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 –

  1. 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

  1. A biotic Factors –
  • 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 –

  1. Organisms – individual
  2. Population – A group of organisms of the same species inhabiting a given area.
  3. Community – A group of different but interdependent species of plants or animals living their physical environment.
  4. Ecosystem – A system formed by the interaction of a community of organisms with their physical environment.
  5. Biome – A major biotic community characterized by the dominant forms of plant life and the prevailing climate.
  6. 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 –
  1. Terrestrial
  2. Freshwater
  3. Estuarine
  4. 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 a biotic(non-living) components.

Factors of ecosystem –

  1. A biotic factors –
  • Climate factors –
  • Temperature
  • Humidity
  • Light
  • Atmospheric pressure
  • Inorganic substances –
  • Water
  • Rocks
  • Gases
  • Minerals – nitrogen, phosphorous, sulphur etc.
  • Organic substances –
  • Carbohydrates
  • Proteins
  • Lipids
  1. Biotic factors
  • Producers – Autotrophs
  • Plants
  • Phytoplankton
  • ) Phytoplankton are mainly unicellular algae
  • ) Spirogyra
  • ) Ulothrix
  • Cladophora
  • ) Diatoms
  • Volvox
  • Consumers – Heterotrophs
  • ) Zooplankton
  • ) Herbivores
  • ) Carnivores
  • ) Omnivores
  • Decomposers – Saprotrophs or Detrivores
  • ) Bacteria
  • ) Fungi

Types of ecosystems –

  1. 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.

  1. 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 –

  1. Tropical rain forest
  • Mostly found in the equatorial regions
  • characterized by high temperature and heavy rainfall
  1. 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
  1. ­Taiga
  • 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
  1. Tundra
  • 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
  1. Savannah
  • 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
  1. Grassland
  • 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.
  1. Deserts
  • 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

  1. Forests
  • ) Tropical rain forests
  • Sub-types
  1. Tropical evergreen forests
  2. Tropical semi-evergreen forests
  • Distribution
  • 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
  • Sub-types
  1. Moist deciduous forests
  2. 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.
  1. Grasslands
  • Subdivisions
  1. Village grazing grounds
  2. 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
  1. Deserts
  • Thar Deserts
  • Thar desert in Rajasthan is an extension of the Sahara desert through Arabian and Persian deserts.
  • They extend from Punjab, Haryana, 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, isabgole 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.
  1. 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.
  • Sub-divisions
  1. Eastern Himalayas or the Assam Himalayas
  2. Central Himalayas or the Nepal Himalayas
  3. Western Himalayas
  4. North-West Himalayas or the Punjab Himalayas
  5. Ghats
  6. 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.
  1. 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
  1. Fresh water ecosystem
  2. Lotic (Running water) ecosystem
  • Rivers
  • Streams
  • Creeks
  • Rivulets
  1. Lentic(Still water) ecosystem
  • Lakes
  • Ponds
  • Swamps
  • Reservoirs
  1. Marine ecosystem
  • Seas
  • Arabian sea
  • Bay of Bengal
  • Ocean
  • Indian Ocean
  • Gulfs
  1. Gulf of Mannar
  2. Gulf of Kutchch
  3. Gulf of Khambhat
  • Continental shelf
  1. Estuaries
  • 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 –

  1. Mangroves – ecotone between marine and terrestrial ecosystem
  2. Grassland
  3. Estuary
  4. 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
  1. Intra specific relationship – relationship or interaction among individuals of the same species.
  2. 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 –

  1. Commensalism –
  • The relation between two different kinds of organisms when one receives benefits from the other without damaging it.
  • g. relationship between trees and epiphytic plants, ferns, mosses etc.
  1. 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 –

  1. Amensalism –
  • Relationship in which one species harms of restricts the other species without itself being affected by the presence of the other species.
  • g. Penicillium kills the bacteria through pencillin to have greater availability of food.
  1. Predation –
  • The relationships in which the predator captures, kills and eats an animal of another species or prey is called predation.
  1. 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 –

  • Neutralism
  • 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 –

  1. 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.
  • g. Grassland ecosystem
  • Inverted –
  • The number of individuals increases gradually from lower trophic to higher trophic level.
  • g. Forest ecosystem
  1. 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.
  1. Energy pyramid –
  • Represents the amount of energy stored in each trophic level.
  • Energy pyramid is never inverted.