By going through these Maharashtra State Board 12th Science Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues students can recall all the concepts quickly.

Maharashtra State Board 12th Biology Notes Chapter 15 Biodiversity, Conservation, and Environmental Issues


  • Biodiversity: A variety of life that includes a vast array of species from microorganisms, viruses, algae, fungi, plants and animals present in different habitats on the earth is called biodiversity.
  • Diversity is seen in shape, colour, form, mode of nutrition, habitats, reproduction, motility, duration of the life cycle, life span, etc. All of these adaptations help in the survival of species and hence diverse forms are seen.
  • The term Biodiversity was coined by Walter Rosen in 1982.
  • Edward Wilson popularised the term. He described it as combined diversity at different levels of biological organisation.
  • Definition of biodiversity: Biodiversity is the part of nature that includes differences in the genes among individuals of a species, variety of animal and plant species in different habitats, regions, countries and the world which form different types of ecosystems within a defined area.
  • Biodiversity was developed for 3.5 billion years when the evolution took place gradually.

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

Levels of biodiversity-

  • Various levels at which diversity can be seen ranging from molecular to ecosystem levels. The three main levels, which form a hierarchy and interrelation: Genetic diversity, species diversity (community), and ecosystem diversity (Ecological diversity).
  • Genetic diversity: Also called intraspecific diversity. The diversity present in the number and types of genes and chromosomes present in different species and variations in them and their alleles in the same species is called genetic diversity. Subspecies and races are also examples of genetic diversity.
  • Species diversity: Also called interspecific diversity. The diversity in the number of species of plants and animals which are present in a particular region is called species diversity. Species diversity decides species richness (variety of species) and species evenness (number of individuals of different species).
  • Ecological or ecosystem diversity: The diversity of different types of ecosystems and habitats
    within a given geographical area is called ecological or ecosystem diversity. E.g. Deserts, rain forests, deciduous forests, estuaries, wetlands, grasslands are different ecosystems with diverse features.

Patterns of biodiversity-

  • Latitudinal and altitudinal gradient and species-area relationship are the two patterns of diversity.
  • Latitudinal species diversity: There is greater species richness at a lower latitude which steadily declines towards the poles. This is called as distribution of diversity along the latitudes.
  • The overall stability of tropical regions, lesser annual climatic changes, availability of plenty of sunlight, lesser drastic disturbances like periodic glaciations, lesser migrations causing reduced gene flow, normal temperature, and higher annual rainfall are all the factors that cause more diversity in these regions.
  • Altitudinal species diversity: The diversity is more at lower altitudes, but at higher altitudes, it declines due to change in climatic conditions and drastic seasonal variations.
  • Species area relationship: The number of species present in any area is directly proportional to the size of this area. Species richness increases with an increase in the area up to a certain limit this was observed by Alexander wan Humboldt.
  • Importance of species diversity to the ecosystem: A stable community has fairly constant average biomass production over a particular time period. It withstands the disturbance and recovers quickly and also resists the invasive species.
  • Productivity stability hypothesis (David Tillman): Rich diversity leads to lesser variation in the production of biomass over a particular time period.
  • Rivet Popper hypothesis (Paul Ehrlich): Relationship between diversity and wellbeing of the ecosystem is not linear. When key species are lost there is a threat in a very short span of time which affects the food chain, food web, energy flow, and natural cycles resulting in an imbalance of the ecosystem.

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

Biodiversity current scenario-

  • According to the IUCN data (2004), over 1.5 million species have been documented so far but still lot more are yet to be studied.
  • Most of the temperate species have been studied but tropical species are yet to be explored.
  • Robert May estimated that there are 7 million species on the earth.
  • India has 8.1% of total global biodiversity. India is one of the 12 mega diversity countries. On total Indian land area which is 2.4% of the world, there are about 45000 plant species and 90000 animal varieties. 22% of global natural wealth has been recorded so far.
  • But due to rapid deforestation and reclamation, many species and varieties could be lost forever before they are documented.

Loss of biodiversity-

1. Imbalance in the ecosystem occurs if biodiversity is lost. Extinction of species means a threat to biodiversity.
2. Three types of extinctions are :

  • Natural extinction: Occurring due to natural causes such as forest fires, earthquakes, volcanic eruptions, etc.
  • Mass extinction: Great impact causing major loss of species.
  • Manmade or Anthropogenic extinction: Habitat destruction, hunting, settlement, overexploitation, reclamation are man-made causes of extinction.

