decrease along food chains.
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The pyramids become smaller at the top because
around 90% of the energy is “lost” between each
level and only 10% is available in the body of the
organism for transfer to the next level.
Energy transfer in a food chain:
First law of thermodynamics
The end!