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Ecosystem

F.Y. B.Sc. Botany

12 February, 2013

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What is Ecosystem ?

Clarke 1954 :

The organism and the physical features of

the habitat form an ecological complex or

more briefly and Ecosystem

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What is Ecosystem ?

E.P. Odum:

The ecosystem is the basic functional unit

of organisms and their environment

interacting with each other and with theirown components

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Defined area in which a community lives with

interactions taking place among the organismsbetween the community and its non-livingphysical environment.

An ecosystem is formed by the interactionsbetween all living and non-living things

All the ecosystems of the earth are connectedto one another

A complete self sufficient ecosystem is rarelyfound in nature

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Structure of Ecosystem

The structure of an ecosystem is basically a

description of the organisms and physical

features of environment including the

amount of and distribution of nutrients in a

particular habitat

It also provided the range of climatic

conditions prevailing in the area

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Structure of Ecosystem

All the ecosystems consists of two basic

componets:

1. Abiotic Components

2. Biotic Components

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Abiotic components

Solar energy provides practically all the energy forecosystems.

Inorganic substances, e.g., sulfur, boron, tend to cycle

through ecosystems. Organic compounds, such as proteins, carbohydrates,

lipids, and other complex molecules, form a linkbetween biotic and abiotic components of the system.

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Light

Quality of light (wavelength or colour):

Light intensity ("strength" of light)

Day length (length of the light period):

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Temperature

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Water

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Atmospheric gases.

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Wind

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Physiographic factors

These factors are those associated

with the physical nature of the area,

such as altitude, slope of land andthe position of the area in relation

to the sun or rain-bearing winds.

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What are Biotic Factors?

Biotic factors are the living organisms in an

ecosystem

They live in Communities (many different

populations) of varied Populations (groups

of interbreeding organisms)

Each organism has a role or NICHE and is

usually participating in a relationship of

some kindF.Y. B.Sc. Botany Ecosystem Structure 12 Feb 13

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Biotic Factors"

Depending on how the living organisms in an

ecosystem obtain, store and utilize release

energy, they are categorized into :

(a) Producers

(b) (b) consumers

(c) decomposers or detritivores.

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Autotrophs Autotrophs (=self-nourishing) are

called primary producers.

Photoautotrophs fix energy from thesun and store it in complex organiccompounds

(= green plants, algae, some bacteria)

photoautotrophs

simple

inorganic

compounds

complex

organic

compounds

light

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Chemoautotrophs (chemosynthesizers) are

bacteria

that oxidize reduced inorganic substances

(typically sulfur and ammonia

compounds)

and produce complex organic compounds.

chemoautotrophs

reduced

inorganic

compounds

complex

organic

compounds

oxygen

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Heterotrophs Heterotrophs (=other-nourishing)

cannot produce their own food

directly from sunlight+ inorganic

compounds. They require energy

previously stored in complexmolecules.

heterotrophssimple

inorganic

compounds

complex

organic

compounds

(this may include several steps, with

several different types of organisms)

heat

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Heterotrophs can be grouped as:

consumers

decomposers

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Consumers feed on organisms or particulate organic

matter.

Decomposers utilize complex compounds in dead

protoplasm.

Bacteria and fungi are the main groups ofdecomposers.

Bacteria are the main feeders on animal material.

Fungi feed primarily on plants, although bacteria alsoare important in some plant decomposition processes.

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F Y B Sc Botany Ecosystem Structure 12 Feb 13