The presentations describes the definition of environment and ecosystem, types of ecosystem and components of ecosystem. It also focuses on the various biotic and abiotic components, concept of food chain and food web, nutrient and energy cycles in ecosystem, trophic levels, ecological pyramids, ecological successions and productivity of ecosystem. It describes in details the forest ecosystem and desert ecosystem.

1. BASIC CONCEPTS OF ECOSYSTEM
Dr. Anupkumar T. Sharma
Assist. Professor
Nanded Pharmacy College, Nanded

2. Introduction
• The science of Environment studies is a multi-disciplinary science
because it comprises various branches of studies like chemistry,
physics, medical science, life science, agriculture, public health,
sanitary engineering etc.
• Douglas and Holland: The term ‘environment’ is used to describe,
in the aggregate, all the external forces, influences and conditions,
which affect the life, nature, behavior and the growth, development
and maturity of living organisms.
• Environmental science is essentially the application of scientific
methods and principles to the study of environmental issues.
• Environmental Issues of Global Concern are –
- Population explosion
- Land degradation
- Environmental pollution

3. Ecosystem
• Definition: First coined by A.G. Tansley in 1935
• Two words – eco (environment) and system
(interacting, inter-dependent complex)
• The system resulting from the integration of all the
living and non-living factors of the environment.
• Interacting system where biotic and abiotic factors
interact to produce an exchange of materials between
the living and non-living factors.
• Thus, ecosystem is a combination of structural and
functional system of communities and their
environment
• Continuous absorption of inorganic matter by biotic
components from abiotic components to produce
organic components and releasing back the inorganic
matter into environment

4. Concept of an Ecosystem
• Nature of the ecosystem - based on its
geographical features (mountains, hills, plains,
rivers, lakes, coastal areas, islands)
• Factors like sunlight, temperature, rainfall also
contribute to nature
• Two components: Abiotic and biotic
• Abiotic components: climatic factors (light,
temperature, rainfall, humidity etc.), geographic
factors (height and directions of mountain chains,
directions of valleys, steepness of slope etc.), and
soil related factors.
• Biotic components: All living organisms

6. • At global level, life exists as on the land
(lithosphere), water (hydrosphere) and air
(atmosphere ) – Collectively called Biosphere

7. • Biogeographical realms: At sub-global level, biosphere is divided
into biogeographical realms as -
- Eurasia (Palearctic realm)
- South and South-east Asia (including India, Oriental realm)
- North America (Nearctic realm)
- South America (Neotropical realm)
- Africa (Ethiopian realm)
- Australia (Australian realm)
• Biogeographic regions: At national or state level, further divided
into biogeographic regions as -
• India has 10 geographic regions as – Trans Himalaya, the Himalaya,
Desert, Semi Arid, Western Ghats, Deccan Peninsula, Gangetic
plain, Coasts, North-East, Islands (Andaman and Nicobar)
• These regions have plants and animals which are adopted to these
regions

8. Ecosystem degradation:
• Continuous disruption of ecosystems by man by
encroachment and harmful activities
• Extinction of many species of plants and animals
• Depletion of natural resources
• Continuous production of large waste materials
• Unequal use of natural resources among rich
people and poor people
• Collectively called as ecosystem degradation
• Proper sharing and control over resources
utilization is necessary to prevent ecosystem
degradation

9. Components of Ecosystem

10. Abiotic components:
Water:
• Essential for life – rainfall – 71% of the earth surface
• Water circulation between atmosphere and earth –
hydrologic cycle
• Evaporation, transpiration – rainfall
• Water availability – type of vegetation
• Plants: Hydrophytes, mesophytes, xerophytes,
• Animals: Desert animals, aquatic animals
• Develop special modifications
• E.g., Xerophytes: Deep, long roots, reduced leaves with
thick cuticle, succulent or with spines (Dry air, high
temperature)
• Desert animals: Lizard (absorb water by skin spines), camel
(water storage in stomach)

