Class X Our Environment (Chapter 15)

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Chapter 15-Our Environment

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Can mosquitoes transmit AIDS?

Can mosquitoes transmit AIDS?
We live in a mosquito-infested part of the world, and even if all the experts reassure us, we want to know why mosquitoes cannot transmit Aids. So, consider three situations in which concerns arise.
In the first scenario, you are in a room with a bunch of people and a cloud of mosquitoes. It is dinnertime, and one of the mosquitoes sups on a gentleman who has Aids. The mosquito wobbles off in search of dessert and chances upon you. Now, without washing its mouth parts, it chooses to feast on your blood. You worry that its fangs are blood-stained; you remember that Aids can be spread through contaminated syringes; you panic: when that mosquito bites you after biting an Aids host, is it injecting Aids-containing blood into you?
In the second scenario, you have just been bitten by a mosquito. You wonder: has this mosquito fed on an Aids host recently? If yes, has the mosquito become a flying host to the Aids virus? Has the virus multiplied inside the mosquito and migrated to the insect's salivary glands? And, has the virus been transmitted to you in the mosquito's saliva during the course of the bite, just as happens with the classical mosquito-transmitted diseases?
In the third and what, to you, seems to be the worst-case scenario, the mosquito has gorged itself on an Aids-infected crowd of people. It can fly no longer and settles down on you to rest. You resent being treated as a landing zone; so, you swat at it. Hooray, for the first time that evening you manage to kill one of these pests. Alas, you are aghast to discover that there's Aids-blood splattered all over your skin in the very place that you have a cut. What are your chances of getting Aids?
Scientists have studied each of these scenarios with a variety of blood sucking insects and here, in a nutshell, are the reasons why mosquitoes do not transmit Aids. As an Aids-infected individual actually has very little Aids virus actively circulating in his bloodstream, estimates suggest that Aids transmission through contaminated mouth parts would require being bitten by ten million mosquitoes that have just fed on Aids-infected individuals.
So, the chances of this form of transmission are virtually nonexistent.
For the same reason, the chances are negligible that a mosquito will ingest sufficient Aids-virus particles in its tiny meal to transmit Aids even if the mosquito is killed directly over a cut on the skin immediately after feeding on an Aids-infected person.
Then, mosquitoes digest the virus that causes Aids. As the virus does not survive to reproduce and later migrate to the salivary glands, the mechanism that most mosquito-borne parasites use to get from one host to the next is not possible for the Aids virus.
Lastly, mosquitoes take in blood through one channel and inject saliva into you through another channel. This is different from the syringe and needle analogy wherein the same channel draws in and flushes out fluids. So, if the mosquito bites you after feeding on an Aids host, it does not flush out Aids blood into your bloodstream. In other words, the syringe and needle analogy is not applicable to mosquitoes. So, although mosquitoes may transmit diseases such as malaria, they do not transmit Aids.

Practical on Plasmolysis

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Study of Plant Cells -Plasmolysis

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Why do we fall ill?

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why do we fall ill

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Animal Kingdom

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Plant Kingdom

Diversity in the Living World

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Activity Questions for Nutrition and Respiration

Given below are some activities that will help you to relate the content of topics related to ‘Nutrition and Respiration’ to your daily lives. These activities will make you understand the various processes that take place in the living organisms. Perform theses activities and answer the questions given at the end of each activity.

Activity no.1

Apply a coat of Vaseline/cooking oil on a leaf of a potted plant, observe the leaf for 4-5 days.

Q.1. What happens to the leaf after 4-5 days?

Q.2. What is the reason for these observations.

Q.3. Which processes are effected when you coat the leaf with Vaseline?

Activity no.2

Chew a piece of bread for 3-4 minutes. Note the change in taste as you chew it.

Q.1. Describe the change in taste observed.

Q.2. Why is there a change in taste.

Q.3. Try to write a chemical equation to show the reaction due to which there is a change in taste.(Chemical formulae are not required)

Activity no.3

Take some starchy water that is obtained after boiling rice. Add 2-3 drops of this water to 4 glass bowls (small transparent katories or glasses), you can name them as A, B, C and D. Add a teaspoon of water to each glass bowl. Now add a teaspoon of your saliva to bowl B. Boil a teaspoon of your saliva over a candle flame for 20 seconds and add this to bowl- C. After 10 minutes add 4-5 drops of iodine in each bowl, except bowl D. Tabulate your observations in the following manner-

Glass Bowl	Quantity of Starchy water	Quantity of water	Quantity of saliva	Colour change observed after 10 minutes.
A
B
C
D

Give reasons for your observations.

Activity no.4

Take a ripe fruit (orange or mango) and place it in a poly-bag. Tie or paste the open end of the bag so that no air can get inside the bag. Leave it at room temperature for 3-4 days. Take out the fruit and observe.

