Download DPS –MODERN INDIAN SCHOOL, DOHA, QATAR CLASS

DPS –MODERN INDIAN SCHOOL, DOHA, QATAR
CLASS-X
BIOLOGY
EXCRETION- NOTES
1. Define excretion.
The biological process which involves the removal of harmful metabolic wastes from
the body is known as excretion.
2. Describe the excretory system of human beings.
a. Kidney-Bean shaped structure present in upper part of abdomen on either side of
vertebral column.
b. Ureter-one pair of long, thin –walled tubular structures opening separately into
urinary bladder.
c. Urinary bladder-Thin –walled distensible sac present in lower part of abdomen.
d. Urethra-Muscular opening for expulsion of urine.
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3. Name the functional unit in a kidney. Describe its structure.
Functional unit- nephron
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Structure of Nephron
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Nephron-structure and function
Internally each kidney consists of about one million renal tubules known as nephrons
which are the structural and functional unit of kidney.
- The renal tubule begins with a double walled cup shaped structure called
‘bowman’s capsule ‘.
- A tuft of capillaries called glomerulus enter into the bowmans capsule. Blood
brought by the glomerulus is filtered by the bowman’s capsue and form the
filtrate (urine).
- Bowman’s capsule continues to form a highly coiled network –proximal
convoluted tubule(PCT) which leads to a U shaped tube called loop of Henle
which continues as another coiled tubular region called distal convoluted
tubule(DCT)
- Some substances in the filtrate such as glucose, amino acids salts and major
part of water are selectively reabsorbed as the urine flows along the tube.
4. Write a short note on excretion in plants.
(i) Plants excrete a number of waste products such as carbon dioxide, oxygen and
water, which are excreted during different processes like respiration, photosynthesis
and transpiration respectively.
(ii) They store some waste products in vacuoles present in the leaves and get rid of
these wastes by shedding their leaves.
(iii) Plants also store some waste products in the old xylem in the form of resins
and gums.
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(iv) They excrete some waste substances in the soil around them.