11. Humidity:
• The amount of water vapour in air
• Relative humidity: Ratio of the actual amount of water
vapour in the air , to the amount that can be held in the air, at
a particular temperature and pressure
• Absolute humidity: The actual amount of water vapour
present in the air
• Influenced by intensity of solar radiations, temperature,
altitude, wind, water status of soil etc.
• Influence transpiration, evaporation – plants and animals
• Measured psychrometer, paper strip hygrometer, thermo-
hydrograph
Temperature:
• Solar radiation – predominant source of energy
• Growth, metabolism, reproduction, movement, behaviour,
death etc.
• Variable – place, time, altitude, region

12. • Rate of reaction doubles with every 10◦C rise in
temperature (Van’t Hoff’s rule)
• Effects: Enzymatic reactions, transpiration,
evaporation, photosynthesis, maturation of gonads in
plants, colours in insects, birds, mammals
Light:
• Most important factor for life – sunlight – energy for
plants – ultimately for animals
• Role in photosynthesis, transpiration, stomatal
functioning, germination, pigmentation, nutrition
requirement in plants
• Role in pigmentation, growth, locomotion, migration in
animals
• Influences microbial growth

13. Atmospheric gases:
• Major: Oxygen, carbon dioxide, nitrogen
• Minor: Argon, neon, helium, krypton, xenon, hydrogen,
methane, ozone

14. Oxygen:
• Necessary for life – respiration and metabolic
processes
• Aquatic animals – skin, gills
• Air- 21%, Water – 4-10ml/L
• High altitude, partial pressure of oxygen is 50% of its
value at sea level – stress factor for mammals
Carbon dioxide:
• Air contains 0.03% of carbon dioxide – essential for
photosynthesis
• Influences pH of water
• Influence respiration, oxygen carrying capacity of
haemoglobin

15. Soil:
• Acts as a substratum for plants and animals
• Bridge between organic and inorganic materials
• Study of soil – pedology or soil science
• Edaphic factors (soil properties) like structure, pH,
temperature, salinity influence soil microbial
communities
• Provide support, water, nutrient, oxygen for plants
• Composition: Mineral matter (40%), organic matter
(humus) (10%), soil water (25%), soil air (25%) and
biological system
• Top soil: Different colours (humus, minerals), Sub soil:
(roots, humus, minerals)

16. Soil profile:
• Horizontal layers (horizons)
arranged one above the other
• Five main horizons: O, A, B, C, R
• O horizon: Top soil, very rich in
organic matter content, dark
coloured, light texture, intense
biological activity and abundant
life
- O1: Upper layer (fresh fallen
dead leaves, twigs, barks,
flowers, fruits, animal
excreta)
- O2: Contains humus

17. • A horizon: Zone of leaching,
humus mixes with minerals,
A1, A2, A3
• B horizon: Forms subsoil,
contains iron and aluminium
compounds with clay and
humus, B1, B2, B3
- B2: Silicate, clay, mineral,
iron, organic matter
• C horizon: Mineral horizon,
large rocks, CaCO3, CaSO4
- Long roots of big plants reach
here
• R horizon: Parent,
unweathered bed rock, water
is collected

18. • Qualities of soil like porosity, texture, aeration, water
holding capacity, mineral and nutritional contents
decides vegetation growth.
• Highly alkaline or saline soil are unproductive
• Contains microbes like bacteria, fungi, protozoa, algae,
helminths, earthworms, rodents – soil properties and
fertility
Biotic components:
Plants:
• Green plants, grasses, certain bacteria, algae containing
chlorophyll – photosynthesis (Autotrophs/producers)
Animals:
• Depends up on producers for food
(Heterotrophs/consumers)
• Primary consumers (herbivores), secondary consumers
(carnivores), tertiary consumers (top carnivores),
omnivores

19. Autotrophs and Heterotrophs

20. Properties of ecosystem:
• Three basic components: Energy, abiotic components, biotic
components
• Occupies certain well-defined area on the spatial dimension
(earth – spaceship)
• Open system characterized by continuous input and output of
matter and energy
• Complex sets of interactions between biotic and abiotic
components and among the organisms on the other hand.
• So many energy sources, predominant is solar energy
• Ecosystems are natural resources systems
• It is a structured and well organized system.

