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Title: Chapter 49: People and the Biosphere


1
Chapter 49 People and the Biosphere
  • Section 1 Human Population

2
Human Population
  • When humans formed permanent settlements, they
    began a long history of profoundly affecting the
    environment
  • They made changes to the environment that were
    not easily undone
  • Because people did not really understand how the
    natural environments on Earth functioned, they
    could not assess the effects of their activities
    on the environment
  • For a long time, the human population was unaware
    that it was harming the world around it

3
Human Population
  • Over time, the human population has increased
    dramatically as has our knowledge of the
    Earths fragile environments
  • Today we are more aware of how our actions affect
    our world
  • But at the same time, we are also more capable of
    permanently damaging not just particular places
    on Earth but the entire biosphere itself

4
Population Growth
  • Many environmental problems seem large and urgent
    today because of the rapid increase in human
    population
  • The huge numbers of humans on Earth are making
    enormous demands on the planet
  • A population grows when the birthrate is greater
    then the deathrate
  • Both of these must be taken into consideration
    when trying to understand the growth of the human
    population

5
Birthrate
  • Vary dramatically from one country to another
  • In the US and much of Europe, the birthrate
    decreased during the 1970s
  • In the 1980s, American birthrates rose slightly
  • If current birthrates are maintained, our
    population will double in less than 100 years
  • In some European countries, the growth rate is so
    low that populations are actually declining

6
Birthrate
  • The situation is quite different in other
    countries
  • More than two thirds of the worlds population
    live in the tropical countries of Africa, South
    America, and Asia
  • In some of these countries, the population
    continues to grow at an annual rate of about 3
  • Although this rate of growth appears to be low,
    it will double the present population in only 23
    years

7
Deathrate
  • The deathrate has decreased worldwide
  • Over the past few hundred years, changes in
    agriculture have made more and better foods
    available throughout the world
  • Improvements in the quality and availability of
    medical care have wiped out many deadly diseases
    and contributed to an increase in the life span
    of the average person

8
Effects of Human Population Growth
  • A high birthrate, a low deathrate, and a longer
    lifespan all contribute to population growth
  • As human populations grow, their effects on the
    environment also grow
  • Countries with a rapidly growing population are
    often unable to produce enough food to satisfy
    the demand

9
Effects of Human Population Growth
  • Today, scientists worry about the destruction of
    tropical forests
  • Such devastation seems to be a high price to pay
    for farmland that is productive for only a few
    short years
  • In addition, many of these tropical forests are
    often cleared by burning
  • The burning produces large amounts of carbon
    dioxide, which is added to our atmosphere

10
Effects of Lifestyles
  • It is not population growth alone that causes
    environmental problems
  • After all, the rate of population growth in many
    industrial countries has actually slowed
  • The lifestyle of a population also contributes to
    the extraordinary environmental demands made on
    the Earth

11
Effects of Lifestyles
  • The population of the US is a good example
  • Population growth has stabilized at a low level
  • We use more energy and natural resources than any
    other country in the world
  • We own many consumer goods
  • Most families have two or more cars
  • Radios, TVs, etc. are staples of most modern
    homes

12
Chapter 49 People and the Biosphere
  • Section 2 Pollution

13
Pollution
  • Materials released into the environment fall into
    two categories biodegradable and
    nonbiodegradable
  • Materials that can be degraded, or broken down,
    by microorganisms into the essential nutrients
    from which they were made are biodegradable
  • Sewage, scraps of food
  • Nonbiodegradable materials cannot be broken down
    by natural processes or are broken down only very
    slowly
  • Glass, plastics and metals, chemicals
  • Once these materials are released into the
    environment, they remain there for a long time
    sometimes forever

14
A consumer society produces extremely large
quantities of wastes. However, some wastes can
prove useful. These automobiles are valuable for
the scrap metal they contain. And some household
wastes can be recycled for further use.
15
Biological Magnification
  • Sometimes pollutants affect the biosphere in ways
    no one expects
  • Many primary producers pick up nonbiodegradable
    pollutants from the water
  • They concentrate them and store them in their
    tissues
  • When herbivores eat producers, they too
    concentrate and store these nonbiodegradable
    compounds in their tissues
  • When carnivores eat herbivores, the compounds are
    further concentrated

