Consider statements about human diseases: 1. Typhoid is caused by Salmonella typhi. 2. Malaria is caused by a virus. 3. Ringworm is a fungal infection. Which are correct? MCQ with Answer and Explanation

Explanation:
Humans have 46 chromosomes in somatic cells (22 pairs of autosomes and one pair of sex chromosomes). Gametes have 23 chromosomes.

Explanation:
The Sinoatrial (SA) node, the natural pacemaker of the heart, is a small, specialized mass of autorhythmic cardiac muscle cells located in the upper wall of the right atrium, just below the opening of the superior vena cava. It spontaneously generates electrical impulses at a regular rate, which spread through the atrial myocardium, causing the atria to contract and push blood into the ventricles. The impulse then reaches the AV node.

Explanation:
Herbivores feed directly on producers, occupying the second trophic level. Carnivores that eat herbivores are secondary consumers.