In roots, the protoxylem (first formed xylem) lies towards the periphery and metaxylem towards the centre; this arrangement is called exarch. In stems, protoxylem is towards the centre, called endarch. Exarch condition is typical of roots. Mesarch is found in ferns. This arrangement aids in understanding anatomical differences between root and stem.
Explanation:
Jonas Salk developed the inactivated polio vaccine (IPV) in 1955, which was the first effective vaccine. Albert Sabin later developed the oral polio vaccine (OPV). Pasteur rabies, Jenner smallpox.
Explanation:
Pneumothorax is the accumulation of air in the pleural space, causing lung collapse. Pneumonia is lung infection, emphysema is alveolar damage, pleurisy is inflammation of pleura. It can be spontaneous or traumatic.
Explanation:
Adventitious roots arise from non-root tissues like stems, leaves, or branches. Examples: prop roots of banyan, stilt roots of maize, aerial roots of orchids. Taproot and fibrous roots develop from the radicle.
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