Diphtheria is a bacterial disease caused by: MCQ with Answer and Explanation

Explanation:
The phylum Echinodermata (spiny-skinned animals like starfish, sea urchins, sea cucumbers) is uniquely characterized by a water vascular system used for locomotion, capture and transport of food, and respiration. The tube feet are the terminal effectors of this system. They exhibit secondary radial symmetry in adults, though their larvae are bilaterally symmetrical. Mollusks have a muscular foot, and arthropods have jointed appendages.

Explanation:
Prokaryotic cells lack a true nucleus; their genetic material is located in a nucleoid region. They possess 70S ribosomes (50S+30S subunits), whereas eukaryotic cells have 80S ribosomes. Prokaryotes generally have a cell wall (except Mycoplasma) and circular DNA, not linear. Membrane-bound organelles like mitochondria, ER are absent. Examples: bacteria and blue-green algae. This distinction is fundamental in cell biology.

Explanation:
Greenhouse gases trap heat in the Earth's atmosphere, contributing to the greenhouse effect and global warming. Carbon dioxide (CO2) and methane (CH4) are potent greenhouse gases emitted through human activities like fossil fuel combustion and agriculture. Oxygen (O2) and nitrogen (N2), which make up the majority of the atmosphere, are not greenhouse gases as they do not absorb infrared radiation. Thus, statements 1 and 2 are correct.