Identify the correct statement about the respiratory pigment: MCQ with Answer and Explanation

Explanation:
Rheumatoid arthritis is a chronic inflammatory autoimmune disease where the immune system mistakenly attacks the body's own healthy tissues, specifically the synovial membranes of joints. This leads to painful swelling, bone erosion, and joint deformity. Other examples of autoimmune diseases include Type 1 diabetes, multiple sclerosis, and systemic lupus erythematosus.

Explanation:
Innate (natural) immunity is the non-specific defense mechanism present from birth, including physical barriers like skin and chemical barriers like stomach acid. Acquired (adaptive) immunity is highly specific and develops after the body is exposed to a specific pathogen or antigen, involving the production of antibodies and memory cells. Vaccines provide artificial immunity (specifically, artificial active immunity), not natural immunity, which is acquired through actual infection or from mother to child. Thus, statements 1 and 2 are correct.

Explanation:
Producers (autotrophs like green plants) form the first trophic level and the base of all food chains, converting solar energy into chemical energy. Decomposers (bacteria and fungi) break down dead organic matter and waste, releasing essential inorganic nutrients back into the soil for producers to use, thus completing the nutrient cycle. Energy flow in an ecosystem is strictly unidirectional, moving from the sun to producers and then to consumers, and is eventually lost as heat; it does not flow bidirectionally. Thus, statements 1 and 2 are correct.