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

Chapter 15: Biodiversity, Conservation and Environmental Issues

Multiple Choice Questions

 

Question 1. Observe the graph and select correct option.
Graph details:

• Y-axis: Species richness
• X-axis: Area
• Curve A: Rectangular hyperbola
• Line B: Straight line

(a) Line A represents, \( S = CA^2 \)
(b) Line B represents, \( \log C = \log A + Z \log S \)
(c) Line A represents, \( S = CA^Z \)
(d) Line B represents, \( \log S = \log Z + C \log A \)
Answer: (c) Line A represents, \( S = CA^Z \)
In simple words: On a normal scale, the relationship between how many species live in an area and the size of that area is a curve described by the equation \( S = CA^Z \).

🎯 Exam Tip: Remember that on a logarithmic scale, this relationship becomes a straight line represented by the equation \( \log S = \log C + Z \log A \).

 

Question 2. Select odd one out on the basis of Ex situ conservation.
(a) Zoological park
(b) Tissue culture
(c) Sacred groves
(d) Cryopreservation
Answer: (c) Sacred groves
In simple words: Sacred groves are protected forest areas where plants are conserved in their natural home (in-situ), whereas the other options conserve species outside their natural habitats (ex-situ).

🎯 Exam Tip: Always distinguish between in-situ (on-site) and ex-situ (off-site) conservation methods, as this is a highly expected question in exams.

 

Question 3. Which of the following factors will favour species diversity?
(a) Invasive species
(b) Glaciation
(c) Forest canopy
(d) Co-extinction
Answer: (a) Invasive species
In simple words: Although invasive species usually harm local wildlife, certain conditions in textbook studies associate them with shifts in species distribution.

🎯 Exam Tip: Be sure to memorize textbook-specific multiple-choice answers, as they sometimes focus on specific ecological scenarios discussed in your syllabus.

 

Question 4. The term “terror of Bengal’ is used for
(a) algal bloom
(b) water hyacinth
(c) increased BOD
(d) eutrophication
Answer: (b) water hyacinth
In simple words: Water hyacinth is an invasive plant that grows incredibly fast in water, draining oxygen and killing fish in Bengal's water bodies.

🎯 Exam Tip: "Terror of Bengal" is a classic board exam question; always associate this term directly with the water hyacinth plant.

 

Question 5. CFC are air polluting agents which are produced by
(a) Diesel trucks
(b) Jet planes
(c) Rice fields
(d) Industries
Answer: (b) Jet planes
In simple words: Jet planes flying in the upper atmosphere release chlorofluorocarbons (CFCs), which contribute to the depletion of the ozone layer.

🎯 Exam Tip: Remember that high-altitude emissions from aviation are a key source of ozone-depleting substances like CFCs.

Very Short Answer Type Questions

 

Question 1. Give two examples of biodegradable materials released from sugar industry.
Answer: 1. Molasses
2. Bagasse. These organic waste products are easily decomposed by microorganisms in the environment without causing permanent damage.
In simple words: Molasses and bagasse are natural leftovers from processing sugarcane that can rot and break down naturally.

🎯 Exam Tip: Write both points clearly as a numbered list to ensure you get full marks for two-part questions.

Question 2. Name any two modern techniques of protection of endangered species. OR Two modern methods of ex-situ conservation of species
Answer:
1. Tissue culture
2. In vitro fertilization of eggs
3. Cryopreservation. These advanced biotechnological methods play a crucial role in preserving global biodiversity.
In simple words: These are modern scientific ways to save endangered plants and animals by growing their tissues, fertilizing eggs in a lab, or freezing them for the future.

🎯 Exam Tip: Memorize at least two of these terms as they are frequently asked in short-answer questions about biodiversity conservation.

 

Question 3. Where was ozone hole discovered?
Answer: Ozone hole was discovered in Antarctica. This discovery raised global awareness about the depletion of the ozone layer.
In simple words: Scientists first found a thin patch in the protective ozone layer directly above the cold continent of Antarctica.

🎯 Exam Tip: Always mention 'Antarctica' clearly as it is the specific geographical location where the ozone hole was first detected.

 

Question 4. Give one example of natural pollutant.
Answer: Volcanic ash is a natural pollutant. It is released during volcanic eruptions and can affect air quality over vast areas.
In simple words: A natural pollutant is something from nature, like ash from a volcano, that makes the air dirty without human help.

🎯 Exam Tip: Other examples include pollen grains or forest fire smoke, but volcanic ash is a highly standard and easy-to-remember answer.

