12th Bio - Botany - Book Back Answers - Chapter 8 - English Medium Guides

 

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Tamil Nadu Board 12th Standard Bio-Botany - Chapter 8: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Chapter 8 – Bio-Botany from the Tamil Nadu State Board 12th Standard Bio-Botany textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Bio-Botany Chapter 8 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 12 students! Prepare well and aim for top scores. Thank you!

Unit 8 - Environmental Issues

I. Multiple Choice Questions

1. Which of the following would most likely help to slow down the greenhouse effect. 
a) Converting tropical forests into grazing land for cattle. 
b) Ensuring that all excess paper packaging is buried to ashes. 
c) Redesigning landfill dumps to allow methane to be collected. 
d) Promoting the use of private rather than public transport.
Answer Key:
c) Redesigning landfill dumps to allow methane to be collected. 

2. With respect to Eichhornia 
Statement A: It drains off oxygen from water and is seen growing in standing water. 
Statement B: It is an indigenous species of our country. 
a) Statement A is correct and Statement B is wrong. 
b) Both Statements A and B are correct. 
c) Statement A is correct and Statement B is wrong. 
d) Both statements A and B are wrong.
Answer Key:
a) Statement A is correct and Statement B is wrong. 

3. Find the wrongly matched pair. 
a) Endemism - Species confined to a region and not found anywhere else. 
b) Hotspots - Western ghats 
c) Ex-situConservation - Zoological parks 
d) Sacred groves - Saintri hills of Rajasthan 
e) Alien sp.Of India - Water hyacinth
Answer Key:
d) Sacred groves - Saintri hills of Rajasthan 

4. Depletion of which gas in the atmosphere can lead to an increased incidence of skin cancer? 
a) Ammonia 
b) Methane 
c) Nitrous oxide 
d) Ozone
Answer Key:
d) Ozone

5. One green house gas contributes 20% of total global warming and another contributes 60%. These are respectively identified as 
a) N2O and CO2 
b) CFCs and N2O 
c) CH4 and CO2 
d) CH4 and CFCS
Answer Key:
c) CH4 and CO2 

6. One of the chief reasons among the following for the depletion in the number of species making endangered is 
a) over hunting and poaching 
b) green house effect 
c) competition and predation 
d) habitat destruction
Answer Key:
d) habitat destruction

7. Deforestation means 
a) growing plants and trees in an area where there is no forest 
b) growing plants and trees in an area where the forest is removed 
c) growing plants and trees in a pond 
d) removal of plants and trees
Answer Key:
d) removal of plants and trees

8. Deforestation does not lead to 
a) Quick nutrient cycling 
b) soil erosion 
c) alternation of local weather conditions 
d) Destruction of natural habitat weather conditions
Answer Key:
a) Quick nutrient cycling

9. The unit for measuring ozone thickness 
a) Joule 
b) Kilos 
c) Dobson 
d) Watt
Answer Key:
c) Dobson 

10. People’s movement for the protection of environment in Sirsi of Karnataka is 
a) Chipko movement 
b) Amirtha Devi Bishwas movement 
c) Appiko movement 
d) None of the above
Answer Key:
c) Appiko movement 

11. The plants which are grown in silivpasture system are 
a) Sesbania and Acacia 
b) Solanum and Crotalaria 
c) Clitoria and Begonia 
d) Teak and sandal
Answer Key:
a) Sesbania and Acacia 

II. Short Answer Questions

1.What is ozone hole?

• The decline in the thickness of the ozone layer over restricted area is called Ozone hole.
• This is takes place by chlorofluorocarbons.

 
2.Give four examples of plants cultivated in commercial agroforestry.

• Casuarina, Eucalyptus, Malai Vembu, Teak and Kadambu trees are the plants cultivated in commercial agroforestry.
• They are of great importance to wood-based Industries.

 
3. Expand CCS.

• CCS-Carbon Capture and Storage

 
4. How do forests help in maintaining the climate?

• Forest are a stabilising force for the climate.
• They regulate ecosystems, project biodiversity, play an integral part in carbon cycle, support livelihood and supply goods and services that can drive sustainable growth.
• One third of the carbon di oxide released from burning fossil fuels.is absorbed by forest every year.
• It reduces the global warming.
• So forests are most important help in the maintaining the climate

5.How do sacred groves help in the conservation of biodiversity?

