Endocrine gland - a group of cells that secretes substances into the blood or directly into an organ.
Differ from exocrine glands, endocrine glands have no ducts and secrete products (hormones) directly into blood.
Hormone - a substance produced by cells that helps specific groups of cells to perform specific functions. It is a product of endocrine gland which functions as chemical messengers to stimulate other cells.
Duct – a channel or tube that conveys a substance. It is part of the exocrine glands (such as salivary glands) which makes contact with surface .
The history of the domesticated sheep goes back to between 11000 and 9000 BC, and the domestication of the wild mouflon in ancient Mesopotamia. Sheep are among the first animals to have been domesticated by humans, and there is evidence of sheep farming in Iranian statuary dating to that time period.
Answer:
Tundra
Explanation:
Permafrost is a layer just beneath the surface of the ground that never thaws.
