In an ecosystem, a large number of species are dependent on one particular species of bird. the species of bird is an example of a/an species.
a. capstone
b. exotic
c. keystone
d. native

And give a detailed description! scientist observes the boundary between two tectonic plates for a decade and finds that no new volcanoes have formed over the course of her investigation. does this result support the theory of plate tectonics? why or why not?

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.

What kinds of molecules can pass through the cell membrane without any problem?