They say too much of anything is back you. believe it or not, that's true of the c oxygen that powers our bodies. if we brec cedar that was more than 75% cryger, we could die within days. our luring couldn't cope. our bodes are used used to air that's 21% keygen - and even that's harmful over a lifetime. the body makes use of around 90% of the cxygen it takes in and the rest transforms into troe radicals - molecules that attack and damage our cells over time. oxygen, then, she ally touch in large doses. but any 3-4 billion years of evolution of on earth should tour bodes be better at processing crugen? to try to answer that question it's important to understand that oxygen wasn't always present in the atmosphere. because of this, scientists believe that the first life forms on the planet were anaerobic; they were able to survive without crygen. it was only water plants established themselves that oxygen appeared in the atmosphere. this occurrence of oxygen in the earth's atmosphere some 22 billion ago is known as the great oxidation event. plants, animals, don't need anything, but produce through 15 photosy: - the process by which they convert suright, water, and carbon energy. because is a by-product of photosynthesis, it took mamemon a billion years tor enough of to build up in the atmosphere and give foss#evidence suggests animals first appeared about 700 million years ago, in 20 oceans. the first life forms had extremely thin bodes in relation to size. scientists believe this allowed them to make maximum use of low amounts of c oxygen present in the ocean. around 500 milion years ago. atmospheric oxygen levels were high enough to enable animalis to venture out of the ocean and onto land. 25 the amount oxygen in our atmoschere has not increased steadly, in fact, 300 milion years ago, oxygen wiss actually more abundant in the ar than it is now, making up 50% of it. as aresit, anmas were much bigger than they are today. there were insects, for example, which measured more than 2.5 feet from the to of one wing to another. scientists recently bred dragonflies this size in 50% oxygen environments. they say the dragonfies were acte to grow so big because in oxygen-rich atmospheres, insects need the large breathing systems which normally limit the size of their bodies. by 240 milion years ago, though, oxygen levels had fallen to just 1256 of the ar. it's surprising that the amount of cargen in the atmosphere has varied during 35 animal evolution, it's perhaps even more surprising to learn that the planet is more dependent on oxygen produced in the oceans than on land. scientists estimate that sea algae replace around 90% of the oxygen in the biosphere. so, today's most complex forms not only onginated in an environment in which they now cannot breathe - the ocean they rely on it for their survival это текст
1. We've been using this machine for three years. It has worked perfectly. 2. I've been thinking all day about what I'm going to say when we come to them. 3. Why are you so excited? —We have been having an argument. 4. This man has been following us all the way from the station. He probably doesn't know the way. 5. What has been going on here? Why is everyone so excited? 6. This noise has been bothering me since morning, and I can't find out where it's coming from. 7. You've been drinking too much coffee lately. 8. He was sure that she had been living in Moscow since 1935. 9. Have you been smoking in the room again? 10. Have you been crying? What's the matter? 11. He had such a feeling that he'd been living here for a long time. 12. The last time she left school, where she had been studying for ten years, she didn't think that she would return to it, but as a teacher. 13. He's been wearing glasses since his childhood.
BASKETBALL The game of basketball is unique among popular Sports. The world (has enjoyed) it for a century. But not all of us (know) the history of the game. It (was invented) by a Canadian, first (was played) in the USA and specially (was planned) to meet a definite need. In 1891 Dr James A. Naismith (was) a physical director of the international Y.M.C.A.* training school in Springfield, Mass.** For some years the interest of young Canadians and Americans in the customary programme of Calisthenics*** and Gymnastics (was weakening). Dr Naismith (was asked) to invent a competitive game that (would hold) the enthusiasm of the students. It (was suggested) that the game (had) simple rules that (could be learnt) easily; it (was to be) free from bodily contact; good for players over a wide range of ages and it (was to have) inexpensive equipment. The game (was to be played) by day and by night in small gymnasiums. Dr Naismith (solved) all these problems in his game. He (called) it basketball, because the players (were to throw) a round ball into a basket-shaped net hung at either end of the gymnasium. At first the game (was played) with as many as nine players on a side. It soon (was realized) that five to a team (resulted) in cleaner and faster play. The inventor (suggested) 13 basic rules, and most of them (are) still in effect; there (have been) some changes in playing conditions and rules of the game.
