What is symmetry? Most animals have bodies that show symmetry. This means that the body can be cut into two halves that have a matching shape. This slide has symmetry. It has been cut into two halves that have matching shapes.
1. Asymmetrical amoeba • An asymmetrical animal has no definite shape. • Therefore, it can not be cut into matching halves. sponge
2. Radial Symmetry • An animal with radial symmetry has body parts that radiate from a center point. • These animals meet their environment equally from all sides. • They move quite slowly. • If they are sessile, their food must float by or they must create water currents. Spiny brittle star Sea anemone
3. Bilateral Symmetry dorsal • Concentration of nerves and sense organs at the anterior end. • Food capturing structures are usually close to the head. • Digestive, excretory and reproductive structures are found closer to the posterior end. • A streamline body allows for faster movement. posterior • This is a shape that is two-sided and produces a mirror image effect. • Right & left side • Anterior end = head • Posterior end = tail • dorsal surface = back • ventral surface = front anterior left right ventral
Which type of symmetry provides animals with the greatest chance for survival? WHY?