. Principles of modern biology. Biology. that an angler may need patience to make a single catch. A study of the fauna in a summer forest reveals a similar arrangement. Vast numbers of aphids and other small herbivorous ani- mals provide a broad food base for the carnivorous species of the region; and a fairly large population of spiders, beetles, and other medium-sized carnivorous animals are able to prosper on this base. But the number of insectivorous birds, such as warblers, will not be very great; and only two or three hawks (Fig. 30-2) or other predatory birds will be able to gain a livi
. Principles of modern biology. Biology. that an angler may need patience to make a single catch. A study of the fauna in a summer forest reveals a similar arrangement. Vast numbers of aphids and other small herbivorous ani- mals provide a broad food base for the carnivorous species of the region; and a fairly large population of spiders, beetles, and other medium-sized carnivorous animals are able to prosper on this base. But the number of insectivorous birds, such as warblers, will not be very great; and only two or three hawks (Fig. 30-2) or other predatory birds will be able to gain a living in a particular forest— even though the range of flight of such hunt- ing birds is Fig. 30-2. Red-shouldered hawk (Bu/eo lineatus) with a field mouse in its talons. (Courtesy of the American Museum of Natural History, New York.) In short, the smallest animals at the base of a food chain, owing to the modesty of their food needs and the efficiency of their reproductive processes, tend to populate a given habitat in great abundance, whereas Ecology and Evolution - 575 the largest animals, at the apex of the food chain, are much more restricted in numerical abundance—with the medium-sized species falling in between the two extremes. More- over, the height of the pyramid is limited, since the population of a dominant species tends to be so sparse that no other animal can gain a living by preying upon it. The Adaptation of Species to Species. During evolution, many species had a profound in- fluence upon the development of other spe- cies. In this regard, the insects provide many good examples. Insects have been abundant since early in the Cenozoic era, at which time the flowering plants began their evolu- tion. Consequently, natural selection had ample time to create a rich variety of modern flowers. Thus, many present-day flowers pos- sess both color and fragrance with which they attract insects seeking food and, inci- dentally, pollinating flowers. Likewise, th
Size: 1410px × 1772px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectbiology
