490 THE CHANGING WORLD 



as in the formation of spores and seeds of plants, make up a world 

 of adaptations in themselves that, since they have to do with the 

 maintenance of species, may be considered as genetic in character. 



Another genetic adaptation, that is so universal as to be properly 

 regarded as a law of nature, is shown in those animals and plants 

 whose reproductive products are particularly exposed to great perils, 

 and which in consequence produce a correspondingly larger number 

 of eggs or seeds than do those whose offspring are better safeguarded. 

 Nest-building in all its diverse forms, as well as the multitudinous 

 devices employed by plants to secure pollination and the dispersal 

 of seeds are further examples of genetic adaptation. 



Ecological Adaptations 



Any group of varying organisms, adjusted more or less imperfectly 

 to a certain habitat, tends in the course of time to branch out and 

 to occupy different neighboring habitats. Adaptation to new habi- 

 tats is ecological adaptation. This type of adaptation has been 

 somewhat amplified in unit II, on the "Biological Conquest of the 

 World," and innumerable examples of conditions met in the great 

 primary habitats of water, land, and air will come to the mind of 

 every observing reader. If animals could talk and had intelligence 

 enough to know what to say, think what tales they could rehearse 

 of the troubles they have known and the satisfactions they have 

 experienced in becoming adapted to their particular niches in nature ! 

 Imagine, for instance, a Thousand and One Nights spent in listening 

 to such representative spokesmen as the hermit crab, the nocturnal 

 earthworm, the carrion beetle, the golden plover, the sperm whale, 

 the liver fluke, the snake in the grass, and the bullfrog on the bank. 

 Even the plant world could be profitably admitted to take part in 

 such a symposium. For example, what might the northern pine 

 and the southern palm, the roadside weed and the head of rice, to 

 say nothing of the bacteria of " Typhoid Mary," have to tell us of 

 ecological adaptation ! 



Physical Adaptations 



Certain factors in the make-up of the physical environment, such 

 as temperature, pressure, and light, set limits within which organ- 

 isms must adapt themselves in order to live. The range of livable 

 possibilities imposed by these physical factors varies greatly with the 

 organism. Professor Brues of Harvard reports that there are algae 



