Societ english1 potx

Carbon Carbon is found in the oceans in the form of bicarbon-ate ions HCO3 −, in the atmosphere, in the form of car-bon dioxide, in living organisms, and in fossil fuels such as coal, oi

waves Tsunamis, or tidal waves, are different They result

from underwater earthquakes, volcanic eruptions, or

landslides, not wind

Energy from the Core

Another source of Earth’s energy comes from Earth’s

core We distinguish four main layers of Earth: the inner

core, the outer core, the rocky mantle, and the crust The

inner core is a solid mass of iron with a temperature of

about 7,000° F Most likely, the high temperature is

caused by radioactive decay of uranium and other

radioactive elements The inner core is approximately

1,500 miles in diameter The outer core is a mass of

molten iron that surrounds the solid inner core

Electri-cal currents generated from this area produce the earth’s

magnetic field The rocky mantle is composed of silicon,

oxygen, magnesium, iron, aluminum, and calcium and is

about 1,750 miles thick This mantle accounts for most

of the Earth’s mass When parts of this layer become hot

enough, they turn to slow moving molten rock, or

magma The Earth’s crust is a layer from four to 25 miles

thick, consisting of sand and rock

The upper mantle is rigid and is part of the

litho-sphere (together with the crust) The lower mantle flows

slowly, at a rate of a few centimeters per year The crust

is divided into plates that drift slowly (only a few

cen-timeters each year) on the less rigid mantle Oceanic

crust is thinner than continental crust

This motion of the plates is caused by convection

(heat) currents, which carry heat from the hot inner

mantle to the cooler outer mantle The motion results in

earthquakes and volcanic eruptions This process is

called plate tectonics.

Tectonics

Evidence suggests that about 200 million years ago, all

continents were a part of one landmass, named Pangaea

Over the years, the continents slowly separated through

the movement of plates in a process called continental

drift The movement of the plates is attributed to

con-vection currents in the mantle The theory of plate

tec-tonics says that there are now twelve large plates that

slowly move on the mantle According to this theory,

earthquakes and volcanic eruptions occur along the lines

where plates collide Dramatic changes on Earth’s

land-scape and ocean floor are caused by collision of plates

These changes include the formation of mountains and

valleys

 G e o c h e m i c a l C y c l e s

Water, carbon, and nitrogen are recycled in the bios-phere A water molecule in the cell of your eye could have been, at some point, in the ocean, in the atmosphere, in

a leaf of a tree, or in the cell of a bear’s foot The

circula-tion of elements in the biosphere is called a geochemical

cycle.

Water

Oceans cover 70% of the Earth’s surface and contain more than 97% of all water on Earth Sunlight evapo-rates the water from the oceans, rivers, and lakes Living beings need water for both the outside and the inside of their cells In fact, vertebrates (you included) are about 70% water Plants contain even more water Most of the water passes through a plant unaltered Plants draw on water from the soil and release it as vapor through pores in their leaves, through a process called

transpiration.

Our atmosphere can’t hold a lot of water Evaporated water condenses to form clouds that produce rain or snow on to the Earth’s surface Overall, water moves from the oceans to the land because more rainfall reaches the land than is evaporated from the land (See the figure

on the next page.)

Carbon

Carbon is found in the oceans in the form of bicarbon-ate ions (HCO3 −), in the atmosphere, in the form of car-bon dioxide, in living organisms, and in fossil fuels (such

as coal, oil, and natural gas) Plants remove carbon diox-ide from the atmosphere and convert it to sugars through photosynthesis The sugar in plants enters the food chain, first reaching herbivores, then carnivores, and finally scavengers and decomposers All these organ-isms release carbon dioxide back into the atmosphere when they breathe The oceans contain 500 times more carbon than the atmosphere Bicarbonate ions (HCO3) settle to the bottoms of oceans and form sedimentary rocks Fossil fuels represent the largest reserve of carbon

on Earth Fossil fuels come from the carbon of organisms that had lived millions of years ago Burning fossil fuels releases energy, which is why these fuels are used to power human contraptions When fossil fuels burn, car-bon dioxide is released into the atmosphere

Since the Industrial Revolution, people have increased the concentration of carbon dioxide in the atmosphere

