Notes-Part-1-Class-12-Biology-Chapter-15-Biodiversity, Conservation and Environmental Issues-Maharashtra Board

Biodiversity, Conservation and Environmental Issues

Maharashtra Board-Class-12th-Biology-Chapter-15


Topics to be Learn : Part-1

  • Introduction
  • Levels of biodiversity
  • Patterns of biodiversity
  • Biodiversity current scenario
  • Loss of biodiversity
  • Conservation and biodiversity
  • Biological Diversity Act 2002

Topics to be Learn : Part-2

  • Environmental  issues
  • Greenhouse effect and global warming
  • Ozone depletion
  • Deforestation
  • Mission Harit Maharashtra

Introduction :

Diversity is variety.

Biodiversity :

  • Biodiversity refers to the variety of life on Earth, which includes a wide range of species such as microorganisms, viruses, algae, fungi, plants, and animals found in various habitats.
  • Diversity is seen in shape, colour, form, mode of nutrition, habitats, reproduction, motility, duration of life cycle, life span, etc. All of these adaptations help in the survival of species and hence diverse forms are seen.
  • Walter Rosen (1982) coined the term biodiversity, but it was popularised by sociologist Edward Wilson to describe combined diversity at all levels of biological organisation.
  • Definition : Biodiversity is the part of nature that includes differences in genes between individuals of a species, a variety of animal and plant species in various habitats, regions, countries, and the world that form different types of ecosystems within a defined area.
  • The biodiversity we see today is the result of over 3.5 billion years of evolutionary history, primarily influenced by natural processes and, more recently, by human influence.

Levels of Biodiversity :

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, specie 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.
  • Genetic diversity or variability is essential for a healthy breeding population of a species.
  • Genetic variations are changes in the allelic genes which lead to individual differences within species.
  • Such variations help in the evolution. The chances of continuation of species in the changing environmental conditions are caused due to such variation and it allows the best organisms to get adapted to survive.
  • Races and subspecies are formed due to genetic diversity.

Examples of genetic diversity:

  • There are 1000 varieties of mangoes and 50,000 varieties of rice or wheat in India.
  • Rauwolfia vomitoria is a medicinal plant that secretes reserpine. This plant is inhabitant of different Himalayan ranges. There is variations in terms of potency and concentration of reserpine, from different locations.

Species diversity :

  • Also called interspecific diversity. The diversity in number of species of plants and animals which are present in a particular region is called species diversity.
  • It can be expressed by variety of species i.e. species richness as well as number of individuals of different species i.e. species evenness.
  • E.g. Species diversity is more in Western Ghats than in Eastern Ghats.
  • Natural undisturbed tropical forests have much greater species richness than monoculture plantation of timber plant, developed by forest plantation.

Ecological or ecosystem diversity :

  • Diversity of different types of ecosystems and habitats within a given geographical area is called ecological or ecosystem diversity.
  • There may be one or many different types of ecosystems in a region.
  • Ecosystem diversity is very high in India while it is quite low in Norway.
  • There are many different types of ecosystems in India, including grasslands, estuaries, wetlands, rain forests, and deserts.
  • In India the Western Ghats exhibit significant ecosystem diversity, whereas Ladakh and the Rann of Kutch do not exhibit the same degree of variation.


Patterns of biodiversity :

There are two patterns viz, Latitudinal and Altitudinal gradient and species-area relationship.

Latitudinal species diversity: There is greater species richness at lower latitude which steadily declines towards the poles.

This is called as distribution of diversity along the latitudes.

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 which cause more diversity in these regions.

Altitudinal species diversity: The diversity is more at lower altitude, but at higher altitudes it declines due to change in climatic conditions and drastic seasonal variations.

Species area relationship : Number of species present in any area is directly proportional to the size of this area. Species richness increases with increase in area up to certain limit this was observed by Alexander wan Humboldt.

Alexander von Humboldt‘s views about species richness and area relationship :

Scientists have tried to establish relationship between species diversity and the size of the habitat. It is considered that number of species present is directly proportional to the area.

