NEET Practice Questions (MCQs) with Answers & Solutions

The NCERT text states: 'Now, we may say that even differentiation in plants is open, because cells/tissues arising out of the same meristem have different structures at maturity.'

The text mentions: 'The final structure at maturity of a cell/tissue is also determined by the location of the cell within.'

Figure 13.8, 'Sequence of the developmental process in a plant cell', clearly illustrates the pathway: MERISTEMATIC CELL → Plasmatic growth → Expansion (Elongation) → Differentiation → Maturation → MATURE CELL.

The text states: 'Plants follow different pathways in response to environment or phases of life to form different kinds of structures. This ability is called plasticity, e.g., heterophylly in cotton, coriander and larkspur.'

The text states: 'During differentiation, cells undergo few to major structural changes both in their cell walls and protoplasm. For example, to form a tracheary element, the cells would lose their protoplasm. They also develop a very strong, elastic, lignocellulosic secondary cell walls...'

The text integrates these concepts: 'Since differentiation in plants is open, the development could also be flexible, i.e., the development is the sum of growth and differentiation. Plant exhibit plasticity in development.'

According to the NCERT text, 'Inspiration can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure... This is achieved by the contraction of diaphragm which increases the volume of thoracic chamber in antero-posterior axis. The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorso-ventral axis. The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intra-pulmonary pressure to less than the atmospheric pressure which forces the air from outside to move into the lungs, i.e., inspiration (Figure 14.2a).'

The NCERT states, 'The volume of air involved in breathing movements can be estimated by using a spirometer which helps in clinical assessment of pulmonary functions.' While many volumes are defined, Residual Volume (RV) and consequently capacities that include RV (like TLC and FRC) cannot be measured directly by a spirometer, as some air always remains in the lungs. Inspiratory Reserve Volume (IRV) is a measurable change in volume during forced inspiration.

The NCERT states, 'Relaxation of the diaphragm and the inter-costal muscles returns the diaphragm and sternum to their normal positions and reduce the thoracic volume and thereby the pulmonary volume. This leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs, i.e., expiration (Figure 14.2b).' Thus, the increase in intra-pulmonary pressure above atmospheric pressure is the primary driver.

The NCERT states, 'The conducting part transports the atmospheric air to the alveoli, clears it from foreign particles, humidifies and also brings the air to body temperature. Exchange part is the site of actual diffusion of O2 and CO2 between blood and atmospheric air.' Thus, the conducting part does not serve as the site of gas diffusion.