The correct option is (a).
Explanation
Hormones are non-nutrient chemicals that act as intercellular messengers and are produced in trace amounts. In animals, the endocrine system consists of ductless glands that regulate various physiological functions through these chemical messengers.
Statement-wise Analysis
- Statement 1 is Correct: Hormones are chemical substances. Chemically, they can be peptides, steroids, iodothyronines, or amino acid derivatives. They serve as signaling molecules that transport information from one set of cells to another.
- Statement 2 is Incorrect: Hormones are secreted by endocrine glands, which are defined as "ductless glands." Unlike exocrine glands (e.g., sweat or salivary glands) that release secretions through ducts, endocrine glands release hormones directly into the bloodstream (or lymph), which then transports them to target organs.
- Statement 3 is Incorrect: Hormones do not act on every cell of the body equally. They are highly specific in their action. A hormone affects only specific target cells or organs that possess specific receptors for that hormone. Cells without the specific receptor for a given hormone do not respond to it.
Key Takeaway
Hormones are chemical messengers secreted by ductless (endocrine) glands directly into the bloodstream and act only on specific target organs possessing the appropriate receptors.