Consider statements about human diseases: 1. Tuberculosis is caused by a virus. 2. Polio is caused by a bacterium. 3. Tetanus affects the nervous system. Which are correct? MCQ with Answer and Explanation

Explanation:
Eutrophication is the excessive enrichment of water bodies with nutrients (primarily nitrates and phosphates from fertilizers and sewage). This leads to rapid growth of algae, known as an algal bloom. When the algae die, their decomposition by bacteria consumes large amounts of dissolved oxygen, leading to hypoxia (low oxygen levels) or anoxia, causing the death of fish and other aquatic organisms.

Explanation:
The Calvin cycle (C3 cycle) occurs in the stroma of chloroplasts, where CO₂ is fixed into sugars using ATP and NADPH from light reactions. Thylakoid membrane is the site of light reactions.

Explanation:
Prophase I of meiosis is divided into five sub-stages: leptotene, zygotene, pachytene, diplotene, and diakinesis. Crossing over, the exchange of genetic material between non-sister chromatids of homologous chromosomes, occurs specifically during the pachytene stage at structures called recombination nodules.