Selina Concise Class 7 Biology Solution Chapter No. 5- ‘Excretion in humans’ For ICSE Board Students.
MULTIPLE CHOICE QUESTION
Put a tick mark against the correct alternative in the following statements.
(i) The kidneys are made up of tiny tubular units called :
(a) Glomerulus (b) Nephrons (c) Capillaries (d) Neurons
Answer: Answer is B Nephrons, because they are the structural unit of kidney.
(ii) In humans urea is produced in :
(a) Liver (b) Kidney (c) Spleen (d) Urinary bladder
Answer: Answer: Answer is A liver because major metabolic processes occur in liver.
(iii) Besides the water, urine mainly contains :
(a) Urea (b) Nitric acid (c) Bile pigments (d) bile pigments
Answer:Answer: Answer is A urea. Humans excrete mainly urea.
(iv) Filtration of excretory waste from the blood occurs in :
(a) Collecting tubule (b) ureter (c) Urinary bladder (d) Nephrons
Answer: Answer is D. Nephron, filtration occurs in nephron.
SHORT ANSWER QUESTION
1.) Fill in the blanks.
(i) Nitrogenous waste in the urine are in the form of : Urea
(ii) The unit of kidney is called :Nephron
(iii) Evaporation of sweat from skin surface has : cooling effect due to evaporation.
2.) Define the following :
(i) Excretion : Excretion can be defined as the removal of nitrogenous compound from the body called as excretion.
(ii) Excretory organs : Kidney, ureters, urinary bladder and urethra.
(iii) Dialysis: When patient have no longer ability to excrete nitrogenous waste naturally, therefore for the removal of ions, salt and molecules. The process is called dialysis.
(iv) Nephron : It is generally regarded as structural and functional unit of kidney.
3.) Write True (T) or False (F) for the following statement in the spaces provided. Rewrite the false statement in correct form.
(i) Removal of solid undigested food is excretion.
Answer: False, the process is called as egestion.
(ii) Medulla of kidney passes urine into urinary bladder.
Answer: False, Medulla of kidney passes urine into pelvis.
(iii) Excess sugar in blood is a symptom of diabetes.
(iv) Urine is devoid of blood cells.
4.) Name the blood vessel that brings blood to the kidneys :
Answer: Renal arteries are blood vessel that brings blood to the kidneys.
5.) Where in the urinary system do the following processes takes place ?
(i) Urine formation : Kidneys
(ii) Transport of urine away from kidney : ureter
(iii) Temporary storage of urine : urinary bladder.
LONG ANSWER QUESTION (Write the answer in your notebook )
1.) Define excretion. Write the four organs of human urinary system in their correct sequence.
Answer: Excretion can be termed as the removal of excess or undigested waste from the body in the form of nitrogenous waste. The process of excretion occurs in the excretory system. Therefore the correct sequence of human urinary system is (1) kidney (2) ureter (3) Urinary bladder (4) Urethra.
2.) Why is excretion is necessary in living beings ?
Answer: The excretory system plays very important role in our day to day life. It is vital system for living organisms. When living organisms intake food then metabolism of molecules starts, body will utilize the required nutrition for the organs and all the excess and undigested food material excreted out from the body. If excretory system does not work at such condition the poison will start accumulating and can cause diseased condition. Therefore the excretion is necessary in living beings
3.) What is meant by osmoregulation ?
Answer: The function of kidney is to excrete urea and excess material from the body but along with this kidney regulate water and ion concentration in the body. This is called as osmoregulation. It helps to control the blood pressure and sugar concentration in the body.
4.) Describe the structure of kidney with the help of a labelled diagram.
The kidney is internally made up of two structures, the outer layer called as cortex whereas inner layer called as medulla. From the medulla urine enters into funnel like renal pelvis. The renal artery and renal vein are responsible for transportation of blood, urea, ions and water.
5.) What are the two ways by which a person can get relief in case of kidney failure?
Answer: there are two ways by which a person can get relief in case of kidney failure such as (1) Dialysis: When kidney is damaged under certain condition excess urea removed from the body with the help of dialysis. (2) Kidney transplant: When there are both kidneys get damaged at that time dialysis cannot be performed.
6.) Draw a diagram of human excretory system and label the following parts:
Kidney, Ureter, urinary bladder, urethra.
7.) How are kidney stones formed ?
Answer: When there is formation of crystals such as calcium oxalate and calcium phosphate and also uric acid, when this molecules are present in excess, than that of fluids they are called as kidney stones. They form due to sticking to each other and becomes larger in size, that’s how the kidney stones form in the body.
8.) What are the symptoms of urinary tract infection ?
Answer: there are various symptoms of urinary tract infection such as pelvic pain, frequent urination, pain in ureters, pain in urethra, pain in urinary bladder etc, these are the symptoms of urinary tract infection.