Theory of food chains, food web, ecological pyramids and components of terrestrial and aquatic ecosystems

1. Environmental Studies
&
Disaster Management
Somanath Sarvade
Assistant Professor (Agroforestry)
College of Agriculture Balaghat
E-mail: somanath553@jnkvv.org
Jawaharlal Nehru Krishi Vishva Vidyalaya,
Jabalpur

2. What is Food Chain?
Flow of energy in an ecosystem is one way process.
The sequence of organism through which the energy
flows, is known as food chain.

3. Important facts
• In a food chain each organism
obtains energy from the one at the
level below.
• Plants are called producers
because they create their own food
through photosynthesis
• Animals are consumers because they
cannot create their own food, they
must eat plants or other animals to
get the energy that they need.

4. Tropic levels in a food chain
• Producers
• Consumers
(i) Primary consumers
(ii) Secondary consumers
(iii) Tertiary consumers
(iv) Quaternary consumers
• Decomposers

5. Types of Food Chain
(i) Grazing Food Chain
•The consumers utilizing plants as their food , constitute grazing food
chain.
• This food chain begins from green plants and the primary consumer
is herbivore.
• Most of the ecosystem in nature follows this type of food chain.
Ex: grass => grasshopper => birds => falcon

7. Grazing Food Chain

8. (ii) Detritus food chain
• This type of food chain starts from dead organic matter of
decaying animals and plant bodies to the micro-organisms and
then to detritus feeding organism and to other predators.
• The food chain depends mainly on the influx of organic matter
produced in another system.
• The organism of the food chain includes algae, bacteria, fungi,
protozoa, insects, nematodes etc.

9. Detritus Food Chain

10. Significance of Food Chain
• The knowledge of food chain helps in understanding the
feeding relationship as well as the interaction between
organism and ecosystem.
• It also help in understanding the mechanism of energy flow
and circulation of matter in ecosystem.
• It also helps to understand the movement of toxic substance
and the problem associated with biological magnification in
the ecosystem.

11. What is food web?
• Food web can be defined
as, "a network of food
chains which are
interconnected at various
tropic levels, so as to form a
number of feeding
connections amongst
different organisms of a
biotic community".
• It is also known as
consumer-resource system.

12. Important facts
• A node represents an individual
species, or a group of related species
or different stages of a single species.
• A link connects two nodes. Arrows
represent links, and always go from
prey to predator.
• The lowest tropic level are called basal
species.
• The highest tropic level are called top
predators.
• Movement of nutrients is cyclic but of
energy is unidirectional and non-cyclic.

13. Types of food web representation

14. Different food webs
• Soil food web
• Aquatic food web
• Food web in forest
• Food web of grassland
• Food web in terrestrial and aquatic ecosystem

16. Aquatic food web

17. Food web in forest

18. Grassland Food Web

19. Food web in terrestrial and aquatic ecosystem

20. Significance of food chains and food webs
1. Food chains and food webs play a very important role in the
ecosystem.
2. Energy flow and nutrient cycling takes place through them.
3. They maintain and regulate the population size of different tropic
levels, and thus help in maintaining ecological balance.
4. They have the property of bio-magnification. The non – biodegradable
materials keep on passing from one tropic level to another. At each
successive tropic level, the concentration keep on increasing. This
process is known as bio-magnification.

21. Significance of Food Web
• Food webs distinguish levels of producers and consumers by
identifying and defining the importance of animal relationships and
food sources, beginning with primary producers such as plants,
insects and herbivores.
• Food webs are important tools in understanding that plants are the
foundation of all ecosystems and food chains, sustaining life by
providing nourishment and oxygen needed for survival and
reproduction.
• The food web provide stability to the ecosystem.

22. What are Ecological Pyramids?
• Ecological pyramids are
graphical representations
of the tropic structure
ecosystem.
• Tropic levels are the
feeding positions in a
food chain such as
primary producers,
herbivores, primary
carnivore etc.

