42 



NATURAL HISTORY 



Zonal distribution of flora on a moun- 

 tain peak rising from a desert area. 

 How would you account for these differ- 

 ent life zones ? 



8200 feet there are forests of Douglas and balsam fir, with such mam- 

 mals as meadow mice, chipmunks, deer, lynx, and puma. Higher still 

 between 8200 and 9500 feet, is a typical Canadian vegetation, timber 



pine, Douglas and balsam fir, 

 and aspens, while the wood- 

 chuck, porcupine, rabbit, mar- 

 ten, fox, wolf, and other northern 

 forms are found. From 9500 to 

 11,500 feet we find a fauna and 

 flora almost like that of northern 

 Canada and called Hudsonian. 

 Stunted spruce and pine exist 

 up to the timber line with a 

 few typical mountain mammals 

 such as the marmot, and pika 

 or mountain hare. Above this 

 area lies the rocky Alpine zone, 

 snow-clad for half the year even 

 in this warm, sunny climate. 

 Lichens on the rocks and a few 

 stunted herbs are the only plant life visible, while a limited number 

 of insects and an occasional mammal from the Hudsonian zone are 

 the only signs of animal life. 



The facts that the chorologist has discovered concerning life zones 

 have been put to practical use by the Biological Survey of the United 

 States Department of Agriculture. A life zone map has been pre- 

 pared so that the settler going into a new region will know at once 

 the kind of plants and animals best adapted to live there. In addi- 

 tion, information is available about the character of the soil, the 

 rainfall, temperature range, and the particular cereals, fruits, and 

 vegetables that can be grown in the region. 



Life Realms 



Different parts of the world, each with its several life zones, have 

 been separated into life regions, or realms. If we plot the distribu- 

 tion of a given family of animals or plants, we often find that species 

 within the group have a wide distribution, in some instances covering 

 more than a single continent. Australia has long been set aside as 

 a distinct realm because its peculiar fauna and flora differ from those 

 in other parts of the earth and so is called the Australian Realm. 



