Biology Questions

Genetic drift or allelic drift is the change in the relative frequency in which a gene variant (allele) occurs in a population due to random sampling and chance.

When is genetic drift a major factor in evolution is

* When there is low gene flow.

* When there is no selective pressure.

* When there is a bottleneck.

Scientists estimate the volume of blood in a human body to be approximately 7 percent of body weight. An average adult body with a weight of 150 to 180 pounds will contain approximately 4.7 to 5.5 liters of blood. An average child with a body weight of 80 pounds will have approximately half the amount of blood as an adult.

The amount of blood in a human body varies, depending on factors such as age, sex, overall health and even where a person lives. For example, men tend to have more blood than women of comparable size and weight.

Interestingly, people who live at high altitudes may have up to two liters of extra blood compared to those who live at lower altitudes. Because the air at higher altitudes has less oxygen, people who live at high altitudes need extra blood to deliver the right amount of oxygen to their lungs.

We know that 1 Pint = 0.473 liters

Hence, an average amount of blood in the human body = 4.7 - 5.5 lit = 10 - 12 pints.

A nitrogenous base, or nitrogen-containing base, is an organic molecule with a nitrogen atom that has the chemical properties of a base. The main biological function of a nitrogenous base is to bond nucleic acids together. A nitrogenous base owes its basic properties to the lone pair of electrons of a nitrogen atom.

In DNA, four bases have been found. They are

1. Adenine (A),

2. Guanine (G),

3. Cytosine (C) and

4. Thymine (T).

The first three of these bases are found in RNA also but the fourth which is Uracil (U) is absent in it.

RNA contains cytosine and uracil as pyrimidine bases while DNA has cytosine and thymine.

A pulse can be detected most easily in Arteries as they are under much greater pressure than veins because they are carrying blood away from the heart which is the pumping machine to force blood to move to all of the body.

Every time the hear contracts, it can be felt in an artery where a surge of blood has just been forced.

A capillary is too small to feel a pulse and a lacteal is part of the lymphatic system found in the small intestine.