How have the terrestrial organisms adapted themselves for conservation of water?
Aquatic animals like bony fishes, aquatic amphibians and aquatic insects exerete ammonia i.e,, they are ammonotelic in nature. This is because ammonia is highly toxic and is readily soluble in water. It is generally excreted by diffusion across body surfaces or through gill surfaces (in fish) as ammonium ions. Excretion of nitrogenous wastes in the form of urea requires a lot of water. Terrestrial animals cannot afford to lose so much of water, thus they convert ammonia into urea or uric acid which are less toxic and can be stored in body for longer.
Terrestrial amphibians and mammals mainly exerete urea and are called ureotelic animals while reptiles, birds, land snails excrete uric acid and are called uricotelic animals. Urea and uric acid are less soluble in water and can be excreted with lesser loss of water. Thus, terrestrial adaptation necessitated the production of urea and uric acid for conservation of water.
Fill in the blanks appropriately.
Organ Excretory wastes
(a) Kidneys ______________
(b) Lungs ______________
(c) Liver ______________
(d) Skin ______________
Match the items of column I with those of column II.
Column I Column II
(a) Ammonotelism (i)Birds
(b) Bowman’s capsule (ii)Water reabsorption
(c) Micturition (iii)Bony fish
(d) Uricotelism (iv)Urinary bladder
(e) ADH (v)Renal tubule
Mention the substances that exit from the tubules in order to maintain a concentration gradient in the medullary interstitium.
Fill in the gaps.
(a) Ascending limb of Henle’s loop is________to water whereas the descending limb is________to it.
(b) Reabsorption of water from distal parts of the tubules is facilitated by hormone________
(c) Dialysis fluid contains all the constituents as in plasma except________
(d) A healthy adult human excretes (on an average)________gm of urea/day.
Indicate whether the following statements are true or false.
(a) Micturition is carried out by a reflex.
(b) ADH helps in water elimination, making the urine hypotonic.
(c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule.
(d) Henle’s loop plays an important role in concentrating the urine.
(e) Glucose is actively reabsorbed in the proximal convoluted tubule.
Sort the following into actively or passively transported substances during reabsorption of GFR. glucose, aminoacids, nitrogenous wastes, Na+, water
The glomerular filtrate in the loop of Henle gets concentrated in the descending limb and then gets diluted in the ascending limb. Explain.
How does tubular secretion help in maintaining ionic and acid-base balance in body fluids?
The following abbreviations are used in the context of excretory functions, what do they stand for?
(a) ANF (b) ADH
(c) GFR (d) DCT
Name the following.
(a) A chordate animal having flame cells as excretory structures.
(b) Cortical portions projecting between the medullary pyramids in the human kidney.
(c) A loop of capillary running parallel to the Henle’s loop.
Complete the following:
(a) Urinary excretion = Tubular reabsorption +Tubular secretion ________
(b) Dialysis fluid = Plasma ________
What is the procedure advised for the correction of extreme renal failure? Give a brief account of it.
Aquatic animals generally are ammonotelic in nature whereas terrestrial forms are not. Comment.
Draw a labelled diagram showing reabsorption and secretion of major substances at different partsof the nephron.