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ECOSYSTEMS & ENERGY FLOW
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Ecosystem
A community and its physical environment
Made up of two essential components: Abiotic factors Biotic factors
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Abiotic factors
non-living components of an ecosystem elements which may be found in the
environment May be:
Physical Chemical
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Physical factors
Sunlight and shade Temperature and wind Amount of precipitation Altitude and latitude Nature of soil
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Chemical factors
Salinity of water Level of dissolved O2 and other gases Level of plant nutrients pH of soil and water Level of natural or artificial toxic
substances
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Biotic factors The organisms in an ecosystem are
either: Autotrophs
photoautotrophic chemoautotrophic
Heterotrophs include humans animals and microorganisms.
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Autotrophs
Photoautotrophs – has chlorophyll and carry on photosynthesis.
Chemoautotrophs – bacteria that obtain energy from the oxidation
of inorganic compounds such as ammonia, nitrites and sulfides.
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Heterotrophs
need a source of pre-formed nutrients consume tissues of other organisms. consumers are classified according to the
type of food they eat.
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Types of Consumers
Herbivores feed directly on green plants.
Carnivores eat other animals.
Omnivores feed on both plants and animals.
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Types of Consumers Decomposers
fungi and bacteria extract energy from dead matter, including
waste return nutrients back to the soil.
Scavengers feed on dead matter.
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Food Chain
illustrates how energy and nutrients move from one organism to another
shows transfer of energy from one trophic level to another
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Food Chain
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Trophic levels A trophic level includes a group of
organisms that obtain food in a similar manner. Producers Primary consumers Secondary consumers Tertiary consumers Quaternary consumers
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Food Webs: Who Eats Whom?
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Food Web
A complex network of interconnected food chains
The feeding relationship that actually exists in nature
May be: Grazing food web Detrital food web
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Energy Flow
Ecosystems are dependent upon solar energy flow and finite pools of nutrients.
The primary source of energy for ecosystems is sunlight.
All energy content of organic matter is eventually lost to the environment as heat.
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Laws of Thermodynamics
Energy can neither be created nor destroyed, but can be transformed into different forms.
When energy is transformed from one form to another, there is always some loss of energy from the system, usually as low grade heat.
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10% Law of Energy Transfer
only 10% of energy at a particular trophic level is incorporated into the next trophic level.
rapid loss of energy explains why a food chain rarely has five links.
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Energy Flow
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Ecological Pyramids
Graphic representations of the relative energy amounts at each trophic level.
3 Types of Pyramids
1. Pyramid of Energy
2. Pyramid of Biomass
3. Pyramid of Numbers
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Pyramid of Energy
Energy content of each trophic level
Unit of energy = Kilocalories/meter2/year
Pyramid has large base and gets significantly smaller at each level.
Organisms use energy for work and respiration, so less energy is available to each successive trophic level.
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Pyramid of Energy
energy at each trophic level expressed in kcal/m2/yr.
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Pyramid of Biomass Biomass is a quantitative estimate of the total mass
(amount) of living material…or
…the amount of fixed energy at a given time.
Measuring biomass: total volume, dry weight, or live weight
A 90% reduction occurs between each trophic level
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Pyramid of Biomass Biomass also
diminishes with the distance along the food chain from the autotrophs which make the organic molecules in the first place.
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Pyramid of Numbers
Illustrates number of organisms at each trophic level
more individuals at the lower trophic levels.
BUT some number pyramids can be inverted.
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Pyramid of Numbers Small animals are
more numerous than larger ones.
If the size of the individuals at a given trophic level is small, their numbers can be large and vice versa.
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Identify the food chains and write the trophic level for each organism in this food web.
Food Web Activity:
