El arte de educar

5 junio, 2008

Seventeenth Century Scientists

Filed under: Jornada Interdisciplinar sobre el Barroco — albayalde @ 4:43 pm

Jornada Interdisciplinar del Barroco
Colegio El Romeral (Attendis)
Málaga, 14 de mayo de 2008

Cristian Sánchez-Bayton Griffth

The seventeenth century was characterized by the Baroque cultural movement and the beginning of modern philosophy and organized scientific thought. Europe was torn by warfare throughout the century, by the Thirty Years’ War, the Great Turkish War, the end of the Dutch Revolt and the English Civil War among others. It was the continuation of the age of exploration; European colonization of the Americas increased throgh this period.

It was the era of Galileo, Isaac Newton, René Descartes and Johannes Kepler. In the seventeenth century, zoology books transitioned into the more rational and organized world of natural science. An important invention of the seventeenth century was the microscope, which enabled scientists to see things in a whole new way.

Seventeenth Century Scientists

The 1st Scientist is Francesco Redi who lived from 1626 to 1697 and was the first to question the theory of spontaneous generation.

The 2nd Scientist is Carl Linneaus who lived from 1707 to 1778 and established the binomial system of classification.

Francesco Redi

Francesco Redi was born in Arezzo, (Italy) the 18 Feb. 1626 and died 71 years later in Pisa March the 1st 1697

Francesco studied at a Jesuit school in Florence and completed his studies in medicine in Pisa in 1647. After taking his degree he entered the service of the Colonna family at Rome as a tutor, and held the position five years. In 1654 he went to Florence, where he acted as physician to the Grand dukes Ferdinand II and Cosimo III. He was constantly engaged in experiments intended to improve the practice of medicine and surgery, and yet found the time for much literary work. He was an active member of several of the academies of the time, and, as an associate of the Crusca Academy, aided in preparing its important Vocabolario. He taught in the Studio at Florence in 1666, as lettore publico di lingua toscana and was one of the first members of the Arcadia.

Redi’s Scientific Works

Francesco Redi’s wrote numerous scientific documents. As an example here are three of his most important works:

a) “Observations concerning Vipers” (1664) was Redi’s first scientific work. Through this memoir Redi identifies the location of the viper’s poison and explains its toxic effect.

b) His major parasitological treatise, “Observations concerning live animals found in live animals” (Osservazioni intorno agli animali viventi che si trovano negli animali viventi) in 1684 was based on the study of parasites and on comparative anatomy.

c) In 1668, Redi published his scientific masterpiece: “Experiments on the Origins of Insects,” (Esperienze intorno alla generazione degli insetti) a milestone in the history of modern science in which he disproved the doctrine of spontaneous generation in insects.

Francesco Redi was not only a scientist but a man of literature as well.

His best known literary work is Bacco in Toscana (1685) or Bacchus in Tuscany considered an exceptional example of the dithyramb in Italian and one of the best literary works of the 17th century.

Spontaneous Generation

Since at least the time of Aristotle (4th Century BC), scientists believed that simple living organisms could come into being by spontaneous generation. This theory was also known as Aristotelian abiogenesis (a-not bio-life genesis-origin).

Spontaneous generation was the idea that living organisms could originate from non-living objects. Scientists believed that simple organisms like worms, beetles, frogs, and salamanders could come from dust, mud, etc., and food left out, quickly “swarmed” with life.

Francesco Redi was the first of his time to try to disprove spontaneous generation.

Redi’s Experiment

In 1668, Francesco Redi performed a simple experiment to check whether maggots (baby flies) really arose spontaneously from decaying meat.

First he observed there were flies around meat carcasses at the butcher shop.

His questions: Where did the flies come from? Did rotting meat turn into or produce the flies?

His Hypothesis was that the rotten meat does not turn into flies. Only flies can make more flies.

To test his hypothesis, he set out decaying meat in a variety of flasks/jars, some open to the air, others covered with gauze, allowing air to circulate, some sealed completely. Several jars were included in each group.

Next he recorded the presence or absence of flies and maggots in each jar.

In the uncovered jars, flies entered and laid eggs on the meat. Maggots hatched from these eggs and grew into more adult flies.

In the gauze-covered jars, flies were observed on and around it; these flies laid eggs on the gauze. And later a few of these eggs or the maggots from them dropped through the gauze onto the meat.

In the sealed jars, no flies could enter, thus no eggs or maggots were seen in those jars. Maggots arose only where flies were able to lay eggs. Therefore, decaying meat could not produce maggots. Only flies could produce maggots.

This experiment disproved the idea of spontaneous generation for larger organisms.

The End of Spontaneous Generation

After Francesco Redi’s experiment, people were willing to acknowledge that “larger” organisms didn’t arise by spontaneous generation. With the development of the microscope in the 1600s, people began seeing all sorts of new life forms. This seemed to add new evidence to the idea of spontaneous generation — it seemed perfectly logical that these minute organisms arose spontaneously. Nonetheless, Spontaneous generation continued to inspire debate.

