Q27 of 30 Page 1

(a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain.

(b) Draw a diagram of human respiratory system and label – pharynx, trachea, lungs, diaphragm and alveolar sac on it.


OR


(a) Name the organs that form the excretory system in human beings.


(b) Describe in brief how urine is produced in human body.


(a) The aquatic organisms depend only on the oxygen present in the dissolved form in the water body. Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

(b)



Human Respiratory System


OR


a. The organs of the Human Excretory System are


1. A pair of Kidneys


2. A pair of Ureters


3. Urinary Bladder


4. Urethra


(b) The main excretory organ in human beings is the kidney that releases about 80% of liquid waste from the body. Urine formation occurs in the kidney in 3 parts-


1. Glomerular Filtration or Ultrafiltration


2. Selective Reabsorption


3. Tubular Secretion.


The afferent arteriole brings blood to the kidney and forms a bunch of capillaries in the Bowman’s capsule. Glomerular filtration occurs in the Bowman's capsule where glucose, salts, amino acids, urea enters the filtrate. Water and solutes that are smaller than proteins are forced into the renal tubule where reabsorption of water, glucose, amino acids and needed ions occurs and returns them back to the blood. Tubular secretion removes additional wastes from the blood and adds them to the filtrate. Further, water is removed from urine and returned to blood. Urine is sent to the collecting ducts.


More from this chapter

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25

Carbon cannot reduce the oxides of sodium, magnesium and aluminium to their respective metals. Why 2 Where are these, metals placed in the reactivity series? How are these metals obtained from their ores? Take an example to explain the process of extraction along with chemical equations.

 26

The position of certain elements in the Modern Periodic Table are shown below.

Using the above table answer following questions giving reasons in each case :


(i) Which element will form only covalent compounds?


(ii) Which element is a non-metal with valency 2 ?


(iii) Which element is a metal with valency 2 ?


(iv) Out of H, C and F which has largest atomic size?


(v) To which family does H, C and F belong?


OR


Define atomic size. Give its unit of measurement. In the modern periodic table what trend is observed in the atomic radius in a group and a period and why is it so?


 28

(a) What is the law of dominance of traits? Explain with an example.

(b) Why are the traits acquired during the life time of an individual not inherited? Explain.


 29

Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed:

(i) between optical centre and principal focus of a convex lens.


(ii) anywhere in front of a concave lens.


(iii) at 2 F of a convex lens. State the signs and values of magnifications in the above-mentioned cases (i) and (ii).


OR


An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm


(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image?


(ii) Find the size of the image.


(iii) Draw a ray diagram to show the formation of image in this case.