1. Choose the correct option.
a. During heavy exercise we get cramps in the legs due to the accumulation of _______
- Ethyl alcohol. ii carbon dioxide iii. water iv. lactic acid.
Answer. iv. lactic acid.
(Lactic acid accumulates in the muscles during intense exercise, causing cramps.)
b. In the earthworm gaseous exchange takes place through _______
i. lungs ii. Gills. iii. Slimy skin. iv. capillaries.
Answer. iii. Slimy skin.
(Earthworms breathe through their skin, which needs to stay moist to facilitate gas exchange.)
c. Which component is utilized during respiration to release energy?
i. Protein ii.Lactic acid. iii. Glucose. iv. Cellulose.
Answer. iii. Glucose.
(Glucose is the primary source of energy, broken down during cellular respiration.)
d.The _____ contains vocal cords responsible for producing sound.
i. Pharynx ii. Larynx iii. trachea. iv. epiglottis.
Answer. ii. Larynx.
(The larynx, or voice box, houses the vocal cords that produce sound.)
e. During exhalation, the ribs ______
i. move outwards ii. move downwards iii. . move upwards. iv. do not move at ll
Answer. ii. move downwards.
(During exhalation, the ribs move downwards to help expel air from the lungs.)
Q2. Assertion – Reasoning questions.
for questions number (i) to (ii) two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c), (d) as given below
(a)both assertion (A)and reason are true, and reason R is the correct explanation of the assertion (A).
(b) both assertion (A) and reason are true and reason R is not the correct explanation of the assertion (A).
(c) Assertion (A) Is true, but Reason (R) is false.
(d) Assertion (A) Is false, but Reason (R) is true.
(i)Assertion (A)The breakdown of glucose occurs in the cell of an organism. Reason (R ):
The inhaled oxygen is used to break down glucose into carbon dioxide and water.
Answer. – (a) both assertion (A) and reason are true, and reason R is the correct explanation of the assertion (A).
(Glucose breakdown (cellular respiration) happens in the cells, and oxygen is used to break down glucose into carbon dioxide and water, releasing energy.)
(ii) Assertion (A) Yeast is a unicellular organism that can respire anaerobically reason (R ): The number of ATP molecules released in anaerobic respiration is 2.
Answer. (a) both assertion (A) and reason are true, and reason R is the correct explanation of the assertion (A).
(Yeast can perform anaerobic respiration, producing 2 ATP molecules per glucose molecule.)
Q3. Answer the following questions in one sentence.
- How are dust particles prevented from entering the lungs?
Answer. Tiny hair-like structures called cilia and mucus in the nasal passages trap dust particles, preventing them from entering the lungs.
- How do plants take in air?
Solution. Plants take in air through small openings called stomata present on the surface of their leaves.
- Name the part that protects the gills.
Answer. The operculum protects the gills in fish.
- What do you understand by the term aerobic respiration?
Answer. aerobic respiration is the process of producing cellular energy involving oxygen, breaking down glucose into carbon dioxide and water to release energy.
Q4. Answer the Following Questions in 2 to 3 Sentences
a. Trachea does not collapse easily. Give reason.
The trachea is reinforced with C-shaped rings of cartilage that provide structural support, keeping the airway open and preventing it from collapsing during breathing.
b. What is internal respiration? What happens during internal respiration?
Answer. Internal respiration is the exchange of gases between the blood and the body’s tissues. Oxygen from the blood diffuses into the cells, and carbon dioxide from the cells diffuses into the blood to be carried back to the lungs.
Q5. Answer the Following Questions in 3 to 4 Sentences
a. How does gaseous exchange take place in insects?
In insects, gaseous exchange occurs through a network of small tubes called tracheae. Air enters the tracheae through openings called spiracles located on the insect’s body surface. Oxygen travels through the tracheae directly to the tissues, and carbon dioxide follows the same path in reverse to be expelled.
b. Why do we experience muscle cramps after heavy physical work?
Muscle cramps after heavy physical work occur due to the accumulation of lactic acid in the muscles. When muscles work hard without enough oxygen (anaerobic respiration), they produce lactic acid as a byproduct. This lactic acid buildup can cause pain and cramps in the muscles.