Asymmetry and Symmetry

Asymmetry and Symmetry - animals (such as humans, Figure 3)...

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Asymmetry and Symmetry Asymmetrical animals (sponges, shown in Figure 4) have no general body plan or axis of symmetry that divides the body into mirror-image halves. Within the animal kingdom this appears to be a primitive condition. More advanced animals have symmetry. Radially symmetrical animals (such as coral and jelly fish, Figure 4) have body parts organized about a central axis, like the spokes in a bicycle wheel, with multiple planes of symmetry. Radially symmetrical animals are often, for some part of their life, nonmotile (termed in animals as sessile), and live attached to a substrate. Radial symmetry allows animals, such as jellyfish, corals, and sea anemones, to reach out in all directions from one central point. Bilaterally symmetrical
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Unformatted text preview: animals (such as humans, Figure 3) have only a single plane of symmetry that produces mirror halves. Bilaterally symmetrical animals tend to be active and to move forward at an anterior end, which eventually led to concentration of sensory organs in the anterior end, or head (a trend known as cephalization). Body Cavity and Development Acoelomate animals (like flatworms and flukes, shown in Figure 4) do not have a coelom (or body cavity) produced during preadult development. Pseudocoelomate animals (such as roundworms) have a body cavity but it does not develop from splitting of the mesoderm embryonic tissue layer. Coelomate animals (humans, fish, shrimp, such as shown in Figure 4) have a body cavity lined with mesoderm cells....
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Asymmetry and Symmetry - animals (such as humans, Figure 3)...

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