Bioaccumulation and Biomagnification

Bioaccumulation –

  • Bioaccumulation is the increase in concentration of a pollutant from the environment to the first organism in a food chain.
  • Persistent toxins accumulate in the fatty tissues of an organism if they cannot process or excrete them.
  • This build up of high concentrations of persistent toxins in an organism is called Bioaccumulation.

Bio magnification –

  • Bio magnification refers to the concentration of pollutants from one trophic level to the next.
  • The concentrations of toxin increase gradually as it passes through successive trophic levels of the food chain.
  • Organisms at the top of the food chain store higher concentrations of toxins than the lower ones.
  • Process –

Step 1: Pesticide such as DDT gets accumulated in the grass of field.

Step 2: A grasshopper accumulates 2 mg of DDT from eating 100 grass plants.

Step 3: A mouse accumulates 20 mg of DDT by eating 10 grasshoppers.

Step 4: A snake accumulates 10 mg of DDT by eating just 5 mice.

Thus at every successive stage, accumulation of toxins gets concentrated rapidly in food webs.

Persistent pollutants –

  • Persistent pollutants are chemically stable toxins which stay in the environment for a long time without degradation.
  • Persistent pollutants include –
  • Pesticides – DDT- Dichloro Diphenyl Trichloreoethane – made by birds’ eggs fragile which led to death of chicks.
  • Heavy metals




  • Radioactive isotopes
  • Flame retardants – PBDEs (Polybrominated diphenyl eithers)
  • Industrial chemicals – PCBs (Polychlorinated biphenyls)

Facts –

  • The amount of toxins are usually measured from fatty tissues of the animals – Measured form breast milk in case of humans

Carbon and Nitrogen Cycles

Carbon Cycle –

  • Carbon cycle: The organic circulation of carbon from the atmosphere into organisms and back again.
  • Photosynthesis
  • Green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water.
  • Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.
  • Forests acts as reservoirs of Co2 as the carbon is fixed in the trees and remain stored in them for long periods.
  • Destruction of trees leads to release of stored carbon back into the atmosphere.
  • Respiration –
  • Process of respiration involves the oxidation of food to liberate energy, CO2 and water.
  • CO2 is released into the atmosphere through this process.
  • Decomposition –
  • Biomass of plants and animals become food to decomposers on their death.
  • Biomass or the dead organic matter is decomposed by microorganisms and CO2 is released into the atmosphere.
  • Combustion –
  • Burning of biomass releases carbon dioxide into the atmosphere.

Nitrogen Cycle –

  • Nitrogen is an essential component of protein which is vitally important for all living organisms.
  • Nitrogen fixation –
  • Conversion of gaseous nitrogen into Ammonia for utilization of plants is called nitrogen fixation.
  • Methods –
  1. Atmospheric fixation – Lightning, combustion and volcanic activity
  2. Industrial fixation – ammonia is synthesized from nitrogen and hydrogen, using an iron catalyst at high temperature and pressure.
  3. Bacteria fixation –
  4. symbiotic bacteria – Rhizobium in root nodules
  5. Independent or synthesis –




  • Nitrification –
  • Nitrogen compounds are essential for plant growth
  • Nitrification is the process of conversion of –

Ammonia into nitrates by Nitrosomonas bacteria

Ammonia into nitrites by Nitrococcus bacteria

  • A soil bacteria called Nitrobacter coverts nitrate into nitrite.
  • Assimilation –
  • Conversion of nitrogen into organic molecules such as proteins, DNA, RNA etc… by plants and animals is called assimilation.
  • Denitrification –
  • Conversion of nitrates back into gaseous nitrogen by denitrifying bacteria is called denitrification.

Ecological Succession

Definition –

The process by which communities of plant and animal species in an area are replaced or changed into another over a period of time is known as ecological succession.

  • This process continues one community replacing another community, until a stable and mature community is established.
  • It finally leads to the establishment of a relatively stable climax community.
  • Ecological succession is characterised by
  • Increased productivity
  • Increased diversity of organisms with multiple niche development
  • Gradual increase in the complexity of food webs.
  • Types –
  • Succession in which, initially the green plants are much greater in quantity is known as autotophic succession.
  • Succession in which, initially Heterotrophs are greater in quantity is known as heterotrophic succession.

