(Notes) Environment and Ecology

Basics –

The totality of surrounding conditions in which organisms survives is called environment.

Environment is composed of both living and non living components.

Proper balance between biotic and a biotic factors is essentials for the survival of living organisms.

Factors of Environment –

    Biotic factors –

  • Plants – Converts a biotic factor into food for animals through photosynthesis.
  • Animals – All living organisms depend on other organisms for food and in-turn become food for other organism.

E.g. grass–>deer–>tiger–>vulture–>micro-organisms–>back to minerals deeded by grass

A biotic Factor –

Light – Essential for photosynthesis and movement

Water –Medium for biochemical reactions

Regulation of body temperature

Habitant for aquatic plants and animals

Temperature –Essential for the functioning of all environment cycles

Certain range of temperature and humidity is essential for survival of Organisms

Atmosphere –Contains life supporting gases.

    Sub-stratum –Soil, deep water vents or any surface supporting life forms.



Basics – Ecology is the scientific study of inter-relationships between organisms and their environment.

The term ecology was first coined in 1869 by the German biologist Ernest Haeckel.

Levels of ecological organisms –

  • Organisms – individual
  • Population – A group of organisms of the same species inhabiting a given area.
  • Community – A group of different but interdependent species of plants or animals living their physical environment.
  • Ecosystem – A system formed by the interaction of a community of organisms with their physical environment.
  • Biome – A major biotic community characterized by the dominant forms of plant life and the prevailing climate.
  • Biosphere – Regions of the surface and atmosphere of the Earth where living organisms survive.


Habitat –

The type of environment in which an organisms or group normally loves or occurs.

Four major habitats

  • Terrestrial
  • Freshwater
  • Estuarine
  • Ocean


Basics –

  • Ecosystem: A system formed by the interaction of a community of organism with their physical environment.
  • Ecosystem is comprised of complex interaction between its biotic (living) and biotic (non-living) components.


Factors of ecosystem –

A biotic factor

Climate factors –

  • Temperature
  • Humidity
  • Light
  • Atmospheric pressure

    Inorganic substances –

  • Water
  • Rocks
  • Gases

    Minerals – nitrogen, phosphorous, sulphur etc.

Organic substances –

  • Carbohydrates
  • Proteins
  • Lipids


  Biotic factors

  • Producers – Autotrophs
  • Plants
  • Phytoplankton
  • Phytoplankton is mainly unicellular algae
  • Spirogyra
  • Ulothrix
  • Cladophora
  • Diatoms
  • Volvox
  • Consumers – Heterotrophs
  • Zooplankton
  • Herbivores
  • Carnivores
  • Omnivores
  • Decomposers – Saprotrophs or Detrivores
  • Bacteria
  • Fungi

Types of ecosystems

Natural ecosystems

Ecosystems totally dependent on solar radiation e.g. forests, grasslands, oceans, lakes, rivers, and deserts.

Ecosystems dependent of solar radiation and alternative energy source such as wind, rain and tides

e.g. – tropical rains forests, tidal estuaries and coral reefs.


    Man made ecosystems –

  • Dependent on solar energy- e.g. agricultural fields and aquaculture ponds
  • Dependent on fossils – e.g. urban and industrial ecosystems


  • Introduction – Biome is a large naturally occurring of flora and fauna occupying a major habitat, e.g. forest or desert.
  • Biomes are characterized by different types of climate, flora, fauna and soil types.
  • Climate of biome and abundance of flora and fauna are determined mainly by the level temperature and precipitation.

Types of biomes –

Tropical rain forest

  • Mostly found in the equatorial regions
  • characterized by high temperature and heavy rainfall

Temperature Deciduous Forest


  • Found across the regions of Central Southern Europe, East and North America, Western China, Japan, New Zealand etc.
  • Trees like birch, oak, maple and cherry are found here
  • characterized by moderate temperature and rainfall



  • Northern subarctic coniferous forests (Boreal forest)
  • Spreading across much of subarctic N America and Eurasia, with tundra to the north and steppe to the south
  • Trees such as spruce, pine and firs are abundant here
  • Animals like Siberian tiger, minks, elks, puma, and wolverines are found here




  • A vast treeless plain in the Arctic regions where the subsoil is permanently frozen
  • characterized by lichens, mosses and dwarfed vegetation
  • Mostly found animals include polar bear, lemmings, reindeer, arctic fox and arctic hare




  • Found mostly in mid tropical regions were comparatively moderate precipitation is seen
  • They are most extensive in Africa
  • Animals such as lions, cheetah, antelopes, buffaloes, zebras, elephants, rhinoceros, hyena and many rodents flourish here



  • These are regions dominated by grasslands
  • Characterized by temperature conditions with low rainfall.
  • Supports large herbivores like bison and antelope, large species of birds, rodents, wolves etc.



