NEET BIOLOGY

Detailed explanation-1: -Key Points. Some animals have a body with no pattern or symmetry, making them asymmetrical. Animals (mostly aquatic) with an up-and-down orientation have a radial symmetry in which there is no definite right or left side, but any longitudinal plane cut produces equal halves.

Detailed explanation-2: -Only sponges (phylum Porifera) have asymmetrical body plans. Some animals start life with one type of body symmetry, but develop a different type as adults; for example, sea stars are classified as bilaterally symmetrical even though their adult forms are radially symmetrical.

Detailed explanation-3: -It is a type of symmetry where no radial plane that passes through the centre of the organisms can divide it into two equal halves. The symmetry is neither visible for the morphological features and nor anatomically. Asymmetrical symmetry is found in snails, flounders and hermit crabs.

Detailed explanation-4: -About Standards. Most active animals have a bilaterally symmetrical body plan. This means that if you draw a line down the middle of the body, both sides are mirror images of each other. With a head and stereo senses leading the way, this body plan is ideal for active hunters.

Detailed explanation-5: -Figure 15.4: Animals exhibit different types of body symmetry. The (a) sponge is asymmetrical and has no planes of symmetry, the (b) sea anemone has radial symmetry with multiple planes of symmetry, and the (c) goat has bilateral symmetry with one plane of symmetry.