For example, The Scottish cleric and naturalist John Needham (1713-1781), was one of the main defenders of spontaneous generation. while Lazzaro Spallanzani, (1765 – 1767), strongly disagreed with Needham. Spallanzani´s experiments refuted spontaneous generation while Needham´s seemed to prove it.

However in the 19th century (1864) the idea of spontaneous generation finally came to an end by Louis Pasteur. With a specially constructed bent flask, Pasteur demonstrated conclusively that decay was produced by air-borne micro-organisms. Pasteur’s experiment refuted the doctrine of spontaneous generation, proving that micro-organisms such as bacteria can only come from other bacteria, and maggots only come from flies just as Francesco Redi had proved in 1668. Scientists finally were convinced that living things, no matter how small, do NOT come from nonliving things.

Carl Linnaeus

Carl Linnaeus was born in the Province of Småland, (southern Sweden) the 13th of May 1707 and died the 10th of January 1778.

From a very young age he showed a deep fascination for plants. Linnaeus studied medicine, first at the University of Lund and then at the University of Uppsala. Medicine at this time was based on herbalism so it meant he also studied plants. Eventually he became a professor of medicine and botany at the University of Uppsala.

At the age of fifty, the already nobilized Carl von Linné adopted the Latinized spelling “Linnaeus”, by which he is most commonly known.

Slide 9 Linnaeus’ System of classification

Until the time of Linnaeus, common plants and animals were referred to by names that not only differed from language to language but even within the same country. To add to the confusion, a common name might be used in different parts of the same country to refer to an entirely different plant or animal. Attempts had been made by others before Linnaeus to organize the living world into some kind of order, but the attempts were meager and not universally recognized.

During the 1700s, naturalists made trips to Africa, Asia, and America and returned to Europe with thousands of specimens. This large influx of new species made naming and arranging them increasingly problematic. The old-fashioned method, linking long chains of adjectives and references into fully descriptive labels, grew unmanagable.

The importance Carl Linnaeus gave to naming is shown in his frase: “If you do not know the names of things, the knowledge of them is lost too,”

The Linnaean system classified nature within a hierarchy(hiarky), starting with three kingdoms (animal plant and mineral). Kingdoms were divided into Classes and they, in turn, into Orders, which were divided into Genre(janra) (singular: genus), which were divided into Species (singular: species).

Slide 10 Systema Naturae

Linnaeus published the first edition of (System of Nature) Systema Naturae in the year 1735, during his stay in the Netherlands. As customary of the scientific literature of its day, the book was published in Latin. In it, he outlines his ideas for the hierarchical classification of the natural world, dividing it into the animal kingdom (Regnum animale), the plant kingdom (Regnum vegetabile) and the “mineral kingdom” (Regnum lapideum).

The classification of the plant kingdom in the book was not a natural one, but one of convenience. This new system of classification became known as the “sexual system” because he recognized that flowers are sexual structures, and he counted and measured (their male and female organs) their stamens and pistils—to characterize his groups. His sexual system recognized, for example, that those flowers with five stamens would not cross with those having six and thereby assigned them to separate species.

The classification of animals was more natural. For instance, humans were for the first time placed together with other primates (as Anthropomorpha).

In view of the popularity of the work Linnaeus kept publishing new and ever expanding editions, growing from eleven pages in the first edition (1735) to three thousand pages in the final and thirteenth edition (1770). Also, as the work progressed he made changes: In the first edition whales were erroneously classified as fishes; in the 10th edition, published in 1758, the whales were moved to the mammals. In this same edition he introduced two part names for animal species, something he had done for plant species in the 1753 publication of Species Plantarum.

Slide 11 Species Plantarum
Species Plantarum was first published in 1753, as a two-volume work. It is considered the primary starting point of plant nomenclature as it exists today. Linnaeus established the Latin binomial system for naming plants, and then he extended it to all species, both plant and animal in the tenth edition of Systema Naturae, published in 1758-59.

In Species Plantarum, Linnaeus continued his plant classification system according to his sexual system earlier applied in Systema Naturae.

However Linnaeus standardized a new system of naming. It was called the binomial (two names) naming system. He designated one Latin name to indicate the genus, and another name for the species. Linnaeus picked Latin because it was the universal language of science, the only language that provided “mutual understanding.

Slide 12 Linnaeus’s contributions to science

Linnaeus’s contributions to the sciences is evident to this day

When he died in 1778 all his specimens, books, and letters were sold to Sir James Edward Smith a wealthy English collector who founded the Linnean Society of London. This Society soon became the focal gathering point for the world’s leading naturalists of the nineteenth century and is the oldest specialized biological society in the world.

The monumental Systema Naturae was internationally accepted by nineteenth century naturalists consider it as the starting point for the modern scientific naming of all organisms. The Linnean hierarchy of kingdom (animal, mineral, or vegetable), class, order, genera, and species is still followed today, but with the addition of several other divisions and subdivisions such as phylum, family, and sometimes subspecies.

Linnaeus devised a system of classification whereby any plant or animal could be identified just by two words. The same name could be used all over the world, in all languages, avoiding difficulties of translation. This system, which we can usually find naming plants and animals in our zoos and museums remains until present day, and simplifies communication between scientists worldwide.

By: Cristian Sánchez-Bayton Griffth


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