  • These are interior regions of the continents with sporadic rainfall and low humidity.
  • They are characterized by plants like cactus and euphorbias and animals such as reptiles, few mammals, and birds.


Terrestrial Ecosystems


  • Tropical rain forests
  • Sub-types
  • Tropical evergreen forests
  • Tropical semi-evergreen forests


Found in places of high rainfall (around 200 cm) and sunlight.

Regions include Western Ghats, West Bengal, Orissa, A&N Islands and north-eastern India

Flora and Fauna

Trees grow up to 60 cm and above

This region has high biodiversity

Important trees in this forest include ebony, mahogany and rosewood.

    Tropical deciduous forests

­Also called as monsoon forests


  • Moist deciduous forests
  • Dry deciduous forests


  • Formed in regions having 75 cm to 200 cm of annual rainfall
  • Major regions include
  • eastern slopes of Western Ghats
  • north eastern parts of the peninsular plateau
  • Valley of the Himalayas
  • Chhotanagpur plarteau
  • parts of Madhya Pradesh, Bihar and Orrisa
  • Important trees of these forests are teak, sal, and sandalwood
  • Temperature broad leaf forests
  • Occurs between 1500-2400 m altitudes in western Himalayas
  • Flora and Fauna
  • Oak species are abundant which shed leaves during summer.
  • characterised by a dense canopy of trees but gasses are generally absent
  • The oak forests are often rich in epiphytic flora

Temperature or coniferous forests

These types of forests are found in the Himalayas over 1700 to 3000 m altitude.

Coniferous forests are characterised by an evergreen canopy of long needle like leaves.

Major trees include

  • Pine (Pinus wallichiana)
  • Deodar (Cedrus deodara)
  • Cypress (Cypressus torulosa)
  • Spruce (Picea simthiana)
  • Siver fir (Abies pindrow)

Alpine and tundra forests

  • Alpine and tundra forests grow at altitudes above 3600 m.
  • The trees include silver, pine, juniper and birch
  • High altitude vegetation such as lichen and mosses are found here

Tidal forests

  • They are found along the costs and rivers
  • Sundari trees or mangroves are abundant in this region.



  • Village grazing grounds
  • Low pastures of dry regions

    Flora and Fauna

  • Grasslands support a large of herbivores, birds and large animals.
  • One horned rhinoceros of India is a grassland animal


    Thar Deserts

  • Thar Desert in Rajasthan is an extension of the Sahara desert through Arabian and Persian deserts.
  • They extend from Punjab, Haryana and Rajasthan to Gujarat state.
  • Rann of Kutch
  • Rann of Kutchch – Bhuj in Gujarat forms a separate zone with in Thar Desert due to its different climate conditions.
  • Rann of Kutchch supports living corals, pearl oyster, sea turtles and migratory birds like kingfisher, cranes, ibis and herons.

    Flora and Fauna

  • Only some thorn forests and dry open grasslands are found here.
  • Food crops include bajra, millet, wheat, barley, maize, jowar and guwar.
  • Medical plants found here are mehndi, hak, isabgol and gugal.
  • Threatened bird species – Great Indian Bustard, Cranes and Sand Grouse.
  • Threatened mammals – Asiatic lion, wild ass, bats, scaly and eater, desert fox, Indian gazelle, four horned antelope and white browed Buchchat.


Mountains – Himalayas

  • Himalayas are spread over Afghanistan, Pakistan, India, Nepal, Bhutan and China.
  • Himalayas are spread partially or completely over 12 states –Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Sikkim, West Bengal, Arunachal Pradesh, Assam, Nagaland, Manipur, Tripura, Mizoram and Meghalaya.


  • Eastern Himalayas or the Assam Himalayas
  • Central Himalayas or the Nepal Himalayas
  • Western Himalayas
  • North-West Himalayas or the Punjab Himalayas


Western Ghats

  • Also called as Sahyadris
  • They run parallel to the west coast of peninsular India.
  • They pass spread six states namely Gujarat, Maharashtra, Goa, Karnataka, Tamil Nadu and Kerala.

    Eastern Ghats

  • They are spread through the states of Orissa, Andhra Pradesh and Tamil Nadu.
  • The Eastern Ghats do not form a continuous range because the great rivers Mahanadi, Godavari and Krishna cut across them.
  • United Nations Conference on Environment held in Rio de Janeiro in 1992 discussed the issue of conservation of this region.

