Welcome To

Digital Classroom
Structure of Ecosystem
Structure of ecosystem
1. Abiotic or non-living components or physical components
2. Biotic or Living components
3. Energy components.
Structure of Ecosystem
Abiotic Components
• Abiotic components enter the body of living directly or indirectly take part
in metabolic activities and return to environment.
• Abiotic components are as follows
1. Atmosphere
2. Lithosphere
3. Hydrosphere
Structure of Ecosystem
Biotic Components
1. Food chain, Food web and trophic structure.
2. Energy flow
3. Cycling of Nutrients (Biogeochemical cycles)
4. Primary and secondary production
5. Ecosystem development programme
Structure of Ecosystem
• Food Chains - Sequence of eating and being eaten in an ecosystem.
Grass - Grasshopper - Frog - snake – Hawk
Grass - Rabbit – Fox
Phytoplanktons - Zooplanktons - Small fish - Carnivores( fish)

• Food Web
An interlocked food chain is called as a food web. (Network of food Chains)
Structure of Ecosystem
Energy Flow in Ecosystem
• Energy is defined as the capacity to do work. For living organisms, it is the basic force responsible for
running all the metabolic activities. The flow of energy from producer level to top consumer level is
called energy flow.
• The flow of energy in an ecosystem is unidirectional. It flows from producer level to consumer level
and never in the reverse direction.
• The process of energy flow involves transfer of energy from autotrophs to various components of
heterotrophs and help in maintaining bio diversity. The main source of energy in the ecosystem is
sunlight. About 80% of energy is lost during flow of energy from one trophic level to the next one.

