Life on Earth
Our planet is remarkable because it contains something that scientists have found nowhere else in space-life. Earth is home to an incredible variety of life forms, from single cell bacteria to complex organisms such as human beings. There are millions of different species of living creatures on Earth, but the origins of life on our planet are nuclear.
Origins of life
Nobody exactly knows what it takes for life to begin, but scientists have considered that living cells were carried to Earth by comets. Halley's comet was investigated by Giotto probe in 1986, and its nucleus was found to contain molecules that were similar to living cells. If a comet such as this collided with Earth at just the right time, life may have taken hold. Others believe that lightening bolts that flashed through Earth's early atmosphere caused chemical reactions in the air. These changes led to living cells being created.
The Earth clock
We can look at the entire history of the Earth as a clock, with 12 o' clock midnight being the time Earth was formed 4.6 billion years ago. Each hour on the clock represents 383 million years, and each minute spans just over 6 million years. We know very little about the first two hours of the Earth clock because the planet was still forming(red). Primitive life evolved over billions of years (blue). The dinosaurs only appeared at 11:30pm and lasted less than half an hour (purple). Mammals have not lived on Earth for half this time (green), and human beings have been around for less than a minute (yellow)!
Some important facts
1) Earth started life as a huge ball of liquid rock. Gradually the surface began to cool and harden.
2) As Earth cooled down, it gave off clouds of steam and gas. The moisture in these clouds eventually turned to rain, which formed the first seas.
3) Around four billion years ago, the first single cell organisms formed in the oceans.
4) Fish developed and evolved into amphibians. As the Earth became drier, amphibians evolved into reptiles that could survive better on land.
5) Dinosaurs lived on Earth between 220 and 65 million years ago. These successful reptiles are believed to have wiped out by a huge meteorite.
6) The first mammals appeared over 200 million years ago but it was less than 2 million years that the early ancestors of modern humans developed.
7) Today, we are realizing that destructive human behaviour may pose a threat to all life.
Facts and Figures
2,500 million years ago : The first organisms developed in the seas.
400 million years ago : Fish developed
280 million years ago : The first insects and reptiles developed.
220 million years ago : Dinosaurs lived on Earth.The first mammals were also developing at this time.
1.6 million years ago : The climate began to alternate between warmer periods and Ice Ages.
More than 1.5 million years ago : Early human species developed.
Our planet is remarkable because it contains something that scientists have found nowhere else in space-life. Earth is home to an incredible variety of life forms, from single cell bacteria to complex organisms such as human beings. There are millions of different species of living creatures on Earth, but the origins of life on our planet are nuclear.
Origins of life
Nobody exactly knows what it takes for life to begin, but scientists have considered that living cells were carried to Earth by comets. Halley's comet was investigated by Giotto probe in 1986, and its nucleus was found to contain molecules that were similar to living cells. If a comet such as this collided with Earth at just the right time, life may have taken hold. Others believe that lightening bolts that flashed through Earth's early atmosphere caused chemical reactions in the air. These changes led to living cells being created.
The Earth clock
We can look at the entire history of the Earth as a clock, with 12 o' clock midnight being the time Earth was formed 4.6 billion years ago. Each hour on the clock represents 383 million years, and each minute spans just over 6 million years. We know very little about the first two hours of the Earth clock because the planet was still forming(red). Primitive life evolved over billions of years (blue). The dinosaurs only appeared at 11:30pm and lasted less than half an hour (purple). Mammals have not lived on Earth for half this time (green), and human beings have been around for less than a minute (yellow)!
Some important facts
1) Earth started life as a huge ball of liquid rock. Gradually the surface began to cool and harden.
2) As Earth cooled down, it gave off clouds of steam and gas. The moisture in these clouds eventually turned to rain, which formed the first seas.
3) Around four billion years ago, the first single cell organisms formed in the oceans.
4) Fish developed and evolved into amphibians. As the Earth became drier, amphibians evolved into reptiles that could survive better on land.
5) Dinosaurs lived on Earth between 220 and 65 million years ago. These successful reptiles are believed to have wiped out by a huge meteorite.
6) The first mammals appeared over 200 million years ago but it was less than 2 million years that the early ancestors of modern humans developed.
7) Today, we are realizing that destructive human behaviour may pose a threat to all life.
Facts and Figures
2,500 million years ago : The first organisms developed in the seas.
400 million years ago : Fish developed
280 million years ago : The first insects and reptiles developed.
220 million years ago : Dinosaurs lived on Earth.The first mammals were also developing at this time.
1.6 million years ago : The climate began to alternate between warmer periods and Ice Ages.
More than 1.5 million years ago : Early human species developed.
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