Environment – Concepts

Material Science : Chapter 6: Polymers
June 30, 2017
Environmental Conservation at Global Level
July 6, 2017
  1. Environment and ecosystem
    1. What is meant by environment?
    2. The components of an environment
    3. What is an ecosystem?
    4. How an ecosystem is different from an environment?
    5. Different types of ecosystem
    6. What is a biome?
  2. Ecological interactions
    1. What is meant by ecological interactions?
    2. What is ecology?
    3. Different biotic interactions
    4. Biotic-abiotic interactions
      1. Energy transfer
      2. Material transfer
    5. Explain the food chains and food webs
    6. Ecological pyramids
    7. Ecological niche
  3. Productivity
    1. What is meant by productivity of an ecosystem?
    2. How productivity and biotic potential related?
    3. Carrying capacity
    4. Ecological footprint
  4. Ecosystem services
    1. Different ecosystem services
    2. How the environmental degradation affects the services?
  5. Biodiversity
    1. Different types of diversities
    2. Keystone species and Foundation species
    3. Endemic and Exotic species
    4. The Evil Quartet
  6. FAQs
    1. Trophic level
  7. Practice Questions

1.Environment and ecosystem

1.1 What is meant by environment?

  • The term environment means ‘what that surrounds’.
  • The environment is the sum total of all material and non-material factors around us.
  • It includes both biotic and abiotic components – plants, animals, soil, water, air etc.
  • It also includes the conditions such as culture, political institutions etc.
  • It can be both natural or manmade. Examples are as shown in the following figure

Image source: NCERT

1.2 What are the components of an environment?

  • Components of Environment can be divided as
    • Natural environment
    • Human environment and
    • Human made environment

A.Natural Environment

  • The natural environment refers to both Biotic(plants and animals) and Abiotic conditions(soil, water, air) existing on the earth
  • It has four domains namely
    • Lithosphere,
    • Hydrosphere,
    • Atmosphere and
    • Biosphere.


  • It is the solid crust or the hard top layer of the earth.
  • It is made up of rocks & minerals and is covered with soil.
  • It has various landforms such as mountains, plateaus, plains etc.


  • It is the domain of water.
  • It comprises of various sources of water – rivers, lakes, seas, ocean etc.


  • It is the thin layer of air that surrounds the earth.

d) Biosphere

  • Plant & animal kingdom together make the Biosphere or the living world.
  • It is the narrow zone of the earth where land, water and air interact with each other to support life.

B.The human environment

  • It refers to the activities, creation and interactions among human beings
  • Ex- family, community etc

C.The human made environment

  • It includes the settlements, infrastructure, industries etc made by human

1.3 What is an ecosystem?

  • Ecosystem is an environmental system consisting of inter related and interdependent elements
  • It denotes the complex interconnection between the different components of the environment
  • It includes both abiotic-biotic interactions and biotic-biotic interactions

1.4 How an ecosystem is different from an environment?

  • The environment forms the elements of the system, and the elements along with the interrelations form the ecosystem
  • It means – an ecosystem is something more than the the sum total of all elements (the environment)
  • For ex, human body can be considered as a system, with the organs as its elements. We know that a human is not merely a sum of all organs, but has life.
  • Similarly in an ecosystem, it is the interactions between the different elements that gives it life

1.5 What are the different types of ecosystem?

  • Ecosystems can be natural and manmade.
  • Plants, animals, insects, microorganisms, rocks, soil, water and sunlight are major components of many ecosystems.
  • Ecosystems are divided based on the different physical conditions.
    • Terrestrial and
    • Aquatic 
  • It can be further divided to specific ecosystems like forest, grassland, desert, marine, pond etc

1.6 What is a biome?

  • Biome is a large terrestrial ecosystem
  • It is characterised by a particular type of natural vegetation and animal life
  • The different biomes are shown in the map below

Image source: kidsdiscover.com

2. Ecological interactions

2.1 What is meant by ecological interactions?

We have seen that the components of the environment interact with each other. The different types of interactions are

  1. Of an organism with the physical environment for food, water, air etc (biotic- abiotic)
  2. Interactions of organisms with each other(biotic-biotic)
    • Ex: competition for food, predator-prey relation, community living etc

2.2 What is ecology?

  • Ecology is the study of the interaction of the living beings among themselves and also living beings as a whole with their environment.
  • Ecology is studied at many levels, including organism, population, community, ecosystem, and biosphere.

2.3 Different biotic interactions?

Biotic interactions are among living organisms themselves. The main types of interactions are

1.Producer – Consumer – Consumer relation (Food relations)

  • Green plants are the primary producers.
  • The food to the whole ecosystem occurs through the complex relations called food chain and food web

2. Other relations

  • The organisms compete, collaborate with each other in different ways to sustain their life.

