Learn Unit II: World of Living with Free Lessons & Tips

• The schematic representation of gaseous exchange in tissues typically involves the movement of oxygen (O2) from the bloodstream into the cells and the exchange of carbon dioxide (CO2) from the cells into the bloodstream. In tissues, oxygen diffuses from the capillaries into the interstitial fluid and then into the cells where it is used for cellular respiration. Simultaneously, carbon dioxide produced during cellular respiration diffuses out of the cells into the interstitial fluid and then into the capillaries to be transported back to the lungs for exhalation.

• Alveoli in the lungs and nephrons in the kidneys serve different physiological functions but share some structural and functional characteristics. Both have a high surface area for efficient exchange processes. Alveoli are tiny air sacs in the lungs where gas exchange occurs, characterized by thin walls and a dense network of capillaries. Nephrons are the functional units of the kidneys responsible for filtering blood and producing urine, consisting of a renal corpuscle and a renal tubule. While alveoli facilitate the exchange of gases (oxygen and carbon dioxide) between the air and the blood, nephrons filter waste products and regulate electrolyte balance and blood pressure through processes such as filtration, reabsorption, and secretion.

Reflex action is an involuntary and rapid response to a stimulus that bypasses conscious thought. It involves a simple neural pathway called a reflex arc, which includes a sensory neuron, interneuron, and motor neuron. Walking, on the other hand, is a voluntary and coordinated movement involving various muscle groups controlled by the brain's motor cortex and cerebellum. Unlike reflex actions, walking requires conscious intention and coordination between different parts of the brain and muscles.

At the synapse between two neurons, neurotransmitters are released from the presynaptic neuron into the synaptic cleft. These neurotransmitters then bind to receptors on the postsynaptic neuron, causing a change in its membrane potential. This results in the propagation of the electrical signal across the synaptic gap from one neuron to the next.

The cerebellum, located at the back of the brain, plays a crucial role in maintaining posture and equilibrium of the body. It receives sensory input from the vestibular system, which detects changes in head position and movement, and integrates this information to coordinate muscle activity and maintain balance.

The smell of an agarbatti (incense stick) is detected by specialized sensory cells called olfactory receptors in the nasal cavity. These receptors bind to odor molecules present in the air, initiating a cascade of chemical signals that are transmitted to the brain's olfactory bulb. The olfactory bulb then processes these signals, allowing us to perceive the smell.

• The closer relation between species can be determined by the number of shared characteristics. If species A shares ten characteristics with species B and species C shares fifteen characteristics with species D, the pair of species C and D share a closer relation because they share a greater number of characteristics.

• The fossilization process depends on various factors such as environmental conditions, burial depth, and presence of minerals. If only species A's body was found as a fossil and not B's, it suggests that species A's remains were buried under conditions more conducive to fossilization, such as rapid burial in sedimentary layers that allowed for the preservation of organic material.

• The insect buried in hot mud is more likely to be preserved better because hot mud can accelerate the process of fossilization by facilitating rapid decomposition of soft tissues and preserving the insect's body structure through mineralization. Additionally, hot mud can create an anaerobic environment that reduces microbial activity, further aiding in preservation.

• An example of how genes control characteristics or traits is the gene responsible for eye color in humans. The gene for eye color (such as the OCA2 gene) determines the amount and type of pigment (melanin) produced in the iris. Variation in this gene can result in different eye colors, such as brown, blue, or green.