31. Invertebrates

Jon found an organism in a pond, and he thinks it's a freshwater sponge. His friend Liz thinks it looks more like an aquatic fungus. How can they decide whether it is an animal or a fungus?

a. See if it can swim.

b. Figure out whether it is autotrophic or heterotrophic.

c. See if it is a eukaryote or a prokaryote.

d. Look for cell walls under a microscope.

Which of these characteristics does not apply to cnidarians?

a. Are diploblastic

b. Possess a gastrovascular cavity with one opening

c. Undergo metamorphosis

d. Have a central nervous system

Which of these choices is an example of homology (similarity due to common ancestry)?

a. Suspension feeding in sponges and clams

b. Ectoparasite lifestyle in aphids and ticks

c. Cnidocytes (stinging cells) in jellyfish and sea anemones

d. Radial symmetry in cnidarians and echinoderms

The smooth feathers on the back of the neck in pigeons can be reversed by a mutation to produce a 'crested' appearance in which feathers form a distinctive spike at the back of the head. A pigeon breeder examined offspring produced by a single pair of non-crested birds and recorded the following: 22 non-crested and 7 crested. She then made a series of crosses using offspring from the first cross. When she crossed two of the crested birds, all 20 of the offspring were crested. When she crossed a non-crested bird with a crested bird, 7 offspring were non-crested and 6 were crested. Which allele is dominant?

In a process known as 'coral bleaching,' high water temperatures cause corals to expel the dinoflagellates that normally reside within their cells. How might coral bleaching affect coral reefs?