The document provides information about ecosystems, including: 1) An ecosystem is a dynamic system consisting of organisms and their environment that influence each other. There are terrestrial and aquatic ecosystems. 2) Ecosystem structure includes stratification, and functions include productivity, decomposition, energy flow, and nutrient cycling. 3) Primary productivity is the production of biomass by plants, while secondary productivity is the production of new biomass by consumers.

1. CHAPTER 14: ECOSYSTEM
GIRISH VAMANRAO TONAPI

2.  It is a dynamic system which includes both organisms
biotic component and abiotic environment influencing
the properties of each other and both are necessary
for the maintenance of life.

3.  There are two basic ecosystems − terrestrial and
aquatic.
 Sir Arthur Tansley coined the term Ecosystem

5. STRUCTURE OF ECOSYSTEM
 The interactions between the various biotic and abiotic factors
of an ecosystem lead to the maintenance of the ecosystem.
 Stratification is the vertical distribution of the different species
occupying the different levels. For example, trees occur at a
higher level then shrubs.

6.  The various aspects taken into consideration to study the
functioning of ecosystem are:
 Productivity
 Decomposition
 Energy flow
 Nutrient cycling

7. PRODUCTIVITY
 A constant supply of sunlight is required for the proper
functioning of any ecosystem.
 The amount of biomass produced per unit area over a time
period by plants during photosynthesis is defined as
the primary productivity.

8.  It is expressed as weight or energy
 Productivity can be mainly divided into gross primary
productivity (GPP) and net primary productivity (NPP). GPP is
the rate of production of organic matter during photosynthesis.
 NPP is the amount of energy left in the producers after
utilization of some energy for respiration
 NPP = GPP − Respiratory losses (R)

9.  Secondary productivity is defined as the rate of
formation of new organic matter by consumers.
 Primary productivity depends upon
 type of plant species inhabiting a particular area
 photosynthetic capacity of plants
 nutrient availability

10. DECOMPOSITION
 It is the process of breakdown of complex organic matter into
inorganic substances such as carbon dioxide, water, nutrients, etc.
 STEPS
 Fragmentation − Breaking down of detritus (dead plant and animal
remains, faecal matter) into smaller particles by detritivores
(decomposers)
 Leaching - Process by which these inorganic matters enter the soil
 Mineralization − Process by which humus further degrades to
release minerals into the soil

11.  Catabolism − Process by which detritus is degraded into
simpler inorganic substances by bacterial and fungal enzymes
 Humification − Accumulation of humus in the soil. Humus is
resistant to microbial action and decomposes at an extremely
slow rate. It acts as a reservoir of nutrients.

12. ENERGY FLOW
 Sun is the sole source of energy for all ecosystems on the
earth.
 Plants and other photosynthetic organisms utilize less than
50% of the solar radiation known as the photosynthetically
active radiation (PAR).
 In an ecosystem, plants are called producers and all animals
depend upon the plants directly or indirectly for their food.
Hence, they are known as consumers or heterotrophs.

13.  The consumers can be further divided into primary consumers
(herbivores), secondary consumers (primary carnivores), and
tertiary consumers (secondary carnivores).

14.  Food chain − The energy flow among the various constituent
animals is known as the food chain.
 Food web − The interconnection of the various food chains is
called the food web.
 Trophic level − Every organism occupies a specific level in
their food chain known as the trophic level.
 Standing crop − Each trophic level contains a certain amount
of living material at a certain time known as the standing crop.

15.  Types of Food chains
 Grazing food chain (GFC) : It begins with produces
,that captures the solar energy through
photosynthesis feeds energy in to food chain

16.  Detritus food chain ( DFC) : It begins with dead
organic matter and decomposes and so it is less
dependent on solar energy. The dead organic
matter is broken down into simple nutrients by
microorganisms like fungi and bacteria. This type of
food chain is found in forest ecosystem.

20. ECOLOGICAL PYRAMIDS
 The concept of ecological pyramid was developed by Charles
Elton; these pyramids are also known as Eltonian pyramids.
 The pyramids are a graphical representation which depicts the
number of organisms, biomass and productivity at each trophic
level.
 All ecological pyramids begin at the bottom with the produces
and proceed through different trophic levels.

21.  Ecological pyramids are of 3 types:
 Pyramid of number
 Pyramid of biomass
 Pyramid of energy

22. Pyramid of number
 The pyramid of numbers depicts the relationship in terms of
the number of producers, herbivores and the carnivores at
their successive trophic levels.
 There is a decrease in the number of individuals from the lower
to the higher trophic levels. The number pyramid varies from
ecosystem to ecosystem

24.  Inverted Pyramid of Number
 This type of ecological pyramid is seen in parasitic food chain
where one primary producer supports numerous parasites
which support more hyperparasites.

26.  Inverted Pyramid of Biomass
This happens when the smaller weight of producers support
consumers of larger weight.
Example: Aquatic ecosystem.

27. Pyramid of energy
 The pyramid of energy or the energy pyramid describes the
overall nature of the ecosystem.
 During the flow of energy from organism to other, there is
considerable loss of energy in the form of heat.
 The primary producers like the autotrophs there is more
amount of energy available.