21. Food Chain: A sequence of organisms,
(herbivores to carnivores to decomposers),
in which each organism serves as a source
of food or energy for another.
• Hence, no waste in a natural ecosystem
• Most consumers feed on more than one
organisms
• Maximum organisms are eaten by more
than one consumers
• Thus, food chain is transfer of food
energy from one group of organisms to
the other group in ecosystem
• The point where food energy transferred
from one group of organisms to the
other is called Trophic level.
Types:
• Grazing food chain (Predominant)
• Detritus food chain

22. Grazing food chain: Starts with green plants (producers), goes to
grazing herbivores and ends on carnivores.
• Each animal attacks on other, law of survival of the fittest
• At each trophic level, only 10% energy transferred

23. Detritus food chain: Starts from dead organic matter produced
by decomposition of plant parts and dead animal parts
(detritus) by decomposers like earthworms, micro-organisms etc.
, eaten by animals (detrivores) – further eaten by animals
(predators)
• Earthworms, wood louse etc. convert complex organic matter
in to simple
• Microbes convert in to inorganic matter

24. Trophic levels: The group of organisms within an
ecosystem which occupy the same level in a food chain.
• The point where food energy transferred from one group of
organisms to the other is called Trophic level.
• Four main trophic levels

25. Trophic level 1:
• Forms the base of food chain – autotrophs
• Green plants produce food via photosynthesis (sunlight, carbon
dioxide, inorganic salts, water)
• For cell and tissue growth
Trophic level 2:
• Trophic level where food energy transferred from producers to
primary consumers
• Organisms depends upon producers for nourishment
• Includes primary consumers (herbivores) like sheep, dairy animals,
rabbits, goats, deers etc.
Trophic level 3:
• Energy transfer from primary consumers to secondary consumers
(carnivores)
• Organisms depend upon primary consumers
• E.g. Beers, lions, eagles et.
Trophic level 4:
• Get nourishment from all above trophic levels (Omnivores and
decomposers)
• E.g. Man, microbes

28. Food Web
• A network of food chains
where different types of
organisms are connected at
different trophic levels, so
that there are a number of
options of eating and being
eaten at each trophic level.
• Several interconnected and
overlapping food chains
(complicated food chain)
• Greater number of species
feed on many kinds
• Extinction of one species
does not affect trophic
levels seriously

29. Significance of Food Chain and Food Web
• Energy flow and nutrient cycling in the ecosystem
• Preservation of ecological stability by regulating population
size of various animals
• Demonstrate the property of biological magnification of few
chemicals (Transfer of nonbiodegradable chemicals like
pesticides, heavy metals, chemicals etc. from one trophic level
to another – concentration expands)
Nutrient Cycles (Biogeochemical Cycles)
• The continuous, circular movement of nutritional compounds
and elements through water, soil, and abiotic components
within ecosystem
• Driven by solar energy and gravity
• Water cycle, nitrogen cycle, carbon cycle, phosphorus cycle

30. Water (Hydrological) cycle:
• Essential for life on the earth
• Describes collection, purification and distribution of water
• Involves interchange of water between atmosphere and
earth’s surface via rainfall and evaporation
• About 90% of water evaporates from soil and plants via
transpiration
• Water from ocean evaporates and repeat the cycle
• Water returns via precipitation by following paths:
- Rainfall on terrestrial ecosystems – run off and flows in to
lakes, streams, rivers
- Converted to ice and glaciers
- Roots of plants absorb small amount of water –
evaporation via leaves

