Nov 30, 2014

History of Biology

The systematic approach to biology started with the Greek philosophers about 2,500 years ago. Aristotle (384-322 B.C.) is considered the "father of biology" for his classification of animals and for performing the first known biology experiments, dissecting plants and animals and studying the development of the chick in its egg. His student Theophrastus (ca. 372-286 B.C.) laid the foundation of botany, describing and classifying more than 500 plants and also describing the ways plants can germinate and grow. In Roman times, Lucretius (99-55 B.C.) proposed one of the earliest theories of evolution. But other than medical knowledge, biology made little progress until after the Middle Ages.

In the 15th and 16th centuries Europeans explored the Americas and some of the Pacific islands, and regular contact between Europe and southern Africa and eastern Asia was instituted. As a result European scholars were exposed to a great variety of plants and animals that were new to them. They responded with books describing and classifying both newfound and familiar plants and animals, starting as early as 1530. A few years later the first botanical gardens began to be established. When the scientific revolution of the 17th century began, scientists undertook more detailed experiments in biology. For example, Jan van Helmont (1579-1694) carefully measured the weight of soil in a tub as a willow grew there, establishing that the increase in mass of the willow was much greater than any diminution of mass of the soil.

Nov 23, 2014

The universe’s invisible web

Something out there holds swarms of galaxies together and keeps their stars from flying apart, but scientists still haven’t learned what this invisible substance is. Known as dark matter, it gathers to form a colossal cosmic scaffolding. Astronomers believe that galaxies formed at the densest points in this weblike structure, and the dark matter continues to hold them in place with its gravity. Its bulky presence can be detected by tracking stars on the outskirts of galaxies, which move at speeds that would be impossible if only visible matter – a galaxy’s other stars and gas – were pulling them. Astronomers have also mapped this unseen substance with the help of an effect predicted by Einstein’s general relativity; Dark matter’s gravity wrinkles space-time, bending light rays as they pass. Such measurements indicate that dark matter could make up 90 percent of the universe’s total mass. These days, cosmologists are searching for the identity of dark matter, trying to detect the elusive substance responsible for arranging everything we see in the sky. 
(National Geographic, May 2005)

Nov 16, 2014

Healthy foods, healthy arteries: is there a connection?

What you eat can help keep your heart and arteries healthy — or lead to excessive weight, high blood   pressure, and high blood cholesterol — three key factors that increase the risk of developing cardiovascular disease, according to the National Heart, Lung, and Blood Institute. Based on the best available scientific evidence, the American Heart Association (AHA) recommends a diet that includes a variety of fruits, vegetables, and grains, while limiting consumption of saturated fat and sodium.  

Fruits and vegetables have lots of antioxidants such as vitamin C and vitamin A that neutralize free radicals and may prevent oxidation in the arteries, dietary experts say. Fruits and vegetables also contain plenty of soluble fiber, a substance that has been shown to reduce blood cholesterol levels, which is healthy for the endothelium.  

Breads, cereals, and other grain foods, which provide complex carbohydrates, vitamins, minerals, and fiber, are associated with a decreased risk of cardiovascular disease, according to the AHA Dietary Guidelines. However, some studies suggest eating less sugar, breads, and other simple and complex carbohydrates can lower blood insulin levels and decrease body fat and weight — three factors that are linked to an increased risk of heart disease and stroke. In recent years, a number of dietary recommendations based on these findings have become popular and are currently catching   the public’s awareness. While contentious, these are important issues and long-term studies are required to determine the risks and benefits of such diets, Dr. Lakatta says. 

Nov 9, 2014

Viruses on other life-bearing planets

It has been proposed that viruses are likely to be encountered on other life-bearing planets. Efforts to discover current or past life on Mars is an active area of research. On 24 January 2014, NASA reported that current studies on the planet Mars by the Curiosity and Opportunity rovers will now be searching for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic and/or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable. The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars is now a primary NASA objective. 
(Wikipedia)

Nov 2, 2014

Ancient Egypt - political history

Ancient Egypt was one of the world's great early civilizations, a nation and culture that dominated northern Africa for nearly 3,000 years and saw hundreds of kings rule over some 30 dynasties. Factors like climate and geography, together with innovative leadership and bureaucratic organization, made possible a legacy that continues to fascinate scholars and amateurs alike: the pyramids, with their staggering scale and mathematical ingenuity; mummies and tombs that provide modern researchers with an enormous body of material to examine; and innumerable carvings of pictures and writing, made decipherable by the Rosetta Stone. The unusually high status of women, the worship of gods of sun and nature, and a fixation on the afterlife are some of the themes that make ancient Egypt alluring to modem students.

As the Ganges was to India and the Yangtze to China, the Nile River was the mother of Egyptian civilization, spurring the rise of agriculture, trade, and one of the most successful societies in the ancient world. Flowing northward out of Burundi into Lake Victoria then through Uganda and Sudan on its way to the Mediterranean Sea, the Nile is the longest river in the world, traversing more than 4,000 miles of the African continent.