23. Types of Ecological Pyramid
Three types of ecological pyramids can usually be
distinguished namely:
• Pyramid of numbers
• Pyramid of biomass
• Pyramid of productivity

24. Pyramid of Numbers
The pyramids of numbers show the relationship between producers,
herbivores and carnivores at successive trophic levels in terms or their
numbers.
• In a grassland the producers, which are mainly grasses, are always
maximum in number.
• This number shows a decrease towards apex, the reason is obvious,
number than the grasses.
• The secondary consumers, snakes and lizards are less in number than
the rabbits and mice.
• In the top (tertiary) consumers hawks or other birds, are least in number.
In this way the pyramid becomes upright. In a pond ecosystem, also the
pyramid is upright as under:
• The producers, which are mainly the phyto-planktons as algae, bacteria
etc. are maximum in number;

25. • The herbivores, which are smaller fish; rotifers etc are less in number than the
• producers;
• The secondary consumers (carnivores), such as small fish which eat up each
other, water beetles etc. are less in number than the herbivores;
• Finally, the top (tertiary) consumers, the bigger fish are least in number.
However, the case is not so in a forest eco-system. There the pyramid of
numbers is somewhat different in shape:—
• Producer, here the producers, are mainly large-sized trees, they are less
in number, and form the base of the pyramid.
• The herbivores, which are the fruit-eating birds, elephants, deer etc. are
more in number than the producers.
• Thereafter there is a gradual decrease in the number of successive
carnivores.

27. • In this way the pyramid is made again upright. However, in a
parasites food chain the pyramids are inverted.
• This is for the reason that a single plant may support the growth of
many herbivores.
• In its turn, each herbivore may provide nutrition to several
parasites, which support many hyper-parasites.
• Consequently from the producer towards consumers, there is a
reverse position.
• In other words the number of organisms gradually shows an
increase, making the pyramid inverted in shape.

28. Pyramids of biomass
• The pyramids of biomass are comparatively more fundamentalism;
as the reason is they instead of geometric factor; show the
quantitative relationships of the standing crops. The pyramids of
biomass in different types of ecosystem may be compared as
under:

29. • In grassland and forest there is generally a gradual decrease in
biomass of organisms at successive levels from the producers to
the top carnivores. In this way, the pyramids are upright.
• However, in a pond the producers are small organisms, their
biomass is least, and this value gradually shows an increase
towards the apex of the pyramid and the pyramids are made
inverted in shape.

30. Pyramid of energy
• The energy pyramid gives the best picture of
overall nature of the ecosystem.
• Here, number and weight of organisms at any
level depends on the rate at which food is
being produced.
• If we compare the pyramid of energy with the
pyramids of numbers and biomass, which are
pictures of the standing situations (organisms
present at any moment), the pyramid of energy
is a picture of the rates of passage of food
mass through the food chain.
• It is always upright in shape.

33. FOREST ECOSYSTEM
Introduction
A forest ecosystem is the one in which a tall and trees grow that
support many animals and birds. The forest are found in undisturbed
areas receiving moderate to hi rainfall. The forest occupies nearly
30.08% of the world’s land area. In India it occupies only 21.67% of its
total land area.
Types of forest ecosystem
Depending upon the climate conditions, forests can be classified into
the following types.
1. Tropical Rain forests.
2. Tropical deciduous forests.
3. Tropical scrub forests.
4. Temperate rain forests.
5. Temperate deciduous forest

34. Features of different. types of Forests
1. Tropical Rain forests: They are forest land near the equator. They are
characterized by high temperature. They have broad leaf trees like teak and
the animals like lion, tiger and monkey.
2. Tropical deciduous forests: They are found little away from the equator.
They are characterized by a warm climate and rain is only during monsoon.
They have different types of deciduous trees like maple, oak and hickary and
animals like deer, fox, rabbit and rat.
3. Tropical Scrub forests: These are characterized by a dry climate for
longer time. They small deciduous trees
and shrubs and animals like maple, oak and hickory and animals like deer,
fox, etc.,
4. Temperate Rain Forests: They are found in temperate areas with
adequate rainfall. They are characterized by
coniferous trees like pines, firs, red wood etc., and animals like, squirrels,
fox, cats, bear etc.,

35. 5. Temperate deciduous forests: They are found in areas with
moderate temperatures. have major trees including broad leaf
deciduous trees like oak, hickory and animals like deer, fox, bear,
etc.,
Characteristics of forest ecosystems
1. Forests are characterized by warm temperature and adequate rainfall,
which make the
2. generation of number of ponds, lakes etc.,
3. The forest maintains climate and rainfall.
4. The forest support many wild animals and protect biodiversity.
5. The soil is rich in organic matter and nutrients which support the growth
of trees.
6. Since penetration of light is so poor, the conversion of organic matter
into nutrients is very fast.

