Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm are called diploblastic animals (e.g., coelentrates). While those animals in which the developing embryo has a third germinal layer, i.e., mesoderm lying between the ectoderm and endoderm are called triploblastic animals. (e.g., chordates).

(a) Roundworm - Ascaris

(b) Fish possessing poison sting - Trygon

(c) A limbless reptile/amphibian - Ichthyophis

(d) An oviparous mammal - Duck billed platypus.

(a) Haemocoel is the blood-filled cavity in arthropods containing haemolymph.

(b) Medusa is a form in cnidarians in which the body is shaped like an umbrella which can float freely in sed water

(c) Nematocytes are capsules of specialised cells in cnidarians which act as a paralysing sting.

(d) Parapodia are the paired unjointed lateral outgrowth in annelids bearing chaetae.

A. $\rightarrow$ (iii) B. $\rightarrow$ (i) C. $\rightarrow$ (iv) D. $\rightarrow$ (ii)

(a) Octopus Tentacles are the appendages in invertebrates that are used for grasping food and for locomotion.

(c) Catta Fins Fins are means of locomotion and are used to generate optimum thrust thus controlling the subsequent motion.

(d) Ctenoplana Comb plates are locomotory organs formed by strong cilia with fused bases.

Differentiation between these are as below

(a)	Open Circulatory System	Closed Circulatory System
	In this type of circulation, blood flows in spaces called sinuses and the cells and tissues are directly bathed in it. e.g., arthropods (grasshopper, cockroach), gastropods (snail).	In this type of circulation, blood is circulated via a series of vessels (arteries, veins and capillaries). e.g., annelids (earthworm) and vertebrates (birds, primates etc).
(b)	Oviparous characteristics Animals	Viviparous Characteristic Animals
	Oviparity is expulsion of undeveloped eggs rather than live young ones Animals that lay eggs. are called oviparous. e.g., fishes, reptiles, amphibians, birds, in sects and monotremes (mammals that lay eggs).	Viviparity is retention and growth of fertilised egg within the material body until the young one is capable of independent existence. Animals which give birth to their young ones and are called viviparous animals. e.g., mammals.
(c)	Direct Development	Indirect Development
	Direct development is the type of development in which there is no larval/nymphal or other intermediate stages in life, cycle between the egg (or birth) and the adult (e.g., mammals)	Indirect development is mostly observed in lower animals. The adult individuals lay eggs, which develop passing into the adult after passing through few to several larval nymphal stages. (e.g., echinoderms, arthropods)