In angiosperms, the functional megaspore undergoes mitotic divisions to form the embryo sac, which typically contains: MCQ with Answer and Explanation

Explanation:
Prokaryotic DNA is typically circular, double-stranded, and found in a nucleoid region without a nuclear membrane. It is not associated with histones (though some Archaea have histone-like proteins). Plasmids are extra-chromosomal DNA. Eukaryotic DNA is linear and complexed with histones. This difference is fundamental in cell classification.

Explanation:
The ozone layer is located in the lower portion of the stratosphere, about 15–35 km above Earth. It absorbs most of the Sun's harmful ultraviolet radiation. Troposphere is the lowest layer, mesosphere and thermosphere above. Ozone depletion by CFCs led to the Antarctic ozone hole.

Explanation:
Antonie van Leeuwenhoek, a Dutch microscopist, designed single-lens microscopes and observed bacteria, protozoa, sperm cells, and RBCs for the first time, calling them 'animalcules'. Hooke observed dead cork cells. Schleiden proposed that plants are composed of cells, Virchow stated 'Omnis cellula e cellula'. Leeuwenhoek is rightly considered the father of microbiology for his pioneering observations of living microbes.