3. There were five mass extinctions during different stages of the history of Earth.
4. The sixth extinction is taking place now which is a hundred to a thousand times faster than that
occurred in pre-human times.50% of diversity is said to be lost and this loss of biodiversity can alter environmental processes such as plant productivity and disease cycles.

5. Causes of biodiversity losses :
(1) Four major causes of biodiversity loss, known as an evil quartet.

  • Habitat loss and fragmentation
  • Overexploitation
  • Alien species invasion
  • Co-extinctions

(2) Extinct species: The species which are totally eliminated from the Earth.
E.g. Dinosaurs

(3) Endangered species: The species having dwindling numbers.

(4) The international union for conservation of nature and natural resources (IUCN) maintains a red data Book or red list to record the conservation status of plant and animal species.

(5) Categories of species according to IUCN:

  • Extinct (EX)
  • Extinct in the wild (EW)
  • Critically endangered (CR)
  • Endangered (EN)
  • Vulnerable (VU)
  • Near threatened (NT)
  • Least concern (LC)
  • Data deficient (DD)
  • Not evaluated (NE)

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

Conservation and biodiversity-

1. Protection, upliftment, and scientific management of biodiversity so that it can remain at optimum level and give us sustainable benefits is called conservation of biodiversity.
2. Reasons for conservation of biodiversity :

(1) Narrowly utilitarian reasons: Humans obtain benefits from biodiversity in the form of resources for food, cloth, shelter industrial products, aesthetic products, ornaments, artifacts, and medicines.
Bioprospecting is done for systematically searching the new sources of chemical compounds, genes, microorganisms, and other valuable products that we could obtain from nature.

(2) Broadly utilitarian reasons: Oxygen supply, seed dispersal, pollination, extra aspects that nature gives us free.

(3) Ethical reasons: Humans share the earth with all the other diverse life forms and all of them have equal rights to survive. Therefore, ethically we should not finish them for our prospective economic use.

3. Conservation of biodiversity :

(1) In situ conservation :

  • The protection of an organism in its natural surrounding or habitat is called in situ conservation.
  • 34 biodiversity hotspots having high species richness and high density are strategically protected under in situ conservation in India.
  • Traditionally used varieties for farming and horticulture are also conserved by this method.
  • The Western Ghats, Indo-Burma, and Eastern Himalayas are 3 of world’s biodiversity hotspots located in India.
  • In India, there Eire 14 biosphere reserves, 90 national parks, 448 wildlife sanctuaries, sacred groves are also typed of in situ conservation in which flora and fauna are protected in the name of God.
  • Sacred groves are found in Khasi and Jaintia hills in Meghalaya, in Western Ghats of Maharashtra (especially Sindhudurg district), and Karnataka, Aravalli hills of Rajasthan and Bastar, Chanda and Sarguja areas in Madhya Pradesh.

(2) Ex-situ conservation :

  • Critically endangered species are protected in captivity, which is called ex-situ conservation.
  • An ex-situ conservation, living beings are protected in wildlife safari parks, zoological parks, botanical gardens, etc.
  • Seed banks, tissue culture, cryopreservation, etc. are modern techniques that are used in this conservation method.

Biological Diversity Act 2002-

1. Earth Summit, held at Rio de Janeiro came out with the Convention on Biological Diversity (CBD-1992).
2. Indian Government has passed Biological Diversity Act (BD Act) in the year 2002 in compliance with CBD.
3. It gives framework for the sustainable management and conservation of our country’s natural resources. The law excludes value added products and human genetic material.
4. The main objectives for proposing this act are

  • Regulation of access to Indian biological resources.
  • Scientific cataloguing of traditional knowledge about ethnobiological materials.

5. There is three tier system in India, comprising of

  • National Biodiversity Authority (NBA) at the national level
  • State Biodiversity Boards (SBBs) at the state level
  • Biodiversity Management Committees (BMCs) at the local level.

Environmental issues-

1. To protect and improve the quality of our environment, Indian Government has passed the Environment Protection Act in 1986.
2. Reasons for rampant loss of natural resources :

  • Exponential growth of human population
  • Industrial development
  • Uncontrolled exploitation of nature
  • Utilization and production of synthetic materials
  • Construction activities
  • Resultant pollution

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

3. Types of pollution :

  • Air pollution, Noise pollution, Water pollution, Radioactive pollution, Soil pollution are different types of pollution.
  • Pollutant: Substance that causes pollution is called a pollutant.