36. Structure and Function of forest ecosystem
I. Abiotic components
Climatic factors (temperature, light, rainfall) and minerals The abiotic
components are inorganic and inorganic and organic substances
found in the soil and atmosphere. In addition minerals, the
occurrence of litter is characteristic features, majority of forests.
II. Biotic components
1. Producers: The plants absorb sunlight and produce
photosynthesis
Eg. Trees, shrubs and ground vegetation..

37. 2. Consumers
(a) Primary consumers (herbivores) :They directly depend on the
plants for their food.
Example : Ants, flies, insects, mice, deer, squirrels.
b. Secondary consumers (primary carnivores): They directly
depend on the herbivores for their food
Examples: Snakes, birds, fox.
c. Tertiary consumers: They depend on the primary carnivores for
their food
Examples : Animals, like tiger, lion, etc.,

38. 3. Decomposers
• Bacteria and fungi.
• They decompose the dead plant and animal matter,
• Decomposition rate in tropical and subtropical forest
is rapid than in the temperate forests.

40. GRASSLAND ECOSYSTEM
Introduction
• Grassland occupies about 25% of earth’s surface addition to grass
species, some trees and shrubs are/also pre in grasslands.
• Limited grazing helps to improve the net primary production of the
grasslands.
• But, overgrazing leads degradation of these grasslands resulting in
desertification

41. Types of grassland ecosystem Depending upon the climate
conditions grassland classified into three types
1. Tropical grasslands.
2. Temperate grasslands.
3. Polar grasslands.

42. Features of different types of grassland
1. Tropical grasslands
• They are found near the borders of tropical rain forests are
characterized by high temperature and moderate rainfall (40 to 100
cm).
• It is also known as Savanna type.
• They ye tall grasses with scattered shrubs and stunted trees and
animals like zebras, giraffes, antelopes, etc.,
2. Temperate grasslands
• They are usually found in the centers of continents, oil sloped hills.
• The are characterized by very cold winters and hot summers.
• Intense grazing and summer fires, do not shrubs or trees to grow.

43. 3. Polar grasslands
• They are found in arctic polar regions.
• They are characterized by severe cold and strong winds along with
ice and snow.
• In summers several small annual plants grow. They ‘e animals like
arctic wolf, weasel, arctic fox, etc.,
Characteristics of Grassland Ecosystems
• Grassland ecosystem is a plain land occupied by grasses.
• Soil is very rich in nutrients and organic matter.
• Since it has tall grass, it is ideal place for grazing animals.
• It is characterized by low or uneven rainfall.

44. Structure and function of the grassland Ecosystems
I. Abiotic components
Nutrients, H, 0, A, P, S, etc.,
These abiotic components are supplied by C02, H2, C, Nitrate, phosphates and
sulphates.
II. Biotic Components
1. Producers: They produce food.
Example: Grasses, forbs and shrubs.
2. Consumers:
Primary consumers (herbivores): They depend on grasses for their food
Examples: Cows, buffaloes, deer, sheep, etc.,
Secondary consumers (carnivores): They feed on herbivores.
Examples: Snakes, lizards, birds, Jackals, fox, etc.,
Tertiary consumers: They feed on secondary consumers
Examples :Hawks, eagle, etc.,
3. Decomposers: They decompose the dead organic matter
Examples: Fungi and bacteria.

