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Differentiate between:
a. Open and closed circulatory system
b. Oviparity and viviparity
c. Direct and indirect development
d. Acoelomate and pseudocoelomate
e. Notochord and nerve cord
f. Polyp and medusa

Answers (1)

a) In the open circulatory system, blood is pumped out the heart, and the cells and tissues are directly bathed whereas, in the closed circulatory system, the blood
circulates throughout the body with assistance of a series of vessels.

b) Oviparous refers to Laying of fertilised and unfertilised eggs whereas viviparous refer to giving birth to young ones. Reptiles, birds, and some mammals fall into oviparous
whereas Scolidon and most mammals fall into the category of viviparous.

c) Direct development refers to a form when a larval stage is absent in the development of the organism. In simple words, when the young ones resemble the adult, it is direct
development. For example- mammals, reptiles, etc.
Indirect development refers to when the larval stage is present in the development of the organism which does not resemble the adult. In other words, when the young ones
are different than the adults, this is indirect development. For example- frog, cockroach, silkworm.

d) Coelomates are the animal possessing no coelom whereas Pseudocoelomates are the animals with the body cavity, which is lined by mesoderm rather than mesoderm, is
present in between ectoderm and endoderm.

e) The nerve cord is a strand comprising of solid nervous tissue while the notochord is a rod-like structure which is mesodermally derived and is formed on the dorsal side during embryonic development.

f) Polyp is a cylindrical and sessile form like Hydra while the Medusa is an free-swimming umbrella-shaped like jellyfish.

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