4. Air pollution :

(1) Unfavourable alteration in air quality causing damage to the respiratory system is called air pollution.
(2) Duration of exposure, concentration of pollutant and type of organism decide the severity of damage caused by air pollution.
(3) In plants, yield of crops are affected. Premature death of plants is another effect of air pollution.
(4) Major cause of air pollution is automobile traffic.

(5) Types of air pollutants : Two main types -> Particulate and Gaseous pollutants.

  • Particles of less than 2.5 micrometres in diameter are extremely harmful to humans.
  • Gaseous pollutants : CO, CO2, SO2, NO, NO2, etc.

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues 2

(6) Control measures for air pollution : For controlling emissions of gases and particulate pollutants which are released through vehicles and industries following devices are used :

  • Electrostatic precipitator
  • Exhaust gas scrubbers
  • Catalytic converters

(7) Noise pollution :

  • Noise is considered as an air pollutant which causes psychological and physiological changes in human beings.
  • Sound level can damage the ear drum causing permanent hearing loss. Other problems that noise causes are sleeplessness, increased heartbeat, altered breathing, psychological stress, interference in learning etc.
  • Sources of noise pollution : Machines, transportation, construction sites and industry.
  • Using sound absorbing material can cause reduction in noise pollution.

5. Water pollution :

  • Most of the water pollution is manmade.
  • Smelling water having many pathogens, heavy metals and oils is called polluted water.
  • Water Prevention and Control of Pollution Act 1974 to safeguard the water resources.
  • Domestic sewage and Industrial effluents cause water pollution.
  • (5) Domestic sewage contains biodegradable organic matter which can be removed by treatment.
  • BOD or biochemical oxygen demand is a measure to estimate biodegradable organic matter present in the polluted water.  It is defined as the amount of dissolved oxygen required by microorganisms for decomposing the organic matter present in water which is expressed in milligram of oxygen per litre (mg/L) of water.
  • Algal bloom : Excessive growth of free floating planktonic blue green algae causes algal bloom. It releases toxins in the water causing death of inhabitant fish. –
  • Water hyacinth (Eichhornia crassipes) : Commonly called Terror of Bengal’ is an invasive species which grows excessively in water bodies and cause nuisance.
  • Natural eutrophication : Ageing of lake over a very long period due to nutrient enrichment of water is called natural eutrophication.
  • Cultural or accelerated eutrophication: Pollutants passing in the water body due to human activities cause cultural eutrophication in which there is accelerated aging process for the water body.
  • Biological magnification or biomagnification : Accumulation of certain pollutant in the tissues of organisms and their increasing concentrations along the food chain is called biomagnification. E.g. DDT and mercury show biomagnification.

6. Thermal pollution : When the temperature of water is raised due to human activities, it causes thermal pollution. E.g. Effluents from thermal and nuclear power plants. Sensitive organisms are killed due to raised temperature, thus thermal pollution causes loss of flora and fauna.

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

7. Ecosan or Ecological sanitation :

  • Use of excreta as agricultural manure in a safe and reusable manner is called ecological sanitation.
  • Principle of recovery and recycling of nutrients is practised in this way.
  • Ecosan is a closed system toilet which requires no water and is an alternative to leach pit toilet.
  • Through such toilets composted organic manure is formed.

8. Reverse osmosis : Sewage water is reused after performing reverse osmosis.
It solves the problem of water scarcity and treatment of sewage water.

9. Rainwater harvesting : By harvesting rainwater, scarcity of water can be solved. For new constructions now it is mandatory to have provision for RWH.

10. Solid waste management :

(1) Everything that is disposed into the trash is called solid wastes.

(2) Municipal wastes : Wastes from homes, offices, stores, schools, hospitals, etc. together are called Municipal wastes. Municipality collects and disposes the same. It may contain paper, food wastes, plastics, glass, metals, rubber, leather, textile, etc.

(3) One of the ways to dispose the solid waste is to burn them. Volume of the waste is reduced by burning but burning creates air pollution.

