Friday, November 6, 2009

Eye Candy

Sponges

A brief introduction before I begin. I've decided to test out a new series of posts about life on earth. Most of these posts will be about different types of animals, but plants will be included intermittently.

Life has been present on earth for over 3.5 billion years. It has since diversified into a vast assortment of different organisms. Animals all share two key features: first, they obtain their energy from food (as opposed to plants, which produce their own food by photosynthesis); second, they are multi-cellular, which distinguishes them from single celled organisms.

My inaugural post on animal life concerns the simplest of all animals...

Sponges (Porifera)

Sponges were once thought to be plants because they spend their entire adult life fixed to the sea floor, unable to move around. On land, animals must move around in search of food. In the ocean, water currents carry an abundant supply of food in the form of microscopic plankton. Fixed animals can take advantage of this by filtering their food from the water, without having to move from place to place.

When it is time to reproduce, they shed sperm and eggs into the water. Currents distribute them to new area, where they can settle and grow.

The anatomy of a sponge has no symmetry, nor do they have distinctive body parts. A sponge consists of a cooperating community of individual cells, which surround a system of canals through which water is pumped. As water passes through, plankton and particles of organic matter are trapped inside. Rigidity is provided by a skeleton of tiny, bony splinters called spicules, scattered throughout the body.

Some sponges grow to about 6 1/2 feet tall. The largest may be hundreds of years old. There are more than 15,000 different types of sponges in a breathtaking variety of colors. Grays and browns predominate in deeper waters, brighter colors in the shallows.

Six species of sponges are considered commercially marketable, especially a type called demosponges, whose populations are now badly affected by over-collection. Mediterranean sponges are the softest and best. These are gathered by divers and then cut into the familiar blocks seen on supermarket shelves. Fortunately, most kitchen and bath sponges are now synthetic, and were never really living sponges at all.

The elegant branches of the tube sponge are easily torn, so this variety is found only in very deep water where wave turbulence is minimal. Tube sponges are most common in the tropical waters of the south Pacific, and they typically grow to about 3 feet in length. It is sometimes seen as a single tube, but more often as a series of branches joined at the base. When this sponge releases its sperm into the water, it resembles a smoking chimney.

Most sponges need a hard surface for attachment, although a few can bore through soft sediment. For this reason they often form beautiful "gardens" in shipwrecks and on coral reefs. The largest populations exist where tidal currents are strong, which brings extra food. Other animals such as crabs and worms sometimes live inside of sponges.

There aren't too many interesting books just about sponges, but there are lots of good ones about all kinds of animal life. Animal: The Definitive Visual Guide, by David Burnie and Don Wilson is a good first step for an interest in animals in general. Ocean, by Philip Eales, David Burnie, and Frances Dipper is a good one about sea life. Both are filled with interesting facts and lots of glossy pictures, perfect for yourself or as a holiday gift.

Wednesday, November 4, 2009

Eye Candy

The History of Civilization

Chapter Twenty: Alexander the Great

King of Macedonia, conqueror of Persia, and one of the greatest military geniuses of all time; Alexander the Great traveled further east than any European until Marco Polo, more than a thousand years later. He is the most famous person from the classical world, with the exception of Christ.

Physically, he was ideal: handsome, charming, and good at every sport. His boyhood tutor, Aristotle, had given him a love for Greek literature and philosophy which enriched his military career with true statesmanship. He liked hard work, dangerous enterprises, and never wanted to rest. Legend claimed he tamed an incorrigible horse, named Bucephalas, when he was only ten years old, apparently unaware of the danger of being trampled to death. He also introduced to Europe the custom of shaving, claiming that a beard was too easy for an enemy to grab during combat. In this little item, perhaps, he had his greatest influence on history.

When Alexander became king, he was faced with wide-scale rebellion through the rest of Greece. His father, Philip, had been assassinated, and the king of Persia believed it would be easy to defeat the immature twenty year-old who was now leading Europe's mightiest army. Meanwhile, there was unrest at home as well. Philip had been unpopular with his Greek subjects, many of whom had been brought into the empire by unwilling conquest. When news of his death reached Athens there was public celebration. Within Macedonia, a dozen factions conspired to kill the young king.

Alexander rose to the situation with an energy that ended all internal opposition, and set the tempo of his career. He arrested and decapitated all the plotters at home in Macedonia, then marched his army south to Greece, arriving at Thebes within a few days. The Greek city-states quickly renewed their allegiance, and sent a profuse apology for celebrating his father's death. Alexander, appeased, declared all dictatorships abolished and let each Greek city live in freedom according to its own laws.

His promptness in crushing the revolt and characteristic generosity in dealing with the defeated brought the other Greek cities into an instant and abject submission.

With Greece now secure, Alexander began his war against Persia in the spring of 334 BC, with an army of 35,000. At Troy he encountered a Persian force of 40,000 and soundly defeated them, losing only 110 of his own soldiers. Continuing his advance southward he encountered the main Persian army in northeastern Syria.

Ancient tradition claims that Darius' army contained 600,000 men, although this is now believed to be a wild exaggeration. In any case, the Battle of Issus, in 333 BC, resulted in a great victory for Alexander. Darius fled, abandoning his mother, wife, and children to Alexander, who treated them with all the respect due to royalty.

Before continuing his campaign, Alexander paused in 332 BC to secure the Mediterranean coastline. While here he founded, on the mouth of the Nile River, the city of Alexandria, which would become the literary, scientific, and commercial center of the Mediterranean world. The city hosted a magnificent harbor and a famous lighthouse, considered one of the Seven Wonders of the ancient world.
Here the Jews came into contact with Greek learning, which profoundly influenced later religious thought; and the Greek translation of the Old Testament, called the Septuagint, came into being.

