Samacheer Kalvi 9th Science Solutions Chapter 24 Pdf

Samacheer Kalvi 9th Science Solutions Chapter 24 Pdf

Tamilnadu Board Samacheer Kalvi 9th Science Solutions Chapter 24: Tamilnadu State Board Solution Class 9 Science Chapter 24 – ENVIRONMENTAL SCIENCE.

Samacheer Kalvi 9th Science Solutions Chapter 24: Overview

Board

Samacheer Kalvi
Class

9

Subject

Science
Chapter

24

Chapter Name

ENVIRONMENTAL SCIENCE

Samacheer Kalvi 9th Science Solutions Chapter 24 Pdf

 

Chapter 24
Environmental science

 

I. Choose the correct answer.

 

1.) All the factors of 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

Ans: b. abiotic factors
Because, Abiotic or nonliving factors which includes all factors like temperature, pressure, water, soil, air and sunlight which affects the ability of organisms to survive and reproduce.

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

Ans: c. sublimation
Because, It the process in which solid is directly converted into gas, without passing through intermediate liquid phase. Ice sheets and ice caps from north and south poles, and icecaps on mountains get converted into water vapour directly, without converting into liquid.

3.) The atmospheric carbon dioxide enters into the plants through the process of _______________.

  • a. photosynthesis
  • b. assimilation
  • c. respiration
  • d. decomposition

Ans: a. photosynthesis
Because, the atmospheric carbon dioxide enters into the plants through the process of photosynthesis to form carbohydrates.

 

4.) 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

Ans: d. carbon dioxide
Because, carbon dioxide is a greenhouse gas and due to the increase in the amount of carbon dioxide, earth becomes warmer and leads to greenhouse effect and global warming.

 

II. Match the following.

Ans:
1. Nitrosomonas: Ammonification
2. Azotobacter: Denitrification
3. Pseudomonas species: Nitrogen fixation
4. Putrefying bacteria: Nitrification

 

III. State whether true or false. If false, correct the statement.

1.) Nitrogen is a greenhouse gas.
Ans: false
Correct statement: Carbon dioxide is the greenhouse gas.

Because, carbon dioxide is a greenhouse gas and due to the increase in the amount of carbon dioxide, earth becomes warmer and leads to greenhouse effect and global warming.

 

2.) Poorly developed root is an adaptation of mesophytes.
Ans:False
Correct statement: The roots of mesophytes are well developed and are provided with root caps.

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

 

4.) Earthworms use the remarkable high frequency system called echoes.
Ans:False
Correct statement: Bats use a remarkable high frequency system called echolocation.

 

5.) Aestivation is an adaptation to overcome cold condition.
Ans: False
Correct statement: when the soil becomes too hot or dry, earthworms become inactive and undergo a process called aestivation.

IV. Give reason for the following.

1.) Roots grow very deep and reach the layers where water is available. Which type of plants develops the above adaptation? Why?

Ans: Xerophytes have well developed roots, which grow very deep and reach the layers where water is available because they grow in dry habitat.

 

2.) Why streamlined bodies and presence of setae is considered as adaptations of earthworm?

Ans: The stream-lined body of earthworms helps them to live in narrow burrows underground and for easy penetration into the soil. And presence of setae helps the earthworm to move through the soil and provide anchor in the burrows.

 

3.) Why is it impossible for all farmers to construct farm ponds in their fields?
Ans: Because the space required for the farm ponds is much larger and due to which more land of farmers is wasted in farm pond. Also, it reduces the water level to the areas which are at lower level.

 

V. Answer briefly.

1.) What are the two factors of biosphere?

Ans: Biosphere is the part of the earth where life exists. All resources of biosphere can be grouped into two major categories namely

  • Biotic or living factors which includes plants, animals and all other living organisms.
  •  Abiotic or nonliving factors which includes all factors like temperature, pressure, water, soil, air and sunlight which affects the ability of organisms to survive and reproduce.

 

2.) How do human activities affect nitrogen cycle?