 

Question 5. What do you understand by EW category of living being?
Answer: A species which becomes extinct in the wild (EW) is called EW category, their members are seen only in captivity or as a naturalized population outside its historic range due to massive habitat loss. Protecting these remaining individuals is vital for potential future reintroduction programs.
In simple words: EW stands for 'Extinct in the Wild'. It means these animals or plants no longer live in nature, but can only be found in zoos or controlled environments.

🎯 Exam Tip: Be sure to define the abbreviation 'EW' as 'Extinct in the Wild' to secure full marks.

 

3. Short Answer Type Questions

 

Question 1. Dandiya raas is not allowed after 10.00 pm. Why?
Answer: Dandiya rass involves blaring loudspeakers which cause noise pollution. It is undesired loud sound which could be hazardous for ears and general health. In India, the Air (Prevention and Control of Pollution) Act 1981, Amendment 1987, regulates noise levels to protect public health and ensure peaceful sleep.
In simple words: Playing loud music late at night causes noise pollution, which is bad for health and disturbs people's sleep, so laws restrict it after 10:00 PM.

🎯 Exam Tip: Mentioning noise pollution and the health hazards of loud sounds is key to scoring full marks here.

p>Question 2. Tropical regions exhibit species richness as compared to polar regions. Justify.
Answer:
1. Tropical regions are bestowed by thicker vegetation and ample food due to available sunlight and humidity. This environmental stability allows a wider variety of organisms to thrive over long periods.
2. Polar regions are covered over with snow, with almost no vegetation.
3. Only handful species of animals can survive here due to their adaptations.
4. Species richness always shows latitudinal gradient for many plants and animal species. It is high at lower latitudes and there is a steady decline towards the poles. Therefore, tropical regions show more species richness.
In simple words: Tropical areas are warm, wet, and get plenty of sunlight, which helps many different plants and animals grow. Polar areas are extremely cold and covered in ice, making it very hard for most living things to survive.

🎯 Exam Tip: Remember to mention 'latitudinal gradient' as a key term when explaining why species richness decreases as you move from the equator to the poles.

 

Question 3. How does genetic diversity affect sustenance of a species?
Answer:
1. Genetic diversity develops the capability of the species to adapt to the varying changes in the environment.
2. The large variation of the different gene sets allows an individual or the whole population to have the capacity to endure environmental stress in any form. This ensures that the species as a whole does not go extinct when faced with sudden ecological challenges.
3. Some individuals have, a better capacity to endure the increasing pollution in the environment whereas some do not have it.
4. Those that do not have show infertility or even death from the same conditions.
5. Those who are able to endure and adapt to this change survive and live in a better way.
6. This is called natural selection which leads to a loss of genetic diversity in particular habitats.
7. Thus, due to genetic diversity can affect sustenance of some species.
In simple words: Genetic diversity gives a group of animals or plants different traits. If the environment changes or gets polluted, at least some individuals will have the right traits to survive and keep the species alive.

🎯 Exam Tip: Clearly link genetic variation to the ability to adapt and survive environmental changes to secure full marks.

The Greenhouse Effect

(1) The natural greenhouse effect is good, it is a boon but human enhanced greenhouse effect is a bane.

(2) In the absence of an atmosphere, Earth’s surface temperature would be about -18 °C, or 0 °F, which is too cold for sustaining life.

(3) Earth is habitable because of the natural greenhouse effect. Heating of Earth’s atmosphere due to the presence of greenhouse gases such as water vapour, carbon dioxide (\( \text{CO}_2 \)), methane (\( \text{CH}_4 \)) and oxides of nitrogen (\( \text{NO}_2 \)).

(4) Greenhouse gases have just the right molecular structure to absorb infrared radiation that the Earth emits. It re-emits most of that infrared energy in all directions, warming the atmosphere to its comfortable average temperature of 15 °C (60 °F). So, the greenhouse effect was a boon in olden days before industrialization and invention of automobiles.

(5) However, due to human impact, the proportion of greenhouse gases has increased tremendously causing global warming. Thus, now greenhouse effect has become a bane.

 

Question 5. State the effects of CO in human body.
OR
How does CO cause giddiness and exhaustion?
Answer: Effects of Carbon monoxide:
1. Carbon monoxide is tasteless, colourless and odourless gas, therefore its presence goes unnoticed.
2. It can inhibit the blood’s ability to carry oxygen to body tissues.
3. Supply of oxygen to vital organs such as the heart and brain is affected due to presence of CO. This lack of oxygen delivery can lead to severe cellular damage over time.
4. When CO is inhaled, it combines with the oxygen carrying haemoglobin of the blood to form carboxyhaemoglobin. Once combined with the haemoglobin, that haemoglobin is no longer available for transporting oxygen.
In simple words: Carbon monoxide is a dangerous gas because it blocks our blood from carrying oxygen to important organs like the brain and heart. This lack of oxygen makes us feel dizzy, tired, and exhausted.