  • It is understood that larger areas may have more resources that can be distributed amongst the inhabitant species.
  • Alexander von Humboldt observed that species richness does increase with the increase in area but only till a certain limit.
  • For many species this curve is a rectangular hyperbola.
  • If we consider S to be species richness, A as area under study, C as the Y intercept and Z as the slope of the line, this relationship can be described by the equation, log S = log C + Z log A.
  • On logarithmic scale this relationship is a straight line, as observed in the figure above.
  • For smaller areas, value of Z ranges between 0.1 to 0.2 regardless of species or region under study.
  • But for the larger areas like the entire continents, slopes are closer to vertical axis i.e. steeper.
  • This observation indicates that in very large areas, number of species found, increase faster than the area explored.

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 production of biomass over a particular time period.
  • Rivet Popper hypothesis (Paul Ehrlich): Relationship between diversity and Wellbeing of ecosystem is not linear. When key species are lost there is threat in very short span of time which affects food chain, food web, energy flow and natural cycles resulting into imbalance of ecosystem.

Biodiversity current scenario :

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.

  • The majority of temperate species have been researched, but tropical species have not.
  • According to Robert May, there are 7 million different species on the planet.
  • 8.1% of the world's biodiversity is found in India.
  • India is one of the 12 nations with the greatest diversity.
  • There are about 45000 plant species and 90000 animal species on the total land area of India, which makes up 2.4% of the world's land area. So far, 22% of the world's natural wealth has been documented.
  • But many species and varieties could go extinct before they are recorded due to the rapid deforestation and reforestation.


Loss of biodiversity :

Imbalance in the ecosystem occurs if the biodiversity is lost. Extinction of species means threat to biodiversity.

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.

There were five mass extinctions during different stages of history of Earth.

The sixth extinction is taking place now which is hundred to 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.

Causes of biodiversity losses :

Causes of biodiversity losses :

Four major causes of biodiversity loss, known as evil quartet.

(i) Habitat loss and fragmentation :

  • The primary factor destroying biodiversity is the loss and fragmentation of habitat.
  • Large natural habitats are disappearing as a result of pollution and habitat degradation. This puts the local living organisms in a crisis.
  • Human activity is largely to blame for this.
  • Migratory birds and animals that require larger territories are also in danger.
  • Over time, the reduction in tropical rain forests decreased from 14% to 6%, which undoubtedly led to the extinction of numerous species.

(ii) Over exploitation :

  • Natural resources have been used by humans beyond what was necessary.
  • Overexploitation is now a problem as a result of excessive consumption and accumulation.
  • Threats to various organisms have resulted from overuse of resources.
  • Due to overexploitation, the dodo bird, stellar sea cow, and passenger pigeon are now extinct.
  • A lack of fish has also been caused by overfishing in the sea.

(iii) Alien species invasion :

  • When invasive species are accidentally or intentionally introduced into a particular region which causes extinction of local and already existing species, it is called alien species invasion.
  • Examples of such invasive plant species are :(a) the carrot grass (Parthenium) (b) Lantana(c) Water hyacinth (Eichhornia).
  • Invasive animal species is African catfish Clarias gariepinus, introduced for aquaculture purpose. This has caused harm to endemic catfish varieties.
  • Invasion by such species is one of the major reasons for extinction of local species.

(iv) Co-extinctions :

  • When two organisms are obligately linked to one another, if either one goes extinct, the other one will follow.
  • When one variety disappears from the ecosystem, its associate variety also disappears. This phenomenon is known as co-extinction.
  • Unique parasites perish when their hosts, fish, perish.
  • Coevolved plant-pollinator also will have such a threat.


 Extinct species : The species which are totally eliminated from the Earth.

E.g. Dinosaurs

Endangered species : The species having dwindling numbers.

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

Categories of species according to IUCN :

Categories of species according to IUCN :

  1. Extinct (EX), a label given to species whose final member has passed away or whose existence has not been verified.
  2. Extinct in the Wild (EW), Species that are only extant in captivity
  3. Critically Endangered (CR), a category containing those species that possess an extremely high risk of extinction with very few surviving members (50).
  4. Endangered (EN), a designation applied to species that possess a very high risk of extinction as a result of rapid population decline of 50 to more than 70 percent over the previous 10 years (or three generations).
  5. Vulnerable (VU), a category containing those species that possess a very high risk of extinction as a result of rapid population decline of 30 to more than 50 percent over the previous 10 years (or three generations).
  6. Near Threatened (NT), a designation applied to species that are close to becoming threatened or may meet the criteria for threatened status in the near future.
  7. Least Concern (LC), a category containing species that are pervasive and abundant after careful assessment
  8. Data Deficient (DD), a condition applied to species in which the amount of available data related to its risk of extinction, is lacking in some way.
  9. Not Evaluated (NE), a category used to include any of the nearly 1.9 million species described by scientists, but not assessed by the IUCN


Conservation and biodiversity

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.

Reasons for conservation of biodiversity :

Reasons for conservation of biodiversity :

The conservation of biodiversity can be done in utilitarian way or for ethical reasons.

Utilitarian reasons are further classified into narrowly utilitarian and broadly utilitarian reasons :

Narrowly utilitarian reasons :

  • Humans obtain benefits from biodiversity in the form of resources for food, cloth, shelter industrial products, aesthetic products, ornaments, artefacts and medicines.
  • Industrial products like resins, tannins, perfume base, etc. are obtained through biodiversity resources.
  • For making ornaments or artefacts for aesthetic purpose, again biodiversity is sacrificed.
  • Many medicines are also obtained through biodiversity resources which shares 25% of global medicine market.
  • Around 25000 species are used for traditional medicines by tribal population worldwide.
  • Bioprospecting which is a systematic search for development of new sources of chemical compounds, genes. Microorganisms, macroorganisms, and other valuable products from nature which is of economically important species is also due to biodiversity.

Broadly utilitarian reasons :

Oxygen supply, seed dispersal, pollination, extra aspects that nature gives us free.

  • Production of oxygen done by all green plants helps human beings to thrive.
  • Amazon forest alone gives 25% of the oxygen to the entire world.
  • Insects carry out pollination and seed dispersal.
  • If insects do not carry out pollination and seed dispersal, man would go hungry without crops and fruits.
  • Biodiversity also is useful in recreation of human beings.
  • Taking all these aspects in consideration, conservation of biodiversity becomes essential. Therefore, to protect and conserve our rich biodiversity on the planet, we have to remember all the utilitarian reasons.

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


Conservation of biodiversity :

In situ conservation :

  • In situ conservation refers to the preservation of an organism in its natural environment or habitat.
  • In situ conservation is a onsite conservation.
  • It is done in natural environment.
  • National parks. Sanctuaries, biosphere reserve, etc. are set up for in-situ conservation.
  • It is a dynamic process. Cheap and convenient to conduct.
  • In India, 34 biodiversity hotspots with high species densities and richness are strategically protected through in situ conservation.
  • This method also preserves varieties that have been used for farming and horticulture in the past.
  • Captive breeding is not successful in all cases of in-situ conservation method.
  • Western Ghats, Indo-Burma and Eastern Himalayas are 3 world’s biodiversity hotspots located in India.
  • In India, there are 14 biosphere reserves, 90 national parks, 448 wildlife sanctuaries, sacred groves are also type 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.

Ex-situ conservation :

  • Critically endangered species are protected in captivity, which is called ex-situ conservation.
  • Ex-situ conservation is done outside the habitat of plants and animals.
  • Plant and animal species are conserved in artificial or manmade place.
  • In 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 which are used in this conservation method.
  • It is static process. Its expensive and commercial process.
  • Captive breeding is successful and can help in increasing the number of endangered organisms.

Biological Diversity Act 2002 :

Biological Diversity Act 2002 :

  • The Rio de Janeiro Earth Summit produced the Convention on Biological Diversity (CBD- 1992).
  • In accordance with the CBD, the Indian government passed the Biological Diversity Act (BD Act) in 2002.
  • It provides a framework for managing and preserving our nation's natural resources in a sustainable way.
  • The law broadly defines biodiversity. It includes plants, animals and microorganisms and their parts, their genetic materials and by-products.
  • Value-added goods and human genetic material are not covered by the law.

The main objectives for proposing this act are

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

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.


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