Image from page 78 of "The American Museum of Natural History : an introduction" (1972)
Title: The American Museum of Natural History : an introduction
Authors: American Museum of Natural History
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: IMLS / LSTA / METRO
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Model of a common octopus, an example of a cephalopod mol- lusk that has lost its shell through evolutionary development.
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Modification of behavior is illustrated in the exhibit of how a flea circus operates. By using a conditioning technique, the trainer obtains fleas that respond to light by remaining quiet. By altering the lighting, he manages the selected fleas so that they appear to do "tricks." Invertebrates show group behavior patterns, from quasi-social groups, such as associations of protozoans responding to chemicals from bacteria, to true social groups with complex social specialization and organization, such as some wasps, social bees, and ants. Some invertebrates show cyclic, or rhythmic, behavior. Plankton migrate in response to daily changes in the intensity of light; mussels feed rhythmically in response to tidal changes; bees go to buckwheat blossoms when they are open in the morning, but go to clover in the afternoon when the preferred buckwheat blossoms close. An animal does not exist apart from its environment, and many diverse forms of invertebrates have evolved in keeping with their environments. For example, some are gigantic in comparison with their close relatives. The giant squid shown in the hall is an example. Animals adjust to their environments in many ways. They receive stimuli from the environment and, in response, may find food, avoid predators, maintain body processes, and find a mate. Heat energy from the sun raises their body temperatures and thus speeds up their body processes; for example, crickets chirp faster at higher temperatures. But, in order to survive, a living animal must have more than light and heat. It must also have food, oxygen, and salts; it must obtain water and excrete wastes. Invertebrates first evolved within the sea. As they encroached upon the land, they adapted to withstand the assaults of this hostile environment. Some found themselves already well equipped to invade a variety of freshwater and terrestrial environments. They became inhabitants of ponds, streams, and fields, and they moved into dark caves. They now live in very varied environments, 77
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