Book Description

Excerpt from Genetic Studies of Rabbits and Rats But in a majority of cases variation due to genetic causes occurs in association with that due to non-genetic or environmental causes; in fact, it is possible to distinguish between the two only by the results of systematic selection. When the environment is kept constant and a race does not change in response to selection, we assume that no genetic variation is present. But if the race does change in response to selection, we have no alternative but to assume that the variation is genetic in character. Body-size in birds and mammals shows well the simultaneous yet distinct action of genetic and non-genetic agencies. The amount and quality of the food supplied to an animal limits its size, yet if food is supplied in abun dance and of proper quality, some races of animals attain greater size than others. This is the result of genetic differences. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.