BIOLOGY AND THE SERVICE OF MANKIND:
The science of biology has been helping mankind in many ways in increasing food production; in combating diseases and in protecting and conserving environment. Biological advances in the field of food and health have resulted in high standard of living.
Plant production has been tremendously increased by improving existing varieties and developing new high-yield and disease – resistant varieties of plants and animals used as food.
Plant and animal breeders have developed, through selective breeding, using the principles of genetics, new better varieties of wheat, rice, corn, chicken, cow and sheep. Poultry breeders have developed broilers for getting quick and cheap white meat. Genes for disease resistance and other desirable characters are introduced into plant, using the techniques of genetic engineering. Such transgenic plants (plants having foreign DNA incorporated into their cells) can be propagated by cloning (production of genetically identical copies of organisms/cells by asexual reproduction)
using special techniques such as tissue culture techniques etc. Plant pathogenic fungi and insect pests of crops which weaken the plants and reduce the yield had traditionally been controlled by using chemical fungicides and insecticides (pesticides). Use of these chemicals poses toxicity problems for human beings as well as environmental pollution. Moreover, there are chances of insects becoming resistant to the effect of these chemicals. Biological control (control by some living organisms) eliminates all such hazards. In biological control, pests are destroyed by using some living organisms that compete with or even eat them up. An aphid that attacks walnut tree is being controlled biologically by a wasp that parasites this aphid.
Even some bacteria are being used as bio-pesticides. Effective control of a particular disastrous disease, or all the common diseases of a plant can be achieved by using all relevant, appropriate methods of disease control. Such an approach of disease control is called “integrated disease management”.
Soil is a complex medium. It is almost impossible to conduct experiments on nutrient requirements of plants by growing them in soil. Hydroponic culture technique is used to test whether a certain nutrient is essential for plant or not. In this technique the plants are grown in aerated water to which nutrient mineral salts have been added. Hydroponic farming, however, is yet not feasible. Astronauts may use it for growing vegetables.
Different techniques of food preservation have been developed for protecting food from spoilage and for its use and transport over long distance without damaging its quality. One of these is pasteurization, developed by Louis Pasteur. It is being widely used for preservation of milk and milk products.
There has been fantastic progress in the area of health and disease control. Three pronged actions are usually taken against various diseases.
- Preventive measures
- Drug treatment/Gene therapy
The advances in biological sciences have provided us information about the causative agents of the diseases and their mode of transmission. For instance the AIDS (Acquired Immune Deficiency Syndrome) is caused by HIV (human immune deficiency virus) and it spreads through free sexual contact, through blood transfusion, by using contaminated syringes or surgical instruments etc. Therefore, doctors advise us to take precautions on these fronts so that we do not contract the disease, which is at present incurable. Similarly hepatitis is caused by H.virus which is spread through blood transfusion by using contaminated syringes and surgical instruments etc. In this case also doctors advise us to be careful and avoid the point of contact.
Vaccination / Immunization
Many diseases such as polio, whooping cough, measles, mumps etc can easily be controlled by vaccination or “shots”.
Edward Jenner first developed the technique of vaccination in 1796, cowpox pus is known as vacca (from Latin vacca=cow). From this word evolved the present term vaccination and vaccine. You will learn more about vaccination in chapter 6. Since then, inoculation or vaccination is carried out to make the people immune from viral or
bacterial epidemics or, for some diseases the individuals are vaccinated in their early life to make them immune to those diseases. It is claimed that small pox has been totally eliminated from the world by using this method. Scientists are making continuous efforts to develop vaccine against other diseases. Even vaccine against AIDS is being administered in humans on experimental basis.
Drug treatment / Gene therapy
If a person becomes sick with disease, he is subjected to the action of antibiotics which can kill bacteria. The antibiotics are, however, useful in bacterial disease and that only when bacteria have not developed resistance to antibiotics. In cancer, radiotherapy and chemotherapy are also used. In radiotherapy, the cancerous part is exposed to short wave radiations from the radioactive material repeatedly at regular intervals. In Pakistan there are several centres which are carrying out radiotherapy to control cancer. Chemotherapy consists of administrating certain anticancer chemicals to the patients at regular intervals. These chemicals may kill both cancerous and normal
Recently a new technique has been developed to repair defective genes. This consists of isolating the normal gene and inserting it into the host through bone marrow cells. This is called gene therapy.
Combating disease utilizing all methods as and when required and ensuring a participation of community in this programme is known as integrated disease management. This requires awareness of the community about the severity of the problem, its causes and its remedies. This is a very effective programme for elimination and control of dangerous diseases from the human society.
Cloning: Cloning is a technology for achieving eugenic aims. A clone is denied as a cell or individual and all its asexually produced offspring. All members of a clone are genetically identical except when a mutation occurs.
Generally no normal animal reproduces naturally by cloning. Several insects and many plants do, in some circumstances whereas few do so regularly. In 1997 scientists in Scotland succeeded in cloning a sheep. Other mammalian species (mice and cows) have since been cloned. In this procedure the nucleus from a fertilized egg is removed and a nucleus from a cell of a fully developed individual is inserted in its place. The altered zygote is then implanted in a suitable womb where it completes its development. The new individual formed in this way is a genetically identical clone of the individual whose nucleus was used. Thus cloning
could make multiple copies of a desired genotype.
Another type of cloning is the division of a single egg or early embryo into one or more separate embryos. This is the same process that normally creates identical twins. Offspring from this type of cloning are genetically identical but carry chromosomes from each of the two parents. This type of cloning has already been used to produce genetically identical cattle and other farm animals.
Man is likely to adopt cloning techniques for commercial production of valuable animals of known pedigree such as horses etc.
At some places scientists are making attempts to clone human embryo which they believe can serve as transplant donor. There is a lot of controversy on this issue as to whether human cloning should be attempted or not.