Select all the following that describe isotopes of an element
_ Different numbers of neutrons
_ Different mass numbers
_ Different atomic numbers
_ Different numbers of protons

In addition to seeds, which of the following characteristics are unique to the seed-producing plants? a) sporopollenin b) lignin present in cell walls c) pollen d) use of air currents as a dispersal agent e) megaphylls

Which of the following is not a defining characteristic of plants?

Which group of algae is characterized by unicellular organisms and includes some members that would be better classified as zooflagellates? euglenophytes red algae sporozoans green algae