The structure of DNA was discovered by: MCQ with Answer and Explanation

Explanation:
Rhizobium species form symbiotic root nodules in legumes and fix atmospheric nitrogen into ammonia. Azotobacter is free-living, Nitrosomonas nitrifies, Lactobacillus ferments.

Explanation:
A pyramid of numbers can be inverted when a single tree (producer) supports many herbivores, or many parasites live on a single host. Energy pyramids are always upright. Biomass pyramid can be inverted in aquatic systems.

Explanation:
Homologous organs share a common ancestral origin and structural plan but may have different functions (e.g., human arm, whale flipper, bat wing). This indicates divergent evolution. Analogous organs have different origins but similar functions (e.g., wings of birds and insects) due to convergent evolution. Vestigial organs are reduced and non-functional, like the human appendix.