Why Are The Fingerprints Of Identical Twins Not Identical?

Identical twins are formed when a single egg that is fertilized divides into two or more after conception and since they are formed from a single zygote (egg) they have the same genetic characteristics. But fingerprints are not characterized by genetics. It is actually determined by the interaction of the genes of the individual and the environment in the uterus and since identical twins develop in different environments their fingerprints are different. 
The final pattern of fingerprints are thought to be influenced by environmental factors such as nutrition, blood pressure, position in the womb and the rate of growth of the fingers. You may find similar patterns of ridges and whorls but there will be differences.

Why Is There No Incidence Of Heart Cancer?

Cancer is a tumor and tumors can be either benign (non-cancerous) or malignant (cancerous). Malignant tumors are further classified as primary or secondary, that is, whether it arises in the organ itself or spread from other organs. There are incidences of cancer of the heart and if it does occur it is usually benign such myxomas (the most common), fibromas, rhabdomyomas, and hamartomas. Malignant tumors of the heart such as angiosarcoma or cardiac sarcoma are know occur but are extremely rare. In fact any tumor of the heart is extremely rare. In a study of 12,487 cases where autopsies were performed only 7 tumors were found. Benign tumors of the heart can be surgically removed and the success rate is almost 100%. The success rate of the treatment of a malignant tumor of the heart depends on the further spread of the cancer to other vital organs.

How Is Blood Grouping Done?

The broad classification of the groups or types is based on the presence or absence of particular antigens that are carried on the surface of red blood cells. Corresponding antibodies are carried in the blood plasma. Broadly the types are A, B, AB and O but the International Society of Blood Transfusion recognizes some thirty types fro the purposes of blood transfusion - the process of transferring blood taken from one person to another person.

A person with a particular antigen in his blood cannot have the same antibody. Thus a person with  blood containing the antigen A cannot have the antibody A in his blood.

A person of the blood group A has the antigen A and the antibody B. Similarly a person belonging to the blood group B will have the antigen B and the antibody A. The person belonging to the blood group AB will have only the antigens A and B and  no antibodies. The person of the blood type O has only the antibodies A and B and no antigens.

Another type of blood group is the Rh blood group. This name is derived from the group first discovered in the Rhesus monkey. In this group there is the Rh Positive and the Rh Negative blood groups.

The other blood groups include the A1 Positive (A1 +ve), A1 Negative (A1 -ve), A2 Positive, A2 Negative, B Positive, B Negative, O Positive and O Negative to name a few.

How Long Can Humans Survive Without Oxygen?

On the whole, oxygen is absolutely required for survival. Loss of oxygen to any part of the body is known as hypoxia. Total loss of oxygen results in anoxia.

Due to the susceptibility of the human brain to oxygen, humans can survive for only a short period of time without a supply of oxygen to the brain. In spite of the fact that the brain weighs only 5% of the body's weight, it consumes some 20% of all the oxygen intake. Oxygen is supplied to the brain by blood. It takes only about 8 to 10 seconds of loss of oxygen to the brain to make us lose consciousness. Loss of oxygen to the brain for a period of 4 to 6 minutes results in destruction of the brain cells. Extended periods of time results in brain damage and ultimately death.

The brain can survive for longer periods of time at lower temperatures. That is due to the fact that at lower temperatures the brain requires less oxygen for its survival. This fact is made of use in major surgeries and is known as induced hypothermia.

The other tissues of the body can survive for longer periods of time without oxygen, which make organ transplantation possible.

What Is Artificial Blood?

Artificial blood is a colloidal substance, an emulsion carrying a compound of oxygen, electrolytes, plasma expander and some other compounds that act as a buffer. The plasma expander gives volume to the blood. The demand for blood for clinical purposes led to the development of artificial blood. Decades of research led to the discovery of an alternative to human blood by genetic engineering. This genetically engineered hemoglobin (blood) is known as rHB 1.1. It is produced by the process of fermentation and purification of cultivated genetically engineered E.Coli bacteria.

rHB 1.1 is thirty times more effective in the supply of oxygen than natural blood. The risk of contracting dreadful disease by blood transfusion is completely eliminated by the use of artificial blood and it also has a long storage life.

Do Birds Sleep? Why Do They Not Fall Off Their Perches?

Yes birds do sleep and some do it standing on one leg. It is an arrangement of tendons that keeps the bird from falling off its perch. There is a tendon known as the flexor tendon from the muscle in the thigh that goes down to the leg, around the ankle and then under the toes. At rest, the weight of the bird makes the bird to bend down on its knees, tightening the tendons and closing the claws. That is why they do not fall of their perches.

Not only do birds sleep they can even be hypnotized into falling asleep by bringing our eyes close to the bird's cage and slowly closing our eyes pretending to fall asleep. The bird will follow suit and fall asleep. You can also make a bird in a cage go to sleep by simply covering its cage. This is because birds rely on sight and with the exception of nocturnal birds, bedtime is when it gets dark.

How Do Trees Reduce Air Pollution?

Pollution is prevented by plants in many ways. The atmosphere contains many elements the ratio of which keeps changing from time to time due to our activities such as changes in land use, afforestation, deforestation and the burning of fossil fuels. This results in the production of large quantities of carbonmonoxide, aerosols, dust and methane.

Trees act in many ways to reduce pollution in the atmosphere by acting as a sink for carbonmonoxide.  The process of photosynthesis synthesizes carbohydrates using the carbon monoxide in the atmosphere, sunlight and water. The resulting oxygen is sent into the atmosphere which living organisms need.

The atmosphere is also cooled by plants by a process known as transpiration where water vapor is released into the atmosphere.

Dust particles and aerosols settle on the dense foliage of the trees and as such as act as curtains and barriers.