Structure and function of Ecosystem

Structure and function of Ecosystem

Learning Outcomes

At the end of this Lecture, students will
be able to

• Explain structural aspects of Ecosystem

• Discuss functional aspects of Ecosystem


• Structural aspects of Ecosystem

• Functional aspects of Ecosystemt

and function of Ecosystem 


Components that make up the structural
aspects of an ecosystem include:

1. Inorganic aspects – C, N, CO2, H2O.

2. Organic compounds – Protein,
Carbohydrate, Lipids – link abiotic to biotic aspects

3. Climatic regimes – Temperature,
Moisture, Light & Topography.

4. Producers – Plants.

5. Macro consumers – Phagotrophs – Large

6. Micro consumers – Saprotrophs, absorbers
– fungi.


1. Energy cycles.

2. Food chains.

3. Diversity-interlinkages between

4. Nutrient cycles-biogeochemical cycles.

5. Evolution

• Since each ecosystem has a non-living and
a living part that are linked to each other, one needs to look around us and
observe this closely

• This is an important aspect that is a
vital part of our lives

• The non-living components of an ecosystem
are the amount of water, the various inorganic substances and organic compounds
and climatic conditions such as rainfall and temperature, which depend on
geographical conditions and location which is also related to the amount of

• The living organisms in an ecosystem are
inseparable from their habitat

The living component of plant life ranges from extremely small bacteria,
which live in air, water and soil, algae which live in fresh and salt water to
the terrestrial plants which range from grasses and herbs that grow after the
monsoon every year, to the giant long-lived trees of the forest

• The 
plants  convert  energy 
from  sunlight  into 
organic  matter  for 
their growth

• They thus function as producers in the

• The living component of the animal world
ranges from microscopic animals to small insects and the larger animals such as
fish, amphibia, reptiles, birds and mammals

• Man is just one of the 1.8 million
species of plants and animals that inhabit the earth


• Every living organism is in some way
dependent on other organisms

• Plants 
are  food  for 
herbivorous  animals  which 
are  in  turn 
food  for carnivorous animals

• Thus there are different tropic levels in
the ecosystem

• Some organisms such as fungi live only on
dead material and inorganic matter

• Plants are the producers in the ecosystem
as they manufacture their food by using energy from the sun

• In the forest these form communities of
plant life

• In the sea these include tiny algal forms
to large seaweed

• Herbivorous animals are primary consumers
as they live on the producers

• In a forest, these are the insects, amphibia,
reptiles, birds and mammals

• Herbivorous animals include for example
hare, deer and elephants that live on plant life

• They graze on grass or feed on the
foliage from trees

• In grasslands, there are herbivores such
as the blackbuck that feed on grass

• In the sea, there are small fish that
live on algae and other plants

• At a higher tropic level, there are
carnivorous animals or secondary consumers, which live on herbivorous animals

• In our forests, the carnivorous animals
are tigers, leopards, jackals, foxes and small wild cats

• In the sea, carnivorous fish live on
other fish and marine animals

• Animals that live in the sea range in
size from microscopic forms to giant mammals such as the whale

• Decomposers or detrivores are a group of
organisms consisting of small animals like worms, insects, bacteria and fungi,
which break down dead organic material into smaller particles and finally into
simpler substances that are used by plants as nutrition

• Decomposition thus is a vital function in
nature, as without this, all the nutrients would be tied up in dead matter and
no new life could be produced

• Most ecosystems are highly complex and
consist of an extremely large number of individuals of a wide variety of