47. • Grasslands form a variety of different ecosystems located in
different climatic conditions, ranging from near-desert conditions
to patches of Shola Grasslands that occur on the hill-slopes
along side the extremely moist evergreen forests in South India.
• In the Himalayas, there are the high cold Pastures.
• There are tracks of tall elephant grass in the low lying Terai belt
south of the Himalayan foothills there are also Semi-Arid
Grasslands in western India, parts of Central India and in the
Deccan plateau.
Grassland types in India

48. • The Shola Grasslands consist of patches on hillslopes that
occur alongside the Shola Forests on the Western Ghats, the
Nilgiri and Anamalai ranges.
• These form patchworks of grassland on the slopes and forest
habitats along the streams and low-lying areas .
Shola Grasslands

49. • The Himalayan Pasture belt extends up to the snow-line the
grasslands at a lower level form patches along with coniferous or
broad level forests and grassland ecosystem as vital part of their
habitat.
• The animals migrate up to the high altitude grasslands and move
down to the forest in winters when snow covers the grassland.
• These Himalayan pastures have large number of variety of grasses
and herbs.
• The Himalayan hill-slope are covered with thousands of colorful
flowering plants as well as large number of medicinal plants
Himalayan Pasture

51. • The Terai-Duar savanna and grasslands is a narrow
lowland ecoregion at the base of the Himalayas, about
25 km wide, and a continuation of the Gangetic Plain.
The world's tallest grasslands are found in this
ecoregion, which are the most threatened and rare
worldwide
Flora
• The Terai-Duar savanna and grasslands are a mosaic
of tall riverside grasslands, savannas and evergreen
and deciduous forests, depending on soil quality and
the amount of rain each area receives. The grasslands
of the Terai in Nepal are among the tallest in the world.
Important grasses include baruwa and kans grass,
which quickly establishes itself after the retreat of the
monsoon waters.
Terai-Duar savanna and grasslands

52. Fauna
• The eco-region is habitat for a huge number of mammalian and bird
species. Notable are the large numbers of the endangered greater
one-horned rhinoceros and Bengal tigers as well as Asian elephants,
sloth bears, Indian leopards. Grazing animals of the grasslands
include five species of deer, barasingha, sambar, chital, hog deer,
muntjac, gaur and nilgai. Endangered mammals found here include
the wild water buffalo and the near-endemic hispid hare. The
grasslands are also home to a number of reptiles including the
gharial, mugger crocodile and soft-shelled turtles.
There are three near-endemic bird species including the vulnerable
Manipur bush quail. The 44 threatened and declining bird species of
the grasslands include the Bengal florican, lesser florican, sarus crane
and rufous-rumped grass bird.

53. • The semiarid plains of western India, central India and the
Deccan plateau are covered with grassland tracts with patches
of thorn forest. Severe mammals such as wolf, blackbuck,
chinkara and birds such as bustards and florican are adapted to
these arid conditions.
• The scrublands of the Deccan plateau are covered with
seasonal grasses and herbs on which its fauna is dependent. It
teams with insects life on which the insectivorous birds feed.
Semiarid plains of western India grasslands

54. DESERT ECOSYSTEMS
Desert occupies about 35% of our
world’s land area. It is characterized by
less than 25 cm rainfall. The
atmosphere is dry and hence it is a poor
insulator .
Types of desert ecosystems
Based on the climatic conditions,
deserts are classified three types.
1. Tropical deserts.
2. Temperate deserts.
3. Cold deserts.

55. Features of different types of deserts
1. Tropical deserts: Tropical deserts are found in
•Africa: Sahara desert.
•Rajasthan: Thar desert.
They are characterized by only few species. Wind blow sand dunes are
very common.
2. Temperate deserts
They are found in
South California: Majave.
They are characterized by very hot summer and very Winter time.
3. Cold deserts
They are found in -
China: Gobi desert.
They are characterized by cold winters and mild summers.

56. Characteristics of Desert ecosystem
The desert air is dry and the climate is hot. Annual rainfall is
less than 25 cm. The soil is very poor in nutrients and organic
matter, Vegetation is poor.
Structure and functions of the desert systems ecosystems
1. Abiotic Components
Examples : Temperature, rainfall, sunlight, water, etc.,
The temperature is very high and the rainfall is very low. The
nutrient cycling is also very low.

