Use the drop-down menus to identify the terms described below. a group of cells that secretes substances into the blood or directly into an organ a substance produced by cells that specific groups of cells to perform specific functions a channel or tube that conveys a substance

How is an environment able to support different varieties of organisms?

Describe the primary and secondary immune response in terms of speed and number of antibodies produced?

Which statement about dna replication is true? a. eukaryotes only have one circular chromosome that unwinds at multiple locations. b. eukaryotes can only replicate one segment of a chromosome at a time. c. prokaryotes can only replicate their single circular chromosome in the nucleus. d. prokaryotes only have one origin of replication to initiate replication.