Help: 6. Describe the range of variation in the nervous systems of invertebrates.

7. Distinguish among asymmetry, radial symmetry, and bilateral symmetry.

6. Although most invertebrates have a nervous system, the complexity of the system varies from one organism to another.

Some invertebrates such as the hydra and starfish have a simplified system of nerves, which is called a nerve net. It consists of just nerves, capable of sense and touch only. Meanwhile, other invertebrates such as the planarian have a more developed nervous system, complete with a brain and nerve cord.

7. Radial symmetry and bilateral symmetry are two different types of biological symmetries found in organisms. ... The key difference between radial and bilateral symmetry is that radial symmetry generates identical body halves around the central axis whereas bilateral symmetry generates only two sides as left and right.

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the circumference of the solar disc is 4375246 km, nearly.

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