Question

Define the following terms
A. Triploblastic
B. Coelomate
C. Notochord
D. Bilateral Symmetry

Answer 1

These are the features of the morphology shown by different members of the animal kingdom. Platyhelminthes are triploblastic, Nematodes are coelomate , presence of notochord is shown by chordates , chordates and annelids are bilaterally symmetrical.

Complete answer:
A. Triploblastic – It is the condition of gastrula which shows the presence of tri germ layer (embryonic layers)-ectoderm, mesoderm and endoderm. The different tissues and organs of the organism differentiate out of these three layers. Molluscs, worms, arthropods are triploblastic.
B. Coelomate - The organisms that possess coelom are called coelomates. Coelom is a body cavity which is filled with fluid. This body cavity runs to the complete length of vertebrates and divides the body into inner tube and outer tube. Coelom helps in shock absorption. It allows the organisms to grow independently away from the body wall. Nematodes are coelomates.
C. Notochord - A cartilaginous flexible rod which supports the body in all stages of life is called a notochord. Notochord is found only in the phylum chordate and in some adult caudates. It is the major skeletal element in the developing embryos.
D. Bilateral symmetry – Bilateral symmetry in an organism that is exactly divided into right and left by a single line of symmetry as present in butterfly, earthworm. Bilateral symmetry provides directional movement to an organism due to which it can move forward.

Note: The above characteristics are the definite distinctive features of the organisms which helps them to adapt with their surroundings. Bilateral symmetry is prevalent in the animal kingdom and it has been evolved through evolution.