NEET BIOLOGY

Detailed explanation-1: -Cnidarians were the first animals to have muscles and nerves to produce behavior. They were also the first to have a mouth and stomach to digest food. We learn about nematocysts when we watch an anemone catching a goby and two anemones fighting. Cnidarians come in various body shapes and have different ways of living.

Detailed explanation-2: -To respond to stimuli, cnidarians use a rudimentary muscular system consisting of muscle cells lying in bands up and down the body wall and in a circle around the mouth cavity (Fig. 3.27). The body shortens when the vertical bands contract. If muscles on only one side contract, the body bends in that direction.

Detailed explanation-3: -The inside of a cnidarian is called the gastrovascular cavity, a large space that helps the organism digest and move nutrients around the body. The cnidarians also have nerve tissue organized into a net-like structure, known as a nerve-net, with connected nerve cells dispersed throughout the body.

Detailed explanation-4: -Cnidarians have nerve cells that are organized in a nerve net – a diffuse network where neurons interact wherever they cross one another. There are two contrasting types of body symmetry: radial and bilateral. Nerve nets are associated with the former and central nervous systems with the latter.