Ans:

  •  Nitrogen is the important nutrients needed for the survival of all living organisms. It is an essential component of protein, DNA and chlorophyll. Atmosphere is a rich source of nitrogen and contains about 78% nitrogen. Plants and animals cannot utilize atmospheric nitrogen. They can use it only if it is in the form of ammonia, amino acids or nitrates.
  •  Human impacts on nitrogen cycle are as follows.
  • Burning fossil fuels, appreciate of nitrogen based fertilizers and other activities can increase the amount of biologically available nitrogen in the ecosystem.
  •  Nitrogen applied to agricultural fields enters rivers and marine systems. It alters the biodiversity, changes the food web structure and destroys the general habitat.

 

3.) What is adaptation?
Ans:  Any feature of organisms or its part that enables it to exist under the conditions of its habitat is called adaptations.

 

4) What are the challenges faced by hydrophytes in their habitat?

Ans: Plants growing in or near water are called hydrophytes. Hydrophytes may be free floating or submerged plants living in lakes, ponds, shallow water, marshy lands and marine habitat. The hydrophytes faces certain challenges in their habitat they are as follows.

  • Availability of more water than they are needed.
  • Water current may damage the plant body
  • Water levels may change regularly.
  • Maintain buoyancy in water

5.) Why is it important to conserve water?
Ans: Water conservation is the preservation, control and management of water resources. It also includes activities to protect the hydrosphere and to meet the current and future human demand. There is importance of water conservation which is as given below.

  • It creates more efficient use of the water resources.
  • It ensures that we have enough usable water.
  • It helps in decreasing water pollution.
  • It helps in increasing energy saving.

 

6.) List some of the ways in which you could save water in your home and school.

Ans: We have made some underground tanks to store the water in rainy season.
We have also made the sprinklers in our garden to water the plants only and the water wasted in kitchen is directly given to the plants in garden through the underground pipes.

  • While washing utensils and cloths we use the buckets and not directly the water from taps.
  • The all the taps in house are checked weekly to avoid the wasting of water.
  • In our school we have made some special types of taps for daily use and the wasted water is given to the plants.
  • The extra flow of water is always regulated and the water is saved.

 

7.) What are the uses of recycled water?

Ans: Water recycling, apart from rainwater harvesting, is also one of the key strategies to conserve water. Water recycling is reusing treated wastewater for beneficial purpose such as agricultural and landscape irrigation, industrial processes, flushing in toilets and ground water recharge.

Following are the uses of recycled water.

  • Agriculture
  • Landscape
  • Public parks
  • Cooling water for power plants and oil refineries
  • Toilet flushing
  • Dust control
  • Construction activities

 

8.) What is IUCN? What is the vision of IUCN?

Ans: IUCN is an international organization working in the field of nature conservation and sustainable use of natural resources. IUCN is the global authority on the status of natural world and measures needed to safeguard it.  The vision of IUCN is ‘ A just world that values and conserves nature’.

 

VI. Answer in detail.

1.) Describe the processes involved in the water cycle.

Ans: Water cycle or hydrological cycle is the continuous movement of water on the earth. In this process water moves from one reservoir to another by process such as evaporation, sublimation, transpiration, condensation, precipitation, surface runoff and infiltration during which water converts itself to various forms like liquid, solid and vapour.

1.) Evaporation:

It is the type of vaporisation where liquid water is converted into gas before reaching its boiling point. Water evaporates from the surface of the earth and water bodies such as ocean, seas, lakes, ponds and rivers.

2.) Sublimation:
It the process in which solid is directly converted into gas, without passing through intermediate liquid phase. Ice sheets and ice caps from north and south poles, and icecaps on mountains get converted into water vapour directly, without converting into liquid.

3.) Transpiration:
It is the process by which plants release water vapour into the atmosphere through stomata in leaves and stems.

4.) Condensation:
It is the changing of gas phase into liquid phase which is the reverse of vaporisation. At high altitudes temperature is low, and hence water vapour at that get condensed into very small particles of water droplets. This particles comes close together to form clouds and fog.

5.) Precipitation:
Due to change in wind or temperature, the clouds combine to make bigger droplets and pour down as precipitation i.e. rain. Precipitation includes drizzle, rain, snow and hail.

6.) Runoff:
As the water pours down, it runs over the surface of the earth. Runoff water combines to form channels, rivers, lakes and ends up into oceans.

7.) Infiltration:
Some of the precipitated water moves deep into the soil. Then it moves down which increases the ground water level.

