Word Environment derived from the french word “ environner”

Which means to surround

• The surrounding in which an organism lives

Biosphere is a shallow life bearing layer

• Ecosystem – Sir Arthur Tansley (1935)

A biological community of interacting organisms and their physical environment.

• Ecology – greek work oikos – house or placeEarnst haeckel (1869)The branch of biology that deals with the relations of

organisms to one another and to their physical surroundings.

HABITAT

• The place occupied by an organism, population or community which is exposed to a particular combination of environmental factors is called habitat.

Trophic Levels• A trophic level is the position occupied by an organism in a

food chain.• Trophic levels can be analyzed on an energy pyramid.• Producers are found at the base of the pyramid and

compromise the first trophic level. • Primary consumers make up the second trophic level.• Secondary consumers make up the third trophic level.• Finally tertiary consumers make up the top trophic level.

Trophic Levels• A tropic level is the position occupied by an organism in a food chain.Trophic levels can be analyzed on an energy pyramid.• Producers are found at the base of the pyramid and compromise the first trophic level. • Primary consumers make up the second trophic level.• Secondary consumers make up the third trophic level.• Finally tertiary consumers make up the top trophic level.

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Modified from: General Ecology, by David T. Krome

Trophic level: All the organisms that are the same number of food-chain steps from the primary source of energy

Standing crop: The amount of living material present in different topic levels

Standing state: The amount of nutrients present in the soil at any given time

Food chain

• A food chain shows the feeding relationship between different living things in a particular environment or habitat.

• The transfer of energy & nutrients from one feeding group of organisms to another in a series.

• It’s a sequence of eaters being eaten, or who eats whom

Food Web

Food Webs are Food Chains that intersect each other. Food webs are what really happens in nature.

A predator from one food chain may be linked to the prey of another food chain

Several food chains linked together

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© 2003 John Wiley and Sons Publishers

Food web of a hot spring

Ecological pyramids

An ecological pyramid is a graphical representation designed to show…….

the number of organisms, energy relationships, and biomass of an ecosystem. They are also called Eltonian pyramids after

Charles Elton, who developed the concept of ecological pyramids.

Charles Elton (1927) developed the concept of ecological pyramids who noted that "…the animals at the base of a food chain are relatively abundant while those at the end are relatively few in number…"

Producer organisms (usually green plants) form the base of the pyramid, With succeeding levels above representing the different trophic levels (respective position of the organisms within ecological food chains).Succeeding levels in the pyramid represent the dependence of the organisms at a given level on the organisms at lower level.

There are three types of pyramids: of numbers, of biomass, and of energy.

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Pyramid of Biomass Biomass is (is the mass of living biological organisms in a given

area or ecosystem at a given time) renewable organic (living) material.

A pyramid of biomass is a representation of the amount of energy contained in biomass, at different trophic levels for a particular time.

It is measured in grams per meter2, or calories per meter2. This demonstrates the amount of matter lost between trophic levels.

Each level is dependent on its lower level for energy, hence the lower level determines how much energy will be available to the upper level. Also, energy is lost in transfer so the amount of energy is less higher up the pyramid.

There are two types of biomass pyramids: upright and inverted.

An upright pyramid is one where the combined weight of producers is larger than the combined weight of consumers. An example is a forest ecosystem.

An inverted pyramid is one where the combined weight of producers is smaller than the combined weight of consumers. An example is an aquatic ecosystem.

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Pyramid of Numbers The pyramid of numbers represents the number of organisms in each

trophic level. This pyramid consists of a plot of relationships between the number herbivores (primary consumers), first level carnivore (secondary consumers), second level carnivore (tertiary consumers) and so forth. This shape varies from ecosystem to ecosystem because the number of organisms at each level is variable

Upright, partly upright and inverted are the three types of pyramids of numbers.

An aquatic ecosystem is an example of upright pyramid where the number of organisms becomes fewer and fewer higher up in the pyramid.

A forest ecosystem is an example of a partially upright pyramid, as fewer producers support more primary consumers, but there are less secondary and tertiary consumers.

An inverted pyramid of numbers is one where the number of organisms depending on the lower levels grows closer toward the apex. A parasitic food chain is an example.

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Pyramid of EnergyThe pyramid of energy represents the total amount of energy consumed by each trophic level. An energy pyramid is always upright as the total amount of energy available for utilization in the layers above is less than the energy available in the lower levels. This happens because during energy transfer from lower to higher levels, some energy is always lost.

If all mankind were to disappear,

The world would regenerate back to the rich state of equilibrium

That existed ten thousand years ago.

If insects were to vanish,

The environment would collapse into chaos.

Edward O Wilson