57. II. Biotic Components
Procedures
Examples: Shrubs, bushes, some grasses and few trees. In deserts mostly
Succulent (e.g., cacti) plants are found available. They have water inside
them to stay alive. They have. r on the outside to protect them from the sun.
Consumers
Examples :Squirrels, nice foxes, rabbits, deer and reptiles.
These animals dig holes in the ground to live in. They come out at night to
find food. Most of the animals can extract water from the seeds they eat.
Decomposers
Examples : Fungi and bacteria
Desert has poor vegetation with a very low amount of dead organic mater.
They are decomposed by few fungi and bacteria.

60. The aquatic ecosystem deals with water bodies. The major
types of organism found in aquatic environments are
determined by the water’s salinity.
Types of aquatic life zone
Aquatic life zones are divided into two types.
•Fresh water life zones
Examples :Pounds, streams, lakes, rivers.
•Salt water life zones
Examples :Oceans, estuaries.
AQUATIC ECOSYSTEMS

61. POND ECOSYSTEMS
A pond is a fresh water aquatic ecosystems, where water is stagnant. It
receives enough water during rainy season. It contains several types of algae,
aquatic plants, insects, fishes and birds.
FRESHWATER ECOSYSTEM
Characteristics of pond
• Pond is temporary, only seasonal.
• It is a stagnant fresh water body.
• Ponds get polluted easily due to limited
amount of water.

62. Structure and functions of pond ecosystems
I. Abiotic components
Examples: Temperature, light, water and organic and inorganic compounds
II. Biotic Components
• Producers: These include green photosynthetic organism. They are of
two types.
• Phytoplankton: These are microscopic aquatic plants, which freely
float on the surface of water.
Example: Algae, small floating plants like volvox, pandorina anabaena,
consmarium.
• Microphytes
Examples: Large floating plants and submerged plants like hydrilla,
Jussiaea, wolfia, demna.

63. Consumers
• Primary consumers (Zooplanktons): These are microscopic animals
which freely float on the surface of water. Zooplanktons are found along
with phytoplankton. They feed on plants (phytoplankton).
Examples: Protozoa, very small fish, ciliates, flagellates and
protozoans.
• Secondary consumers (Carnivores): They feed on zooplankton
Examples: Insects like water beetles and small fish.
• Tertiary consumers: They feed on smaller fish
Examples: Large fish like game fish.
Decomposers: They decompose the dead plant and animal matter and
their nutrients are released and reused by the green plants.
Examples: Fungi, bacteria and flagellates

65. LAKE ECOSYSTEM
Lakes are large natural shallow water bodies. Lakes are used for
various purposes. Lakes are supplied with water from rainfall,
melting snow and streams.
Types of lakes
Some important types of lake are
• Oligotrophic lakes: They have low nutrient
concentrations
• Eutrophic lakes: They are over nourished
by nutrients like N and P
• Dystrophic lakes: They have low pH, high
humic and content and
brown waters.
• Volcanic lakes: They receive water from
magma after volcanic

67. Zones of Lake
Depending upon their depth and distance from the shore, likes
consists of four distinct zones.
1. Littoral zones: It is the top layer of the Lake. It has a shallow
water.
2. Limnetic zone: Next to the littoral zone is limnetic zone, where
effect penetration of solar. light takes place.
3. Préfundal zone: The deep open water, where it is too dark.
4. Benthic zone: This zone is found, at the bottom of the lake.

69. Characteristics of lake ecosystem
1. Lake is a shallow fresh water body;
2. It is a permanent water body with large Water resources.
3. It helps in irrigation and drinking.
Structure and function of lake ecosystem
I. Abiotic components
Temperature, light, proteins and lipids, O2 CO2
II. Biotic Consumers
Producers: They are green plants, may. be submerged, free floating
ad amphibious plants.
Examples: Phytoplanktons, algae and flagellates.

