Recent extinctions of species can be attributed to several causes.  Which of the following is not considered a major cause of such extinctions?  

What features of charophytes provides evidence for charophytes being the closests relative to land plants?

Evidence suggests that an asteroid struck the Gulf of Mexico near what is now the Yucatan Peninsula about 65 million years ago.  What was likely the cause of the cause of the loss of many plants?

Which organ system plays the least role in maintaining optimal conditions of the animal body? 

Homeostasis in animals can be generally defined as the _____.

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.