Name: Class Mammalia and Its Characteristics
Uploaded: 2019-07-19
Duration: 4 min 10 s
Description: "Endoskeleton is common among all my creatures; mammary glands are one of my key features! Who am I?" Watch and find out for yourself! Are you ready?

Question

Observe and identify body symmetry of given animals:

Accepted Answer

Symmetry is the body arrangement in which parts that lie on the opposite side of an axis are identical. The simplest body plan is seen in sponges. They do not display symmetry and are asymmetrical. Such animals lack a definite body plan or are irregular shaped and any plane passing through the centre of their body does not divide them into two equal halves. The first image given below depicts the picture of a sponge with asymmetric body.

The second image is showing that the body can be divided into similar halves by more than two planes passing through one main axis. When any plane passing through the central axis of the body divides an organism into two identical parts, it is called radial symmetry. They have a body plan in which the body parts are organised in a circle around an axis. It is the principal symmetry in diploblastic animals. Cnidarians such as sea anemone, and corals are radially symmetrical.

Animals which have two similar halves on either side of the central plane show bilateral symmetry. It is an advantageous type of symmetry in triploblastic animals, which helps in seeking food, locating mates and escaping from predators more efficiently. Animals that have dorsal and ventral sides, anterior and posterior ends, right and left sides are bilaterally symmetrical and exhibit cephalisation, in which the sensory and brain structures are concentrated at the anterior end of the animal. This type of symmetry is exhibited by annelids, arthropods, chordates etc.

Observe and identify body symmetry of given animals:

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