The scientist who developed the concept of 'natural selection' independently of Darwin was: MCQ with Answer and Explanation

Explanation:
Rheumatoid arthritis is an autoimmune disease where the immune system attacks the synovial membranes of joints, causing inflammation and joint damage. Tetanus is bacterial (Clostridium tetani), typhoid is bacterial (Salmonella typhi), malaria is protozoan (Plasmodium). Autoimmune diseases result from failure of self-recognition by immune cells. Other examples: type 1 diabetes, multiple sclerosis, lupus.

Explanation:
Normal blood pressure is around 120/80 mmHg (systolic/diastolic). Systolic pressure is during ventricular contraction; diastolic during relaxation. Hypertension is >140/90 mmHg.

Explanation:
The Sinoatrial (SA) node, located in the right atrium, is the natural pacemaker because its cells are autorhythmic; they can spontaneously generate action potentials without external neural input. Crucially, the SA node has the highest intrinsic rate of depolarization (about 70-80 beats per minute) compared to other autorhythmic tissues like the AV node or Purkinje fibers. Therefore, it sets the pace for the entire heart, overriding slower pacemakers.