Consider statements about cell organelles: 1. Chloroplasts are found in all plant cells. 2. Vacuoles are larger in plant cells than animal cells. 3. Centrioles are present in higher plant cells. Which are correct? MCQ with Answer and Explanation

Explanation:
In 1953, Stanley Miller and Harold Urey conducted an experiment to test the Oparin-Haldane hypothesis of chemical evolution. They simulated the reducing atmosphere of primitive Earth, which they believed lacked free oxygen. The gas mixture used was methane (CH4), ammonia (NH3), hydrogen (H2), and water vapor (H2O). By applying electrical sparks (simulating lightning), they successfully synthesized amino acids and other organic compounds.

Explanation:
Ethylene (C₂H₄) is a gaseous hormone that promotes fruit ripening, senescence, and abscission. It is the only gaseous plant hormone.

Explanation:
Cross-pollination (allogamy) involves transfer between genetically different plants of the same species, promoting genetic variation. Self-pollination occurs within the same flower or plant. Fertilization is gamete fusion, dispersal is seed/fruit spread. Agents of cross-pollination include wind, insects, water, birds.