Food chains show energy transfer between organisms. the size of a food chain can vary, yet there is a limit to the number of levels that a food chain can reach. why is there a limit to the number of levels that a food chain can reach?

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.