class 11th

Following 10 biogeographical regions have been identified in India:

  • Trans-Himalaya with 2 provinces.
  • Himalaya with 4 provinces.
  • Desert (Kutch and Thar) with 2 provinces.
  • Semi-arid zone with 2 provinces.
  • Western –Ghats with 2 provinces.
  • Deccan peninsula with 5 provinces.
  • Gangetic plain with 2 provinces.
  • North East India with 2 provinces.
  • Indian Islands with 2 provinces.
  • Marine coasts with 3 provinces.
  • India as biocentre of origin of cultivated plants

India is one of the 12 centres of origin of cultivated plants.India has been considered as the origin place of 167 cultivated plant species and more than 320 their wild relatives.India is centre of origin of 30,000-50,000 varieties of rice,sugarcane,turmeric,ginger,mango,pigeon-pea etc.

  • World heritage sites

India is home to 5 worldheritage sitesand 6 Ramsar wetlands,amongst the protected areas.Heritage sites are the places that attractTourists. SUNDERBAN NATIONAL PARK, NANDA DEVI NATIONAL PARK, KEOLODEO GHANA NATIONAL PARK, MANAS WILD LIFE SANCTUARY & KAZIRANGA NATIONAL PARK.

  • There are 33 Botanical Gardens,89 National parks, 492 Wildlife sanctuaries and14 biosphere reserves in India.
  • There are about 47,000 species of plants and 81,000 species of animals identified in India. About 60% of the above diversity has been reported from Western Ghats, which is one of the hot spots of diversity in India.Out of the Above 81,000 animals’ species recorded from India.372 are mammals,1228 areBirds,428 reptiles,200 amphibians,2550 fishes,about 57,000 insects and5025Molluses and many other species of invertebrates.

Living resources conservation has three specific objectives:

  1. To maintain essential ecological processes and life support system.
  2. To preserve biological diversity.
  3. To ensure that any utilization of species and ecosystems is sustainable.

Biological diversity includes two related concepts,genetic diversity and ecological diversity.Genetic diversity is the amount of genetic variability among individuals of a single species as also between species.


Biodiversity has great importance to mankind due to its many uses:

  1. Ecosystem (ecological) role of biodiversity.
  2. Scientific importance.
  3. Drugs and medicine about 75% of world’s population depends upon plants or plant extracts for medicines. Some examples of drugs and medicenes extracted from plants are:
  4. Morphine(papaveysomniferum) is used as analgesic.
  5. Quinine(chinchonaledgeriana) for treatment of malaria.
  6. Taxol extracted from bark of Taxusbrevifolia and T.baccata is used as anticancer drug.
  7. Penicillin used as antibiotic is derived from a fungus called penicillium.
  8. Tetracycline is got from a bacterium.
  9. Digitalin a drug used for cure of heart ailments is got from digitalis.

Plants are also useful for making many synthetic products called botanochemicals.Twenty five % of drugs in pharmacy are got from only about 120 species of plants.About seventy five % of anticancer drugs are derived from plants found in tropical rainforest.

  • Food

One of the most fundamental values of bio-diversity is in providing food.

  • Industrial importance.

Wildlife is a renewable source and is beneficial to mankind in many ways.

  • Fur,skin and other products like leather,honey,lac,cochineal(a redpigment),guano,pearls,etc.obtained from wild animals are sources of trade.
  • Lvory of elephants,horns of rhino,antlers of deer,etc. fetch large amount ofmoney in foreign currency market.In fact, tourist industry of Kenya is based onits wildlife.


Extinction is the complete elimination of a wild species.It is anatural but slowProcess but due to unplanned activities of man. The rate of decline of wild life has been particularly rapid in the last one hundred years.India alone has a totalof 459 threatened species of which include 86 mammals,70 birds,25 reptiles, 3 amphibians, 8 fishes,23 invertebrates and 244 plants.There are a number of causes which are known to cause extinction of wildlife.

  1. Destruction of habitats and fragmentation: It is the most serious threat to wildlife. It is due to:
  2. Pollution due to automobiles,etc.leading to degradation of a number of important habitats.
  3. Deforestation leads to decrease in the area of movement so decreasing theirreproductive powers.In Tripura,deforestation of dense forests is posing a serious threat to the precious barbe’s leaf monkey,better known as spectacledmonkey,or Lajvanti Bandar,(shy-monkey).
  4. Soil erosion.
  5. Agricultural expansion.
  6. Overgrazing.
  7. Forest fires due to certain human activities or by chance.
  8. Indiscriminate hunting for various uses of animals,like food,hide,musk,tuskHorn,fur,plumage,recreation,etc.Other causes of indiscriminate hunting of wild Animals are: their increased demand as museum specimens and increased trade for the animal products like hides,skins,fur,leather,feathers,horns,ivory,meat etc.Excessive hunting is known to cause.
  9. Extinction of Dodo bird.
  10. Extinction of Cheetah.

important characteristics of population

population is defined as the total number of individuals of a Species in a specific geographical area, can interbreed under natural conditions to produce fertile off springs and functions as a unit of biotic Community.


