What causes giantism and dwarfism?

Being very tall or short does not constitute either gigantism or dwarfism. Men and women can range in height from 4 feet 7 inches (140 centimetres to 6 feet 7 inches (201 cm) and still be considered normal.

Giantism and dwarfism are specific growth disorders that can usually be traced to something that has gone awry in the pituitary, but sometimes dwarfism can be caused by malnutrition or by diseases of the kidney, heart, or liver. As a rule, too much GH (growth hormone) leads to giantism and too little dwarfism, but the timing of the secretions is also important.

If the pituitary overproduces GH before the end of adolescence, the outcome is likely to be excessive growth. But if the oversecretion comes after adolescence, the hormone acts unevenly. Because growth in stature has essentially ceased, and because GH acts only on the parts of the skeleton still not completely hardened by mineralization, the excess hormone may cause large extremities or, in rare instances, a condition called acromegaly, marked by enlargement of the face, feet, and hands.

Is the Sahara on the move?

The southern fringe of the Sahara, known as the Sahel, is believed by some scientists to be advancing by as much as 9 miles (15km) a year. Horrifying reports of drought, starvation and death in Ethiopia, Somalia and Sudan have shocked the world. But is the Sahara really moving southwards or are the devastating crop failures being caused by politics and by bad management of land?

Global warming caused by increased carbon dioxide in the atmosphere from human activities is often blamed for the Sahel famines, but there is little proof. There is, however, plenty of evidence that the climate has fluctuated in log cycles over the past 2 million years. Stone Age paintings depict antelopes, elephants and lions at Tassili N’Ajjer in the Algerian Sahara. And roman cities all over North Africa, such as Leptis Magna in Libya, once ruled over the granaries of the Roman Empire where fields grew grain – without any need for irrigation – to be exported to Rome. Now the former farms are dusty plains of semi-desert. This is part of the natural climatic cycle – each cycle taking thousands of years – that is brought about by changes in the Earth’s orbit around the Sun. it is the same cycle that caused the Ice Ages, and could now be at work to cause the Sahara to march in the Sahel.

However, the growth of deserts can also be blamed on man’s treatment of the land. Cutting down trees and scrub to open up land for farming can expose soil to the ravages of erosion. Bad management of land on slopes, such as ploughing furrows up and down a hill instead of around it, can cause soil to be washed down or blown away. Bad farming practice in the American Midwest during the 1930s reduced an area of farmland nearly the size of England to a dust bowl. This type of soil erosion happens on the edges of the Sahara when grassland with poor oil is ploughed up to grow crops.

Overgrazing by farm animals is also alleged to cause erosion, but the evidence is inconclusive. Animals can actually encourage plant growth by fertilizing the soil with their manure. Nomadic farmers, who have roamed and flourished in the deserts for thousands of years, never stay in one place for long. They move their flocks frequently, giving grass time to grow again. Only if they are stopped from moving on will their animals over-graze the land.

In the short term, politics are probably as strong a factor as climate change is causing the Sahel famines. Wars in Ethiopia and Somalia have forced refugees to migrate into semi-arid land that cannot support them. Social and economic pressures, such as government settlement policies, have also forced people to give up traditional nomadic farming and change to static Western farming methods that are not suited to the land and climate, and so lead to ‘dust bowls’.

Climatic change is an easy scapegoat for countries suffering from famine, but the case has not yet been proved.

Early Life on Earth

About 3.5 billion years ago

Earth was covered by one gigantic reddish ocean. The colour came from hydrocarbons. 

The first life-forms on Earth were Archaea (single-celled microorganisms with a structure similar to bacteria) that could live without oxygen. They released large amounts of methane gas into an atmosphere that would have been poisonous to us. 

About 3 billion years ago

Erupting volcanoes linked together to form larger landmasses. And a new form of life appeared - cyanobacteria, the first living things that used energy from the sun. 

Some 2 billion years ago

The cyanobacteria algae filled the air with oxygen, killing off the methane-producing Archaea. Coloured pools of greenish-brown plant life floated on the oceans. The oxygen revolution that would someday make human life possible was now underway. 

