BIO153H5 Chapter Notes - Chapter 32: Animal, Deuterostome, Blastocoel
Document Summary
Chapter 32 - an introduction to animal diversity. Lecture outline: biologists have identified 1. 3 million living species of animals, estimates of the total number of animal species run far higher, from 10 to 20 million to as many as 100 to 200 million. Animals take in preformed organic molecules through ingestion, eating other organisms or organic material that is decomposing: animal cells lack cell walls that provide structural support for plants and fungi. The multicellular bodies of animals are held together by extracellular structural proteins, especially collagen. Animals have other unique types of intercellular junctions, including tight junctions, desmosomes, and gap junctions, which hold tissues together. In most species, a small flagellated sperm fertilizes a larger, nonmotile egg. The zygote undergoes cleavage, a succession of mitotic cell divisions, leading to the formation of a multicellular, hollow ball of cells called the blastula.
