Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

When was earth formed? What was its conditions at that time?

Name the type of cell division that takes place in the zygote of an organism exhibiting haplontic life cycle.

In a pond, we see plants which are free-floating, rooted-submerged, rooted emergent, rooted with floating leaves. Write the type of plants against each of them.

1. Hydrilla.
2. Typha.
3. Nymphaea.
4. Lemna.
5. Vallisnaria.

Why does hnRNA need to undergo splicing? Where does splicing occur in the cell?

The number of trophic levels in a food chain is limited. Justify.

Demand for mushroom as food has led to its culturing on a large scale. Similarly, it is perceived that microbes too would become acceptable as food. Identify a microbe which can be cultured as a food source and give the applicability of its culture in the given context.

Amniocentesis for sex determination is banned in our country. Is this ban necessary? Comment.

Why does a beekeeper keep beehives in crop fields during the flowering periods? State any two advantages.

What is census? Give India's population according to 1991 and 2001 census.

Differentiate between the Homo habilis and Homo sapiens.