28.  The least energy is available in the tertiary consumers. Thus,
shorter food chain has more amount of energy available even
at the highest trophic level
 However, the pyramid of energy is always upright.

30. NUTRIENT CYCLING
 The amount of nutrients present in the soil at a given time is
known as the standing state.
 Nutrients are never lost from the ecosystem. They are only
recycled from one state to another.

31.  The movement of nutrients through the various components of
the ecosystem is called nutrient cycling or biogeochemical
cycles. They are of two types:
 Gaseous − Reservoir for these types of cycles exist in the
atmosphere.
 Sedimentary − Reservoir for these types of cycles exist in
the earth’s crust.

32. Carbon Cycle
 About 49% of the dry weight of living organisms is made up of
carbon.
 The ocean reserves and fossil fuels regulate the amount of
CO2 in the atmosphere.
 Plants absorb CO2 from the atmosphere for photosynthesis, of
which a certain amount is released back through respiratory
activities.

33.  A major amount of CO2 is contributed by the decomposers who
contribute to the CO2 pool by processing dead and decaying
matter.
 The amount of CO2 in the atmosphere has been increased
considerably by human activities such as burning of fossil
fuels, deforestation.

35. PHOSPHORUS CYCLE
 Phosphorus is an important constituent of cell membranes,
nucleic acids, and cellular energy transfer systems.
 Rocks contain phosphorus in the form of phosphate.
 When rocks are weathered, some of the phosphate gets
dissolved in the soil solution and is absorbed by plants.
 The consumers get their phosphorus from the plants.
 Phosphorus returns back to the soil by the action of
phosphate-solubilising bacteria on dead organisms

37. ECOLOGICAL SUCCESSION
 The composition of all ecosystems keeps on changing with
change in their environment. These changes finally lead to the
climax community.
 Climax community − It is the community which is in
equilibrium with its environment. Gradual and fairly predictable
change in the species’ composition of a given area is called
ecological succession.

38.  Sere(s) − It is the sequence of communities that successively
change in a given environment. The transitional communities
are called seral stages or seral communities.
 Succession happens in areas where no life forms ever existed
as in bare rocks, cool lava, etc. (primary succession), or in
areas which have lost all life forms due to destructions and
floods (secondary succession).

39.  Primary succession takes hundreds to thousands of years as
developing soil on bare rocks is a slow process. Secondary
succession is faster than primary succession since the nature
does not have to start from scratch.
 During succession, any disturbances (natural/man-made) can
convert a particular seral stage to an earlier one.

40.  Hydrarch succession − It takes place in wet areas and
converts hydric conditions to mesic.

41.  Xerarch succession − It takes place in dry areas and
converts xeric conditions to mesic.

42.  Pioneer species − These are the species that first invade a
bare area. On land, these could be lichens that secrete
enzymes to dissolve the rock surfaces for soil formation while
in water, pioneer species could be phytoplanktons.
 The ultimate result of all successions is a climax community, a
mesic

43. ECOSYSTEM SERVICES:
The products of ecosystem processes are named as ecosystem
services.
 Healthy forest ecosystems purify air and water.
 Mitigate droughts and flood.
 Cycle nutrients.
 Generates fertile soil.

44.  Provide wildlife habitat.
 Maintain biodiversity.
 Pollinate crops.
 Provide storage site for carbon
 Provides aesthetic, cultural and spiritual values

45. ASSIGNMENTS
1. What is food web? 1
2. Explain phosphorus cycle – 5
3. Explain carbon cycle -5
4. What is ecological succession ? -1
5. Mention any three ecosystem services -3
6. Name any two man – made ecosystem? -2
7. Define stratification?-1
8. Name the ecological pyramid that is always upright?-1

46. 9.What is meant by ecological pyramid? With the help of one
example each, show that pyramid of number can be both
upright as well as inverted.
10. Describe the components of an ecosystem? -5
11. Define standing crop? -1
12. Differentiate between Production & decomposition? -2
13. What is decomposition – Describe the different processes
involved in decomposition?-5

47. 14. What are the products of decomposition?
15. Mention one similarity between hydrach & Xerach
secession?-1
16. Differentiate between primary productivity & secondary
productivity? -2
17. With the help of a diagram, represent the energy flow through
different trophic level?-3

48. MCQS
 Which one of the following is not a functional unit of
an ecosystem?
 Productivity
 Stratification
 Energy flow
 Decomposition
 Stratification

49.  Which one of the following is not a gaseous
biogeochemical cycle in ecosystem?
 Nitrogen cycle
 Carbon cycle
 Sulphur cycle
 Sulphur cycle

50.  Identify the possible link "A" in the following food
chain: Plant → insect → frog → "A" → Eagle
 Cobra
 Parrot
 Rabbit
 wolf
 Cobra

51.  The type of ecosystem with the highest mean plant
productivity is
 Tropical rain forest
 Temperate grassland
 Desert
 Tundra
Tropical rain forest

52.  In an aquatic ecosystem, the trophic level
equivalent to cows in grasslands is
 Nekton
 Zooplankton
 Phytoplankton
 Benthos
 Zooplankton

53.  Trophic levels in ecosystem is formed by :
 only herbivores
 only plants
 only bacteria
 Organisms linked in food chain
 Organisms linked in food chain