ECOSYSTEMS & ENERGY FLOW

May 2014

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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.

How do organisms get food? Producers (use photosynthesis)

Consumers (use cellular respiration)

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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 Pyramids1. Pyramid of Energy2. Pyramid of Biomass3. 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: