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Biodiversity, Conservation and Environmental Issues · Maharashtra Board STD 12 Science (MSBSHSE - English Medium). 13 questions.

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Question 14 Marks
Mission Harit Maharashtra.
Answer
  1. Government of Maharashtra in 2016, undertook an ambitious project of planting 50 crore trees in four years.
  2. Yearly targets were given to each district for plantations.
  3. The plantations are under the guidelines of National Forest Policy (NFP).
  4. For information about plantation, protection and mass awareness, a 24-hour toll free helpline number 1926 called ‘Hello Forest’ has been set up.
  5. There is also a mobile application called ‘My Plants’ which is set up by Forest Department. It records details of the plantation such as numbers, species and location.
  6. Following number of saplings were planted. 2.87 crore saplings in 2016, 5.17 crore saplings in 2017, 15.17 crore saplings in 2018, 33 crore saplings in 2019. Authorities are taking care of these plantations.
  7. Also Japanese Miyawaki method of plantation is adapted by State Forest Department and Social Forestry Department. Such plantations are in districts of Beed, Hingoli, Pune, Jalgaon, Aurangabad, etc.
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Question 24 Marks
Greenhouse effect.
Answer
1. Greenhouse effect is caused due to heating up of earth’s surface and atmosphere. This heating is due to trapped infrared rays that are reflected from the earth’s surface by atmospheric gases.
2. The solar energy reaches the earth in the form of ultraviolet radiations, visible light and infrared and radio waves. Clouds and gases reflect about Vith radiations and absorb some of it.
3. Harmful UV radiations are absorbed by the ozone layer of the stratosphere and thus do not reach the earth’s surface.
4. Infrared radiation has heating effect thus it warms up the earth’s atmosphere and various objects. A part of the infrared radiations falling on the earth surface which have longer wavelength is reflected back into the outer space.
5. But there is a layer of carbon dioxide in the lower region of the atmosphere along with other atmospheric gases such as methane, nitrogen oxide, etc.
6. Due to these gases radiations cannot escape out. Carbon dioxide, along with methane, nitrogen oxides and CFCs can absorb infrared radiations reflected from the earth’s surface. They are therefore called greenhouse gases.
7. The blanket of these greenhouse gases in the atmosphere traps the reflected infrared rays and produces heat on the earth’s surface. This results in greenhouse effect which in turn causes global warming.
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Question 34 Marks
Sanitary landfills.
Answer
  1. Sanitary landfills are the places where wastes are dumped in depression or trench. Wastes are dumped here on everyday basis.
  2. In large metro cities, landfills are over-filled rapidly. Landfills are unhealthy and they may emit foul odour.
  3. Also there is a danger of chemicals percolating and reaching down to ground water and contaminate this water source.
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Question 44 Marks
Ecosan.
Answer
  1. Ecological sanitation (Ecosan) is a sanitation provision that safely reuses excreta in agriculture as a manure.
  2. By Ecosan the need for chemical fertilizers is reduced. Ecosan toilet is a closed system without water and it is an alternative to leach pit toilets.
  3. They are useful in places of water scarcity or places with risk of ground water contamination.
  4. The principle of recovery and recycling of nutrients from excreta to create a valuable resource for agriculture is used here in Ecosan.
  5. The pit of an ecosan toilet fills up after some time, then it is closed and sealed for about 8-9 months.
  6. In this time the faeces gets completely composted to organic manure.
  7. It is a practical, efficient and cost-effective solution for human waste disposal.
  8. There are working Ecosan toilets in many areas of Gujarat, Kerala, Tamil Nadu and Sri Lanka.
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Question 54 Marks
Thermal pollution.
Answer
  1. Thermal pollution of water is caused when heated water is added to the water body which results into rise in temperature of water.
  2. Thermal and nuclear power plants cause thermal pollution of adjoining water bodies.
  3. The power plants use water as coolant and release back this hot water.
  4. Many resident organisms which are sensitive to temperature die due to sudden rise in temperature.
  5. This leads to loss of flora and fauna of the water body.
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Question 64 Marks
Gaseous pollutants.
Answer
$(1)$ Gaseous pollutants are gases which cause air pollution.
$(2)$ Some common gaseous pollutants are $CO_2, CO, SO_2, NO, NO_2,$ etc.
$(3)$ Carbon dioxide $(CO_2)$ : It is a greenhouse gas which is continuously produced due to human activities such as burning of fossil fuels and rampant deforestation. Photosynthesis carried out by plants can balance $CO_2 : O_2$ ratio in the air, provided there is good green cover. $CO_2$_ is also removed from the air by weathering of silicate rocks forming limestone. Aeroplane traffic especially release lot of $CO_2. CO_2$ is the main cause for global warming and climate change.
