. Biology and man. Biology; Human beings. Seal Walrus TEETH OF FLESH-EATERS The large canine, or "dog", teeth act as weapons in fighting or grasping. The short incisors cut tough tissues, and the heavy molars break and crush bones Takers and Sharers Nearly every species of plant and animal acts as an unwilling "host" to one or more life forms that live at its expense. Com- mon examples of parasites, as such uninvited guests are called, are the leech, the sheep tick, the liver-fluke and the bedbug. Many diseases result from the destructive action of parasites, such as the ma
. Biology and man. Biology; Human beings. Seal Walrus TEETH OF FLESH-EATERS The large canine, or "dog", teeth act as weapons in fighting or grasping. The short incisors cut tough tissues, and the heavy molars break and crush bones Takers and Sharers Nearly every species of plant and animal acts as an unwilling "host" to one or more life forms that live at its expense. Com- mon examples of parasites, as such uninvited guests are called, are the leech, the sheep tick, the liver-fluke and the bedbug. Many diseases result from the destructive action of parasites, such as the malaria plasmodium, the Treponema pallidum, or syphilis parasite, the hookworm, and the bacteria of many common diseases. An interesting partnership between two species is seen in the symbiosis or "living together", of a species of termite and certain protozoa that live within its digestive tract (see illustration, p. 179). The termite lives in dead wood, in the forest or in buildings, mining through it by chewing the wood into small bits, which it swallows. Within the digestive tract live the pro- tozoa which produce enzymes that change the cellulose into soluble sugars. Periodic Feast and Famine All animals convert some of their surplus food into fat. This is stored within the body and is used in times of emer- gency or of food shortage. Some species, the bear and the woodchuck, for example, feed and fatten during the summer months and spend the cold months in a deep sleep, called hibernation, or "wintering". At this time they live on the food stored during the summer feasting. Another illustration of getting food while the getting is good is seen in the distinct stages characteristic of many species of insects (see illustration, 177. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gruenb
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Keywords: ., book, bookcentury1900, booksubjectbiology, booksubjecthumanbeings
