20 Apr 2022

Samacheer Kalvi 9th Science Book Back Unit 7 Term 3

Samacheer Kalvi 9th Term III Science Book Back Question and Answers – Unit 7:

Samacheer Kalvi 9th Standard New Science Book Back 1 Mark and 2 Mark Question & Answers PDF uploaded and available below. Class 9 New Syllabus 2021 to 2022 Book Back Question & Answer solutions available for both English and Tamil Medium. Class 9 Science Book Term 3 Unit 7 – Environmental Science Answers/Solutions are provided on this page. 9th Std Science Book is of Term 1st, 2nd, 3rd, and consists of 9 Units in each Term. All 9 Units of Term 1st, 2nd, 3rd Science Book Back One, and Two Mark Solutions are given below.

Check Unit wise and  9th New Science Book Back Question and Answers Guide/Solutions PDF format for Free Download. English, Tamil, Maths, Science, and Social Science Book Back Questions and Answers available in PDF. Check Science – Physics, Chemistry, and Biology, Social Science – History, Geography, Civics, Economics below. See below for the Samacheer Kalvi 9th Science Book Back Unit 7 Term 3 PDF:

Samacheer Kalvi 9th Science Book Back Term 3 Unit 7 Environmental Science Guide PDF:

Science Subject 1 Mark and 2 Mark Solutions Guide PDF available below. Click the Download option to download the book back 1 Mark & 2 Mark questions and answers. Take the printout and use it for exam purposes.

Term – 3

Unit – 7 Environmental Science

I. Choose the correct answer:

1. All the factors of the biosphere which affect the ability of organisms to survive and reproduce are called as
a) biological factors   b) abiotic factors
c) biotic factors          d) physical factors

2. The ice sheets from the north and south poles and the icecaps on the mountains, get converted into water vapour through the process of
a) evaporation         b) condensation
c) sublimation    d) infiltration

3. Free living soil bacteria such as Pseudomonas sp. Are responsible for the process in the nitrogen cycle.
a) ammonification   b) nitrogen fixation
c) nitrification          d) denitrification

4. The atmospheric carbon dioxide enters into the plants through the process of
a) photosynthesis   b) assimilation
c) respiration                d) decomposition

5. Increased amount of in the atmosphere, results in greenhouse effect and global warming.
a) carbon monoxide   b) sulphur dioxide
c) nitrogen dioxide    d) carbon dioxide

6. Which of the following is not an adaptation of hydrophytes?
a) poorly developed root system
b) reduced plant body
c) water-storing parenchymatous tissues
d) finely divided submerged leaves

7. In some xerophytes, leaves are modified into spines as an adaptation
a) to reduce transpiration rate         b) to store water
c) to reduce consumption of water  d) all of the above

8. Identify the incorrect statement with respect to adaptations of earthworm.
a) Earthworm has a stream lined body with no antennae or fins.
b) Each segment of earthworm has setae.
c) many earthworms became inactive in a process called hibernation, during winter season.
d) Earthworms remain in its burrow during day time, to avoid sunlight.

9. What of the following is one of the strategies to conserve water?
a) water recycling
b) using large overhead water tanks
c) increasing the number of bore wells
d) watering the plants using hose

10. Specific constituents such as nitrogen, phosphorus, suspended solids and heavy metals found in the wastewater are removed during treatment of water recycling process.
a) primary     b) secondary
c) tertiary   d) none of the above

II. Match the following:

1. Nitrogen fixation   a) Nitrosomonas
2. Ammonification    b) Azotobacter
3. Nitrification           c) Pseudomonas species
4. Denitrification       d) Putrefying bacteria
Ans: 1- b; 2 –d; 3- a; 4-c.

III. State whether the statements are true or false. Correct the false statements:

1. Nitrogen is a greenhouse gas.
Ans: False – Carbon-di-oxide is a greenhouse gas.

2. Poorly developed root is an adaptation of mesophytes.
Ans: False -Poorly developed root is an adaptation of hydrophytes. (Well developed root is an adaptation of mesophytes)

3. Bats are the only mammals that can fly.
Ans: True

4. Earthworms use the remarkable high frequency system called echoes.
Ans: False – Bats use the remarkable high frequency system called echoes.

5. Aestivation is an adaptation to overcome cold condition.
Ans: False – Aestivation is an adaptation to overcome dry conditions.

IV. Short Questions & Answers:

1. What are the two factors of biosphere?
i) Biotic or living factor.
ii) Abiotic or non-living factor.

2. According to you, which process of water cycle is adversely affected by human activities?
Infiltration and percolation of water is adversely affected by human activities.

3. How do human activities affect nitrogen cycle?
Burning fossil fuels and application of nitrogen based fertilizers increase available nitrogen in air ecosystem. Nitrogen (fertilizer) applied to agricultural fields enters rivers and marine systems. It alters the biodiversity, changes the food web structure and destroys the general habitat.

4. What is adaptation?
Any feature of an organism or its part that enables it to exist under conditions of its habitat is called adaptation.

5. What are the challenges faced by hydrophytes in their habitat?
Hydrophytes face the following challenges in their habitat
(i) Availability of more water than needed.
(ii) Water current may damage the plant body.
(iii) Water levels may change regularly.
(iv) Maintain buoyancy in water.

6. How does Hydrilla plant adapt itself to its habitat?
Hydrilla plants adapt itself to its habitat as its roots are poorly developed. The submerged leaves are narrow or finely divided.

7. Why is it important to conserve water?
i) It creates more efficient use of the water resources.
ii) It ensures that we have enough usable water.
iii) It helps in decreasing water pollution.
iv) It helps in increasing energy saving.

8. List some of the ways in which you could save water in your home and school?
All of us have the responsibility to conserve water. We can conserve water by the following activities.
i) Using a bucket of water to take bath instead of taking a shower.
ii) Using low flow taps.
iii) Using recycled water for lawns.
iv) Repairing the leaks in the taps.
v) Recycling or reusing water wherever it is possible.

9. What is greywater?
Grey water is reusable waste water from residential, commercial and industrial, bathroom sinks, bath tub, shower drains and washing of clothes.

10. What are the uses of recycled water?
Recycled water is used in the following activities:
• Agriculture
• landscape
• Public parks
• Golf course irrigation
• Toilet flushing
• Dust control
• Construction activities
• Cooling water for power plant and oil refineries.

11. What is IUCN? What is the vision of IUCN?
IUCN is the International Union of Conservation of Nature and Natural Resources. The vision of IUCN
is ‘A just world that values and conserves nature’.

V. Give reason:

1. Roots grow very deep and reach the layers where water is available. Which type of plants develop the above adaptation? Why?
Xerophytes develop the above adaptation: To absorb as much water as they can get from the surroundings the roots grow very deep and reach the layers where water is present.

2. Why are streamlined bodies and presence of setae considered as adaptations of earthworm?
The cylindrical, elongated and segmented body helps the earthworm to live in narrow burrows underground. The streamlined body allows for easy penetration into the soil. The setae help the earthworm to move through the soil and provide anchor in the burrows.

3. Echolocation serves as an adaptation in bats. Justify the given statement.
Bats fly around and hunt for insects in the dark. They use a remarkable high-frequency system called echolocation. These sounds are reflected back from its prey and perceived by the ear. Bats use these echoes to locate and identify the prey.

4. Farm ponds serve as an excellent water conservation strategy. Why is it impossible for all farmers to construct it in their fields?
Farm ponds reduce water flow to other tanks and to ponds situated in lower lying areas. Moreover, ponds occupy a large portion of farmer’s land. So it is impossible for all farmers to construct farm ponds in their fields.

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