8.) Percolation:
Some of the precipitated water flows through the soil and porous or fractured rock. Infiltration and percolation are two related but different processes describing movement of water through soil.

 

2.) Explain carbon cycle with the help of a flow chart.
Ans:

  • Carbon occurs in various forms on earth like charcoal, diamond and graphite are elemental forms of carbon.
  • Combined forms of carbon includes carbon monoxide, carbon dioxide and carbonate salts. All living organisms are made from carbon containing molecules like proteins and nucleic acids.
  • The atmospheric carbon dioxide enters into the plants through the process of photosynthesis to form carbohydrates. From plants, it is passed on to herbivores and carnivores. During the process of respiration, plants and animals release carbon into atmosphere in the form of carbon dioxide.
  • Carbon dioxide is also returned to the atmosphere through decomposition of dead organic matter, burning fuel cells and volcanic activities.

Fig. Carbon Cycle

 

3.) List out the adaptations of xerophytes.
Ans: Plants that grow in dry habitat are called xerophytes. The adaptations of xerophytes are as follows. They have well developed roots. Roots grow very deep and reach the layers where water is available as in Calotropis. They store water in succulent water storing parenchymatous tissues.

For example: Opuntia, Aloe Vera.

  • They have small sized leaves with waxy coating. For example: Acacia
  • In some plants leaves are modified into spins. For example: Opuntia.
  • Some of the xerophytes complete their life cycle within a very short period when sufficient moisture is available.

 

4.) How does a bat adapt itself to its habitat?

Ans: Bats are the only mammals that can fly. Mostly bats lives in caves and also live in trees, hollowed logs and rock cervices. They are extremely important to humans as they reduce insect population and helps to pollinate plants. Adaptations of bats in related to their habitat are explained below.

1.) Nocturnality:
Bats are active at night. This is useful adaptation to them as flight requires lots of energy during day. Their thin black wing membrane may cause excessive heat absorption during the day. This may lead to dehydration.

2.) Flight adaptations:
Foreimbs are modified serve wings. Tail supports and controls movement during flight. Muscles are well developed and highly powerful and achieve in beating of wings. Tendons of hind limbs provide a tight grasp when the animals are suspended upside down at rest.

3.) Hibernation:
It is state of inactivity in which the body temperature drops with a lowered metabolic rate during winter. Bats are warm blooded animals but unlike other mammals, they let their internal temperature reduce when they are resting. They go to the state of decreased activity to conserve energy.

4.) Echolocation:
Bats use a remarkable high frequency system called echolocation. Bats gives out high frequency sounds i.e. ultrasonic sounds. This sound reflected back from its prey and precived by the ear. Bats use this echo to locate and identify the prey

 

5.) What is water recycling? Explain the conventional wastewater recycling treatment methods.
Ans: Water recycling, apart from rainwater harvesting, is also one of the key strategies to conserve water. Water recycling is reusing treated wastewater for beneficial purpose such as agricultural and landscape irrigation, industrial processes, flushing in toilets and ground water recharge. The conventional waste water treatment consists of a combination of physical, chemical biological processes which remove solids, organic matter and nutrients from the waste water.

The waste water treatment involves the following stages.

1.) Primary treatment:
It involves the temporary holding of the wastewater in a tank. The heavy solids get settled at bottom while oil, grease and lighter solids floats on the surface. The settled and floating materials are removed and the remaining liquid undergoes secondary treatment.

2.) Secondary treatment:
Secondary treatment is used to remove biodegradable dissolved organic matter. This is performed in the presence of oxygen by aerobic microorganisms. The microorganisms must be separated from treated waste water by sedimentation. And after separating the sediments of biological solids, the remaining liquid is discharged for tertiary treatment.

3.) Tertiary treatment:
It is advance final step of sewage treatment. It involves removal of inorganic constituents such as nitrogen, phosphorus and microorganisms.
The fine colloidal particles in the sewage water are precipitated by adding chemical coagulants like alum or ferric sulphate.

 

Here is your solution of Samacheer Kalvi 9th Science Chapter 24 ENVIRONMENTAL SCIENCE.

Dear Student, I appreciate your efforts and hard work that you all had put in. Thank you for being concerned with us and I wish you for your continued success. 

Updated: June 15, 2021 — 1:17 pm

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