Erythropoietin is a hormone that stimulates production of red blood cells (RBCs) in bone marrow. This hormone is secreted by which secondary endocrine organ?

Kidneys.

Explanation:

Erythropoietin is a hormone that is produced by the kidney and stimulates the production of red blood cells (RBCs) in the bone marrow. Erythropoietin stimulates the bone marrow to generate more RBC's.

By nature, Erythropoietin is a protein with having attached sugar. It is known as the glycoproteins that help in the stimulation for the specific types of RBC's growth in the bone marrow.

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.