There are  different types of interactions depending on the effect of the interactions on the corresponding species

Different Biotic Interactions
Biotic Interactions Effect on species A Effect on species B Example
Mutualism Positive effect Positive effect Corals(A) and zooxanthellae algae(B) live together
Commensalism Positive effect No effect Orchid(A) growing on a tree(B)
Amensalism No effect Negative effect Allelopathy – certain plants, algae, bacteria, coral, and fungi (A) suppress the growth other species (B) by release of toxic substances
Parasitism Positive effect Negative effect Micro-organism plasmodium(A) infect humans(B) causing malaria
Predation Positive effect Negative effect Tiger(A) feeds on deer(B)
Competition Negative effect Negative effect Woodpeckers(A) and squirrels(B) compete for nesting in same place

Let us take one example – mutualism

  • In mutualism, both species are gainers
  • The relation of coral polyps and algae zoothanthellae is a well known example. Coral provides habitat for the algae and the algae gives food to the coral polyps.

Image source: gbrmpa.gov.au

  • When zooxanthellae is expelled/dead due to any factors, the coral also dies.
  • Such a close and often long-term interaction between two or more different biological species is called Symbiosis

2.4 Biotic-abiotic interactions

Both energy and materials are transferred from one element to another in an ecosystem. The two main interactions are

  • The energy flow and
  • The material cycle.

a) Energy transfer

  • The sun is the main source of energy.
  • Only the photosynthetic plants can directly use this energy and produce biomass.
  • The energy flow is unidirectional.
  • The energy flow in an ecosystem is represented through food chains and food webs
  • As per Lindeman’s law, only 10% of energy is transferred from one trophic level to another, while 90% is used for metabolic processes or lost as heat.
  • The percentage of energy transferred from one level to another is called ecological efficiency
  • Earth is an open system with respect to energy

Image modified from NCERT

b) Material transfer

  1. Water, nutrients, oxygen, carbon etc are the main materials which are transferred between the biotic and abiotic world continuously.
  2. Earth is a closed system with respect to material transfer. It means that the materials used gets recycled here itself
  3. In this process materials passes through various chemical, geographical and biotic forms. Hence these cycles are called biogeochemical cycles

A Carbon Cycle (Image source: NCERT)

2.5 Explain the food chains and food webs?

Food chains shows the transfer of energy in an ecosystem.

Image source : NCERT

In an ecosystem food chains are not always simple as shown in above figure. But it is a complex web of feeding relations.

Image source : NCERT

2.6 Ecological pyramids

Ecological pyramid is a graphical representation of biomass or energy or population at each trophic level [FAQ 1]in an ecosystem. Thus pyramids can be of different kinds like energy pyramid, biomass pyramid or population pyramid.

Image : Pyramid of Energy

2.7 What is an ecological niche?

  • In nature, many species occupy the same habitat but they perform different functions. The functional characteristics of a species in its habitat is referred to as ‘niche’.
  • Habitat of a species is like its ‘address’ (i.e. where it lives) and niche can be equated to its ‘profession’ (i.e. activities and responses of the species).
  • It is the sum of all the activities and relationships of a species by which it uses the resources in its habitat for its survival and reproduction.
  • A niche is unique for a species, ie no two species in a habitat can have the same niche. This is because if two species occupy the same niche they will compete with one another until one is displaced.
  • Ex- In a tree habitat, the bird’s niche will be centered around the fruits, pollination, nesting etc. Where as a snake in the same habitat feeds differently and behaves differently from a bird.
  • There can be similar niches in different geographic regions


3.1 What is meant by productivity of an ecosystem?

  • Productivity is the efficiency at which energy and matters are stored in different trophic levels.
  • It is expressed in terms of weight per year or energy per year 
  • Ex- The annual net primary productivity of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter
  • Primary productivity
    • means the rate at which solar energy is converted to energy in biomass by the photosynthetic organisms
    • productivity depends on different environmental factors like availability of nutrients and also the photosynthetic capacity of plants
    • Primary productivity varies in different types of ecosystems
  • Secondary productivity
    • means the rate at which energy is stored in different consumer levels

3.2 How productivity and biotic potential related?

  • Biotic potential is the potential of a species to reproduce at the maximum rate
  • The productivity can be a limiting factor for the organism to achieve the biotic potential
  • When environmental factors are not favourable, biotic potential cannot be achieved

3.3 What is carrying capacity?

  • The maximum number of a species that can be accommodated in a given area
  • It takes  into consideration availability of food sources, water, and all the other necessities to sustain life
  • It also takes into consideration the capacity of environment to assimilate the waste generated
  • Is usually calculated as the number of individuals of a species per square kilometre
  • Example, For human, carrying capacity refers to the maximum number of persons that can be sustained per sq. km of the given area.
  • If the population increases beyond carrying capacity, the population decline will happen. This concept is known as “The Limits to Growth