Process –

  • Primary succession

Primary succession takes place over an area where no community has existed previously.

  • Places of primary succession include –
  • outcrops of cocks
  • newly formed deltas and sand dunes
  • emergent volcanic islands
  • lava flows
  • glacial moraines
  • Process of succession –
  • Pioneer species: Species that invades first bare land, where soil is initially absent are called pioneer species.
  • The pioneer species over a few generations alter the habitant by their growth and development.
  • Organisms continues to develop and becomes more diverse and competition increases along with diverse niche opportunities.
  • Pioneer community – Group of pioneer plants is collectively called as pioneer community.
  • The pioneer community after some time gets replaced by another community with different species combination.
  • The process of succession continues until a stable and long lasting community called as climax community is formed.
  • Types of primary succession –
  • Xerarch –

 Succession that occurs on land where moisture content is low e.g. bare rock


  • Hydrarch-

Succession that takes place in a water body, like ponds of lakes

  • Secondary succession –
  • Secondary succession is the succession of biotic communities after the complete or partial destruction of the existing community.
  • A community is formed after the removal of existing of natural vegetation by hurricane, forest fire or agricultural practices.
  • Secondary succession occurs faster than primary succession
  • Due to presence of well developed soil already at the site, large pool of seeds and other dormant stages of organisms.


Background –

  • Diversity of plants and animals in a region is called biodiversity.
  • Status of India’s biodiversity –
  • India is one of the 17-mega-biodiversity countries of the world.
  • It is situated at the tri-junction of the Afrotropical, Indo-Malayan and Palaearctic realms.
  • With only 2.4% of the land area, India already accounts for 7-8% of the recorded species of the world.
  • Over 46,000 Species of plants and 81,000 species of animals have been recorded in India
  • India has 10 bio-geographic zones and is home to
  • 85% of the mammalian species
  • 66% of avian species
  • 91% of reptiles
  • 66% of amphibians
  • 72% of fishes
  • 80% of plants
  • Four of the 35 globally identified biodiversity hotspots are represented in India –
  • Himalayas
  • Indo-Burma
  • Western Ghats-Sri Lanka
  • Sundaland
  • India is and acknowledged centre of crop diversity, and harbours
  • Many wild relatives and breeds of domesticated animals and fish.
  • Millions of microbial diversity, insects and other species.

Classification –

  1. Species biodiversity –
  • The total different taxonomical or biological species within a geographical area.
  • Measurement –
  • Species richness –

Number of various species in a defined area

Species richness is high in equatorial regions and decrease gradually towards the polar-regions.

Species richness in marine ecosystems is found highest along the coasts in continental shelves.

  • Species abundance – Relative numbers among species
  • Taxonomic diversity – Genetic relationships between different groups of species.
  1. Genetic biodiversity –
  • Different variety of genes contained within species of plants, animals and micro-organisms is called genetic diversity.
  • Species with more genetic variation can adapt better to the changed environmental conditions.
  • The amount of genetic variation present in an inter-breeding population is decided by the process of natural selection.
  • India has high genetic diversity and is regarded as a Vavilov’s centre of high crop genetic diversity.
  1. Ecosystem biodiversity –
  • Biodiversity of ecosystems such as lake, estuaries, wetlands, desert, coast, mangroves, coral reefs etc.
  • Biodiversity in land ecosystems generally decreases with increasing altitude.
  • Terrestrial biodiversity is higher than marine biodiversity.

Factors Affecting Biodiversity

  1. Loss of habitat –
  • Increased demand for land due to urbanization.
  • Clearance of natural forests for development projects.
  • Landfills on wetlands
  1. Invasive species –
  • Foreign species that spread rapidly in a new ecosystem due to lack of predators or competitors are called invasive species.
  • Invasive species disturbs the normal functioning of the organisms living in an ecosystem.
  • Major causes –
  • International cargo transport
  • Growing volume of international travel
  • Most invasive species in our country –
  • Parthenium –North America shrub
  • Argemone – A plant of the prickly poppy genus Argemone
  • Lantana – Tropical evergreen shrub
  1. Overexploitation –
  • Consumption of resources by humans at the rates higher than they can be replaced is termed as overexploitation
  • Examples –
  • Overgrazing
  • Over harvesting of fish
  • Collection of fire-wood
  • Hunting of wild animals for skin, medicine, oils etc…
  1. Pollution –
  • Pollution leads to global warming and other environment changes.
  • Species that are slow to adjust to the changed environment are eventually lost.
  1. Environment degradation –
  • Many actions of humans have led to gradual destruction of environment.
  • These include –
  • Global warming
  • Increased CO2 emissions
  • Nuclear radiation
  • UV-exposure due to ozone hole
  • Oil spills etc.

