Excretion is the elimination of waste products from the body of an
organism. Waste products are unwanted and toxic by-product which are
removed to maintain homeostalis and protect the body from their toxicity.
Defaecation is eliminated of undigested food residue from alimentary
canal while secretion is discharge of specially syntheised product.
Example, hormone by endocrine gland, saliva from salivary glands.
Osmoregulation is the regulation of water content and salt concentration
in the body of an organism.
Homostasis is maintenance of a constant favourable internal environment
despite fluctuations in water content, solute concentrations formation of
toxic waste metabolites.
It is solute concentration expressed as molarity or moles of solute per litre
of solution. Unit of measurement is milliosmole ( 1000 of osmole which is
amount of solute forming one mole of active particles), osmolarity of fresh
water is less than 50 mosm/lt, fresh water vertebrates 200-300 mosm/lit,
human blood 300 mosm/lt. While sea water has an osmolarity of about
Two solutions of same osmolarity are isotonic, one with higher osmolarity
or concentration is hypertonic, while the one with lower concentration or
dilute solution is known as hypotonic.
Excretory Products and their Elimination topic less important, Easy Weightage is 1.48%
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