3.4 What is meant by ecological footprint?

  • Is  measure of the ecological impact of an entity
  • It is expressed as the land area needed to completely sustain the entity, ie global hectares per capita (gha/ cap)
  • For example the ecological footprint of a human being would be the equivalent unit of area needed by each human to maintain that individual’s current style of life till death
  • If the ecological footprint of a human population exceeds the carrying capacity of its environment, the situation is unsustainable
  • Presently, worldwide the total human ecological footprint is almost 1.5 times the total worldwide carrying capacity
  • It means we are living on the capital of the planet rather than its income

4. Ecosystem services

  • The products of ecosystem processes are called as ecosystem services
  • For ex – healthy forest ecosystems purify air and water, mitigate droughts and floods, cycle nutrients, generate fertile soils, provide wildlife habitat, maintain biodiversity, pollinate crops, provide storage site for carbon and also provide aesthetic, cultural and spiritual values.
  • Out of the various ecosystem services, the soil formation is said to be most costliest service

4.1 What are the different ecosystem services?

Image source:WWF

Ecosystem services are classified into four types of services:

a)Provisioning Services:
  • Includes the products, raw materials, energy outputs
  • Examples are food, water, medicines, wood, biofuels
  • They also provide conditions for these resources to grow
b)Regulating Services:
  • These services regulate the ecological balance
  • Examples are regulating air quality, preventing soil erosion, controlling greenhouse gases etc
c)Supporting services:
  • These services form the basis for other services
  • Examples are providing habitat for different life forms, retaining biodiversity, nutrient cycling, soil formation etc
d)Cultural services:
  • Provides recreational, aesthetic, cultural and spiritual services
  • Examples are tourist and religious locations like landscapes, mountains, caves etc

4.2 How the environmental degradation affects the services?

  • Unsustainable exploitation – provisioning services are being used at unsustainable rates depleting the resources
  • Improper use – for example, present  agricultural practices have depleted the sources of water, excessive nutrient or pesticide use are harmful and causes soil loss 
  • Modifying the ecosystems – alters the regulating services such as disease and climate regulation
  • Altering the biogeochemical cycles – for example, land use changes has increased the amount of carbon dioxide and other greenhouse gases such as methane and nitrous oxide in the atmosphere
  • Changes in biodiversity – Hampers the capacity of ecosystems to adjust to changing environments ,causes irreversible changes in ecosystem processes, increase the potential for infectious disease transmission, increases the risk of crop failure  etc

5. Biodiversity

Biodiversity is the totality of genes, species and ecosystems

5.1 Different types of diversities

  • Genetic Diversity: Diversity of genes within a species.

  • Species Diversity: Variety of species in a given region.

Image source : NCERT

  • Ecological Diversity: Variation of habitats, community types and abiotic environment of given area. For example India has rich ecosystem diversity due to the presence of a variety of ecosystems such as Himalayan Mountains, Northern Plains, Peninsular Plateau, Desert, Coastal Plains, Islands, different types of forests, mangroves, coral reefs, wetlands, estuaries, alpine meadows  etc.

5.2 Keystone species

  • In architecture,  keystone is a single stone supporting an arch. Arch cannot exist without that stone
  • Similarly keystone species is a species whose presence and role within an ecosystem is very important for the survival of ecosystem itself
  • They are comparatively lesser in numbers compared to other species in an ecosystem
  • Example are pollinators and some predators like tiger, parrot fish
  • Foundation species are found in abundance and they support the needs of the entire ecosystem
  • Primary producers are example of foundation species

5.3 Endemic and exotic species

  • Endemic species are plants and animals that exist only in one geographic region.Examples of endemic species in India are
    • Greater One-Horned Rhinoceros.
    • Nilgiri Tahr.
    • Bengal Tigers.
    • Asiatic Lion.
    • Black Buck.
    • Lion Tailed Macaque.
    • Snow Leopard. Etc
  • They are special because they are found in only one location on the planet, and nowhere else.
  • Exotic or Alien Species are that introduced into ecosystem from the outside.
  • Non-native species can have various positive and negative effects on the local ecosystem.
  • Indigenous species are those whose presence in that region is the result of only natural process, with no human intervention.
  • All indigenous species may not be endemic

5.4 The Evil Quartet

The phrase ‘the evil quartet’ is used to describe the four main human-induced causes of biodiversity loss. They are

  1. Habitat degradation and fragmentation
    • This is the most important cause of extinction of species
    • Habitats are broken up into small fragments due to various human activities
    • Mammals and birds requiring large territories and certain animals with migratory habits are badly affected
  2. Alien species invasions
    • Introduced species can turn invasive, and cause decline or extinction of indigenous species
  3. Over exploitation
    • When ‘need’ turns to ‘greed’, it leads over-exploitation of natural resources
  4. Co-extinctions
    • When a species becomes extinct, the plant and animal species associated with it also may become extinct



