People and the planet

Chapter 6Biology(part1)

Scientists believe that the human species first developed in East Africa about 200000 years ago, gradually spread north over the next 100000 years and then moved into the lands to the east and the west.

Over this 200000 years period , human life

has changed for most people. Those people lived in small groups and they use weapons to hunt. In designing them, they considered two topics of scientific study, although they did not realise it. These topics are energy and forces.

Earliest people are called : Hunter-gatherers.

Early times

Example: The best wood to use to make a bow, which would store plenty of energy as they pulled it back to make the arrow fly. The force generated when the bowstring was released set the arrow on its journey to the target.

Only a few people today live as hunter-

gatherers as they live in small groups and collected enough food for themselves from their surroundings. When food supplies fell, they moved on, letting the plants and animals breed back to their former numbers, so in the future the people could return and harvest them again. Also they use materials as wood for fuel and making temporary buildings, as they moved around.

About 10000 years ago, people living in the lands that are now Turkey, Iraq, Iran, and parts of Saudi Arabia began farming . Afterwards farming spread to Egypt and North Africa, and into Europe and Asia.

Farming involved clearing the land of its natural habitats to make fields for the growing of crops.

Farming provided food for larger numbers of people

also it allowed some people to work in other jobs, example: pot making, furniture making, cloth making and metalworking, and a trade in goods built up between neighboring countries.

During this time, the sources of power for farming, for making goods and for transport were the people themselves and the animals they domesticated example : cattle, horses and donkeys.

N:B animal power was much greater than human power.

Wood has been used as a fuel to provide heat

energy for cooking, for keeping warm and for preparing materials such as pottery and metals.

Fuel wood is still used in many places today.

About 2200 years ago, the Ancient Greeks

invented a machine that used the power of running water to grind up flour.

This machine was the watermill. It had a wheel that was turned by the water

and a mechanism to transfer this turning motion to stones for grinding up flour.

Early machines

The first windmills were invented between

1500 and 1100 years ago in Persia, which is now Iran. The sail turned round a vertical axis. Later, in Europe, the windmill was developed with horizontal axis. Its main purpose was grinding grain and pumping water.

In 1698, in England, Thomas Savery invented

the steam engine. It produced an up-and-down movement and was used for pumping water out of mines , but because of occasional boiler explosions other inventors got to work on improving it.

Steam engines

By 1783, James Watt had built a much safer steam

engine, which could produce rotary motion like water wheels and windmills. In time, these engines became very powerful and were used to drive all kinds machines in factories and this is Industrial revolution.

They require large amount of fuels as coal. The industrial revolution drove people to work in

cities in the factories as they could earn more money. Smoke is released from the factory chimneys which

polluted air in the city they are found in.

In the first half of the 19th century, an English

scientist called: Michael Faraday found that, if a magnet was made to move quickly on a wire, a current of electricity was generated in the wire. This discovery lead to the development of the electrical generator, in which a large magnet is made to pin around inside an even larger coil of wire and produce electricity. Today in many power stations the magnet is attached to a turbine, which is made to spin by driving steam over it.

Generating electricity

The water to provide the steam was originally

heated by burning coal, and many power stations still use coal today, but other sources are also used.

Sources of energy

Renewable Non-renewable

-Water.-Wind

-Fossil fuels as:Oil.

Coal.Gas

-Nuclear fuel:Uranium.

Geothermal energy from the hot rocks in the earth. Solar energy from sunlight and energy from

burning the unwanted remains of crop plants, such as sugar can.

Energy can also be obtained by growing plants specially for burning, such as oil palms, which are called : biofuels.

Methane gas produced from the wastes stored in landfill sites ,garbage, can also be

burnt to provide energy.

Soon after the steam engine was invented,

engineers began to put it to use in transporting people and goods.

They developed steam locomotives, in which a steam

engine powers wheels to drive the machine along as they needed to transport heavy loads over large distances.

Transport

Petrol and diesel engines were developed from steam

engine and have replaced it as main power source in cars, trucks and buses today.

Petrol and diesel are made from oil. Jet engines were developed in the middle of the 20th

century and are now used on most air craft carrying people and goods around the world.

These run on a fuel called: Kerosene that is made from oil.

Waste product of burning fuels is carbon dioxide which keeps heat inside atmosphere from sun.