Extract from a lecture about immunization

Historically, being immunized against diseases is a relatively new thing but that doesn`t mean the idea hadn`t been thought before. If we go as far back as 429 BC, the historian Thucydides noted that after a smallpox plague in Athens survivors did not become infected again. This was a time before there was even recognition of such things as bacteria and viruses.

Nowadays we take it for granted that we will be vaccinated and avoid diseases like polio, but how many of us actually stop to ask ourselves what is behind the injection we have? How does vaccination work?

Basically, it is the process by which a person is exposed to an agent so that his or her immune system develops against that agent. The immune system makes antibodies which fight against infection. Once the human immune system is exposed, that is, made open to a disease, it is able to act against any future infection. Vaccination exposes a person to an immunogen – something which helps develop immunity – in a controlled way by using a weak dose so he or she doesn`t become ill while being immunized.

The good thing about a vaccination programme is that it can limit the spread of a disease among a population, reducing the risk for people who have not been vaccinated, so we have something which is known as herd immunity. That means when the number of non-immune people has dropped to a certain level, the disease will disappear from the whole population. This is how we have achieved the elimination of many diseases.

Quick check:

1. What does pasteurization mean?

2. What is the difference between pasteurization and sterilization?

3. What does the word vaccination mean?

4. Do we need vaccination?

5. What vaccinations have you had?

6. Are there any negative aspects to vaccination?

7. Do you know of any diseases for which we cannot be immunized?

8. What vaccines would you like to see developed?

9. In what way do Pasteur`s vaccines differ from those of Jenner?

■ Text 2. Gregor Mendel

Gregor Mendel was born on 20^th July, 1822, and died on 6^th January, 1884. He was a biologist and botanist whose scientific research showed that inheritance proceeds according to certain scientific laws.

Mendel was a brilliant student and his family encouraged him to study, but they were very poor so Mendel entered a monastery in 1843. There he taught Mathematics, Physics and Greek to his school students. Eight years later, in 1851, the monastery sent him to the University of Vienna where he was able to continue his education. In 1853, he returned to the monastery and began teaching and researching again.

Mendel`s theories of heredity based on his work with pea plants are well known to students of Biology. But his findings were so different from the accepted views on heredity at the time that his work was ignored until long after his death. His paper, ‘Experiments in Plant Hybridisation”, in which he described how traits were inherited, has become one of the most influential publications in the history of science.

Mendel was the first person to trace the characteristics of successive generations of an organism. In Mendel`s day, a number of hypotheses had been suggested to explain heredity. The most popular one was the so-called blending theory. According to this theory, inherited traits blended from generation to generation. For instance, a red rose crossed with a white rose would, over time, produce a pink rose. Another theory put forward by Charles Darwin was called pangenesis. This stated that there were hereditary particles in our bodies, and that these particles were affected by our actions. The altered particles could be inherited by the next generation. These theories were disproved by Mendel.

The first thing he noticed when he began his experiments was that traits were inherited in certain numerical ratios. This observation led him to come up with the idea of the dominance of genes and he tested it in peas. For seven years he crossed thousands of plants to prove the Laws of Inheritance. From his experiments, Mendel developed the basic laws of heredity. Those laws are the following: that traits do not combine, but are passed whole from generation to generation (which disproved the blending theory and Darwin`s theory); each member of the parental generation passes on only half of its hereditary information to each offspring (with certain traits dominant over others); and different offspring of the same parents receive different sets of hereditary information.

Mendel`s research formed the beginning of the modern science of genetics. Genetic theory has had a huge impact on our lives. Many diseases, for example haemophilia, are known to be inherited, and family histories can be traced to determine the probability of passing on a hereditary disease. Scientists can now design plants that are easier to grow, or which can produce more food. This practical side of the results of Mendel`s research is being used to improve the way we live.

Quick check:

1. How did the blending theory explain heredity?

2. What did the pangenesis theory state?

3. What was the first thing that Mendel noticed when experimenting with peas?

4. How are characteristics passed on from generation to generation?

5. How does modern science change this? Why?

■ Text 3. Vladimir Vernadsky

Vladimir Ivanovich Vernadsky was a Russian scientist who was born on 12^th March, 1863 in St. Petersburg. His most important contributions to science were the development of the ideas of the biosphere (from the Greek word bios meaning life) and the noosphere (from the Greek word noos meaning mind).

He graduated from the Physics and Mathematics Department of St Petersburg University in 1885. From 1890 to 1911 he taught mineralogy and crystallogaphy at the University of Moscow. In 1912 he was made a full member of the Russian Academy of Sciences where he was actively involved for 33 years, until his death in Moscow on 6^th January, 1945.

Through his work in mineralogy, Vernadsky became interested in the distribution of chemical elements in the Earth`s crust, hydrosphere and atmosphere – the field known as geo chemistry. Vernadsky published many papers on the geochemistry of various elements, including the geochemistry of radioactive compounds.

Vernadsky was one of the first scientists to suggest the possibility of using radioactive elements as sources of energy, and he organized a special commissions to look for uranium ores in Russia. In 1916, the first uranium deposits were discovered. But Vernadsky was aware of the danger of putting atomic energy into the hands of man. He said that scientists carried the huge responsibility of making sure their discoveries did not lead to destruction.

However, Vernadsky is probably best known for his development of the idea of the biosphere of the Earth and his ideas on the evolution of the biosphere into the noosphere.

The biosphere is the layer of the Earth in which all life exists. The term biosphere was coined in 1875 by the geologist, Eduard Suess, but it was Vladimir Vernadsky who recognized its ecological importance in 1929. He believed that all living organisms together with their environments make up the biosphere. These environments include the air (the atmosphere), land (the geosphere), rocks (the lithospere) and water (the hydrosphere). The exact thickness of the biosphere on Earth is difficult to calculate, but most scientists would agree that it is from about 5000 metres above sea level to around 9000 metres below sea level. Thus, there is a 14-kilometre zone within which life exists.

Vernadsky defined the boundaries of the biosphere by showing that the biosphere includes all the hydrosphere, part of the troposphere – the lowest layer of the atmosphere where most weather changes take place – and the upper part of the Earth`s crust down to a depth of two or three kilometers, in short, everywhere that life exists. For Vernadsky, the biosphere had existed since the very beginning of the Earth`s history and it was constantly evolving. Our present living world is the product of a long and complex evolution of the biosphere.

Vernadsky believed that the technological activities of mankind were a stage in this evolution. He believed that human reason and combined scientific efforts could overcome the negative results of technology and could lead to a safe future for everyone. This positive evolutionary stage of the biosphere of the Earth is for him the noosphere, the sphere of reason.

In his paper, Several Words on the Noosphere (1944, the last paper he published before his death), Vernadsky outlined the conditions that were required for the creation of the noosphere: equality for all people and an end to wars, poverty and hunger. Today, Vernadsky`s vision of the world is more important than ever before.

Date: 2016-02-19; view: 509; Нарушение авторских прав