70. 2. Consumers
(a). Primary Consumers (Zooplanktons): They feed on
phytopankton
Examples: Cilictes, protozoans, etc.,
(b) Secondary consumers (carnivores): They feed on
zooplankton.
Examples: Insects and small fishes.
(c) Tertiary consumers: They feed on smaller fish Examples: Large
fishes like game fish.
3. Decomposers
They decompose the dead plants ad animals
Examples: Bacteria, fungi and aclinonrcetes.

73. The running water of a stream or a river is usually well
oxygenated, because it absorb’s oxygen from the air.
The number of animals are low in river or stream.
Characteristics of River or Stream.
• It is a fresh water, and free flowing water systems.
• Due to mixing of water, dissolved oxygen content is.
more.
• River deposits large amount of nutrients.
RIVER (or) STREAM ECOSYSTEM

74. Structure and function of River or Stream Ecosystem
I. Abiotic components
Examples : River, Light, Temperature, Chemistry, Substrate
II. Biotic Components
Producers: Phytoplankton, algae, water grasses, aquatic masses
other amphibious plants.
Consumers
(i) Primary consumers: They feed on phytoplankton.
Examples : Water insects, snails, fishes:
(ii) Secondary consumers: They feed on primary consumers
Examples : Birds
Decomposers: They decomposes the dead animals and plants.
Examples : Bacteria and fungi.

76. OCEAN (MARINE) ECOSYSTEMS
Oceans cover more than two thirds of the earth’s surface. Ocean environment is
characterized by its high concentration of salts and minerals. It supplies huge
variety of products and drugs. It also provides us iron, magnesium, iron, natural
gas.
Zones of Oceans
The oceans have two major life zones.
(a) Coastal zone: It is relatively warm, nutrient rich shallow water. It has
high primary productivity because of high nutrients and sunlight.
(b) Open sea: It is the deeper part of the ocean. It is vertically divided into
three regions.
(i) Euphotic zone: It receives abundant light and shows high
photosynthetic
(ii) Bathyal zone: It receives dim light and is usually geologically active.
(iii) Abyssal zone: It is the dark zone and is very deep (2000 to metres).
SALTWATER ECOSYSTEMS

78. Characteristics of Ocean Ecosystem
1. It occupies a large surface area with saline water.
2. Since ship, submarines can sail in ocean, commercial
activities may be earned out.
3. It is rich in biodiversity.
4. It moderates the- temperature

79. Structure and function Ecosystems
I. Abiotic components
Examples: Temperature, light, NaCl, K, Ca, and Mg Salts
alkalinity
II. Biotic components
1. Producers : Phytoplanktons (diatoms, unicellular algae, etc., )
and marine plants (sea weeds, chlorophycela, phaeophyceae).

80. 2. Consumers
These are heterotrophic macro consumers. They depend on
producers for their nutrition.
• Primary consumers (herbivores): They feed on producers
Examples :Crustaceans, moiluscs, fish
• Secondary consumers (carnivores): They feed on herbivores
Examples: Herring sahd, mackerel, etc.,
• Tertiary Consumers: They are the top consumers. They feed on
small
Examples: Cod, Haddock, -etc.,
3.Decomposers: They decompose the dead organic matter.
Examples: Bacteria and some fungi.

84. An estuary is a partially enclosed coastal area at the’ mouth of a river, where
sea water mixes with freshwater. It is strongly affected by tidal action.
Estuaries are generally : abundant of nutrients. Estuaries are useful to
human beings due to their high food potential. It is essential to protect the
estuaries from pollution.
Characteristics of Estuarine ecosystem
1. Estuaries are transition zones, which are strongly affected by tides of the
sea.
2. Water characteristics are periodically changed.
3. The living organism in estuarine ecosystems have wide tolerance.
4. Salinity remains highest during the summer and lowest during the winter.
ESTUARINE ECOSYSTEM

85. Structure and function of Estuarine Ecosystem
I. Abiotic Components
Examples :Temperature, pH, sodium and potassium salts and
various nutrients.
II. Biotic Components
•Producers
Examples: Marsh grasses, seaweeds , sea-grasses and
phytoplankton.
•Consumers
Examples: Oysters, crabs, seabirds, small fishes
•Decomposers
Examples: Bacterias, fungi and actenomycetous.

88. Thank You