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In the Fact File section we bring you a new collection of quick facts each week. (Click on the links below for more facts)

 
 

2801/ Charles Darwin's On the Origin of Species was first published on the 24th of November in 1859.

2802/ In the absence of an adequate fossil record, for a long time it was essentially impossible to determine the geological age of many evolutionary lineages. However, Zuckerkandl and Pauling (1962) showed that many, perhaps most, molecules have a rather constant rate of change over time. Such molecules can serve as a molecular clock. Well-dated fossils with modern descendants provide us with a yardstick for calibrating a given molecular clock.

2803/ It was by the molecular clock method that the branching point between chimpanzee and man was shown to be as recent as 5-8 million years ago, rather than 14-16 million years, as had been previously generally accepted.

2804/ The earliest fossil life was found in strata about 3.5 billion years old. These earliest fossils are bacteria like, indeed they are remarkably similar to some blue-green bacteria and other bacteria that are still living.

2805/ About a third of the early fossil species of prokaryotes are indistinguishable from still living species and nearly all of them can be placed in modern genera.

2806/ After about 1,000 million years of exclusively bacterial life on Earth, perhaps the most important and dramatic event in the history of life took place - the origin of the eukaryotes. Eukaryotes differ strikingly from prokaryotes by the possession of a nucleus surrounded by a membrane and containing individual chromosomes.

2807/ Genome size is measured in terms of the number of base pairs, although for practical reasons the units are megabases (1,000 base pairs, abbreviated Mb). The genome of humans is about 3500 Mb. In a bacterium it may only be about 4 Mb. Very large figures are also found in salamanders and lungfishes.

2808/ When the pharaohs' tombs were opened in Egypt early in the nineteenth century, not only human mummies were found but also those of sacred animals such as cats and ibises. When the anatomy of these animal mummies, estimated to be about 4000 years old, was carefully compared by zoologists with living representatives of these species, no visible differences could be found.

2809/ Certain deep-sea fish have dwarf males that are attached to the females, because free-swimming males might have difficulty finding females in these vast and rather lifeless spaces.

2810/ In certain species of seals, like the elephant seal, males may be several times larger than females because larger males can better defeat their rivals in territorial fights and so acquire larger harems.

2811/ Emperor Penguins court and lay their single egg under the most adverse conditions at the beginning or in the middle of the Antarctic winter, a season of frequent blizzards. The advantage of this timing is that the young hatch at the beginning of the Southern Spring and are raised during the southern summer, when conditions for their survival and growth are at an optimum.

2812/ Darwin marvelled that such a wonderful structure as an eye could have evolved through natural selection, but comparative anatomists have shown not only that eyes evolved in the animal species at least 40 times independently, but also that among the existing photosensitive organs every intermediate step is found between a simple light-sensitive spot on the epidermis and a perfect eye with all its accessories.

2813/ About three new species of bird are discovered each year.

2814/ In 1758 Linnaeus knew some 9,000 species of plants and animals. By now about 1.8 million species of animals have been described (excluding agamospecies) and the grand total of species is estimated to be at least 5 to 10 million. Most of these live in the canopy of the tropical rain forest and, with 1-2 percentof this forest being destroyed every year, this number will soon be reduced appreciably.

2815/ There are currently thought to be about 9,800 species of warm-blooded aerial birds and 4,800 species of terrestrial warm blooded mammals.

2816/ Beetles are the largest group of animals. It is believed that the number of species of beetles range from approximately 250,000 to 350,000.

2817/ Almost 50 percent of North American species of cricket were discovered only by their different songs, they are that similar to each other.

2818/ During a drought period in the Pliocene (ca. 6 million years ago), the softer grasses in North America were largely replaced by harsher grasses, which had three times as much silica content.

2819/ Among the browsing horses, all species became extinct except those with the longest teeth.

2820/ Particularly in the Americas, the native populations were ravaged by epidemics caused by European infectious diseases, particularly smallpox. The native population of the Americas, which was estimated to have been 60 million when Columbus first landed in the Bahamas, had crashed to 5 million only 20 years later.

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