1.Trophic levels

  • The word trophic means relating to feeding and nutrition.
  • Trophic levels denotes the different hierarchical levels in an ecosystem.
  • Each level consists of organisms sharing the same function in the food chain and the same nutritional relationship to the primary sources of energy
  • Example,
    • All green plants are at the first level,
    • The worms, cattle etc feeding on plants them forms the second level,
    • Tigers feeding on cattle and birds feeding on worms  form the third level.
  • The numbers of trophic levels in an ecosystem is limited by the energy availability.
  • As we have seen, only 10% of energy is transferred to next level. Normally after 3-4 levels, the energy level will be so less so that no more higher levels can exist
  • Predators like tiger and omnivores like human occupy the highest trophic level in an ecosystem.

Hey.. Do not Ignore Me!

Hi there.. We know, you just need single reading to grasp the concepts…Please prove us right


  1. RAHUL WATHRA says:



  2. Shashank says:

    Great work Sir, content is very concise & helpful for understanding the subject, & I four websites very interactive & student friendly.
    We need more people like you not just in education but in other fields as well.

  3. satendra bhokhandi says:

    really awesome work sir … easy to understand the whole concept via diagrams

  4. Himanshu says:

    Wonderful job, Thanks a lot

  5. Himanshu says:


  6. SOURAV KUMAR says:

    excellent piece of work sir…
    thanks for this

  7. Yogesh Deshmukh says:

    great notes sir aisehi sab notes nikalo sir may god bless u always
    awsome cration


    A Big Thanks sir…

  9. MIHIR says:

    Awesome materials sir… Hats off to you. Keep doing this wonderful activity.

    Thanks a lot………..

  10. Neerajmishra says:

    Great work………. please keep it

  11. Akhil says:

    Awesome sir…

  12. Kuldeep Gupta says:

    How to chk the correct answers??

  13. Yacon Root says:

    Awesome Blog. Very much enjoyed reading.

  14. DIGGI says:


  15. mukesh says:

    great job content is very useful

  16. Dhiraj kumat tiwari says:

    Thank u sir.

  17. Shivam says:

    Just awesome…. =D

  18. shobhan says:

    Very lucid way u have taught these topic
    Ecosystem definition was nice
    Thank u sir

  19. PRINCE says:

    Very nice sir ji

  20. Amrit raj says:

    Nice material is provided by u sir I salute to u

  21. Raj says:

    Ist day task completed sir..according to study plan

  22. gautam says:

    great work sir.i have started following your strategy and the notes are very clearly unerstood.
    thank u vw
    ery much sir……..god bless u.

  23. anoop says:

    i think option A is right in question no 3

  24. Varma says:

    Sir,So much Thankful for your efforts,we love your material but a small request from my side,if this material available in pdf,it wil be easy to highlight and for revision even in offline..

  25. Anupam says:

    I have a doubt in question 2, Can’t biomes be classified as aquatic and terrestrial? Here it is specified that only terrestrial systems can be called biomes. Why aquatic systems can’t be a biome? It satisfies all the criterion, right?


  26. Divyesh says:

    Sir please can u provide it in pdf format by so we can have it in hardcopy..which will be helpful in quick revision.

  27. Abhishek Mishra says:

    Sir, pls provide the PDF format so we can print out and easily study it.

  28. aman says:

    great sir

  29. aman says:

    thanks alot, got an oportunity to study,may i continue to the
    end ,,i cheated in exam,in third attempt.

  30. aman says:

    i printed in firefox using foxit,good pdf to revise,no problem of data:jio jio

  31. Kalyan kumar says:

    Thanks a lot sir….

  32. SAGAR SUROSHI says:

    Sir in Net productivity order …. Coral reef>Estuary>Tropical rainforest. Is the order correct ?

  33. Dinesh bhati says:

    Great effort thnku u so much

  34. KULPRIYA KUMAR says:

    sir please prove pdf of all these notes… awesome notes

  35. Karthik Vasista says:

    Sir really great work…hats off…really enjoying the subject..

  36. vivek says:

    thanks sir..

  37. sk sariful islam says:

    great work,
    thanks sir 10000000000000000 times

  38. Sushobhan das says:

    this is the most perfect notes ever….. hats off sir.

  39. pravendra says:

    sir iska pdf avilable ho sakta ha ky plzzz

  40. Salute to u sir.Sir will u try to provide a concise notes for current affairs in month of November or December

  41. Sumitrathod says:

    Thank you sir …it is very much helpfull for student like me who is preparing by themselves.

  42. Vishal says:

    Thank you sir….


    Thank u so much IES GS team, Great work. Is this sufficient for UPSC 2019 aspirants?

  44. sivakumar says:


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