Chapter 32 Reading Quiz

2. Chapter 32 Reading Quiz • From which kingdom did animals most likely evolve? • What is the only group of animals that do not possess “true tissues”? • A sea anemone exhibits which type of symmetry? • The evolutionary trend toward concentrating sensory equipment at the anterior end is called… • The blastopore will either become the mouth or the ____ of the animal.

4. 1. List characteristics that distinguish animals from organisms in the other four kingdoms. • Multicellular eukaryotes • Heterotrophy by ingestion • Carbohydrate reserves as glycogen • No cell walls • Highly differentiated body cells  tissues  organs  organ systems • Nervous and muscle tissue is unique 

6. 2. Distinguish between radial and bilateral symmetry. • Radial  have a top and bottom but no “sides” – can be divided along any plane for roughly equal halves • Bilateral  have dorsal, ventral, anterior and posterior body surfaces  exhibit “cephalization” – an evolutionary trend towards concentration of sensory structures towards the anterior end 

8. 3. Page 591  Outline the major phylogenetic branches of the animal kingdom, which are based upon grade of organization; symmetry and embryonic germ layers; absence or presence of a body cavity; and protostome-deuterostome dichotomy. • Symmetry  none, radial, bilateral • Germ layers  ectoderm, mesoderm, endoderm • Body cavity  acoelomate, pseudocoelomate, coelomate • Coelomates divided into two lines: 1. The protostomes: mollusks, annelids, arthropods 2. The deuterostomes: echinoderms & chordates  This division is based on cell cleavage, coelom formation, and the blastopore fate (comparisons on a later slide) 

9. 4. Distinguish among acoelomate, psuedocoelomate and coelomate. • Acoelomate  an animal body plan characterized by no body cavity between the digestive tract and outer body wall • Pseudocoelomate  a fluid filled body cavity that separates the digestive tract and outer body wall • Coelomate  fluid-filled body cavity completely lined with tissue derived from mesoderm and separates the digestive from the outer body wall 

12. 5. Distinguish between spiral and radial cleavage; determinant and indeterminate cleavage; schizocoelous and enterocoelous. • Spiral cleavage  cleavage in which the planes of cell division are diagonal to the vertical axis of the embryo • Radial cleavage  cleavage during which the cleavage planes are either parallel or perpendicular to the vertical axis of the embryo continued…

15. #5 continued… • Determinate  the developmental fate of each embryonic cell is established very early  if a cell is isolated from the 4-cell stage the embryo will not fully develop • Indeterminate  early embryonic cells retain capacity to develop into a complete embryo if isolated from other cells: this type of cleavage in the human zygote results in identical twins 

17. #5 continued… • Schizocoelous  descriptive term for coelom development during which, as the archenteron forms, the coelom begins as splits within the solid mesodermal mass; this is found in protostomes • Enterocoelous  coelom development during which the mesoderm arises as lateral outpocketings of the archenteron with hollows that become coelomic cavities; formation found in deuterostomes 

18. Protostomes Spiral cleavage Determinate cleavage Schizocoelous coelom formation Blastopore forms the mouth Deuterostomes Radial cleavage Indeterminate cleavage Enterocoelous coelom formation Blastopore forms the anus  6. Compare developmental differences between protostomes and deuterostomes including:plane of cleavage, determination, coelom formation, fate of the blastopore

20. 7. Describe the hypothesis about animal origins from unicellular ancestors. • The animal kingdom probably originated from colonial protists related to choanoflagellates • Colonial protist  an aggregate of identical cells - can be the beginning of specialization and division of labor among a group of cells 

22. 8. Explain why it is difficult to resolve what the first animals looked like. • Animals diversified so rapidly that it is difficult from the fossil record to sort out the sequence of branching in animal phylogeny 

24. 9. Describe two views about discontinuities between Ediacaran and Cambrian fauna. • Ediacaran fossils  appear to represent cnidarians, but soft-bodied mollusks and worms were also present • Cambrian  the ancient animals of the Ediacaran appeared to die out early - debate still exists on the phylogenetic conditions between the animals on the Cambrian boundary 

25. Ediacaran Cambrian