Why do animals evolve?
Evolution has produced all the creatures found on Earth. The evidence for this comes from fossils, and from comparing the structure and chemistry of living creatures. But what makes evolution happen? Scientists believe that the answer is something called 'natural selection'. All animals and plants produce more young than can possibly survive. Some die, while others go on to produce young of their own. In general, the one that are best suited to their environment survive, while the weakest die out. Because the best adapted survive and are most likely to pass on their genes to the next generation, the species gradually becomes more suited to its environment.
Saturday, November 17, 2007
The evolution of the horse
Horse belong to a family of animals 50 million years old. The earliest ancestor of the horse. called Hyracotherium, was a size of the dog, and had four-toed feet. Its descendants grew bigger, and evolved longer legs with fewer toes. Today's horses have just one toe or hoof on each foot.
From tadpole to frog
The ancestors of frog were fish that could pull themselve around using strong, fleshy front fins. About 300 million years ago, these fish gradually started to crawl out onto dry land. Today, frog still re-enact this part of their past, because they start life as todpoles, which swim around by lashing their tails. After a few weeks tadpoles start to lose their tails. They grow legs and take up life on land.
Horse belong to a family of animals 50 million years old. The earliest ancestor of the horse. called Hyracotherium, was a size of the dog, and had four-toed feet. Its descendants grew bigger, and evolved longer legs with fewer toes. Today's horses have just one toe or hoof on each foot.
From tadpole to frog
The ancestors of frog were fish that could pull themselve around using strong, fleshy front fins. About 300 million years ago, these fish gradually started to crawl out onto dry land. Today, frog still re-enact this part of their past, because they start life as todpoles, which swim around by lashing their tails. After a few weeks tadpoles start to lose their tails. They grow legs and take up life on land.
Friday, November 16, 2007
EVOLUTION STORY
Every living thing on Earth is descended from one common ancestor that lived long ago. We know this because, although living things different genes, they have all inherited the same genetic code to make those genes work. That ancestor was probably a creature similar to a bacterium. But how could a bacterium produce descendants as different as sharks, daisies, cucumbers and camels? Living things slowly change, or evolve. Over millions of years, tiny differences have built up to produce completely new species.
Our tiny ancestors
When dinosaurs were striding about the Earth, our ancestors were there, too, although Tyrannosaurus rex probably never noticed them as they scurried past his toes. They were timid creatures, rather like modern-day shrews but larger. After the dinosaurs died out, these unlikely ancestors began to flourish and gave rise to all the mammals, including ourselves.
Our tiny ancestors
When dinosaurs were striding about the Earth, our ancestors were there, too, although Tyrannosaurus rex probably never noticed them as they scurried past his toes. They were timid creatures, rather like modern-day shrews but larger. After the dinosaurs died out, these unlikely ancestors began to flourish and gave rise to all the mammals, including ourselves.
Creation Or Evolution?
Is evolution just a theory? You can prove creation.
Is evolution just a theory? You can prove creation.
Is there life in outer space?
Despite listening very carefully for radio signal, scientists have not found any signs of life in space. But many of them think it likely that life has developed elsewhere. How many other planets might be inhabited? To answer this difficult question, an astronomer devised the equation :
1. Formed a stars in the Milky Way
2. Percentage of these stars form planet
3. Percentage of the planets are suitable for life
4. Percentage of these has life evolved
5. Percentage of these planets have intelligent life
6. Percentage of these can communicate
7. Communicating civilisation last
Despite listening very carefully for radio signal, scientists have not found any signs of life in space. But many of them think it likely that life has developed elsewhere. How many other planets might be inhabited? To answer this difficult question, an astronomer devised the equation :
1. Formed a stars in the Milky Way
2. Percentage of these stars form planet
3. Percentage of the planets are suitable for life
4. Percentage of these has life evolved
5. Percentage of these planets have intelligent life
6. Percentage of these can communicate
7. Communicating civilisation last
Thursday, November 15, 2007
Why does the Earth have life?
Several things about planet Earth make it uniquely suite to life. The main one is abundant water. No other planet that we know of has the huge oceans we have, nor the many lakes and rivers. Water is a very important ingredient of all living things because it has many properties that no other substance has. All the important reactions that occur inside our cells require water, and all the organs in our bodies, such as the heart and lungs and liver, rely on being surrounded by water. Without water, life as we know it could not go on. Could there be a completely different kind of life form that is not based on water? Scientists have tried to imagine such life forms, but it is hard to see what could take the place of water.
