The specific gravity of normal urine is approximately: MCQ with Answer and Explanation

Explanation:
Selman Waksman coined the term 'antibiotic' in 1942 to describe chemical compounds produced by microorganisms that inhibit or kill other microbes. Fleming discovered penicillin, Ehrlich developed the concept of chemotherapy, Domagk discovered sulfa drugs.

Explanation:
Xylem vessels and tracheids are dead, hollow cells at functional maturity, providing a continuous tube for water transport. Phloem sieve tube elements are living cells at maturity, though they lack a nucleus, and are responsible for transporting organic nutrients. Cambium (vascular and cork) is a lateral meristem responsible for secondary growth (increase in girth), while apical meristems are responsible for primary growth (increase in length). Thus, statements 1 and 2 are correct.

Explanation:
The ozone layer is in the stratosphere (15-35 km altitude), absorbing harmful UV-B and UV-C radiation. CFCs cause its depletion.