Chapter 33, Problem 6TY

Summary Introduction

Introduction: Biologists traditionally classified animal diversity in terms of developmental and morphological features of animal body plans. The main features included body symmetry, number of germ layers and specific characteristics during embryonic development. The embryo becomes a multicellular embryo by a process called cleavage during the early stage of embryonic development. Rapid cell divisions produce a hollow sphere of cells called a blastula. The growing embryo then develops different layers of cells called germ layers.