Q.1. The fruit may be spoilt and may smell of alcohol. Give a reason for this observation.

Q.2. Which type of microorganisms could be responsible for spoiling the fruit. Do they respire in presence of oxygen of absence of oxygen.

Q.3. Try to write a chemical equation to show the reaction due to which there is a change in smell.(Chemical formulae are not required)

2. Answer the following questions:

2.1 What would happen if :

a) Amoeba did not have pseudopodia

b) Liver did not secrete bile juice

c) Rings of cartilage were not present in the throat.

d) Blood did not have haemoglobin

e) There was no transpiration in plants

f) Villi in small intestine did not have blood vessels.

2.2 Differentiate between:

a) Arteries and veins

b) Large intestine and small intestine

c) Aerobic and anaerobic respiration

d) Blood and lymph

e) Mesophyll cells and epidermal cells of a leaf

f) Respiration in man and fish.

Management of Natural Resources

Very Short Answer Questions

1. What does the presence of coliform bacteria in water indicate?

2. What are coliform bacteria?

3. Which areas on earth are considered as ‘biodiversity hot spots’?

4. Name two measurable factors that are used to quantify pollution and the quality of water.

5. Name a renewable and a non renewable resource.

6. Name some industries based on forest produce.

7. What are kulhs?

8. Name two traditional water harvesting systems.

9. What are khadins?

10. Name a green house gas.

11. Name the toxic gases released on combustion of coal and petroleum.

Short Answer Questions

1. Define the following terms:

a) Natural Resource

b) Water Harvesting

c) Sustainable Management

d) Recycling

2. How does sustainable development help us to take environment friendly decisions?

3. Why protection of biodiversity is considered important?

4. How is water pollution measured?

5. Mention any one change that you will make in your habit to become more environment friendly.

6. What is the main aim of conservation?

7. Different groups of people depend on forests in many ways. Discuss.

8. What are the harmful effects of deforestation?

9. How does mining cause pollution?

10. What is water shed management?

11. What is the major cause of energy crisis?

Short Answer Questions

1. What are the disadvantages of continued use of coal and petroleum as fuels?

2. Discuss the relationship between efficiency of our machines and the environment.

3. Discuss the relationship between efficiency of our machines and use of coal and petroleum.

4. What can you do as a student for judicious management of natural resources?

5. What are the factors that govern implementation of Sustainable development?

6. Why do we need to use our resources carefully?

7. How is biodiversity connected to ecological stability?

8. Discuss the contribution of Amrita Devi Bishnoi in conservation of forests.

9. Prejudice against traditional use of forest areas may, at times, be harmful to the environment. Explain giving an example.

10. Explain the three main functions of forests.

11. What are the advantages of storing water as ground water?

12. How are coal and petroleum formed?

13. What is the composition of coal and petroleum? (relate it to bio mass)

14. Write a short note on Natural Resource Management.

Long Answer Questions

1. Following the 3Rs can help us to save the environment. Discuss.

2. Many environmental problems are connected with exploitation of resources. Discuss this statement giving two examples.

3. Participation of local people can lead to efficient management of resources. Explain this in context of the ‘Chipko Movement’?

4. Explain, with an example, people’s participation in management of forests.

5. Mention the various stakeholders in the forest. Explain the role of each.

6. Quality and quantity of ground water are a cause of concern in today’s world. Explain.

7. Discuss the social , economic and environmental problems related to dams.

8. What are the advantages of water shed management?

9. List the advantages and disadvantages of dams.

10. Explain the structure of water harvesting system in a largely level terrain.

More Questions for 'Nutrition and Respiration'

Life Processes

(Nutrition and Respiration)

Very Short Answer Questions

1. Which process fulfils the carbon and energy requirements of autotrophic organisms?

2. In what form are carbohydrates usually stored in a) Plants, b) animals.

3. Write the chemical equation for photosynthesis.

4. Name two parasitic plants.

5. Name two parasitic animals.

6. Name the energy currency of the cell.

Short Answer Questions

1. What is the basic characteristic that you would look for in an organism to determine whether it is alive or not?

2. Why are molecular movements needed for life?

3. Why are maintenance processes required in living organisms?

4. Why are enzymes known as biocatalysts?

5. How do plants obtain nitrogen?

6. How is the mode of nutrition in bread moulds different from mode of nutrition in man?

7. When we eat something we like, our mouth waters. Give the scientific reason behind this.

8. Is it right to say that digestion starts in mouth? Give reasons for your answer.

9. How does the food move in the human alimentary canal?

10. What is the role of HCl in digestion of proteins?

11. How is the exit of materials controlled from stomach and anus?

12. Plants may not release C0₂ during day. Explain.

13. How do aquatic animals get oxygen?

14. What is the function of fine hair present in our nostrils?

15. Rings of cartilage that surround the air passage play an important role. Discuss.

16. How are CO₂ and O₂ transported in the human body?

17. What is the role of respiratory pigment in human beings?

Short Answer Questions

1. Define the following terms: Life Processes, Respiration, Nutrition, excretion

2. Explain the most common method of molecular breakdown for release of energy in living organisms.

3. ‘Survival of heterotrophs depends directly or indirectly on autotrophs.’ Explain