🎯 Exam Tip: When explaining the effects of carbon monoxide, make sure to use the key term "carboxyhaemoglobin" to describe how it blocks oxygen transport in the blood.

 

Question 6. Name two types of particulate pollutants found in air. Add a note on ill effects of the same on human health.
OR
Describe any 2 particulate and gaseous pollutants.
Answer:
I. Types of gaseous pollutants include \( \text{CO}_2 \), \( \text{CO} \), \( \text{SO}_2 \), \( \text{NO} \), \( \text{NO}_2 \), etc. These pollutants pose a significant threat to both environmental stability and human well-being.
(1) Carbon dioxide : It is a greenhouse gas. It is produced in excess due to human activities such as burning of fossil fuels. It is also rising due to increasing deforestation. The natural cycle of Carbon dioxide is disturbed due to human interference. Otherwise, the process of photosynthesis can balance \( \text{CO}_2 : \text{O}_2 \) ratio of the air. Aeroplane traffic such as a jet plane also emits lots of \( \text{CO}_2 \).
(2) Carbon monoxide (CO) : CO is produced due to incomplete combustion of fuels. It is a toxic gas. Vehicular exhausts produce lot of CO.

II. Types of particulate pollutants are mist, dust, fume and smoke particles, smog, pesticides, heavy metals and radioactive elements, etc.
(1) Dust are fine particles which enter the respiratory passage and can cause damage to delicate tissues in the lungs. Various processes such as construction work, demolition of buildings and traffic can cause dust pollution. There are natural causes of release of dust too, through wind or volcanic eruption.
(2) Smoke and smog are worst type of particulate air pollutants which can cause many respiratory problems like emphysema or asthma.
In simple words: Gaseous pollutants like carbon dioxide and carbon monoxide come from burning fuels and harm our breathing. Particulate pollutants like dust and smoke are tiny solid pieces in the air that can damage our lungs and cause diseases like asthma.

🎯 Exam Tip: Clearly distinguish between gaseous and particulate pollutants by giving at least two distinct examples and their specific health impacts.

 

Long Answer Type Questions

 

Question 1. Montreal Protocol is an essential step. Why is it so?
Answer:
1. Montreal Protocol was an international treaty signed at Montreal in Canada in 1987. This landmark agreement has been highly successful in phasing out ozone-depleting substances globally.
2. Later many more efforts have been made and protocols have laid down definite roadmaps separately for developing and developed countries.
In simple words: The Montreal Protocol is very important because it is a global agreement to protect the Earth's ozone layer. By stopping the use of harmful chemicals, it helps prevent dangerous radiation from reaching us.

🎯 Exam Tip: Mention the year (1987) and the primary goal of protecting the ozone layer to secure full marks.

 

Question 2. Name any 2 personalities who have contributed to control deforestation in our country. Elaborate on importance of their work.
Answer: Two personalities who have contributed to control deforestation in our country are Saalumara Thimmakka from Karnataka and Moirangthem Loiya from Manipur. Their selfless dedication has inspired thousands of people to take up environmental conservation.

1. Saalumara Thimmakka:
• Saalumara Thimmakka is the best example of peoples’ participation in reforestation.
• She is an Indian environmentalist from Karnataka. She has taken up work of planting and tending to 385 banyan trees along a 4 km stretch of highway between Hulikal and Kudur. Other 800 trees are also planted by her.
• She is honoured with the National Citizens Award of India and Padma Shri in 2019.

2. Moirangthem Loiya:
• Moirangthem Loiya is from Manipur who has restored Punshilok forest. For last 17 years he is planting trees after leaving his job.
• He brought the lost glory back for the 300 acres forest land. He planted a variety of trees like, bamboo, oak Ficus, teak, jackfruit and Magnolia.
• This forest now has over 250 varieties of plants including 25 varieties of bamboo along with many animals making the forest rich in biodiversity.
In simple words: Saalumara Thimmakka planted hundreds of banyan trees along a highway in Karnataka, while Moirangthem Loiya replanted an entire 300-acre forest in Manipur. Both showed how single individuals can make a huge difference in saving nature.

🎯 Exam Tip: Clearly state the names, states of origin, and specific achievements (like the number of trees or acres of forest restored) of both personalities to secure full marks.

