Pre-Lab 7: Introduction to Metazoa (Score:
Question 1. Study the phylogeny of animals in figure 7.3. Where are humans on this phylogeny? What are the defining features of the phylum to which humans belong?
Humans are on the chordata. The defining features are notochord, dorsal hollow nerve chord, and post-anal tail.
Question 2. Study the phylogeny of animals in figure 7.3. What feature of the phylogeny supports the fact that deep relationships among animals remain unresolved?
Polytomy:shows uncertainty w/lineage relationships
Question 3. Provide one additional example each of animals with radial, pentaradial, and bilateral symmetry.
An animal with radial symmetry is a jellyfish. An animal with pentaradial symmetry is a sand dollar. An animal with bilateral symmetry is a spider.
Question 4. Provide one additional example of a filter feeder OR a deposit feeder.
A clam is a filter feeder.
Question 5. Which of these terms apply to human digestive systems: intracellular digestion, extracellular digestion, blind gut, complete gut, one-way gut, two-way gut, processing guts, gizzards?
Complete gut, one-way gut, extracellular digestion
Question 6. Radial and spiral cleavage can be distinguished at the eight-cell stage. Examine figure 7.9 and describe the difference in relative cell positions that distinguishes the two
cleavage patterns.
Radical has the cells perfectly stacked on top of each other, while spiral has the cells stacked on top but in between the cells below.
Question 7. Human monozygotic (identical) twins are produced when a developing embryo splits in half in the early stages of cleavage. What kind of cleavage do humans (and other vertebrates) have?
Regulative Cleavage
Question 8. Molluscs, such as clams, have mosaic cleavage. Is it possible for molluscs, or any other animal with mosaic cleavage, to have monozygotic twins?
No because they are given their fate early so their future is predetermined, unlike regulative
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cleavage where cells are not yet given a fate, so they can separate in half to make monozygotic twins.
Question 9. Cnidarians lack an internal skeletal system. Using the information on tissue layers above, explain why this is so.
Cnidarians don’t have an internal skeletal system because they are diploblastic so they only make two embryonic tissues (they would need three).
Question 10. Using information in the above descriptions, which of the following terms describe humans and other vertebrates: radial cleavage, spiral cleavage, regulative
cleavage, mosaic cleavage, diploblastic body, triploblastic body, ectoderm present,
endoderm present, mesoderm present, deuterostome or protostome, blastopore becomes mouth, blastopore becomes anus?
Regulative cleavage, triploblastic body, mesoderm present, deuterostome, blastopore becomes anus
Question 11
Cnidaria - coral and sea fans
Platyhelminthes - tapeworms
Annelida - leeches
Mollusca - octopus and slugs
Nematoda - hookworms and the worm causing elephantiasis
Arthropoda - spiders, ticks, crabs
Echinodermata - brittle stars and sea cucumbers
Chordata - humans, sharks, and lizards
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