Several things about planet Earth make it uniquely suite to life. The main one is abundant water. No other planet that we know of has the huge oceans we have, nor the many lakes and rivers. Water is a very important ingredient of all living things because it has many properties that no other substance has. All the important reactions that occur inside our cells require water, and all the organs in our bodies, such as the heart and lungs and liver, rely on being surrounded by water. Without water, life as we know it could not go on. Could there be a completely different kind of life form that is not based on water? Scientists have tried to imagine such life forms, but it is hard to see what could take the place of water.
Oxygen
Oxygen changes everything
The earliest living things were bacteria, which grew by using chemicals in the sea. When the chemicals started to run out, it became harder for life to survive. Some living thing, called cyanobacteria, found a new way of growing, called photosynthesis. Photosynthesis works by using the energy in sunlight, and it produces oxygen as a waste product. As this new gas began to build up, the Earth's atmosphere changed, creating the kind of air we breathe today.
Oxygen avoiders
Some prehistoric bacteria from the start of life have descendants that we can study. This bacteria cannot tolerate oxygen, because it was not part of Earth's ancient atmosphere. They live in the black mud at the bottom of marshes, or in other places without oxygen. They make food by chemical reactions, and do not rely on sunlight like other living things.
The earliest living things were bacteria, which grew by using chemicals in the sea. When the chemicals started to run out, it became harder for life to survive. Some living thing, called cyanobacteria, found a new way of growing, called photosynthesis. Photosynthesis works by using the energy in sunlight, and it produces oxygen as a waste product. As this new gas began to build up, the Earth's atmosphere changed, creating the kind of air we breathe today.
Oxygen avoiders
Some prehistoric bacteria from the start of life have descendants that we can study. This bacteria cannot tolerate oxygen, because it was not part of Earth's ancient atmosphere. They live in the black mud at the bottom of marshes, or in other places without oxygen. They make food by chemical reactions, and do not rely on sunlight like other living things.
Wednesday, November 14, 2007
HOW LIFE BEGAN
How did life on Earth begin?
We can never know for sure, but scientists are certain that it cannot have happened all at once. Instead, they believe that it developed very gradually, through a series of chemical reactions. Scientists test this idea by re-creating the conditions of the early Earth in laboratory experiments. In one experiment, they put a smal amount of water in a glass container, to imitate the sea. Next, they remove all the air above the water, and replace it with the gases they think were in the atmosphere 4 billion years ago. After this, they seal the container, and pass electric sparks through the gases, to imitate lightning flashing through the air. When they open the glass container, they find that the water contains some of the complex chemicals that up living thing. Experiments like these suggest that life could have started quite by acciddent, most probably in the sea.
If you could go back 4 billion years in time, you would find the Earth a very strange place. You would not be able to breathe because the air would be filled with poisonous gases, and you would not be able to eat because there would be no food, and no living things. There would be nothing flying in the sky and nothing swimming in the water. Most of the ground would be bare rock. But in the sea, somewhere, the beginnings of life would be stirring.
We can never know for sure, but scientists are certain that it cannot have happened all at once. Instead, they believe that it developed very gradually, through a series of chemical reactions. Scientists test this idea by re-creating the conditions of the early Earth in laboratory experiments. In one experiment, they put a smal amount of water in a glass container, to imitate the sea. Next, they remove all the air above the water, and replace it with the gases they think were in the atmosphere 4 billion years ago. After this, they seal the container, and pass electric sparks through the gases, to imitate lightning flashing through the air. When they open the glass container, they find that the water contains some of the complex chemicals that up living thing. Experiments like these suggest that life could have started quite by acciddent, most probably in the sea.
If you could go back 4 billion years in time, you would find the Earth a very strange place. You would not be able to breathe because the air would be filled with poisonous gases, and you would not be able to eat because there would be no food, and no living things. There would be nothing flying in the sky and nothing swimming in the water. Most of the ground would be bare rock. But in the sea, somewhere, the beginnings of life would be stirring.
INTRODUCTION
Here is the main topic of the living world :
- How life began
- Evolution story
- Fossil trails
- The life of Microscopic
- Mushrooms and toadstools (fungi)
- Plants live
- Plants reproduce
- Tree life
- Prehistoric animals
- Dinosaurs
- Moving animals on land and water
- Animals in flight
- Animal senses
- Hunters and hunted
- Animal defences
- Camouflage and mimicry
- Animal homes
- Animal behaviour
- Surviving extremes
- Great animal journeys (migration)
- Animal reproduction
- Growth and development
- Ecology that connecting the living world
- Wildlife conservation
Also get the better knowledge of :
- The classified of living thing
- invertebrates animals
- vertebrates animals
- Plants and fungi
- The new discoveries of endangered species
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