$(4)$ Carbon monoxide $(CO)$ : $CO$ is a toxic gas produced by incomplete combustion of different fuels. Therefore, vehicular exhausts are the largest source of $CO.$
$(5)$ Nitrogen dioxide $(NO_2)$ and nitrogen monoxide $(NO)$ : Nitrogen oxides are released through automobiles and chemical industries as waste gases. $NOa$ can form nitric acid after reacting with water vapour, this causes irritation to eyes and lungs. Injury to lungs, liver and kidneys is caused due to these gases.
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Question 74 Marks
Particulate air pollutants.
Answer
  1. Particulate air pollutants are either solids or liquids.
  2. Particles having larger diameter of 10 pm settle in the soil but finer particles with 1 pm or less remain suspended in the air.
  3. Central Pollution Control Board (CPCB) has declared that, particulate matter of size 2.5 pm or less in diameter (PM 2.5) are responsible for causing the greatest harm to humans.
  4. These fine particulates can be inhaled deep into the lungs and are responsible for irritation, inflammation and damage to lungs.
  5. In addition to this, it causes breathing and respiratory disorders and premature deaths.
  6. Examples of particulate pollutants are : Smoke, smog, pesticides, heavy metals, dust and radioactive elements.
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Question 84 Marks
Write a note on BD Act 2002.
Answer
  1. The law broadly defines biodiversity.
  2. It includes plants, animals and microorganisms and their parts, their genetic materials and by-products.
  3. It excludes value added products and human genetic material.
  4. Regulation of access to Indian biological resources as well as scientific cataloguing of traditional knowledge about ethnobiological materials were the main objectives for proposing this Act.
  5. There is three-tier system, viz. National Biodiversity Authority (NBA) at the national level, the State Biodiversity Boards (SBBs) at the state level and Biodiversity Management Committees (BMCs) at the local level that gives approval of utilization of any biological resource for commercial or research purpose.
  6. It is mandatory for foreigners, NRIs as well as Indian citizens and institutions to seek permission from NBA before exploiting local resource.
  7. NBA has powers of civil court. Not seeking approval of NBA, can incur jail and fine up to 10 lakh rupees.
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Question 94 Marks
Co-extinctions.
Answer
  1. When one organism is associated with other one in an obligatory way, then, if one is extinct, the other also gets extinct.
  2. Extinction of one variety leads to loss of associate variety from the ecosystem. Such phenomena is called co-extinction.
  3. Extinction of host fish causes extinction of unique parasites.
  4. Coevolved plant-pollinator also will have such a threat.
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Question 104 Marks
Alien species invasion.
Answer
  1. 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.
  2. Examples of such invasive plant species are
    (a) the carrot grass (Parthenium)
    (b) Lantana(c) Water hyacinth (Eichhornia).
  3. Invasive animal species is African catfish Clarias gariepinus, introduced for aquaculture purpose. This has caused harm to endemic catfish varieties.
  4. Invasion by such species is one of the major reasons for extinction of local species.
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Question 114 Marks
Over-exploitation.
Answer
  1. Humans have exploited natural resources beyond their needs.
  2. The excessive consumption and accumulation have resulted into problem of over¬exploitation.
  3. Overexploitation of resources has caused threats to various organisms.
  4. Dodo bird, stellar sea cow and passenger pigeon are extinct due to overexploitation.
  5. Over exploitation of fish from sea has also resulted into dearth of fish.
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Question 124 Marks
Habitat loss and fragmentation.
Answer
  1. Habitat loss and fragmentation is the prime cause of destruction of biodiversity.
  2. Due to degradation and pollution there is reduction in vast natural habitats. This creates crisis situation for resident living organisms.
  3. This is largely due to human activities.
  4. There is also a threat to migratory birds and for animals which need larger territories.
  5. Reduction in tropical rain forests has been reduced from 14% to 6% over the years, which has surely destroyed many species.
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Question 134 Marks
Ecological (Ecosystem) diversity.
Answer
  1. Different types of ecosystems or habitats within a given geographical area forms ecosystem diversity.
    On Earth there are a large variety of ecosystems.
  2. Each ecosystem has its own complement of distinctive interlinked species, based on the differences in the habitat. It is also specific for particular geographical region.
  3. In one region, generally, there may be one or many different types of ecosystems.
  4. In India, there are varieties of ecosystems such as deserts, rain forests, deciduous forests, estuaries, wetlands, grasslands, etc.
  5. In India, the Western Ghats show great ecosystem diversity. However, regions like Ladakh and Rann of Kutch have less ecosystem diversity.
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