About 530 million years ago

The Cambrian explosion occurred. It's called an explosion because it's the time when most major animal groups first appeared in our fossil records. Back then, Earth was made up of swamps, seas, a few active volcanoes, and oceans teeming with strange life. 

More than 450 million years ago

Life began moving from the oceans onto dry land. About 200 million years later dinosaurs began to appear. They would dominate life on Earth for more than 150 million years. 

5 Animals Battling Climate Change

Polar Bear

Where it lives

Canada, Greenland, Russia, Norway, and Alaska, The U.S.A.

Why it is threatened

Due to shrinking amounts of sea ice in the Arctic, polar bears are losing their habitat - and changing sea temperatures are reducing the prey that polar bears rely on for food. 

Adelie Penguin

Where it lives

Antarctica

Why it is threatened

By 2099, 58 per cent of the habitat where Adelie penguins lay their eggs could be too warm and too wet to host colonies. 

American Pika

Where it lives

Mountaintops of the western U.S. and southwestern Canada.

Why it is threatened

Rising temperatures are causing changes in vegetation in the pika's range, making it difficult for the animal to find food. 

Orange-Spotted Filefish

Where it lives

Indo-Pacific coral reefs.

Why it threatened

Not only are coral reefs - the fish's habitat - in decline, but filefish are especially sensitive to warmer waters. 

Gila Monster

Where it lives

Southwestern U.S., northwest Mexico.

Whey it is threatened 

Hotter, drier conditions in the deserts mean this colourful lizard is not getting enough water to survive, causing a decline in its numbers. 

DINO Classification

Classifying dinosaurs and all other living things can be a complicated matter, so scientists have devised a system to help with the process. Dinosaurs are put into groups based on a very large range of characteristics. 

Scientists put dinosaurs into two major groups:

• The bird-hipped ornithischians and
• The reptile-hipped saurischians. 

Bird-hipped (pubis bone in hips points backwards)

Ornithischians have the same-shaped pubis as birds of today, but today's birds are actually more closely related to the saurischians. 

Example: Styracosaurus

Reptile-hipped (pubis bone in hips points forward)

Saurischians are further divided into two groups: the meat-eating Theropoda and the plant-eating Sauropodomorpha. 

Example: Tyrannosaurus rex

Within these two main divisions, dinosaurs are then separated into order and then families, such as Stegosauria. Like other members of the Stegosauria, Stegosaurus had spines and plates along the back, neck, and tail.

5 Amazing Facts About History

Fact#1

Attila The Hun, who sought to conquer much of the Roman Empire in the fifth century, was a calculating and ruthless leader. He even killed his own brother, Bleda, in order to secure his rule. 

Fact#2

Dentists in ancient Egypt recommended putting a mouse that had just been killed in your mouth as a remedy for bad breath.

Fact#3

The cure for a headache in ancient Peru was skull drilling. Many people survived the early form of brain surgery. Some even wore their skull chips around their necks to drive away evil spirits. 

Fact#4

When the Vikings attacked Paris, France, in 885, the French defended themselves by pouring boiling oil on the invaders. 

Fact#5

In 1969, Buzz Aldrin became the first man to pee on the moon. 

ENJOY!

Otzi - The Iceman

In September 1991, two German hikers on a remote pass in the Tyrolean Alps stumbled on a body of a man lying half-buried in the snow, with one hand shielding his head and eyes as if to protect himself from a snowstorm. The corpse was first thought to be that of one of the many climbers who have perished in the mountains over the last 200 years, later it was discovered by fascinated scientists to be the mummified remains of a Bronze Age man more than 5000 years old. The dead man was about 5ft  2in (1.57m) tall and weighed 121lb (55kg). He wore leather shoes and a leather tunic and leggings which had been padded with dry grass for insulation against the cold. The stone bead strung on a leather thong around the neck may have been worn as jewellery or was perhaps a badge of rank. He also carried hunting tools. Scientists who examined his remains at the University of Innsbruck in Austria gave him the nickname Otzi, after the Otztaler Alps where he met his death. The body is now in a museum at Bolzano, Italy.