Chapter 32 introduction to animal diversity. After completing this chapter, students will be able to: List the characteristics that combine to define animals; summarize key events of the Paleozoic, Mesozoic, and Cenozoic eras; compare the developmental differences between protostomes and deuterostomes. | Chapter 32 An Introduction to Animal Diversity Overview: Welcome to Your Kingdom The animal kingdom Extends far beyond humans and other animals we may encounter Figure Concept : Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers Several characteristics of animals Sufficiently define the group Nutritional Mode Animals are heterotrophs That ingest their food Cell Structure and Specialization Animals are multicellular eukaryotes Their cells lack cell walls Their bodies are held together By structural proteins such as collagen Nervous tissue and muscle tissue Are unique to animals Reproduction and Development Most animals reproduce sexually With the diploid stage usually dominating the life cycle After a sperm fertilizes an egg The zygote undergoes cleavage, leading to the formation of a blastula The blastula undergoes gastrulation Resulting in the formation of embryonic tissue layers and a gastrula Zygote Cleavage Eight-cell stage Cleavage Blastula Cross section of blastula Blastocoel Blastocoel Gastrula Gastrulation Endoderm Ectoderm Blastopore Early embryonic development in animals Figure In most animals, cleavage results in the formation of a multicellular stage called a blastula. The blastula of many animals is a hollow ball of cells. 3 The endoderm of the archenteron de- velops into the tissue lining the animal’s digestive tract. 6 The blind pouch formed by gastru- lation, called the archenteron, opens to the outside via the blastopore. 5 Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic tissues: the ectoderm (outer layer) and the endoderm (inner layer). 4 Only one cleavage stage–the eight-cell embryo–is shown here. 2 The zygote of an animal undergoes a succession of mitotic cell divisions called cleavage. 1 All animals, and only animals Have Hox genes that . | Chapter 32 An Introduction to Animal Diversity Overview: Welcome to Your Kingdom The animal kingdom Extends far beyond humans and other animals we may encounter Figure Concept : Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers Several characteristics of animals Sufficiently define the group Nutritional Mode Animals are heterotrophs That ingest their food Cell Structure and Specialization Animals are multicellular eukaryotes Their cells lack cell walls Their bodies are held together By structural proteins such as collagen Nervous tissue and muscle tissue Are unique to animals Reproduction and Development Most animals reproduce sexually With the diploid stage usually dominating the life cycle After a sperm fertilizes an egg The zygote undergoes cleavage, leading to the formation of a blastula The blastula undergoes gastrulation Resulting in the formation of embryonic tissue layers and a gastrula Zygote Cleavage Eight-cell stage