31. • Vapourization from sea surface – cloud formation –
condensation – droplet formation – rainfall
• Drastic changes due to human activities (pollution) - Large
withdrawal and less replacement – change in rainfall patterns
• Draughts and floods
Nitrogen cycle:
• Essential component of vitamins, amino acids and nucleic
acids
• 78% in atmosphere
• Can not be used by plants or animals
• Nitrogen fixation: Nitrogen converted into ammonia and
nitrate by –
- Lightening in the atmosphere
- Nitrogen fixing bacteria in soil

32. • Transferred from plants to animals
• Dead organic matter, animal waste decomposed by bacteria,
fungi, ants, insects and converted to ammonia gas or free
nitrogen in atmosphere
Carbon cycle:
• Found in biotic as well as abiotic components
• Building blocks of plant and animal tissues
• Occurs as CO2 (0.038% ) in atmosphere
• Photosynthesis - CO2, sunlight and water – carbohydrates and
O2 produced
• Regulation of both gases
• Animal excreta and dead animals return fixed carbon to soil
• High level of CO2 due to deforestation – global warming

33. Phosphorus cycle:
• Important sedimentary cycle
• Does not include atmosphere
• Occurs as reservoirs in rocks and deposits
• Erosion release phosphates – maximum portion goes into sea
as sedimentation

34. Energy Cycle
• Energy is the ability to do work, essence of life
• Energy flow through food chains in ecosystem – keeps
ecosystem going
• Energy pattern and flow governed by –
First law of thermodynamics: In any system of constant mass,
energy is neither created nor destroyed, but it can be
transformed from one type to another type.
• Solar energy to biochemical energy of plants and then of
animals
• Energy inflow balanced by energy outflow.
Second law of thermodynamics: When work is done, energy is
dissipated and the work is done when one form of energy is
transformed into another form.

35. • During energy flow in ecosystem, dissipation of energy at each
trophic level
• Respiration, locomotion, running, hunting, digestion and
other activities
• 90% energy loss and 10% transfer at each trophic level

36. Ecological Succession
Definition: An orderly and progressive replacement
of one community by another till the development
of a stable community in that area
• The process of formation of new communities
• The stable community – climax community
• Various development stages called as ‘sere’ and
each stage under development called ‘seral
stage’.
• The composition and structure of any community
changes drastically in longer time span (unstable)
• A particular community in a geographical area is
replaced by a series of communities

37. • E.g. Pond/lake community – fills with slit –
shallow lake – sand and mud - marshy land
community – grassland/ dry forest land
community
Types of ecological succession:
Primary succession: Development of community
begins on a sterile area, not occupied by any
community previously
• First organism – pioneer community
• E.g. Landslide in mountains – rock surface
exposed – lichens (pioneer community) – moss
mat – grasses – herbs – shrubs – trees – forest
community (climax community)

38. Primary Succession
Lichens Mosses

39. Secondary succession: Community development starts on areas
previously occupied by well developed communities
• Organic matter/ some organisms from previous community
may remain
• E.g. areas burned by fire, cut over forests

40. Types of Succession on the Basis of Moisture Content:
• Hydrach or Hydrosere (Aquatic environment like
ponds, lakes etc.)
• Mesarch or Mesosere (Area with adequate
moisture)
• Xerarch or Xerosere (Deserts or rocks)

41. Productivity of Ecosystem
Definition: Refers to rate of production.
Primary productivity: The rate at which solar energy is stored by
photosynthetic and chemosynthetic activity of producers which
can be used as food materials.
• Gross primary productivity: The solar energy trapped by the
photosynthetic organisms.
- Includes all organic matter produced, depends upon the
photosynthetic activity and environmental factors.
• Net primary productivity: This is estimated by the gross
productivity minus energy lost in respiration.
NPP = GPP – Energy lost by respiration
• Includes net energy stored in the plants, food for the animals,
measured as the amount of organic matter produced in a
community in given time.

