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Left Right Front and Back Symmetry in Biology

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Left, Right, Front and Back: Symmetry in Biology Standards:3.1.7C. Identify patterns as repeated processes or recurring elements in science and technology.- Identify different forms of patterns and use them to group and classify specific objects.- Identify repeating structure patterns. 3.1.10C. Apply patterns as repeated processes or recurring elements in science and technology.- Examine and describe recurring patterns that form the basis of biological classification, chemical periodicity, geological order and astronomical order.3.3.7A. Describe the similarities and differences that characterize diverse living things.- Describe how the structures of living things help them function in unique ways.- Account for adaptations among organisms that live in a particular environment.Introduction:Animals and plants come in a great variety of shapes - but not every shape. We don't see people with three arms, elephants with one leg, or dogs with two mouths. Such organisms are biologically possible, but they would be so inefficient (think of the one-legged elephant) that Mother Nature never evolved them. The morphology (i.e. shape) of an organism has to be tuned to the environment it lives in. That's where symmetry enters the picture. Symmetrical objects are said to have a balanced and regular arrangement ofparts. In biology, there are several kinds of symmetry. The kind of symmetry an organism has tells us a great deal about its life style and ecology.Vocabulary:Spherical symmetry - the symmetry of a bubble or tennis ball. Every plane extendingthrough the center cuts the object into two identical halves. Some tiny protist plankton in the oceans have spherical symmetry. Why? They are too small to swim, so water currents tumble them about. Since they cannot orient themselves, they simply show the same face to the environment in all directions. Radial symmetry – the symmetry of a cylinder. There is a top and bottom, but the sides are circular. Any cut through the center along the top-bottom axis divides the cylinderinto equal halves. Examples: some sponges, coral animals, jellyfish, and many plants. These organisms are sessile (can't move), sedentary (don't move much), or float helplessly in thewater. Since they can't move by themselves, they look the same all around their sides. They have a top and bottom (one of which has the mouth) but no left or right. 1Spherical symmetry Radial symmetry Five-fold radial symmetry(marine plankton) (sea anemone) (sea star)A variation on radial symmetry is the five-sided symmetry of sea stars, sea urchins, and theirRelatives.Bilateral symmetry – a single plane of symmetry extends from the anterior end (the head) to theposterior end (the tail), running through the midline of the body. The two sides of the organism are mirror halves. The great majority of animals have bilateral symmetry – worms, insects, vertebrates, people, you. Extra InfoFor an example of bilateral symmetry, just look at a classmate's face. In bilateralsymmetry, all the features in the midline of the face are single, and all the features off to the side are paired.Thus, we have one nose, mouth, and tongue in the midline of our faces. Our eyes, ears, and nostrils are present in identical pairs off to the sides. Our teeth are in paired sets on the sides of the jaw. Face of typical classmateMobile animals are nearly all bilaterally symmetrical. Movement – crawling, running,swimming, or flying – is most efficient when the animal has paired legs, fins, or wings on itssides. The nerves and muscles are easiest to coordinate in pairs. Bilateral symmetry andlocomotion go together. What direction should an animal move in? The end that moves first into a new environment is the head or anterior end. Bringing up the rear is the tail or posterior end. Since the anterior end is the "exploratory" end, that is where the sense organs are – the organs of touch, sight, hearing, smell, and taste. To control all that sensory machinery, the brain is also in the head (if its brain was in its tail, an animal would never figure out what was going on).Finally, an animal with a head and a tail will have a dorsal surface (the back) and a ventral surface (the belly). Bilateral symmetry is part of a package. The rest of the package is the 2anterior head with sensory structures and brain, a posterior tail, and both a dorsal and a ventral surface. Mosquito Ray CougarBilateral symmetryExtra infoSome animals and plants have no symmetry. Oysters, for example, have lumpy, irregular shells,although other bivalve clams are symmetrical. . Plant stems and leaves have a degree of radialSymmetry. Fir and spruce trees, including branches have a rough radial symmetry. The shells ofmost snails make a spiral pattern that has a definite shape, but no simple plane or axis of symmetry. The snail shell has no symmetry. A Christmas tree with radial symmetry. SHAPE \*MERGEFORMAT 3Symmetry in Biology WorksheetQuestions to answer:1. a. What kind of symmetry does this warm, fuzzy animal have?__________________ b. Draw the plane of symmetry through the animal. c. Label the following directions of orientation of the animal: anterior, posterior, sides (label both), dorsal, ventral.2. For each organism in the kit or picture (i) give the type of symmetry and (ii) give the style of locomotion. Choose from sessile, sedentary, floater, fast mover. a.SEA STAR: symmetry?_________________ locomotion?________________ b.SNAIL: symmetry?________________ locomotion?_________________ c.PINE TREE symmetry?________________locomotion?________________ d. FAKE LEAF symmetry?________________4e. SEA COOKIE symmetry?________________locomotion?________________ f. CORAL symmetry?________________locomotion?_________________ g. CLAM symmetry_________________locomotion?_________________ (consider both shells) h. FAKE symmetry________________ locomotion?_________________ PLANKTON i. MOSQUITO symmetry?________________locomotion?_________________ j. SCALLOP CLAM symmetry?_______________locmotion?________________ (just one shell shown)


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