Question

12. How is radial symmetry an advantage to sessile or planktonic animals? 13. The embryo becomes layered during gastrulation, and these germ layers form the various tissues and organs of the body. The names of the germ layers describe where they are found in the early embryo: 14. Each germ layer forms specific tissue types. For example, where is the ectoderm, and what does it give rise to? 15. What are three functions of the body cavity? 16. What is the difference between a protostome and a deuterostome? 17. What is the difference between determinant and indeterminate cleavage? 18. You will notice that most animals have spiral and cleavage or radial and cleavage 19. What are six categories of data used in constructing the phylogenetic tree showing the diversification of Animals? 20. Use the phylogenetic trees to answer these questions. Which phylum or phyla... a. form the clade of animals? b. forms the basal taxon for animals? c. includes animals with a backbone? d. forms the clade Deuterostomia? e. is the sister group of Bilateria? f. are your closest relatives?

Answer 1

15. Body cavity

The human body, like that of many other multicellular organisms, is divided into a number of body cavities. A body cavity is a fluid-filled space inside the body that holds and protects internal organs. Human body cavities are separated by membranes and other structures. The two largest human body cavities are the ventral cavity and dorsal cavity. These two body cavities are subdivided into smaller body cavities. Both the dorsal and ventral cavities and their subdivisions

Functions of body cavity

1.They provide space for devlopment

2. Expansion of organs

3. Movement of organs

16. Proterostom vs dueterostom

Proterostomic (First mouth)

1st Development of mouth from the balastopore during embryonic stages

Ex. Arthropoda,Annelida..etc

Dueterostorm

1st Development of _Anus from the blastopore

Ex. Human beings

PROTOSTOMES (mollusks, annelids, arthropods) Eight-cell stage DEUTEROSTOMES (echinoderms, chordates) Eight-cell stage (a) CLEAVAGE Spiral and determinate Radial and indeterminate Coelom (b) COELOM FORMATION Archenteron Coelom Mesoderm Blastopore Blastopore Mesoderm Schizocoelous: solid Enterocoelous: masses of mesoderm folds of archenteron split to form coelom form coelom Anus Mouth (c) FATE OF BLASTOPORE 0 Digestive tube Mouth Mouth develops from blastopore Anus Anus develops from blastopore 1999 Addison Wesley Longman, Inc.