42. Secondary productivity: Rate of energy storage at the
consumer’s level. It keeps moving from one organism to another.
Net productivity: Rate of storage of organic matter not used by
consumers.
- Rate of increase of biomass of the primary producers
Unit of Productivity: Typically, productivity is expressed in units
of mass per unit volume (or surface) per unit time.

43. Ecological Pyramids
• Charles Elton in 1927 first described ecological pyramids.
• The diagrammatic expression of the fact - the number,
biomass and energy of organisms gradually decrease from
producer level to the consumer level.
• Graphic representation of number, biomass and energy at
various trophic level.
• Producers form base and final consumers form apex.
Types:
• Pyramid of Numbers
• Pyramid of Biomass
• Pyramid of Energy

44. Pyramid of Numbers:
• Show relationship between producers, herbivores and
carnivores at successive trophic levels in terms of number
• Decreases from producers to consumers
• Pyramid is upright
• Consider only number of organisms, not the size – no clear
idea about total biomass
• E.g. 1. (Grassland ecosystem) Crops > grasshoppers > frogs >
snakes
2. (Pond ecosystem) Phytoplankton > Zooplankton > fishes >
snakes
3. (Forest ecosystem, somewhat different) Producers (big trees)
< herbivores (birds, elephants etc.) > carnivores
4. (Parasitic food chain – inverted) Microbes > bugs > herbivores
> producers (single tree)

46. Pyramid of Biomass:
• Refers to the total weight of living matter per unit area
• Total weight of organisms at each trophic level
• Decreases from producer (large base)level to consumer level
(narrow top)
• Grassland and forest ecosystem – upright pyramid
• Pond ecosystem – inverted pyramid

47. Pyramid of Energy:
• Most informative, provides a clear picture
• Energy level decreases from producers to carnivores
• Solar energy > producers > herbivores > carnivores
• Pyramid is always upright

48. Types of Ecosystems

50. Forest Ecosystem
• Formed by community of plants like trees, shrubs,
grasses, climbers, ground cover
• Homogenous or heterogenous
• National parks, wildlife sanctuaries
Components:
Abiotic components:
• Forest type depends up on type of soil and organic and
mineral contents of soil
• Forest at mountains, hills, river valleys
• Vegetation – rainfall and temperature, altitude

51. Biotic components:
Producers:
• Plants specific to each forest type
• Tropical rain forests: Trees, herbs, shrubs, climbers, lichens,
algae
• Himalayas: Coniferous trees
• River deltas: Mangrove trees
• Flowering and non-flowering plants (ferns, bryophytes, fungi,
algae)
Consumers:
• Himalayas: Snow leopard, sheep, goats, birds
• Evergreen forests of Western Ghats and North-East India:
Rich in plants and animal species – mammals, birds, reptiles,
amphibians, fishes, insects, invertebrates etc.
• Primary consumers: Small animals like ants, flies, leaf
hoppers, bugs, spiders, squirrels etc., large animals like
elephants, neelgai, deer, wild buffaloes etc.
• Secondary consumers: Snakes, birds, lizards, foxes etc.
• Tertiary consumers: Lion, leopard, tiger etc.

52. Decomposers:
• Fungi, bacteria, actinomycetes
• Decomposition faster in tropical forests than
temperate and polar forests
Types of forests in India:
Coniferous forests:
• Himalayan mountain region, low temperature
• Trees with needle-like leaves sloping branches
• Produce cones in stead of seeds – gymnosperms
Broad leaved forests:
• Large leaves of various shapes
• Evergreen forests, deciduous forests, thorn forests,
mangrove forests