Everywhere he went, Alexander founded Greek cities as part of his strategy of "conquest by civilization". Each city was designed along Greek lines with help from the king's architects and city planners. The vast network of new towns (about 70 in all) was the key to the Hellenization of the territory he had conquered.

Alexander had some impressive early victories, but the Persian King Darius was still at large, and the Macedonian army had yet to make a move into Persian territory beyond the Euphrates River. He wanted to defeat the Persian powers which had threatened Greek civilization for centuries. To do this he had to move his army into unknown territory.

To be continued...

Naturally, there are a lot of great books about Alexander. He's one of the most famous people of all time. My personal favorite is In the Footsteps of Alexander the Great: A Journey from Greece to Asia, by Michael Wood.

For my previous posts on the History of Civilization click here.

Tuesday, November 3, 2009

Eye Candy


Quotations

I cannot pretend to feel impartial about colors. I rejoice with the brilliant ones, and am generally sorry for the poor browns.
Winston Churchill (1874 - 1965)

Do not go where the path may lead, go instead where there is no path and leave a trail.
Ralph Waldo Emerson (1803 - 1882)

One needs to be slow to form convictions, but once formed they must be defended against the heaviest odds.
Mahatma Gandhi (1869 - 1948)

Make money your god and it will plague you like the devil.
Henry Fielding (1707 - 1754)


One man practicing sportsmanship is better than a hundred teaching it.
Knute Rockne (1888 - 1931)

It is a rough road that leads to the heights of greatness.
Seneca (4 BC - 65 AD)


The discovery of a new dish does more for human happiness than the discovery of a new star.
Anthelme Brillat-Savarin (1755 - 1826)

A single day is enough to make us a little larger.
Paul Klee (1879 - 1940)

To find fault is easy, to do better is difficult.
Plutarch (46 - 120)

Birds sing after a storm; why shouldn't people feel as free to delight in whatever sunlight remains to them?
Rose Kennedy (1890 - 1995)

Eye Candy

Tyrannosaurus Rex

Tyrannosaurus Rex and its subgroup, the Tyrannosaurids, were some of the largest land predators the world has ever known. They were several times larger than the largest land predators of today, such as the grizzly bear, which weighs less than one metric ton. Tyrannosaurus Rex weighed more than five metric tons. The mouth was wide enough to swallow an adult human, and the bite was three times as powerful as that of a lion. Possibly the best known of all dinosaurs, it was considered the "king of the dinosaurs" until the discovery of larger allosaurids, such as gigantosaurus in the 1990s.

About 20 skeletons of Tyrannosaurus Rex have been excavated, so the appearance of this dinosaur is known with some confidence. It was present at the mass extinction event, 65 million years ago, which ended the ended the age of dinosaurs.

It was first discovered in the Hell Creek Formation in Montana, probably the best record anywhere on earth of life at the end of the Cretaceous era, just before and during the mass extinction event that wiped out 35 percent of all species including the dinosaurs. This formation has yielded thousands of fossils, including the T-Rex skeletons in the American Museum of Natural History and the Smithsonian Institution. During the Cretaceous era the area was warm and humid with open forests and rivers. It was not swampy.

Scientists debate the lifestyle of Tyrannosaurus: was it a fearsome predator, as has always been portrayed? Or was it a slow-moving animal, living as a scavenger on the corpses of animals that had died or had been killed by more active hunters?

Evidence for the first theory includes the position of the eyes. The fields of vision overlap, so the animal had good depth perception, essential for a hunter of fast-moving prey. The teeth and skull certainly seem very strong, able to withstand the stress caused by struggling prey. Although they are much larger, the teeth are almost exactly the same shape as those of monitor lizards, the most vicious predatory reptiles of modern times. The ear structure is like that of crocodiles, which have good hearing.
Marks that match Tyrannosaurus teeth have been found on the bones of Triceratops, and Tyrannosaurus teeth have been found wedged in the bones of the duck-billed dinosaur Hypacrosaurus.

On the other hand, animals as big as Tyrannosaurus might not have been capable of much sustained speed or activity. Once up to speed the animal could stumble easily, resulting in a crash that might have been fatal.

It is very likely that both theories are true to a degree: Tyrannosaurus was probably an occasional hunter when threatened with starvation, but did not pass up the chance to devour any corpse it came across. Trackways suggest that it might have followed great herds of plant-eating dinosaurs, preying on easy victims such as the young and the injured.

The small arms of Tyrannosaurus Rex have always been a mystery. What good is a pair of arms that is too short to reach the mouth, or anything else?

There are three main theories: First, that they were used to pull prey toward the chest so that the jaws could reach it. Second, that they were used to grasp the female while mating. Third, that they could help the animal get up from a lying down position.
The arms were surprisingly powerful: the same length as a human arm, but three times as thick. Still more peculiar, the arms end in only two clawed fingers, useless for grasping.

No one can explain any of this for certain, and it's a good example of how some aspects of dinosaur behavior cannot be solved by the fossil record.

There are a lot of terrific books about dinosaurs, perfect for holiday gifts. A few of my favorites include the Illustrated Encyclopedia of Dinosaurs, by Dougal Dixon; National Geographic Dinosaurs, by Paul Barrett; and Dinosaurus: The Complete Guide to Dinosaurs, by Steve Parker. All are available online at our sponsor, Barnes & Noble.

For my previous posts on dinosaurs, click here.