4 NATURAL IIISTOHY 



buttercups, Jack-in-the-pulpit, bog arrow-grass, and a few shrubs 

 such as button-bush and willow. The vegetation shows a zonal 

 arrangement of, first, submerged or floating water plants, then emer- 

 gent forms, growing in the water and along the banks, while other 

 plants such as grasses and shrubs are found at a little distance from 

 the water. This zonal distribution is characteristic of shore associa- 

 tions of plants and animals. 



In the slow-flowing stream live two species of sunfish, two or three 

 species of pickerel, bass, three species of frogs, bullfrogs, green frogs, 

 and pickerel frogs with their tadpoles, also an occasional painted 

 turtle and water snake. Of birds, the redwing blackbirds are numer- 

 ous, with occasional kingfishers, and more rarely a great blue heron. 

 Although no mammals are in sight, a telltale mound of sticks shows 

 that muskrats live there. Of the smaller organisms, the nymphs and 

 larvae of the dragonfly and Mayfly are the most abundant. The 

 water swarms with two species of water bugs and diving beetles, while 

 beetle larvae and the larvae of mosquitoes are numerous. Many 

 crustaceans, tiny amphipods and isopods, may be seen swimming or 

 feeding on the aquatic plants. The snails, Physa and Lymnaea, are 

 very abundant, while a few aquatic worms, Tuhifex, may be found in 

 the mud. Colonies of bryozoans may also be found, incrusting the 

 stems of water plants, as well as an occasional mass of fresh-water 

 sponge. 



These two regions, the lake shore and the stream, although only a 

 few yards apart, present tremendous differences in populations. 

 Why these differences? At first sight, one might say it was due 

 entirely to abundance of food, but this is only begging the question. 

 Evidently many factors are at work. The fauna and flora of other 

 localities visited would show even greater changes. Across the 

 meadow and up into the nearby woods each locality would be found 

 to be inhabited by groups of living plants and animals differing in 

 many respects from those in neighboring localities. In each of these 

 localities there would be certain dominant organisms better fitted 

 than any others to live there. These become permanent species in 

 that locality. 



How to Study Ecology 



To understand much al)out ecology, one must be able to do much 

 more than simply study a book. The place to study the stage setting 

 is the stage. The place to learn about the relation of living things 



