1. multicellular
2. consumers of organic compounds (heterotrophic)
3. monophyletic
1. all derived from common ancestor
1. sponge-like
2. variations on the theme of a tube
1. in most groups, the tube has a liquid-filled center
2. hydrostatic skeleton
3. concentric layers of tissue
1. endoderm
2. mesoderm
3. ectoderm
4. bilateral or radial symmetry
1. most successful groups are bilateral
4. phylogenetic relationships (fig. 30.6)
1. phylogeny from morphology and DNA sequences in general agreement
2. groupings (taxonomy):
1. diploblastic
1. jelly fish, cnidaria, sea anemones
2. acoelomate
1. triploblastic
2. no coelom
3. flat worms, round worms
3. pseudocoelomate
1. coelom bordered by endoderm and mesoderm
2. roundworms (nematodes)
4. coelomate
1. coelom bordered by mesoderm
2. two groups of coelomate organisms
3. these are sister groups
5. protostomate organisms
1. early cleavage is spiral
2. gastrulation pore becomes mouth
3. coelom develops as splitting block of mesoderm tissue
4. arthropods, annelids, molluscs
6. deuterostomate organisms
1. early cleavage is radial
2. gastrulation pore becomes anus
3. coelom develops as outpocketing of mesoderm from endoderm
4. echinoderms, vertebrates
5. Organization
1. cells
2. tissues: a group of cells with the same structure and function
3. organs: a structure consisting of several tissue types, with a specialized function
4. organ system: tissues and organs that are functionally inter-related

1.  If a biologist found an organism at the beach, what simple test could she do to determine if it was multicellular sponge or a colony of unicellular protists?

2.  We have discussed the protists and the animals.  Why do biologists say that protists are not monophyletic but that animals are?

3.  There are two other forms of skeletons in addition to the hydrostatic skeleton:  exoskeletons found in arthropods like insects, and endoskeletons found in vertebrates.  Why would the hydrostatic skeleton be less effective than these other two?

4.  Evolutionary success is generally measured by current species diversity (i.e., the more different kinds of species that are found in a group, the more successful it is deemed to be).  By this definition, organisms with bilateral symmetry are far more successful than those with radial symmetry.  Why do you think this is true?

5.  The echinoderms (starfish, sea urchins, and their relatives) are radially symmetrical.  Their distant ancestors were bilaterally symmetrical, and their immediate ancestors (the crinoids) were sessile (attached to the substrate).  What advantage to a sessile life style might result from radial symmetry? (i.e., why would a radially-symmetrical echinoderm eat more and leave more offspring than a bilaterally symmetrical one?)

6.  What are the three developmental differences between protostomate and deuterostomate animals?  Which is evolutionarily more advanced, and what basis do you have for your answer?

7.  What is the difference between pseudocoelomate and coelomate anatomy?  What advantages might exist for animals with coelomate anatomy compared to pseudocoelomate anatomy?  Why do you think the psuedocoelom considered to be ancestral to the "true" coelom?

8.  Why are the vertebrates usually drawn into the phylogeny of animals at the far right-hand branch, and does this reflect a position in the "ancestral / derived" continuum?

9.  Provide examples for acoelomate, psuedocoelomate, deuterostomate and protostomate animals.

10.  Scaling influences maintenance of internal body temperature.  Monitor lizards and anolis lizards are both reptiles, close to opposite ends of the size range in extant lizards.  They are both "cold" blooded.  Speculate on the amount of monitoring and rapidity of response required by each.

11.  Which of the following are not examples of feedback in a biological system?

1. you feel warm, so you take off your sweater
2. when a plant's cells start to become flacid, the pores in the leaves (stomata) close to prevent further water loss
3. following meoisis, the daughter cells have half as many chromasomes as the parent cell
4. spiders that capture few or no prey will build a larger web the next day
5. geese need water in order to swallow their food

Answers