4. List the major events that occur during photosynthesis.

5. How is photosynthesis in desert plants different from photosynthesis in other land plants?

6. How do plants obtain CO₂ ?

7. How do stomata open and close?/

8. How does paramecium obtain food?

9. When we chew a piece of bread or chapatti for 2-3 minutes, it starts tasting sweet. Explain.

10. What would happen if mucus was not present in the inner lining of stomach?

11. What is the relationship between small intestine and food habit of animals?

12. Why is emulsification of fats necessary in the digestive system? How is it achieved?

13. Explain how the digested food enters our blood stream.

14. What is the function of pancreas?

15. Fill in the blanks:

Breakdown of ____________ , which is a 6-carbon compound, to _______________ which is a 3- carbon compound, takes place in the _____________. Then , this 3- carbon compound moves to ____________ where it is further broken using oxygen.

16. What is the cause of muscle fatigue in athletes?

17. Differentiate between aerobic and anaerobic respiration.

18. Rate of breathing in aquatic animals is faster than terrestrial animals. Explain.

19. What is the similarity between organs that absorb oxygen in different animals?

20. Lungs are designed in humans to maximise gaseous exchange. Explain.

Long Answer Questions

1. Simple diffusion process for various activities like taking in food, exchange of gases etc. is not sufficient in multicellular organisms. Why? What is the solution to this problem?

2. Explain the process of nutrition in amoeba.

3. Explain the function of glands associated with the digestive system of man.

4. The fate of pyruvate would differ in yeast, man and a man involved in heavy physical exercise. Explain.

5. Draw neat , well labelled diagrams of:

a) Stomata

b) Digestive system in humans

c) Respiratory system in humans.

Try this before starting the Topic-Nutrition and Repiration

1. What is the meaning of the word ‘sapro’?
2. Name a parasitic plant and a parasitic animal.
3. Besides human beings, name two organisms that exhibit holozoic nutrition.
4. Name the two types of photoreceptor molecules present in plants.
5. Expand – ATP, NADP.
6. Name the products produced during light reaction that are utilized in the dark reaction.
7. Name the chloroplast containing tissue in the leaves.
8. Name the most common types of chlorophyll present in green plants.
9. Which molecule accepts CO₂ in the dark reaction?
10. Which is the ideal temperature for photosynthesis.
11. What is the process of obtaining food known as?
12. Name the excretory organs of grasshoppers.
13. How does grasshopper obtain food?
14. What is the approximate length of the human alimentary canal?
15. Which structures in amoeba are involved in ingesting food?
16. Name three glands associated with human digestive system.
17. Name the parts that provide enzymes in the digestive system of grasshopper.
18. Name the enzyme present in human saliva.
19. Which enzyme converts starch to maltose in human beings?
20. The stomach environment is acidic due to the presence of which substance?
21. What are the finger-like-projections in the small intestine known as?
22. What is the function of pepsin?
23. Which substance emulsifies fats present in food?
24. Hoe does the duodenal environment become alkaline?
25. What are the components of bile?
26. Which gland of the human digestive system secretes enzymes and hormones?
27. In what form is the energy released during respiration stored?
28. Hoe does exchange of gases take place in the tree trunk?
29. Where does anaerobic respiration take place in the human body?
30. Name two end products of anaerobic respiration.
31. What are extensions of epidermal cells of root known as?
32. Which process is responsible for respiratory gas exchange in leaves?
33. Name the respiratory organs in mussels.
34. Name the respiratory organ in earthworm.
35. Name the respiratory organs in housefly. .
36. Which structure separates nasal cavity from the oral cavity?
37. Which structure prevents the trachea from collapsing?
38. How is the thoracic cavity separated from the abdominal cavity?
39. Name the structure that prevents entry of food into the windpipe.
40. What is the protruding cartilage of voice box in males known as?
41. How many vocal cords are present in the larynx?
42. What is the rate of breathing in human beings under normal conditions?
43. In which cavity are the lungs present?
44. How is oxygen transported from lungs to other parts of the body?
45. In which disease is the area for gaseous exchange in the lungs reduced?
46. Which part of the root is involved in exchange of respiratory gases?
47. Name a unicellular organism that respires anaerobically.
48. Which ‘juice’ is involved in the complete digestion of food in the small intestine?
49. Name the enzymes present in pancreatic juice.
50. How many salivary glands are associated with the human digestive system?