Which bird works the hardest in formation like V-shaped alphabet during flight of birds and why?

The bird in the lead (at the forward point of the 'V' formation) works the hardest by being the first to 'break through' the air, which offers resistance to its flight. Just as a boat leaves a V-shaped wake of smoother water behind it, the lead bird leaves a V-shaped wake of 'smoother' air behind it (actually the lead bird creates a trail of air turbulence that helps lift along the V-shaped direction), and it is a bit easier for the birds to fly in the wake of the lead bird.

If you watch a V-formation carefully, you'll notice that the lead bird does not stay in that position for very long and will drop back into the formation, while another, not-as-tired bird takes the lead, breaking through the air first.

Why do people feel sleepy while reading?

Feeling sleepy while reading for many is due to the posture in which they read. While reading a person rarely moves, this lack of physical activity causes decreased blood flow to muscles, which results in accumulation of lactic acid (a product of incomplete combustion in the cells).

This lactic acid is a highly reducing or oxygen absorbing agent, which quickly reacts with oxygenated blood. This ensures lack of oxygenated blood flowing to the brain, which makes us feel sleepy.

To tackle this problem we must avoid reading in a single stretch, instead its better to take some breaks and indulge in physical activity at short intervals.

What is meant by Embryonic Stem Cells

The only way to cure the diabetes disease is by pancreas re-plantation. However, due to the shortage of organ donations and other factors there remains a greatly insufficient supply of organs. But this can be overcome by obtaining organs generated in the lab by culturing certain cells of our body, called 'Stem Cells'. The stem cells are capable of self-renewal and have the ability to divide and differentiate through a variety of stages to produce the mature tissues.

There are two types of stem cells in our body 1. Somatic Stem Cells, 2. Embryonic Stem Cells. The somatic stem cells are cells taken from mature tissues. The stem cells of bone marrow are an example. The bone marrow stem cells are pluripotent and give rise to progenitor cells, which differentiate to form which myeloid series are derived. The embryonic stem cells are cells taken from blastocyte, which is an embryo removed from the womb or brought from the fertility clinic.

The embryonic stem cells are more flexible the somatic stem cells. They can proliferate far more than stem cells from adults, producing far more descendant cells. This is important because many millions of cells are needed to repair organs. In addition the embryonic stem cells can differentiate into all the tissues of the body while a given type of adult stem cells seems to differentiate into only a small set of tissue types destined to them. The derivatives of embryonic stem cells can be optimised to produce differentiated growth. For, example, by adding and removing certain proteins these cells are directed to develop in the lab into new heart, bone, pancreas or other cells.