Book Description

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 edition. Excerpt: ... animal environment is a combination of moisture, temperature, light, pressure, materials for abode and food, all of which factors taken together constitute a complex of interdependences. These various factors are so dependent upon one another that any change in one usually affects several others. This property of environmental complexes is what makes ecology one of the most complex of sciences, and experimentation in which the environment is kept normal except for one factor, an ideal rarely realized in practice, even under the best conditions. The efforts of ecologists, geographers, and climatologists have long been directed toward the finding of a method of measuring the environment which shall include a number of the most important environmental factors. De Candolle undertook to base the efficiency of a climate, for supporting plants, upon the mean daily temperatures above 6 C, this temperature being taken as the starting-point of plant activity. Merriam has followed this lead and calculated total temperatures for many places in North America and made maps and zones based upon such totals. This system, however, has been rejected by botanists and plant ecologists on account of much evidence, both experimental and observational, which is quite out of accord with this view. The scheme has not been generally accepted by zoologists outside of the United States Biological Survey. There is practically no evidence of an experimental sort for the application of such a scheme to animals. Relative humidity has been suggested as an important index (128) but does not properly express the influence of atmospheric humidity upon the animal body (125, p. 53). The saturation deficit has also been suggested but does not take temperature into account. I..