Different populations can be compared by measuring these characteristics

Population size and population density.

Birth or Natality rate.

Death or Mortality rate.


Age distribution.

Population growth.

Biotic or Reproductive potential.

Environmental resistance.

Carrying capacity.

Sex ratio.

Age ratio.

Population fluctuations and population cycles.

Population size and population density. Population size indicates the total Number of organisms of a specific species present in a specific geographical area at a specific time. Population density of a species is the number of individuals of a species per unit area or volume.

  • Birth or Natality rate. It is generally expressed as number of births per 1,000 individuals of a population per year.
  • Death or Mortality rate. It is opposite to natality rate .It is commonly Expressed as the number of deaths per 1,000 individuals of a population per year.


Temperature is the degree of hotness or coldness of a substance. It is the most important ecological factor affecting almost all the metabolic activities of the Organism. Every physiological function has an optimum temperature at which it show the maximum metabolic rate.

The vertical temperature gradient over Earth’s surface is called lapse rate. This value comes equal to 6.50C per 1000mElevation.Change in temperature is affected by factors like latitude, altitude, Topography, vegetation and slope. Temperature shows a great amount of variation altitudinally and latitudinally.

The bacteria and cyanobacteria are known to survive even in thermal spring (60-900C) or permafrost (–30 to –500C) But most of the organisms are killed By higher temperatures due to denaturation of enzymes while others are killed By very low temperature due to freezing of body fluids except dry seeds, spores And cysts which have no water.

Tolerance power to the extremes of temperature varies from species to species.


Synthesis of pigments: The plants grown in the absence of light become etiolated.

Photosynthesis: The light intensity at which rate of photosynthesis is just sufficient to meet the requirements of respiration is called compensation point.

Photoperiodism: angiosperms are divided into three categories. Long-day plants(e.g. Radish, Spinach, Scale cereale, etc.) short-day plant(e.g. xanthium, Chrysanthemum, Cosmos, Datura, salvia, Cannabis)and day-neutral Plants(e.g. Cotton Gossypium, Tomato—Lycopersicum, Potato solanum)


Plant growth

Stomatal opening

what is Ecosystem (part – 1)

The interaction between the living organism and the non-living environment is called ecosystem.

ECOSYSTEM – STUCTURE AND FUNCTION: Interaction of biotic and abiotic components results in a physical structure that is characteristic of each type of ecosystem. Identification and description of plant and animal species of an ecosystem gives its species composition. Vertical distribution of different species occupying different levels is called stratification.

The components of the ecosystem are seen to function as a unit:

  • Productivity.
  • Decomposition.
  • Energy flow and
  • Nutrient cycle.

Description of pond as an ecosystem

The abiotic components include all dissolved inorganic and organic substances and the rich soil deposit at the bottom of the pond. The solar input, cycle of temperature, day length, regulates the rates of function of the entire pond.

The producer (autotrophic) includes phytoplankton, some algae and the floating, submerged and marginal plants found in edge of pond.

  • The consumers are represented by zooplankton, free swimming and bottom dwelling animals.
  • The decomposers are the fungi, bacteria especially abundant at the bottom of the pond.
  • Basic events (in terms of function) in an ecosystem:
  • Conversion of inorganic into organic material (photosynthesis) by producers.

Consumption of the autotrophs by heterotrophs.

Decomposition and mineralization of the dead organic matter to release them back for reuse by the autotrophs there is unidirectional flow of energy towards the higher trophic levels and its dissipation and loss as heat to the environment.

most important tissue Skeletal tissues

Skeletal tissues: it is the hard connective tissues that forms supportive framework of body. It is of two types:

  1.  Cartilage – this tissue is elastic, harder than connective tissue proper but softer than bone. Its elasticity is due to presence of protein chondrin. Spaces in its matrix are called lacunae, which contain cartilage forming cells called chondrocytes. It is of three type’s hyaline, fibrous and calcified. It form supportive framework of nose, pinna, etc.
  2. Bone – it is hardest connective tissues its matrix is so much hard due to presence of salts, such as calcium phosphate, etc. it help in locomotion. It protect internal delicate organ.