Growth

Abstract

Growth begins with fertilization of the ovum, although initial growth is rather slow in some vertebrates. Embryonic growth and postnatal development are discussed in detail in numerous textbooks, and these topics generally lie beyond the realm of vertebrate natural history. There are included in this chapter, however, distinctive adaptive patterns that characterize reproductive specializations of vertebrates. In egg-laying ectotherms, growth reflects the light, oxygen and temperature to which the eggs are exposed, and growth rates are very responsive to these factors. Viviparous ectotherms, of which there are many, have developed a variety of behavioral and physiologic procedures that tend to remove growth and growth rates from total dependency on the environment. Viviparity in fishes, amphibians and reptiles constitutes an adaptation for several situations.