Aquatic Ecosystems


Aquatic Zones –

  • Aquatic ecosystems are divided into distinct life zones, with regions of relativity distinct plant and animal life.
  • The differences between various aquatic zones are due to-
  • depth of sunlight penetration
  • levels of dissolved nutrients
  • level of salinity
  • temperature of the water
  • abundance of food


    Fresh water ecosystem

Lotic (Running water) ecosystem

  • Rivers
  • Streams
  • Creeks
  • Rivulets

Lentic (Still water) ecosystem

  • Lakes
  • Ponds
  • Swamps
  • Reservoirs

Marine ecosystem

  • Seas
  • Arabian sea
  • Bay of Bengal
  • Ocean
  • Indian Ocean


  • Gulf of Mannar
  • Gulf of Kutchch
  • Gulf of Khambhat

Continental shelf


  • Estuaries include ecosystems of bays, river mouths and tidal marches.
  • Estuaries are highly productive than river or sea ecosystems.



Definition –


  • Ecotone is a zone of junction between two or more diverse ecosystems.


Examples of ecotone –

  • Mangroves – ecotone between marine and terrestrial ecosystem
  • Grassland
  • Estuary
  • River Banks

Characteristics of ecotone –

  • It may be very narrow or quite wide.
  • Ecotone is a zone tension
  • Ecotone may contain specially evolved organisms are entirely different from the adjoining communities.

Biological Relationships

Basics –

  • Ecosystem is complex network of relationship among various organisms.
  • Form of relationship
  • Intra specific relationship – relationship or interaction among individuals of the same species.
  • Inter specific relationship – relationship or interaction among individuals of different species.
  • Inter specific relationship may be direct and close or indirect and remote.


Types of relationships –


Positive Relationship –

Commensalism –

  • The relation between two different kinds of organisms when one receives benefits from the other without damaging it.
  • Relationship between trees and epiphytic plants, ferns, mosses etc.

Mutualism –


  • Relationship between two different species of organisms that are interdependent; each gains benefit from the other.
  • This is a close association between two species in which both the species benefit.
  • Symbiotic mutualism: Mutualism in which the interacting can no longer live without each other as they depend totally on each other to survive.

Negative Relationships –

Amensalism –


  • Relationship in which one species harms of restricts the other species without itself being affected by the presence of the other species.
  • Pencillium kills the bacteria through penicillin to have greater availability of food.


    Predation –

  • The relationships in which the predator captures kills and eats an animal of another species or prey is called predation.

Parasitism –

  • The relation between two different kinds of organisms in which one receives benefits from the other by causing damage to it.
  • Many organisms like animals, bacteria and viruses are parasites of plants and animals.


Neutral Relationships –


  • Relationship between two species which do interact but do not affect each other in neither positive nor negative ways.

Food Chains, Food webs and ecological pyramids


Food Chain –

  • Community of organisms where each member is eaten in turn by another member is called food chain.
  • Trophic level: Each successive stage in the food chain is called Trophic level e.g. Grasses>Deer>Tiger>Vulture, Grass represent first trophic level, deer the second and so on.
  • In every stage, some energy is lost into the system as heat energy and is not available to the next trophic level.

    Types of food chains –

  • Grazing food chains – Autotrophs>Herbivores>Carnivores
  • Detritus food chains – Dead organic matter>Detritus Feeders>Carnivores

Food Web –

  • Food web is a network of interconnected food chains in an ecosystem.
  • An ecosystem may consist of several interrelated food chains called food web in totally.
  • Single organisms can take part in multiple food chains.
  • Energy flow in food web is similar to the flow of energy in food chains.

    Difference –

  • A food chain traces only one pathway of the food or energy transfer among few organisms in an ecosystem.
  • A food web illustrates all possible transfers of energy and nutrients among the organisms in an ecosystem.


Ecological Pyramid –

  • Ecological pyramids are the graphic representations of trophic levels in an ecosystem.
  • Ecological pyramids are pyramidal in shape.

Types of pyramids –


Pyramid of numbers –

    Upright –

  • Represents the number of organisms at each trophic level.
  • The number of individuals decreases gradually form lower trophic level to higher trophic level.

     Grassland ecosystem

    Inverted –

  • The number of individuals increases gradually from lower trophic to higher trophic level.

Forest ecosystem

Biomass pyramid –

  • In the pyramid of biomass, individuals in each trophic level are weight instead of being counted.
  • In calculates the total dry weight of all organisms at each trophic level at a particular time.
  • Biomass pyramid of terrestrial is upright.
  • Biomass pyramid of aquatic ecosystem is inverted.


    Energy pyramid –

  • Represents the amount of energy stored in each trophic level.
  • Energy pyramid is never inverted.


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