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

The non-living components of an ecosystem

Consists of the elements which may be found in the environment

Abiotic factors 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 Heterotrophs

Autotrophic organisms may be photoautotrophic or chemoautotrophic.

The heterotrophs include humans, animals and microorganisms.

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Autotrophs

Photoautotrophs possess chlorophyll and carry on photosynthesis.

Chemoautotrophs are bacteria that obtain energy from the oxidation of inorganic compounds such as ammonia, nitrites and sulfides.

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Heterotrophs

Heterotrophic organisms need a source of pre-formed nutrients and consume tissues of other organisms.

Consumers are classified according to the type of food they eat.

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Types of Consumers

Herbivores are animals that feed directly on green plants.

Carnivores are animals that eat other animals.

Omnivores feed on both plants and animals.

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Types of Consumers Decomposers are fungi and bacteria that

extract energy from dead matter, including waste and return nutrients back to the soil.

Scavengers are animals that feed on dead matter.

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Food Chain

Artificial devices that illustrate how energy and nutrients move from one organism to another though the ecosystem

Shows transfer of energy from one trophic level to another

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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 Chain

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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

In general, about 10% of energy at a particular trophic level is incorporated into the next trophic level.

This rapid loss loss of energy explains why a food chain rarely has five links.

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Energy Flow Energy enters ecosystems from an

external source. What is it?

Energy flows linearly and exits an ecosystem through ___________.

What happens to the amount of energy as it travels through an ecosystem?

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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 The figures represent

the amount of 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

Most pyramids show that there are many more individuals at the lower trophic levels. For example: the number of herbivores on the African plains (zebra, wildebeests) is far greater than the number of carnivores (lions).

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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Write the trophic level that each organism belongs to in this food web.