30% by burning fossil fuels and cutting down forests,

which reduce the concentration of carbon dioxide

Car-bon dioxide in the atmosphere can trap solar energy—a

process known as the greenhouse effect By trapping solar

energy, carbon dioxide and other greenhouse gases can

cause global warming—an increase of temperatures on

Earth In the last 100 years, the temperatures have

increased by 1° C This doesn’t seem like much, but the

temperature increase is already creating noticeable

cli-mate changes and problems Many species are migrating

to colder areas, and regions that normally have ample

rainfall have experienced droughts Perhaps the most

dangerous consequence of global warming is the melting

of polar ice Glaciers worldwide are already melting, and

the polar ice caps have begun to break up at the edges If

enough of this ice melts, coastal cities could experience

severe flooding

Reducing carbon dioxide concentrations in the atmosphere, either by finding new energy sources or by actively removing the carbon dioxide that forms, is a challenge to today’s scientists (See the figure on the next page.)

Nitrogen

The main component of air in the atmosphere is nitro-gen gas (N2) Nitrogen accounts for about 78% of the atmosphere However, very few organisms can use the form of nitrogen obtained directly from the atmosphere This is because the bond between two atoms in the nitro-gen gas molecule is tough to break, and only a few bac-teria have enzymes that can make it happen These bacteria can convert the nitrogen gas into ammonium ions (NH4+) Bacteria that do this are called nitrifying or

nitrogen-fixing bacteria.

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Run-off from

glaciers,

snow rivers,

and lakes

Precipitation Precipitation

Evaporation and transpiration Ocean

Groundwater flow

Another source of nitrogen for the non-nitrogen-fixing

organisms is lightning Lightning carries tremendous

energy, which is able to cause nitrogen gas to convert to

ammonium ions (NH4+) and nitrate ions (NO3 −)—fixed

nitrogen

Plants, animals, and most other organisms can only

use fixed nitrogen Plants obtain fixed nitrogen from soil

and use it to synthesize amino acids and proteins

Ani-mals obtain fixed nitrogen by eating plants, or other

animals When they break up proteins, animals lose

nitrogen in the form of ammonia (fish), urea

(mam-mals), or uric acid (birds, reptiles, and insects)

Decom-posers obtain energy from urea and uric acid by

converting them back into ammonia, which can be used

again by plants

The amount of fixed nitrogen in the soil is low,

because bacteria break down most the ammonium ion

into another set of molecules (nitrite and nitrate),

through a process called nitrification Other bacteria

con-vert the nitrite and nitrate back into nitrogen gas, which

is released into the atmosphere This process is called

denitrification.

This limited amount of nitrogen has kept organisms

in balance for millions of years However, the growing human population presents a threat to this stability In order to increase the growth rate of crops, humans man-ufacture and use huge amounts of fertilizer, increasing the amount of nitrogen in the soil This has disrupted whole ecosystems, since, with extra nitrogen present, some organisms thrive and displace others In the long run, too much nitrogen decreases the fertility of soil by depriving it of essential minerals, such as calcium Burning fossil fuels and forests also releases nitrogen All forms of fixed nitrogen are greenhouse gases that cause global warming In addition, nitric oxide, a gas released when fossil fuels are burned, can convert into nitric acid, a main component of acid rain Acid rain destroys habitats

People are already suffering the consequences of the pollution they have caused Preventing further damage

to the ecosystem and fixing the damage that has been done is another challenge for today’s scientists

CO2 in atmosphere

Photosynthesis (land)

Photosynthesis (water)

Burning fossil fuels Burning

forests

Respiration (organisms on land and in water)