Biological Diversity Act, 2002

Biodiversity Act – 2002 addresses the issues –

  • Of conservation and sustainable use of biological resources in the country.
  • Of access to genetic resources and associated knowledge
  • Of fair and equitable sharing of benefits arising from utilization of biological resources.
  • Of transfer of research results and application for intellectual property rights.

Implementation –

  • The Act and the Rules are implemented in India through a decentralized system.
  • The Act covers foreigners, non-resident Indians, body corporate, association or organization that is either not incorporated in India or incorporated in India.
  • A three tiered structure has been established under the Act at the national, state and local levels.
  • National level –
  • National Biodiversity Authority(NBA)
  • National Biodiversity Authority was established in 2003 to implement India’s Biological Act (2002)
  • NBA is Statutory, Autonomous Body and it performs facilitative, regulatory and advisory functions.
  • NBA headquarters is located at Chennai, Tamil Nadu.
  • NBA has supported creation of SBBs in 29 States and , facilitated establishment of around 34,135 BMCs
  • All foreign nationals or organisms require prior approval of NBA for obtaining biological resources and/or associated knowledge for any use.
  • Funds –

The monetary benefits, fees and royalties, as a result of approvals by NBA are to be deposited in National Biodiversity Fund.

The funds will be used for conservation and development of areas from where the resource has been accessed, consultation with local self government.

  • State level –
  • State Biodiversity Boards(SSB)
  • State Biodiversity Boards (SSBs) focus on advising the State Governments, subject to any guidelines issued by the Central Government.
  • All Indian nationals or organizations will require to give prior intimation to the concerned SSB about any biological resources being important for commercial use.
  • SSB may prohibit the import if found to violate the objectives of conservation, sustainable use and benefit sharing.
  • Local level –
  • Biodiversity Management Committees (BMC) in local bodies.
  • To be established by institutions of local self-government for implementation of specific provisions of the Act and Rules.
  • Biodiversity Management Committees (BMCs) are responsible for prompting conservation, sustainable use and documentation of biological diversity.
  • Documentation on biological diversity includes –

Preservation of habitats, conservation of land, folk varieties and cultivars

Domesticated stocks and breeds of animals


Chronicling of knowledge relating to biological diversity

  • All of these institutions are statutory, autonomous bodies established under the Biological Diversity Act, 2002.

Exemptions –

  • Exemptions to local people and communities of the area for free access to use biological resources within India.
  • Exemptions to growers and cultivators of biodiversity and to Vaids and Hakims to use biological resources.
  • Exemption through notification off normally traded commodities from the purview of the Act only when used as commodity.
  • Exemption for collaborative research through government sponsored or government approved institutions.

People’s Biodiversity Register (PBR) –

  • BMC needs to develop PBR.
  • It is legal document containing details of biological resources occurring within a BMC and associated knowledge.
  • PBR acts as a source of inventory of biological and knowledge and for benefit sharing purposes under the ABS component.

Biodiversity Heritage sites –

  • BHS are areas of biodiversity importance, which harbour
  • Rich biodiversity
  • Wild relatives of crops
  • Areas lying outside the protected area network.
  • The purpose is not to cover the already designated protected areas as national parks and wildlife sanctuaries.

Facts –

  • There is no overlap in the functions of NBA and SSBs on issues of Access and Benefit Sharing.
  • The Indian researches neither require prior approval nor need to give prior intimation to SSB for obtaining biological resource for conducting research in India.
  • It is necessary to obtain the approval of the NBA before seeking any IPR based on biological material and associated knowledge obtained from India.
  • There is a enabling provision for setting up a framework for protecting traditional knowledge.
  • Value added product have been excluded from the definition of biological resources
  • Human genetic material is excluded from the definition of biological resources and prior approval of NBA is not needed.