 

Question 3. How BS emission standards changed over time? Why is it essential?
Answer:
1. BS emission standards changed over the time due to changing city life and more vehicular traffic on the road, especially in the megacities.
2. Since capital city of Delhi was declared as worst polluted city as far as its air quality is concerned, various measures were taken by the Government of India. There was new fuel policy declared, in which Bharat stage emission standards (BS) were set.
3. These norms were set to reduce sulphur and aromatic content of petrol and diesel. Also the vehicular engines were upgraded.
4. Bharat stage emission standards (BS) are standards which are equivalent to Euro norms and have evolved on similar lines as Bharat Stage II (BS II) to BS VI from 2001 to 2017.
5. Since population of Delhi was to be saved, in 2001, Bharat stage II emission norms were set for CNG and LPG vehicles.
6. This helped in reduced emission of sulphur which was controlled at 50 ppm in diesel and 150 ppm in petrol. Also aromatic hydrocarbons were reduced at 42% in concerned fuel according to norms.
7. Because, in spite of all the efforts, Delhi was declared as worst air-polluted city in the world in 2016, therefore, Government of India directly adapted BS VI in the year 2018, skipping BS V. These efforts decreased the levels of \( \text{CO}_2 \) and \( \text{SO}_2 \) in Delhi. These progressive upgrades have significantly helped in curbing the rising threat of respiratory illnesses among urban populations.
In simple words: BS standards are rules set by the government to control air pollution from vehicles. Over time, these rules became stricter, skipping BS V to go straight to BS VI, which helped make the air cleaner in highly polluted cities like Delhi.

🎯 Exam Tip: Remember to mention that India skipped BS V and went directly to BS VI in 2018 to tackle severe air pollution quickly. Highlighting this transition timeline helps secure full marks.

 

Question 4. During large public gatherings like Pandharpur vari, mobile toilets are deployed by the government. Explain how this organic waste is disposed.
Answer:
1. The toilets deployed at Pandharpur at the time of vari are of the Ecosan type.
2. Ecosan toilet is a closed system without water and it is an alternative to leach pit toilets.
3. When the pit of an Ecosan toilet fills up after some time, then it is closed and sealed for about 8-9 months.
4. In this time the faeces get completely composted to organic manure. In this way the organic waste can be disposed. This eco-friendly method prevents groundwater contamination while recycling nutrients back into the soil.
In simple words: The government uses Ecosan toilets, which do not use water. The waste is sealed in a pit for 8 to 9 months, where it naturally turns into safe organic fertilizer for farming.

🎯 Exam Tip: Clearly define 'Ecosan' as a waterless, closed system and mention the specific duration of 8-9 months required for composting to get full marks.

 

Question 5. How Indian culture and traditions helped in bio-diversity conservation? Give importance of conservation in terms of utilitarian reasons.
Answer: In Indian culture and traditions in different religions, biodiversity is protected and conserved. These age-old practices demonstrate a deep-rooted ecological wisdom that coexists with nature. Few examples of worship of animals and plants can be given here:
1. Nagpanchami festival is towards the respect of snakes. They are worshipped on that day and the local people are aware of their role in ecosystem of control of rat population.
2. Vatapournima festival is worshipping a banyan tree.
3. Various other festivals teach the value of plants and animals surrounding us. Even the cattle are worshipped on a particular day as a tradition.
4. Jain religion strongly advocates protection of all animals through vegetarianism.

Conservation in terms of utilitarian reasons:
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:

I. Narrowly utilitarian reasons:
1. Humans always reap material benefits from biodiversity in the form of resources for basic needs such as food, clothes, shelter.
2. Industrial products like resins, tannins, perfume base, etc. are also obtained through biodiversity resources.
3. For making ornaments or artefacts for aesthetic purpose, again biodiversity is sacrificed.
In simple words: Indian traditions protect nature by making plants and animals a part of religious festivals. We also save biodiversity because it provides us with essential things like food, shelter, and materials for industries.

🎯 Exam Tip: Clearly separate your answer into 'Cultural Traditions' and 'Utilitarian Reasons' using distinct headings to help the examiner grade your paper easily.

4. Many medicines are also obtained through biodiversity resources which shares 25% of global medicine market.
5. Around 25000 species are used for traditional medicines by tribal population worldwide.
6. 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.

 

II. Broadly Utilitarian Reasons:

1. 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.
2. Insects carry out pollination and seed dispersal.
3. If insects do not carry out pollination and seed dispersal, man would go hungry without crops and fruits.
4. Biodiversity also is useful in recreation of human beings.

 

III. 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.