Biology Questions

RNA is not a lipid among the given options.

A lipid is a substance of biological origin that is soluble in nonpolar solvents. It comprises a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, and phospholipids.

The central nervous system ( brain and spinal card ) are invested with the meninges which nourish and protect the system .This again is enclosed inside a bony box which has the skin above it

The receptor molecules, which receive signals from outside the cell, passing the signal to the inside.

In order for a nerve cell, or any cell, to perceive its environment, it needs a sensory apparatus. And for an individual cell, most of that sensation is derived at the cell surface. So, it expresses on its cell surface proteins that span across the membrane.

In the outside world, these proteins can act to receive signals, catching molecules on the outside and then as the molecule passes to the inside of the cell, they can send signals like alarm signals that can tell the cell that a particular molecule is outside.

Hence, here B is the receptor cell.

Meiosis ::

Meiosis is a type of cell division that reduces the chromosome number by half in daughter cells, creating four haploid cells, each genetically distinct from the parent cell that gave rise to them.

Why it is called as Reduction Division ::

1. As the Meiosis division process involves in reduction of chromosome number in the daughter cells to half the number in the parent cell, this process is called Reduction Division.
Meiosis creates gametes (egg and sperm cells).

2. The resulting gametes have 23 new chromosomes, one member of each of the 23 pairs, representing unique combinations of the original maternal and paternal copies.

The persons with 'O' blood group do not have antigens in the red corpuscles. So that blood will not cause agglutination of corpuscles if mixed with any type of blood. So group 'O' persons are called universal donors.