Which of the following is an example of a mutualistic relationship where a fungus and an alga live together? MCQ with Answer and Explanation

Explanation:
A population is a group of individuals of the same species living in a specific geographic area and capable of interbreeding. A community comprises all the interacting populations of different species (plants, animals, microbes) living together in a defined area. An ecosystem is a functional unit of nature that encompasses both the biotic (living community) and abiotic (non-living physical environment like soil, water, sunlight) components, interacting as a complex system. All statements are correct.

Explanation:
Modern cell theory states that all living organisms are composed of cells and cell products, the cell is the basic unit of structure and function, and all cells arise from pre-existing cells (Omnis cellula e cellula). Not all cells have a nucleus (e.g., prokaryotes, mature RBCs). Cell theory was formulated by Schleiden, Schwann, and Virchow. Spontaneous generation was disproved.

Explanation:
HIV is a retrovirus with RNA genome and reverse transcriptase, which converts viral RNA into DNA. This defines retroviruses, and the reason correctly explains the assertion.