Which of the following are correct? (i) Sponges : Cellular level of organisation (ii) Cnidaria : Tissue level of organisation (iii) Platyhelminthes : Organ level of organisation (iv) Annelids, Arthropods, Molluscs, Echinoderms and Chordates : Organ system level of organisation.
A
(i) and (ii) only
B
(ii) and (iv) only
C
(ii) and (iii) only
D
(i), (ii), (iii) and (iv)
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Correct option is D)
Animals show four different grades of organization: (i) Protoplasmic grade found in protozoans. (ii)
Cellular grade is the characteristic of sponges and mesozoans because
in a sponge, cells exhibit division of labour for performing specialized
functions. (iii) Tissue grade is of two types : Cell-tissue grade is
seen in coelenterates as there are cells not only specialised for
different functions but also certain similar cells gather together to
form tissue as well. Tissue - organ grade appears in flatworms
(Platyhelminthes) with arrangement of tissues to form organs. (iv) In
organ system level of organisation, organs are joined in a system to
perform basic functions. It is found in higher invertebrates and all
vertebrates.