1 London is the capital of Great Britain. 2 Yes, it is. 3 London's population is more than 8,400,000. 4 London stands on the River Thames. 5 London is divided into 4 parts: the City, the West End, the East End and Westminster. 6 The City is called the business centre of London because thousands of companies, business organizations, banks and offices are situated there. 7 Westminster includes the Palace of Westminster, Buckingham Palace, Westminster Abbey and Westminster Cathedral. 8 Many famous people wereburied in Westminster Abbey: Geoffrey Chaucer, Oliver Cromwell, admiral Robert Blake, Charles Darwin, Isaac Newton, Henry Irving. 9 The West End is famous for its theaters, museums, galleries, posh shops and restaurants. 10 The name Trafalgar Square commemorates the Battle of Trafalgar, a British naval victory of the Napoleonic Wars over France and Spain which took place on 21 October 1805 off the coast of Cape Trafalgar, Spain 11 The East End is the place where working class lives.
2. I've been thinking all day about what I'm going to say when we come to them.
3. Why are you so excited? —We have been having an argument.
4. This man has been following us all the way from the station.
He probably doesn't know the way.
5. What has been going on here? Why is everyone so excited?
6. This noise has been bothering me since morning, and I can't find out where it's coming from.
7. You've been drinking too much coffee lately.
8. He was sure that she had been living in Moscow since 1935.
9. Have you been smoking in the room again?
10. Have you been crying? What's the matter?
11. He had such a feeling that he'd been living here for a long time.
12. The last time she left school, where she had been studying for ten years, she didn't think that she would return to it, but as a teacher.
13. He's been wearing glasses since his childhood.
BASKETBALL
The game of basketball is unique among popular Sports. The world (has enjoyed) it for a century. But not all of us (know) the history of the game. It (was invented) by a Canadian, first (was played) in the USA and specially (was planned) to meet a definite need.
In 1891 Dr James A. Naismith (was) a physical director of the international Y.M.C.A.* training school in Springfield, Mass.** For some years the interest of young Canadians and Americans in the customary programme of Calisthenics*** and Gymnastics (was weakening). Dr Naismith (was asked) to invent a competitive game that (would hold) the enthusiasm of the students. It (was suggested) that the game (had) simple rules that (could be learnt) easily; it (was to be) free from bodily contact; good for players over a wide range of ages and it (was to have) inexpensive equipment. The game (was to be played) by day and by night in small gymnasiums. Dr Naismith (solved) all these problems in his game. He (called) it basketball, because the players (were to throw) a round ball into a basket-shaped net hung at either end of the gymnasium. At first the game (was played) with as many as nine players on a side. It soon (was realized) that five to a team (resulted) in cleaner and faster play. The inventor (suggested) 13 basic rules, and most of them (are) still in effect; there (have been) some changes in playing conditions and rules of the game.
2 Yes, it is.
3 London's population is more than 8,400,000.
4 London stands on the River Thames.
5 London is divided into 4 parts: the City, the West End, the East End and Westminster.
6 The City is called the business centre of London because thousands of companies, business organizations, banks and offices are situated there.
7 Westminster includes the Palace of Westminster, Buckingham Palace, Westminster Abbey and Westminster Cathedral.
8 Many famous people wereburied in Westminster Abbey: Geoffrey Chaucer, Oliver Cromwell, admiral Robert Blake, Charles Darwin, Isaac Newton, Henry Irving.
9 The West End is famous for its theaters, museums, galleries, posh shops and restaurants.
10 The name Trafalgar Square commemorates the Battle of Trafalgar, a British naval victory of the Napoleonic Wars over France and Spain which took place on 21 October 1805 off the coast of Cape Trafalgar, Spain
11 The East End is the place where working class lives.