54. Evergreen forests:
• In high rainfall areas of western Ghats, North-east
India, Andaman and Nicobar islands
• Monsoon – several months, green through out the
year, little leaf shedding through year
• Very little sun light reach to floor
• Rich in orchids, ferns, animal life, abundant insects
Deciduous forests:
• In regions with moderate seasonal rainfall
• Teak trees common
• Leaf shedding in winter and hot summer months
• March/April – regain leaves
• Thick undergrowth as light reach easily at ground

56. Thorn forests:
• In semi-arid regions in India
• Trees sparsely distributed, surrounded by
grassy area
• Xerophytic plants, waxy leaves to conserve
water, thorns to reduce transpiration and to
protect from herbivores
Mangrove forests:
• In river deltas (coasts)
• Plants grow in saline, fresh water and muddy
areas

58. Uses of forests:
• Timber, fire-wood
• Climate and water regimes
• Shelter for wild animals
• Fruits, roots, herbs, medicinal plants, fodder, building
material, fibre, cane, gum, honey etc.
Threats to forest ecosystem:
• Overutilization – waste land (Population growth,
industrialization, urbanization, consumer goods like paper
pulp, timber etc. )
• Forest cover of India – from 335 to 11% last century
• Mining, dams
Effects:
• No survival of tribal people
• Houses, farm implements
• Insect population
• No rain – agriculture, drinking water, extinction of species

59. Conservation of forest ecosystem:
• Use of alternate source of energy instead of
wood
• Grow more trees
• Afforestation to be done
• Set up of national parks, wildlife sanctuaries

60. Desert Ecosystem
• In India, Western India and Deccan plateau (Desert and
semi-arid area).
• Extremely dry, hot temperature
• Cold desert, Ladakh, high plateaus of Himalayas
• In desert areas, rainfall is very scanty and sporadic
• Evaporation is more than rainfall, snow fall etc.
• Latin term ‘desertus’ – waste or something that has been
left.
• Rainfall than 25cm a year
• Covers approx. 1/3rd land of the world.
• Atmosphere is very dry – so weak insulator – days are very
hot and nights are very cool.

61. Types of Deserts: On the basis of climatic
conditions-
• Tropical deserts: Thar (Rajasthan, Punjab,
Sindh, Pakistan, the largest desert of India)
Sahara (North Africa, the largest desert of the
world), Namib (Africa), Rajasthan, Arabian
desert (Saudi Arabia)
• Temperate deserts: Mojave in California,
Arizona (US)
• Cold deserts: Gobi desert (China), Tibetian
desert

63. • Animals and plants have typical adaptations
for water conservation
• Plants: Reduced, scaly leaves, succulent
leaves, flattened stems with chlorophyll, deep
roots, waxy thick cuticle over leaf
• Animals: Insects, reptiles have thick outer
covering, leave inside burrow.
• Desert soil: Rich in nutrients, lacks water

64. Components:
Biotic components:
Producers: Shrubs,
bushes, some grasses,
very few trees,
microphyllus plants,
spreading trees with
deep roots, cacti,
succulent plants,
xerophytes, lichens etc.

65. Consumers: Highly specialized insects, reptiles,
rodents, birds, some mammalian vertebrates,
tortoise, sand snakes, desert cats, desert fox etc.
• Grazing animals like cattle, goat, sheeps,
camels.
Uromastix Kangaroo rats

66. Great Indian Bustard Florican
Patridge Sandgrouse

67. Decomposers: Thermophilic bacteria, fungi in
small numbers
Threats:
• Human population growth, developmental
strategies
• Extensive irrigation systems affecting natural
characteristics
• Rapid evaporation of water – salt on surface –
saline and unproductive soil
• Excessive tube wells – lowering water level

68. Conservation:
• Desert people
traditionally protect their
water resources
• Bishnois in Rajasthan
protect khejdi trees and
black buck antelope for
several generations
• Special need of
sustainable development

69. (Disclaimer: The images and diagrams in this presentation have
been downloaded from the Google source. I am grateful to all the
concerned Authors, Publishers & the Google.)
Thank You…!!!