The materials cycled through ecosystems during the nitrogen cycle and the carbon cycle a. remain at constant levels, although the form and location of the materials can change. b. decrease steadily until more of the materials are added from outside systems. c. increase or decrease based on the number of producers in the ecosystem. d. remain at constant levels and cannot change form or location within the ecosystem.

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.

What does it mean for an allele to be dominant?

Explain how negative feedback caused the changes in plasma glucagon concentration observed during the experiment.