(4) Sanitary landfills : Dumping the trash in open can attract rats and flies causing open dumps as the breeding ground for these pests. Therefore, sanitary landfills are created. At sanitary landfill sites, the wastes are compacted and buried in trenches. Everyday newer trash is added to landfills.

(5) However, this method is not a fool proof solution for the waste management as in large metro cities amount of trash is increasing day by day and hence such landfills are falling short. There is also seepage of dangerous chemicals from the sanitary landfills which results into the pollution of underground water reserves.

(6) Therefore, every human being should be sensitized towards the environmental issues. Common man should have ecological conscience to reduce the non-biodegradable trash.

(7) The solid wastes are categorized into three types :

(1) Bio-degradable
(2) Recyclable
(3) Non-biodegradable.

(8) The generated garbage should be sorted prior to disposal. The matter that could be reused or recycled should not be thrown into trash but to be given to kabadiwallahs and rag¬pickers.

(9) The biodegradable materials undergo natural breakdown. Therefore they can be buried deep down in the ground in pits.

(10) The non-biodegradable material should be reduced at source to curb the garbage generation. Packaging material, plastics, polybags, etc. which are used to a greater extent in modern times cause environmental pollution. Use of eco-friendly packaging and reduction in plastic has been advocated by the State Governments.

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

(11) Biomedical wastes : Hazardous wastes generated by hospitals contain disinfectants, harmful chemicals and disease-causing pathogenic microorganisms. Therefore such wastes should be carefully handled, treated and then disposed. For disposal of harmful biomedical wastes the incinerators are used.

(12) Electronic wastes (e-wastes) :

  • e-wastes are any material of electronic origin, such as irreparable computers, mobile phones, CDs, floppies, batteries, etc.
  • e-wastes are managed by burying them in landfills or they are incinerated.
  • e-wastes generated in the developed world are exported to developing countries for further recycling and disposal.
  • In China, India and Pakistan, metals like copper, iron, silicon, nickel and gold are recovered from e-wastes during recycling process.
  • Developed countries, have facilities for recycling of e-wastes. But it involves manual participation and this exposes the workers to toxic substances present in e-wastes. For treating e-wastes, recycling is the only control measure. But it has to be done in an eco-friendly r manner.

11. Anti-plastic notifications : Government of Maharashtra has banned used of plastic by notification (23rd June 2018). This is a mission to make ‘Plastic Free Maharashtra’.

Greenhouse effect and Global warming-

1. Greenhouse effect :

  • The greenhouse effect is the phenomenon that occurs naturally on the earth.
  • The average temperature at surface of earth is increased due to greenhouse effect. If it would
    not have been there, the temperature of the earth would have been -18 °C. But due to the greenhouse now it is at the average 15 °C. This was called a good greenhouse effect.
  • But in recent years the excessive greenhouse effect is causing generalized global warming and climate change.
  • Infrared radiations are trapped due to atmospheric gases such as carbon dioxide, methane, etc. These gases absorb a major fraction of it and re-radiate the heat energy back to the earth’s surface. This exchange of heat goes in a cyclic manner.
  • Carbon dioxide and methane are main greenhouse gases; additionally, chloroflorocarbons (CFC), Nitrous oxide (N2O) and water vapours add to this effect.

2. Global warming :

(1) Due to air pollution and increased burning of fuels there is an increase in the proportion of greenhouse gases. The loss of forests and tree cover also adds to the increased CO2 concentration. All this has led to global warming.
(2) In the last 100 years there is an increase in the Earth’s temperature by about 0.6 °C. Especially in last three decades the climate change is severe. Problems like El Nino effect; melting of polar ice caps, Alps and Himalayas, etc. and increasing sea level leading to coastal submergence are all due to global warming.

3. Measures to reduce greenhouse effect and Global warming : Reduction in use of fossil fuel, improving efficiency

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

Ozone depletion-

1. In the upper stratosphere strata there is ozone layer. It is continuously formed by action of ultraviolet radiations on molecular oxygen. Molecular oxygen also degrades back into ozone in the stratosphere. Ozone layer absorbs ultraviolet radiation from the sun and protects the flora and fauna from deleterious effects of radiation.

2. Living organisms are affected due to UV radiation because it causes damage to their DNA and proteins by breaking the chemical bonds within DNA and proteins.
3. The unit for measuring thickness of ozone is Dobson unit (DU).