• Sun - Producer - Herbivores - Carnivores - Top carnivores - Decomposers

Structure of Ecosystem
Food Chain
• Plants by photosynthesis convert solar energy
into protoplasm. Small herbivores consume the
vegetable matter and convert into animal
matter which in turn eaten by large carnivores.
This sequence of eaten and being eaten,
produces transfer of food energy known as food
chain.
Structure of Ecosystem
Structure of Ecosystem
Food Web
• The food relationship between various
organisms is being depicted by linking all the
possible prey and predators of different food
level. In an ecosystem linking of feeding habit
relations will provide a food web..
Structure of Ecosystem
Food Web
• The food relationship between various organisms is being depicted by linking all the possible prey
and predators of different food level. In an ecosystem linking of feeding habit relations will provide a
food web.
Difference between food chain and food web
• In a linear food chains, if one species gets affected or becomes extinct, then the species in the
subsequent trophic levels are also affected.
• But, in a food web, if one species get affected, it does not affect other tropic levels so seriously.
There are number of options available at each trophic level.
Structure of Ecosystem
Ecological Pyramids
• The energy biomass and number of organisms gradually decreases from the producer level to the
consumer level.
• The total mass of herbivores in an ecosystem will generally be less than the total mass of plants.
• Similarly the total mass of carnivores will be less than the total mass of herbivores.
• The graphical representation of the number, biomass and energy of various energy levels is called
ecological pyramid.
• In any ecological pyramid the producer forms the base and the successive levels form the tires which
can make the apex. The ecological pyramids represent the tropic structure and also tropic function of
the ecosystem.
Structure of Ecosystem
Types of ecological pyramids:
a) Pyramid of numbers
b) Pyramid of biomass
c) Pyramid of energy
(a) Pyramid of number
• It depicts the number of individual organisms at different tropic levels of food chain.
• The animals at the lower end (base of pyramid) of the chain are the most abundant.
• Successive links of carnivores decrease rapidly in number until there are very few carnivores at the
top.
• The pyramid of number ignores the biomass of organisms and it also does not indicate the energy
transferred or the use of energy by the groups involved.
• The grassland ecosystem provides a typical example for pyramid of number.
Structure of Ecosystem
Structure of Ecosystem
(b) Pyramid of biomass
• The biomass of the members of the food chain
present at any one time forms the pyramid of
the biomass. Pyramid of biomass indicates
decrease of biomass in each tropical level
from base to apex.
• For example, the total biomass of the
producers ingested by herbivores is more than
the total biomass of the herbivores in an
ecosystem.
• Likewise, the total biomass of the primary
carnivores (or secondary consumer) will be
less than the herbivores and so on.
Structure of Ecosystem
(C) Pyramid of Energy
• When production is considered in terms of
energy, the pyramid indicates not only the
amount of energy flow at each level the actual
role the various organisms play in the transfer
of energy. The pyramid of energy is
constructed is the quantity of organisms
produced per unit time.
Major Types of Ecosystem
(A) Forest Eco-system
• It is a natural ecosystem consisting of dense growth of trees and wild animals
• Tropical rain forests → found near the equator, high temperature, have broad leaf trees like sandal,
lion, tiger
• Tropical deciduous forest → Found away from equator, warm climate, deciduous trees like maple,
oak, deer, fox, rabbit etc.
• Temperate rain forests → adequate rainfall areas, coniferous trees like pines, firs, squirrels, fox, cats,
bear etc.
• Temperate deciduous forest → found in moderate temp., trees like oak, hickory, animals – deer, fox,
bear etc.
• Tropical scrub forests → dry climate for longer time, small deciduous trees & shrubs, animals – deer,
fox etc.
Major Types of Ecosystem
Characteristics of Forest Ecosystem
• Characterized by warm temperature, adequate rainfall
• Maintain climate & rainfall
• Support many wild animals & protect biodiversity
• Soil is rich in minerals, so support growth of trees
• Penetration of light is poor so conversion of organic matter is very fast
Major Types of Ecosystem
Components of Forest Ecosystem
• Abiotic Components → abiotic components are physical components present in soil & atmosphere
(Ex) tempereature, light, rainfall, minerals
Biotic Components
Producers → plants absorbs sunlight & produce food by photosynthesis. Ex-trees, shrubs, plants
Primary consumers → Called herbivores/plant eaters- depend on plants for food. Ex. Insects, rat,
goat, deer, cow, horse etc
Secondary consumers → Called primary carnivores/meat eaters. Depend on herbivores for food Ex.
Frog, birds, cat, snakes, foxes etc.
Tertiary consumers → Called Secondary carnivores, feed on secondary consumers. Ex. Tigers, lions
etc.
Decomposers: fungi, bacteria
Major Types of Ecosystem
(B) Grassland Eco-system
• Dominated by grass –few shrubs and trees are also found – rainfall average but erratic – overgrazing
leads to desertification.
1. Tropical grass lands – found near the boarders of tropical rain forests.
Eg. Savannas in Africa. Animals– Zebra, giraffes etc. – fires are common in dry seasons – termite mounds
produce methane – leads to fire – high in photosynthesis – deliberate burning leads to release of high
CO2 – global warming.
2. Temperate grasslands – flat and gentle slopes of hills. Very cold winter and very hot summer
- dry summer fires do not allow shrubs and trees to grow – soil is quite fertile – cleaned for agriculture.
3. Polar grasslands – found in arctic polar region – organism – arctic wolf, fox, etc. – A thick layer of ice
remains frozen under the soil surface throughout the year – known as permafrost – summer insects and
birds appear
Major Types of Ecosystem
Structural Components:
• I. Abiotic Components → abiotic components are physical components present in soil & atmosphere
(Ex) tempereature, light, rainfall, minerals
• II. Biotic Components
• Producers → plants absorbs sunlight & produce food by photosynthesis. Ex-trees, shrubs, plants
• Primary consumers → Called herbivores/plant eaters- depend on plants for food. Ex. Insects, rat,
goat, deer, cow, horse etc
• Secondary consumers → Called primary carnivores/meat eaters. Depend on herbivores for food Ex.
Frog, birds, cat, snakes, foxes etc.
• Tertiary consumers → Called Secondary carnivores, feed on secondary consumers. Ex. Tigers, lions
etc.
• Decomposers → Organisms which feed on dead organisms, plants & animals & decompose into
simpler compounds Ex.
Major Types of Ecosystem
(C) Dessert Eco-system
• Desert occupies about 35% of our world‟s land area. It is characterised by less than 25 cm rainfall.
The atmosphere is dry and hence it is a poor insulator.
Types:
1. Tropical desert-found in Africa-Sahara and Rajasthan – Thar
2. Temperate desert-south California-Majave
3. Cold desert-China-Gobi desert

