Consider statements about microorganisms: 1. Bacteria can be beneficial or harmful. 2. Fungi are used in food production. 3. Viruses are living outside a host. Which are correct? MCQ with Answer and Explanation

Explanation:
Senescence in plants is the biological process of aging, culminating in the structured, programmed death of plant organs (like leaves, flowers, or fruits) or the entire plant. It involves the coordinated breakdown of macromolecules (proteins, nucleic acids, chlorophyll) and the mobilization of nutrients (like nitrogen and phosphorus) from the senescing organ to other growing parts of the plant (like developing seeds). It is a highly regulated process influenced by hormones like ethylene and abscisic acid, and delayed by cytokinins.

Explanation:
Homologous organs are structures that have a similar fundamental anatomical plan and evolutionary origin but may perform different functions. The forelimbs of humans (for grasping), whales (for swimming), bats (for flying), and cats (for running) all have the same basic bone structure (humerus, radius, ulna, carpals, metacarpals, phalanges), indicating divergent evolution from a common ancestor.

Explanation:
The sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum in muscle cells that stores and releases calcium ions, which trigger muscle contraction. Mitochondria produce ATP, Golgi processes proteins, nucleus controls gene expression.