4. A balance between production and degradation of ozone in the stratosphere is lately disturbed due to excessive proportion of chlorofluorocarbons (CFCs) in the atmosphere.

5. Chlorofluorocarbons are used in refrigerators. When released they move upward and reach stratosphere. The ultraviolet rays in stratosphere, react with CFC and release Cl- atoms. Ozone is degraded by Cl “atoms.

6. This later causes ozone depletion or formation of ozone hole as it is clearly seen over the Antarctic region.

7. Deleterious effects of Ozone depletion :

  • Aging of skin.
  • Damage to skin cells causing skin cancers.
  • Inflammation of cornea of human eye causing snow-blindness cataract.
  • Permanent damage to the cornea.
  • UV-B radiation cause damage to DNA and mutations.

8. Montreal Protocol : An international treaty signed at Montreal (Canada) in 1987 (effective in 1989) to control the deleterious emission of ozone depleting substances like CFCs.

Deforestation –

1. Converting forested land into barren land is called deforestation.
2. Tropical forests are reduced by about 40% whereas temperate forests are lessened by 1% in the temperate region.
3. India is facing severe deforestation. There was 30% of forests in Indian land in early twentieth century. Now it has reduced to 19.4%.
4. It is recommended by National Forest Policy (1988) of India that the hilly area should have 67% while the plain area should have 33% forest cover.
5. Causes of deforestation :

  • Unplanned human activities.
  • Creation of agricultural land by cutting down forests.
  • For the timber and firewood, trees are felled and forests are cleared.
  • Clearing forests for cattle ranching.
  • Slash and burn agriculture or Jhum cultivation in the north-eastern parts of India.
  • Severe deforestation is caused due to increasing human population and repeated cultivation that resulted into shortening of recovery phase.

6. Consequences of deforestation :

Enhanced carbon dioxide concentration.

  • Carbon held in the biomass is lost with deforestation.
  • Loss of biodiversity due to habitat destruction.
  • Disturbance in the hydrologic cycle.
  • Soil erosion.
  • Desertification.

7. Reforestation : Restoring a forest that once existed is called reforestation.
There can be a natural reforestation or it can be due to human efforts by planting trees. However, when it is due to human efforts the natural biodiversity may be lost.

Maharashtra Board Class 12 Biology Notes Chapter 15 Biodiversity, Conservation and Environmental Issues

8. Environmental heroes : Reforestation undertaken by these two environmentalists.

  • Saalumara Thimmakka. (Karnataka)
  • Moirangthem Loiya (Manipur).

9. Case study of people’s participation in conservation of forests : Following examples show people’s participation in the conservation of forests :

(1) In 1731, Amrita Devi had sacrificed her life to save trees along with other people of Bishnoi’s community. It was the example of sacrificing lives for the cause of saving trees and environment.
Amrita Devi Bishnoi Wildlife Protection Award for individuals or communities from rural areas has been installed by the Government of India.

(2) Chipko Movement is people’s participation for the protection of trees. This happened in 1974 in Garhwal region of Himalayas. Chipko movement has now spread world-wide in which people hug the trees and save it from the axe of tree-cutters.

(3) Joint Forest Management (JFM) has been introduced by the Government of India in 1980s for working with the local communities for protection and management of the forests. It is an attempt to conserve forests in a sustainable matter.

Mission Harit Maharashtra-

  • Government of Maharashtra has decided to plant 50 crore trees, district-wise in 4 years, starting from in the year 2016.
  • National Forest Policy (NFP) aims at maintaining 33% forest cover in India. This decision of government is in tune with NFP
  • Helpline number 1926 called ‘Hello Forest’ has been set up to provide information regarding plantation, protection and for mass awareness.
  • Mobile application called ‘My Plants’ to record details of the plantation such as numbers, species and location.
  • Japanese Miyawaki method of plantation has been adapted in districts like, Beed, Hingoli, Pune, Jalgaon, Aurangabad, etc.

Know your conservatonist;

  • Seed mother of Maharashtra, Rahibai Popere, from Ahmednagar district, runs seed bank for 54 crops and 116 varieties.
  • Crops include wild varieties of brinjal, guava, mango, spinach, methi, millets, pulses, hyacinth beans and peas.
  • Farmers and students are also trained by her for seed selection, enhancement of soil fertility, pest management and control.
  • She is on BBC list of ‘100 women, 2018, along with 3 more Indian women.