Characteristics:
1 Air is dry
2 Climate is hot
3 Annual rainfall is less than 25 cm
4 Vegetation is poor
Major Types of Ecosystem
Structural Components:
• Abiotic Components - Eg. Temperature, rainfall, sunlight, water, etc.
• Biotic Components
1. Producers - Eg. Shrubs, bushes, some grasses and few trees.
In deserts mostly Succulent (e.g., cacti) plants are found available. They have waxy layer on the outside
to protect them from the sun.
2. Consumers - Eg. Squirrels, mice, foxes, rabbits, deer and reptiles
These animals dig holes in the ground to live in. Most of the animals can extract water from the seeds
they eat.
Major Types of Ecosystem
(D) Aquatic Eco-system
• Deals with water bodies and biotic communities present in them- Classified as fresh water and
marine ecosystems. Fresh water systems are classified as lentic and lotic ecosystems.
Types:
1. Pond ecosystem: Small fresh water ecosystem – seasonal in nature
– organisms: algae, aquatic plants, insects, fishes etc. Ponds are very often exposed to anthropo genic
pressure like cloth washing, bathing, cattle bathing, swimming etc.
2. Lake ecosystem: Big fresh water ecosystem –
Zonation or stratification, Especially during summer is a common one.
Major Types of Ecosystem
Lake Eco-system
• Top layer – shallow, warm, prone to
anthropogenic activities –
• Littoral Zone - Second layer – enough sunlight,
high primary productivity
• Limnetic zone Third layer – very poor or no
sunlight –
• Profundal zone Eg. Dal lake in Srinagar, Naini lake
in Nainital
Major Types of Ecosystem
Lake Eco-system
• Organisms: planktons – phytoplankton eg. Algae – zooplankton eg. Rotifers Nektons – that swims in
water eg. Fishes Neustons – that float on the surface of water Benthos – that attached to sediments
eg. Snails
• Types of lakes: Many types- oligotrophic lakes – with less nutrient content – Eutrophic lakes – with
very high nutrient content due to fertilizer contamination – desert salt lakes – that contains high
saline water due to over evaporation – volcanic lakes – formed by water emitted from magma due to
volcanic eruptions – dystrophic lakes – that contains highly acidic water (low pH) – endemic lakes –
lakes that contain many endemic species etc.
Major Types of Ecosystem
Streams
• fresh water ecosystem where water current plays a major role. Oxygen and nutrient content are
uniform. Stream organisms have to face extreme difference in climatic conditions but they do not
suffer from oxygen deficiency as pond and lake organisms. This is because large surface area of
running water provides more oxygen supply. The animals have very narrow range of tolerance
towards oxygen deficiency. Thus stream are worst victims of industrial pollution.
• River ecosystem: large streams flowing from mountain highlands are rivers.
• Three phases of River Eco-System:
1. mountain high lands – rushing down water fall of water – large quantity of dissolved oxygen –
plants attached to rocks and fishes that require more oxygen are found.
2. Second phase – gentle slopes of hills – warmer – supports the growth of plants and fishes that
require less oxygen are seen.
3. Third phase: river shapes the land – lots of silts, nutrients are brought – deposited in plains and
delta – very rich in biodiversity.
Major Types of Ecosystem
Oceans
• Gigantic reservoirs of water covering >70% of earth surface – 2,50,000 species – huge variety of sea
products, drugs etc. – provide Fe, Mg, oils, natural gas, and etc. – major sinks of carbon di oxide –
regulate biochemical cycles.
• Two zones: coastal zone – warm, nutrient rich, shallow – high sunlight – high primary productivity.
• Open sea – away from continental shelf – vertically divided in to zones.
1. euphotic zone – abundant sunlight
2. bathyal zone – dim sunlight 3.abyssal one dark zone – world’s largest ecological unit.
Major Types of Ecosystem
Characteristic features of Ocean Ecosystem
1. It occupies a large surface area with saline water & rich in biodiversity
2. Since ship, submarines can sail in ocean, commercial activities may be carried out.
3. It moderates the temperature of the earth.
Structure and function of Ocean Ecosystems
Abiotic Components - Eg. Temperature, light, NaCl, K, Ca, and Mg Salts, alkalinity.
Biotic Components
1. Producers - Eg. Phytoplanktons (diatoms, unicellular algae, etc.) and marine plants (sea weeds,
chlorophyceal, phaeophyceae).
2. Consumers –
Primary Consumer - Eg. Crustaceans, moiluscs, fish.
Secondary Consumer - Eg. Herring sahd, mackerel
Tertiary Consumer – Eg. Cod, Haddock, etc.,
Decomposers - Eg. Bacteria and some fungi
Major Types of Ecosystem
Estuary: coastal area where river meet ocean – strongly affected by tidal actions – very rich in nutrients
– very rich in biodiversity also – organisms are highly tolerant – many species are endemic – high food
productivity – however to be protected from pollution.
Characteristics:
Structural Components:
Abiotic: pH, nutrients, D.O, temp, climatic conditions, etc.
Biotic: Phytoplankton, fishes, snails insects, birds, etc.
Energy flow:
Phytoplankton - Insects - small fishes - huge fishes