Mammary glands are a defining feature of which class of animals? MCQ with Answer and Explanation

Explanation:
Phagocytosis is receptor-mediated or non-specific engulfment of large particles, forming a phagosome that fuses with lysosomes. Key in immune defense.

Explanation:
The skin and mucous membranes form the first line of defense (innate immunity), acting as physical barriers that prevent pathogens from entering the body. White blood cells (leukocytes), including phagocytes and lymphocytes, are the cellular components of the immune system that identify, attack, and destroy pathogens. Antibiotics are drugs specifically designed to kill or inhibit the growth of bacteria by targeting their unique structures or metabolic pathways; they are completely ineffective against viruses. Thus, statements 1 and 2 are correct.

Explanation:
The macula lutea is a yellowish spot near the center of the retina. Its central depression, the fovea centralis, is the point of sharpest vision. The fovea is packed exclusively with cone cells and lacks blood vessels and rods. This high density of cones, combined with the displacement of overlying retinal layers, allows for maximum visual acuity and color discrimination in bright light. The blind spot is the optic disc.