This document defines key concepts in ecosystems, including their structure and functions. It describes how ecosystems consist of biotic and abiotic components that interact, with energy flowing through the system and biogeochemical cycles circulating nutrients. It outlines the major groups - producers, primary and secondary consumers, decomposers - and their roles. Food chains and webs demonstrate how energy transfers between organisms, while ecological pyramids and succession illustrate how communities change over time.

1. ECOSYSTEM AND ITS
FEATURES

2. WHAT IS AN ECOSYSTEM?
• The term ecosystem was coined in 1930
by Roy Clapham, to denote the physical
and biological components of an
environment considered in relation to each
other as a unit.
• Ecosystem means a dynamic complex of
plant, animal and micro-organism
communities and their non-living
environment interacting as a functional
unit.

3. EXAMPLES

4. EXAMPLES

5. EXAMPLES

6. STRUCTURE AND FUNCTIONS
OF AN ECOSYSTEM
STRUCTURE
An ecosystem usually consists of :
• Biotic components
• Abiotic components
• Interaction between them
• Source of energy

7. STRUCTURE AND FUNCTIONS
OF AN ECOSYSTEM
FUNCTIONS
In an ecosystem there are two processes
proceeding simultaneously:
1 . Energy flow
2 . Biogeochemical cycle

8. Functions
Energy flow
• The energy flow is in a single direction
and is non-cyclic.
• Energy cannot be used indefinitely and is
continuously being lost to the environment
in the form of heat of being used by the
organism for its processes such as
digestion, respiration,etc.

10. Functions
Biogeochemical cycles :
• The cyclic flow of nutrients between non-
living environment (soil, rocks, air, water)
and living organisms is known as
biogeochemical cycle.
• The major nutrient elements i.e.
carbon, hydrogen, oxygen and
nitrogen, which form about 95% mass of
the living organism, are circulated again
and again between living and non-living
components of the ecosystem.

12. Carbon Cycle

13. BIOTIC COMPONENETS OF AN
ECOSYSTEM
• Producers
• Consumers
o Primary consumers
o Secondary consumers
o Tertiary consumers
• Decomposers

14. Producers
• In an ecosystem, producers are those
organisms that use photosynthesis to
capture energy by using sunlight, water
and carbon dioxide to create
carbohydrates, and then use that energy
to create more complex molecules like
proteins, lipids and starches that are
crucial to life processes.
• Producers, which are mostly green
plants, are also called autotrophs.

15. Producers
• Role:
Producers funnel into the ecosystem the
energy needed for its biological processes.
• Shaping the ecosystem :
The efficiency of the producers in adding
energy to the ecosystem determines how
robust that ecosystem will be.
Efficient producers can enable an
ecosystem to support secondary, tertiary or
even quaternary consumers.

16. Consumers
• Primary consumers:
Primary consumers feed directly upon
primary producers to obtain their nutrients
and energy.

17. Consumers
• Tertiary consumers
They feed on secondary consumers.

18. Decomposers
• Decomposers are the organisms that
clean up after the producers and
consumers.
• They obtain their own energy by breaking
down the remains of the producers and
consumers.

19. ENERGY FLOW
• Each organism requires energy for
survival.
• On average about 10 percent of net
energy production at one level is passed
on to the next level.
• Energy is not recycled during
decomposition, but rather is
released, mostly as heat .

21. ECOLOGICAL SUCCESSION
• The process by which the structure of a
biological community evolves over time is
called as ecological succession.
• There are two different types of ecological
succession:
1. Primary succession
2.Secondary succession

22. Primary Succession
• Primary succession occurs when all
previous living organisms have been
removed from an area.
• Thus, organisms that enter into the
uninhabited area start the process of
ecological succession.

23. Secondary Succession
• It is set in motion by disturbances in the
environment which are insufficient to wipe
out the previously existing species.

24. Climax Communities
• The relative end point of ecological
successions referred to as climax
communities.
• The climax community is an environmental
system in which there is little or
extraordinarily slow change.

25. FOOD CHAIN
• A food chain shows how each living thing
gets its food.
• Each link in this chain is food for the next
link. A food chain always starts with plant
life and ends with an animal.

26. EXAMPLES

27. Characteristics of food chains
1. There are more herbivores than
carnivores.
2. The further along the food chain you
go, the less food (and hence energy)
remains available.
3. Most food chains have no more than four
or five links.

28. FOOD WEB
• Most animals are part of more than one
food chain and eat more than one kind of
food in order to meet their food and energy
requirements. These interconnected food
chain form a food web.
• A food web differs from a food chain in that
the latter shows only a portion of the food
web involving a simple, linear series of
species connected by feeding links

29. Example

30. ECOLOGICAL PYRAMIDS
• An ecological pyramid is an illustration of
the reduction in energy as you move
through each feeding (trophic) level in an
ecosystem.

31. Example

32. ECOLOGICAL PYRAMIDS
There are three ways an ecological
pyramid can be represented.
1. Pyramid of Numbers can be generated by
counting all the organisms at the different
feeding levels.

33. Example

34. • Pyramid of Biomass where organisms are
collected from each feeding level, dried
and then weighed. This dry weight
(biomass) represents the amount of
organic matter (available energy) of the
organisms.

35. Example

36. • Pyramid of Energy Flow This approach
necessitates measuring the caloric value
of the different organisms that make up
the community

37. Example

38. Summary
• Concept of an ecosystem
• Structure and function of an ecosystem
• Producers,consumers and decomposers.
• Energy flow
• Ecological succession
• Food chains and food webs
• Ecological pyramids

39. THANK YOU