Assertion (A): Human blood is a connective tissue. Reason (R): Blood cells are embedded in a liquid extracellular matrix called plasma. MCQ with Answer and Explanation

Explanation:
About 70% CO₂ is carried as bicarbonate. The main stimulus is high CO₂; external respiration is in lungs; diaphragm moves downward (contracts) during inhalation.

Explanation:
Evolution, at its most fundamental genetic level, is defined as the change in the frequency of alleles within a population over successive generations. Speciation is the evolutionary process by which populations evolve to become distinct, reproductively isolated species. Evolution does not have a predetermined goal or direction towards complexity; it simply results in adaptation to the current environment, which can sometimes lead to simpler forms (like parasites losing complex structures). Thus, statements 1 and 2 are correct.

Explanation:
Biological magnification (or biomagnification) is the process where the concentration of persistent, non-biodegradable toxic substances (like DDT, mercury, or PCBs) increases progressively at each successive trophic level in a food chain. Because these substances are not metabolized or excreted, they accumulate in the tissues of organisms. Top predators end up with the highest, often lethal, concentrations of these toxins.