Double fertilization in angiosperms was discovered by: MCQ with Answer and Explanation

Explanation:
Accommodation involves lens shape change via ciliary muscles. The blind spot lacks photoreceptors; fovea has high cone density; pupil adjusts via iris.

Explanation:
Arthropoda is the largest phylum, characterized by jointed appendages, segmented body, and chitinous exoskeleton. Examples: insects, crustaceans, arachnids. Mollusca have a muscular foot and shell, Annelida have segmented worms, Echinodermata have spiny skin and radial symmetry. Arthropods have an open circulatory system.

Explanation:
Carbon dioxide (CO₂) is the primary greenhouse gas, along with methane (CH₄), nitrous oxide (N₂O), water vapor, and CFCs. These trap heat in the atmosphere, leading to global warming and climate change. CO₂ levels have risen due to fossil fuel burning and deforestation. The greenhouse effect is natural and essential, but enhanced levels cause global temperature rise.