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Chapter: 12th Botany : Chapter 8 : Environmental Issues

Answer the following questions (Pure Science Group)

Botany : Environmental Issues : Pure Science Group Book Back and Important Questions Answers - Brief Questions Answers, Short Questions Answers

Botany : Environmental Issues

Answer the following questions (Pure Science Group)

16. What is ozone hole?

Answer: The ozone shield is being damaged by chemicals released on the Earth’s surface notably the chlorofluorocarbons widely used in refrigeration, aerosols, chemicals used as cleaners in many industries. The decline in the thickness of the ozone layer over restricted area is called Ozone hole.

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

Answer: The major species cultivated in commercial Agroforestry include Casuarina, Eucalyptus, Malai Vembu, Teak and Kadambu trees which were among the 20 species identified as commercial timber. They are of great importance to wood-based industries.

18. What are agrochemicals?

Answer: (vii) An agro-chemical is useful in managing agriculture or in farming area which is one of the major issues of the environment.

(viii) Agro-chemicals includes fertilizers, liming and acidifying agents, soil conditioners, pesticides and chemicals used in animal husbandry, such as antibiotics and hormones.

19. Expand CCS.

Answer: Carbon Capture and Storage.

20. How do forests help in maintaining the climate?

Answer: (i) Forest act as carbon sink. Any system having the capacity to accumulate more atmospheric carbon during a given time interval than releasing CO2 is called a carbon sink. Thus forests are ideal carbon sink since the trees utilize CO2 for photosynthesis.

(ii) Carbon sequestration is the process of capturing and storing CO2 which reduces the amount of CO2 in the atmosphere with a goal of reducing global climate change. Carbon sequestration is naturally done by green plants.

(iii) Trees provide micro climate for crops and maintain O2 - CO2 balance, atmospheric temperature and relative humidity.

(iv) If the atmospheric CO2  level increases it will lead to global warming. There will be a drastic change in weather patterns bringing more floods or droughts in some areas. This can also cause frequent heat waves.

(v) Thus forests play a major role in maintaining the climate.

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

Answer: (i) These are the patches or grove of cultivated trees which are community protected and are based on strong religious belief systems which usually have a significant religious connotation for protecting community.

(ii) 448 grooves were documented throughout Tamil Nadu.

Example: Banagudi shola

(iii) These groves provide a number of ecosystem services to the neighbourhood like protecting watershed, fodder, medicinal plants and micro climate control.

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

Answer: CO2  (Carbon dioxide) is the most abundant among green house gases.

Effects on plants:

(i) Low agricultural productivity in tropics.

(ii) Frequent heat waves (Weeds, pests, fungi need warmer temperature).

(iii) Increase of vectors and epidemics.

(iv) Strong storms and intense flood damage.

(v) Water crisis and decreased irrigation.

(vi) Change in flowering seasons and pollinators.

(vii) Change in species distributional ranges

(viii) Species extinction

23. Distinguish between endangered, vulnerable and rare species.



1. A taxon is Endangered when the best available evidence indicates that it meets any of the criteria A to E for Endangered, and it is therefore considered to be facing a very high risk of extinction in the wild.

2. Ex: Elaeocarpus venustus, Pogostemon nilagricus


1. A taxon is Vulnerable when the best available evidence indicates that it meets any other criteria A to E for Vulnerable, and it is therefore considered to be facing a high risk of extinction in the wild.

2. Ex: Dalbergia latifolia, Santalum album.

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

Answer: Rain water harvesting - RWH (Solution to water crisis - A ecological problem)

Rainwater harvesting is the accumulation and storage of rain water for reuse in-site rather than allowing it to run off. Rainwater can be collected from rivers, roof tops and the water collected is directed to a deep pit. The water percolates and gets stored in the pit. RWH is a sustainable water management practice implemented not only in urban area but also in agricultural fields, which is an important economical cost effective method for the future.

Environmental Benefits:

(i) Promotes adequacy of underground water and water conservation.

(ii) Mitigates the effect of drought.

(iii) Reduces soil erosion as surface run-off is reduced.

(iv) Reduces flood hazards.

(v) Improves groundwater quality and water table / decreases salinity.

(vi) No land is wasted for storage purpose and no population displacement is involved.

(vii) Storing water underground is an eco-friendly measure and a part of sustainable water storage strategy for local communities.

25. Explain afforestation with case studies.

Answer:  Afforestation is planting of trees where there was no previous tree coverage and the conversion of non-forested lands into forests by planting suitable trees to retrieve the vegetation. Example: Slopes of dams afforested to reduce water run-off, erosion and siltation. It can also provide a range of environmental services including carbon sequestration, water retention.

Tamil Nadu Afforestation Project (TAP):

(i) With an aim of ecological restoration and biological up-gradation of degraded forests and other lands, the government of Tamil Nadu launched the project in 2 phases.

(ii) Tap I (1997-2005) it aimed to uplift the quality and life of villagers abutting forest areas and to resolve the degraded forests in Tamil Nadu. This is a massive joint Forest Management Programme.

(iii) TAP II (2005-2013) had 2 main objectives. To restore the ecological equilibrium of the forests, watersheds and adjacent villages of Tamil Nadu.

(iv) To improve the quality of the life of inhabitants through reforestation, water conservation and sustained community action.

26. What are the effects of deforestation and benefits of agroforesty?

Answer: Effects of deforestation:

(i) Burning of forest wood release stored carbon, a negative impact just opposite of carbon sequestration.

(ii) Trees and plants bind the soil particles. The removal of forest cover increases soil erosion and decreases soil fertility. Deforestation in dry areas leads to the formation of deserts.

(iii) The amount of runoff water increases soil erosion and also creates flash flooding, thus reducing moisture and humidity.

(iv) The alteration of local precipitation patterns leading to drought conditions in many regions. It triggers adverse climatic conditions and alters water cycle in ecosystem.

(v) It decreases the bio-diversity significantly as their habitats are disturbed and disruption of natural cycles.

(vi) Loss of livelihood for forest dwellers and rural people.

(vii) Increased global warming and account for one-third of total CO2 emission.

(viii) Loss of life support resources, fuel, medicinal herbs and wild edible fruits.

Benefits of agroforestry:

(i) It is a solution for the problem of soil and water conservation and also to stabilise the soil (salinity and water table) reduce landslide and water run-off problem.

(ii) Nutrient cycling between species improves and organic matter is maintained.

(iii) Trees provide micro climate for crops and maintain O2 – CO2 balance, atmospheric temperature and relative humidity.

(iv) Suitable for dry land where rainfall is minimum and hence it is a good system for alternate land use pattern.

(v) Multipurpose tree varieties like Acacia are used for wood pulp, tanning, paper and firewood industries.

(vi) Agro-forestry is recommended for the following purposes. It can be used as Farm Forestry for the extension of forests, mixed forestry, shelter belts and linear strip plantation.

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