When scientists study organisms in nature (i.e. outside of the laboratory), carefully controlled experimentation is not always possible.  In a case involving mating behavior of birds, data might be gathered by

The lungs and heart are located in the _____.

Why do viruses only infect specific types of cells?

An organism has the following features: diplontic life cycle, protostome development, segmentation, a septate coelom, closed circulatory system, and setae. To which phylum does this organism belong?

In the vascular bundles of most dicot stems, primary phloem differentiates toward the ________of the stem, while primary xylem differentiates toward the ________of the stem.

The closest extant relative of the Tyrannosaurus rex is the _____

*In fungi, plasmogamy results in _____.

*Adult echinoderms display radial symmetry. What evidence suggests that echinoderm ancestors evolved from bilaterally symmetrical ancestors?

The first stage in the gametophyte generation is  _____.

A small island has stable populations of plants and animals, including one species of hawk as the only predator. The removal of the hawks could cause ____________ population size.