(a)(i) What is excretion?
(ii) List the excretory organs in humans and name one waste product excreted by each organ
(B) Name the excretory organs in:
(i) insects
(ii) earthworms.
Explanation
(a)(i) Excretion: The elimination of waste products; of metabolism; from the body of an organism.
(ii) Excretory organs in Humans with their waste products.
Excretory Organs in humans Waste Products
Kidney - Nitrogenous wastes/urea/water/salts/urine
Skin - Urea/SaltsNVater/Sweat
Liver - Bile/excess cholesterol
Lungs - CO2/water vapour.
(b) Functioning of kidney as excretory: Blood from the renal artery enters the bowman's capsule; through the afferent arteriole; ultra filtration occurs in the Bowman's capsule; high pressure in the glomerulus causes the filtration of small molecules/amino acids/ glucose/ minerals salts/ water/ urea; out of the blood plasma into the cavity of the capsule; the filtrate/glomerular filtrate passes through the nephron; where selective reabsorption of useful metabolites/glucose/amino acids take place; in the descending/first proximal convoluted/coiled tubule; the reabsorption of salts and water is regulated in the loop of Henle; and the ascending/second/distal convoluted tubule/large waste molecules like creatine secreted at loop of Henle; depending on blood concentration; the filtrate continues into the main collecting duct/tube; where further reabsorption of water and salt takes place; the remaining fluid in the duct becomes urine.
(c) Excretory organs in;
(i) Insects → Malpighian tubules
(ii) Earthworm →Nephridia/Nephridium