Some plants lift their strong arms high into the air to intercept the sunbeams before they strike the earth, while others clothe the surface with a dress of varied green. In some plants, odor, nectar or juicy berries attract the animals whose aid is needed for fertilizing and scattering their seeds, while in others, noxious odors, prickles, thorns and acrid secretions warn away animals destructive to their welfare. The highest perfection of beauty, utility and productivenessamong plants has been reached by those of the land.
The animals of the land, surrounded by the air, which bears no food solutions to inert mouths, must be well endowed with the power of motion in order to procure their food. They must either crawl over theBIRD"S NEST.
A simple home.
surface or be provided with appendages to support their weight against gravity. There is no floating supinely in the air as in the water. Movement, exertion, search are the requisites of this realm. The eggs and young, as a rule, cannot be cast adrift to hatch and care for themselves; the nest, the burrow, the den must be provided. This is the realm of homes.
The land animals are also the most intelligent. Birds long ago solved the problem of flight for a body heavier than air, which is now being successfully solved by man afteryears of effort. Certain animals, like the bee, the ant and the squirrel, have the provident habit of storing up food in the summer against a day of need. Other animals, like the birds, have learned to migrate t o a w a r m e r c l i m e w h e nwinter comes. The beaver is probably the pioneer in hydraulic engineering. When he feels the need of a water reservoir, he builds a dam and makes it. Today manya swamp in the northern
states owes its origin to him.
A BEAVER DAM.
Notice the two beavers on top of the dam.
Wonderful indeed is the intelligence of many of the land animals, due in large part to their development amid varied geographical conditions.
117.Distribution of Animals. -An examination of a globe shows(1) that the land is massed around the north pole, (2) that the three continental masses to the south are separated from each other by wide seas, and (3) that while two of these are connected by narrow strips of land to northern continents, the third is entirely separated from all other land.
OSTRICHES.
The largest of all birds.
But slight changes in elevation would connect the northern continents with each other. As they are so closely related to each other, it might be expected that the animals of these continents w o u l d r e s e m b l e e a c h o t h e r , particularly in the more northern parts. This is true. Bears, wolves, foxes, elk, deer and sheep of nearly related species are founddistributed over the northern continents.
The animals of the southern continents are much less nearly related. The ostrich, giraffe, zebra and hippopotamus are among the characteristic animals of Africa whichare not found elsewhere. In South America the tapir, great ant eater, armadillo and llama are among the animals not represented elsewhere. Both of these continents, however,have animals closely related to those of other great divisions, showing thatOPOSSUM.
Many opossums have no pouch but carry their young on their backs.
their present isolation has not continued far back in geological time.
The animals of Australia differ greatly from those of the other continents. The quadrupeds here are marsupials, animals which usually carry their young in a pouch. The only members of the family existing at present elsewhere are the American opossums. The largest of the marsupials is the great kangaroo which measures between seven and eight feet from its nose to the tip of its tail. Although it has four feet, yet it runs by making extraordinary leaps with its strong hind feet. Here is also found one of the most singular of all living animals, the duckbill, the lowest of all quadrupeds, which in its characteristics resembles both quadrupeds and birds.
All this seems to show that the distribution and development of the animals of the different continents have been largely dependent upon the former geographical relations of the land masses. The native animals of a region are not necessarily the only ones suited to it; animals from other places may be even better adapted, but they haveA KANGAROO FEEDING.
Notice the peculiar position it is forced to take because of its short front legs.
been kept out by some natural barrier. This is particularly evident in the case of Australia, where the weak native animals would have been readily displaced by the stronger animals of Asia could these have reached that isolated continent.
118.Life as Affected by Climate. -Climate has had a great effectupon the distribution and development of life. But the life on the earth cannot be grouped into climatic belts, as certain animals and plants are able to endure a wide range of climatic conditions. Moisture, sunlight and temperature are the chief factors which determine the growth andTIMBER LINE ON A HIGH MOUNTAIN.
development of plants. If the temperature is too high or too low, they cannot exist. If sunlight or moisture is wanting, they cannot build their tissues.
In regions where the temperature is constantly below freezing, there can be no plant life. Where the temperature is above freezing for only a short time in the year, plant growth is slight and whatever plants there are must be small and stunted. Only where there is a long growingMESQUIT BEANS.
From this desert plant some Indian tribes made their bread.
AN OASIS IN THE MOJAVE DESERT.
period can large plants exist. That is why there is almost no plant and therefore almost no animal life on the upper parts of lofty mountains, while somewhat farther down the life is stunted, and still lower down life flourishes. Changes in latitude have the same effect.