TAILIEUCHUNG - Lecture Biology (6e): Chapter 32 - Campbell, Reece
Chapter 32 - Introduction to animal evolution. 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 INTRODUCTION TO ANIMAL EVOLUTION Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A: What is an animal? 1. Structure, nutrition, and life history define animals 2. The animal kingdom probably evolved from a colonial, flagellated protist Animal life began in Precambrian seas with the evolution of multicellular forms that lived by eating other organisms. Early animals populated the seas, fresh waters, and eventually the land. Introduction Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings While there are exceptions to nearly every criterion for distinguishing an animal from other life forms, five criteria, when taken together, create a reasonable definition. (1) Animals are multicellular, heterotrophic eukaryotes. They must take in preformed organic molecules through ingestion, eating other organisms or organic material that is decomposing. 1. Structure, nutrition and life history define animals Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings (2) Animal cells lack cell walls that provide structural supports for plants and fungi. The multicellular bodies of animals are held together with the extracellular proteins, especially collagen. In addition, other structural proteins create several types of intercellular junctions, including tight junctions, desmosomes, and gap junctions, that hold tissues together. (3) Animals have two unique types of tissues: nervous tissue for impulse conduction and muscle tissue for movement. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings (4) Most animals reproduce sexually, with the diploid stage usually dominating the life cycle. In most species, a small flagellated sperm fertilizes a larger, nonmotile eggs. The zygote undergoes cleavage, a succession mitotic cell divisions, leading to the formation of a multicellular, hollow ball of cells called the blastula. Copyright © 2002 Pearson Education, Inc., publishing as .
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