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-k Nwokenkno STRUCTURAL ADAPTATIONS urpose of this lab is to observe certain structural adaptations that organisms have evolved in order to survive. exercise, read the introduction and observe the specimen(s) on display. Then answer the series of questior Eling the specimen or the comparison of several specimens. If possible, work with others in the lab to complet cercise. The Horseshoe Crab The horseshoe crab Limulus polyphems) lives along the Atlantic Ocean coast of North America in shallos water. The horseshoe crab is more closely related to spiders and other Arachnoids) than it is to other crab Crustaceans). Horseshoe crabs get around in one of two ways walking or swimming on their backs (upside Bown). They rest buried under the sand. They feed at night upon marine worms or snails. The mouth is locate at the base of their legs. They pick up their food with their picers and grind it with the spines located at the buse of their legs. The horseshoe crabs mate during summer along the beaches in large masses. The females are larger han the males. The female digs out a shallow nest in the sand and prepares to deposit her eggs while the males Elamber to mount her and fertilize her eggs. The adults then return to the ocean leaving the eggs strewn all over he beach. Many are caten by predators but those remaining hatch into a larval stage that then returns to the sea o grow and develop into new adults. This whole scenario has played out again and again over many millions of years. Fossils of the horseshoe crab have been discovered in layers of rocks that were layered down some 250 million years ago. These fossils indicate that the horseshoe crab has remained virtually unchanged in outward appearance for 250 million years. Answer the following questions 1 What kinds of adaptations does the horseshoe crab have for burrowing? 2. What to you suggest the purpose of the long, stif spin-like til may be? To help them turn over when they are upside down and to steer act like this a rudde to plow alon 3. Could it be assumed that there is no variation in the species? That is, do you believe that all horseshoe crabs are genetically identical? Why or why not? 4. Traits are coded for by genes. New traits arise from new genes. How do new genes originate within a species? s. Which environment is characterized by the greatest amount of variation in physical conditions the temperature, light, etc.) - land, ocean surface or ocean floor? Why?