 O r i g i n a n d E v o l u t i o n o f t h e

E a r t h S y s t e m

Earth Basics

Most people know that the Earth is round and revolves

around its axis in about 24 hours It is a part of the solar

system, with the sun in its center Eight other planets and

their moons orbit the sun as well These planets include

Mercury and Venus, which are closer to the sun than the

Earth is, and Mars, Jupiter, Saturn, Uranus, Neptune, and

Pluto, which are further away from the sun

It takes about one year for the Earth to complete its

orbit around the sun The rotation of the Earth around

its axis causes the change between day and night The tilt

in the Earth’s axis gives rise to seasons

Rocks and Rock Cycles

Rocks are made up of one or more minerals,

homoge-neous inorganic materials Three types of rocks are

igneous, sedimentary, and metamorphic Igneous rocks

result from cooling of molten rock If the cooling from

molten rock occurred quickly on or near the earth’s

sur-face, it is called volcanic igneous rock If the cooling took

place slowly, deep beneath the surface, it is called plutonic

igneous rock Sedimentary rocks are formed in layers in

response to pressure on accumulated sediments

Meta-morphic rocks are formed when either igneous or

sedi-mentary rocks are under intense heat and pressure deep

beneath the earth’s surface

Rock cycle is the transformation of one rock type into

another Molten rock material cools and solidifies either

at or below the surface of the earth to form igneous

rocks Weathering and erosion break the rocks down into

smaller grains, producing soil The soil is carried by

wind, water, and gravity and is eventually deposited as

sediment The sediments are deposited in layers and

become pressed firmly together and cemented or

lithi-fied, forming sedimentary rocks Variations in

tempera-ture and pressure can cause chemical and physical

changes in igneous and sedimentary rocks to form

meta-morphic rocks When exposed to higher temperatures,

metamorphic rocks may be partially melted, resulting in

the creation once again of igneous rocks, starting the

cycle all over again

Molten material from inside the earth often breaks

through the floor of the ocean and flows from fissures

where it is cooled by the water, resulting in the formation

of igneous rocks As the molten material flows from the fissure, it forms ridges adjacent to it

Origin of the Earth and the Solar System

The sun, the Earth, and the rest of the solar system

formed 4.6 billion years ago, according to the solar

neb-ula theory This theory states that the solar system was

initially a large cloud of gas and dust, which most likely originated from the explosions of nearby stars This cloud is named the solar nebula The sun formed at the central, densest point of the nebula One argument that supports this hypothesis is that planets closer to the sun are composed of heavier elements, while light, gaseous planets are farthest from the sun The solar nebula the-ory also states that planets form in conjunction with stars This component of the theory is supported by the fact that other stars have planets and that the age of moon rocks is comparable to the age of the Earth

 O r i g i n a n d E v o l u t i o n o f t h e

U n i v e r s e

Nobody knows for sure how the universe originated

According to the Big Bang theory, the universe began in

a hot, dense state under high pressure between ten and

20 billion years ago The Big Bang theory also postulates that the universe has been expanding since its origina-tion The universe is still expanding and cooling Some data suggest that the rate of expansion of the universe is increasing

Whether the universe will continue to expand forever, eventually reach an equilibrium size, or shrink back into

a small, dense, hot mass is unknown

Stars are formed by the gravitational attraction of countless hydrogen and helium molecules The stars became gravitationally bound to other stars, forming galaxies The solar system is part of the Milky Way galaxy, which, in addition to the sun, contains about 200 billion other stars

The energy of stars stems from nuclear reactions, mainly the fusion of hydrogen atoms to form helium Nuclear processes in stars lead to the formation of elements

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WH I L E S C I E N C E I S the systematic study of the natural world, technology is the application of

sci-entific knowledge to create tools, equipment, and procedures that often simplify and improve our lives For every scientific discovery, there are dozens of potential applications of that knowl-edge Technological advances often lead to further advances in the sciences Therefore, science and technology are highly interdependent

 A b i l i t i e s o f Te c h n o l o g i c a l D e s i g n

Students tend to have a positive image of science They associate science with medicine and nature At the same time, students realize that technology plays multiple roles in our lives There are positive applications, including the use of technology for medical diagnosing, communication, transportation, and everyday chores However, technology often leads to pollution and problems While pollution and problems may unfortunately be a byprod-uct of certain technological processes, they are also the byprodbyprod-ucts of science In reality, science and technology are extremely interrelated and similar in many ways

One of the goals of technology is to apply the principles of science to make life more comfortable and work easier The aim of technology is not to create problems, but to solve them Technology is responsible for deliver-ing the electricity we use every day, for the refrigerator that prevents our food from spoildeliver-ing, for the ability to cross

C H A P T E R

Science and Technology

THIS CHAPTER discusses the aims of technology, the

relation-ship between science and technology, and the way in which needs and advances in one lead to needs and progress in the other You will also learn what drives technological progress and what is involved in technological design

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