• Sacred groves are the patches of cultivated trees which are community protected.
• They are based on strong religious belief systems.
• They usually have a significant religious connotation for protecting community.
• Each grove is an abode of a deity mostly village God Or Goddesses like Aiyanar or Amman
• Tribals Don't allow anyone to cut even a single branch.
• Sacred groves have been free from all types of exploitation.
• So sacred groves help in the conservation of biodiversity

 
6. Which one gas is most abundant out of the four commonest greenhouse gases? Discuss the effect of this gas an the growth of plants?

• CO2 (Carbon dioxide) is most abundant greenhouse gases.
• Effects on Plants
• Low agricultural productivity in tropics
• Frequent heat waves (Weeds, pests, fungi need warmer temperature)
• Increase of vectors and epidemics
• Strong storms and intense flood damage
• Water crisis and decreased Irrigation
• Change in flowering seasons and pollinators
• Change in Species distributional ranges
• Species extinction

 
7.Suggest a solution to water crisis and explain its advantages.

• Rain water harvesting is a solution to water crisis.
• Accumulation and storage of rain water for reuse in-site rather than allowing it to run off is called rainwater harvesting.
• Rainwater can be collected from rivers, roof tops and the water collected is directed to a deep pit.
• The water percolates and gets stared in the pit.
• It is a sustainable water management practice implemented not only in urban area but also in agricultural fields,
• It is an important economical cost effective method for the future.
• Environmental advantages of Rain water harvesting
• Promotes adequacy of underground water and water conservation.
• Mitigates the effect of drought.
• Reduces soil erosion as surface run-off is reduced.
• Reduces flood hazards.
• Improves groundwater quality and water table/decreases salinity.
• No land is wasted for storage purpose and no population displacement is involved..
• Storing water underground is an eco-friendly measure. 

    
8. Explain afforestation with case studies.

• The conversion of non-forested lands into forests by planting suitable trees to retrieve the vegetation is called afforestation.
• Example: Slopes of dams afforested to reduce water run-off, erosion and siltation.
• It provides a range of environmental services including carbon sequestration, water retention.
• The Man who Single Handedly Created a Dense Forest
• Jadav "Molai" Payeng (born 1963) is an environmental activist.
• He has single-handedly planted a forest in the middle of a barren wasteland.
• He is called Forest Man of India.
• He transformed the world's largest river island, Majull, located in Brahmaputra river, into a dense forest
• It has rhinos, deers, elephants, tigers and birds.
• Today his forest is larger than Central Park.
• Sudhir Kumar Sopory (former vice-chancellor of Jawahar Lal Nehru University) named Jadav Payeng as Forest Man of India, in the month of October 2013.
• He was honoured at the Indian Institute of Forest
• Management during their annual event 'Coaluscence'.
• In 2015, he was honoured with Padma Shri, the fourth highest civilian award in India.
• He received honorary doctorate degree from Assam Agricultural University and Kaziranga University for his contributions

 
9. What are the effects of deforestation and benefits of agro forestry?
Effects of deforestation

• Burning of forest wood release stored carbon, a negative impact just opposite of carbon sequestration.
• Trees and plants bind the soil particles.
• Increases soil erosion and decreases soil fertility
• Deforestation in dry areas leads to the formation of deserts.
• The amount of runoff water creates flash flooding, thu; reducing moisture and humidity.
• It leads to drought conditions in many regions.
• It triggers adverse climatic conditions and alters wate cycle in ecosystem.
• It disturbed and disruption of natural cycles.
• Loss of livelihood for forest dwellers and rural people.
• Increased global warming and account for one-third of total CO2 emission.
• Loss of life support resources, fuel, medicinal herbs and wild edible fruits
• Benefits of agroforestry
• It is an answer to the problem of soil and water conservation.
• To stabilise the soil (salinity and water table) reduce landslide and water run-off problem.
• Nutrient cycling between species improves and organic matter is maintained.
• Trees provide micro climate for crops.
• Maintain O₂- CO₂ balanced, atmospheric temperature and relative humidity.
• Suitable for dry land. (rainfall is minimum)
• It is a good system for alternate land use pattern.
• Multipurpose tree are used for wood pulp, tanning, paper and firewood industries. Ex Acacia.

 

III. Long Answer Questions

12th bio botany

IV. Exercise

12thbio botany