16
Biological Magnification
  • At each step in a food chain, the compounds are
    concentrated more and more
  • In other words, the amount of the compounds in
    each organism in a food chain increases
  • This phenomenon is known as biological
    magnification
  • Biological magnification occurs with many
    pesticides and industrial waste products

17
If the plants in the pond in which this moose is
dining have been contaminated by toxic materials,
they may actually poison the moose. The
concentrations of toxic chemicals in the plants
will increase in the tissues of the moose.
The toxic chemicals DDT became part of many food
chains when it was widely used as a pesticide.
These falcon eggs show the dramatic effects of
DDT poisoning.
18
Air Pollution
  • The air supplies the oxygen our cells need to
    metabolize food and receives the waste products
    we give off as a result of our life processes
  • But the air also contains many other
    chemicalschemicals that are not part of the
    natural composition of the atmosphere

19
Smog
  • If you live in a city, you may be familiar with
    the dirty-brown haze called smog
  • Smog smoke fog
  • Contains different pollutants in different places
  • The causes of smog also differ from one location
    to another

20
Smog
  • Weather conditions called temperature inversions
    can make smog a serious health hazard
  • Normally, cooler air is at higher altitudes than
    warmer air
  • The warmer air closer to the Earths surface
    contains pollutants
  • But because it is warm, it is less dense than
    cool air and rises
  • As it rises, it slowly cools, and the pollutants
    it contains are carried away by winds

21
Smog
  • During an inversion, a layer of cool polluted air
    is trapped beneath a layer of warm air
  • Because the cool air is denser than the warm air
    above it, it cannot rise
  • As a result, the pollutants are kept near the
    ground
  • Temperature inversions can last for hours, days,
    and even weeks

22
The skyline of Los Angeles, California, is barely
visible through a curtain of smog. This city and
many others like it depend upon automobiles and
buses to move people from place to place. The
vehicles produce waste gases that contribute to
the formation of smog.
23
Acid Rain
  • Certain pollutants in the air combine with water
    vapor to form droplets of acid
  • When these droplets fall to the Earth in rain,
    the rain is called acid rain
  • In many areas, the coal and oil burned in
    factories and power plants to generate energy
    contain large amounts of sulfur
  • When sulfur is burned, it forms sulfur dioxide
  • Sulfur dioxide dissolves in water to form a
    strong acid sulfuric acid

24
Acid Rain
  • Sulfur dioxide is often carried on prevailing
    winds far from where it is produced
  • The effects of acid rain on the environment are
    numerous and serious to life
  • Acid rain damages plants, rivers, lakes, etc.

25
Acid rain is a serious threat to the environment.
Its effects on forest trees can be seen in this
picture of evergreens that are now never green.
Their needles have been burned off the branches
by rains.
26
The Greenhouse Effect
  • The amount of carbon dioxide in the atmosphere is
    increasing as a result of human activity in the
    biosphere
  • Carbon dioxide is produced when carbon-containing
    fuels are burned
  • Carbon-containing fuels include wood and charcoal
    as well as fossil fuels such as coal, oil, and
    natural gas
  • Over the years, the burning of trees and fossil
    fuels for energy has released vast quantities of
    carbon dioxide into the atmosphere

27
The Greenhouse Effect
  • Energy from the sun is absorbed by the Earth and
    changed into heat
  • Later, this energy is radiated back from the
    Earth to the atmosphere
  • Carbon dioxide and other gases in the atmosphere
    absorb this heat energy
  • Greenhouse effect

28
The Greenhouse Effect
  • As levels of carbon dioxide in the air increase,
    more heat is absorbed and the temperature of the
    Earth increases
  • The effects of this global warming are unclear
  • Melting of the polar icecaps
  • Major changes in agriculture

29
Venus, although much like the Earth in many ways,
has an atmosphere that consists mostly of carbon
dioxide. As a result, Venus is considerably
hotter than Earth. Scientists are concerned that
the temperature of Earth will increase as levels
of carbon dioxide in the atmosphere increase. If
this happens, the huge polar ice caps will melt
and sea levels will rise, flooding many coastal
regions.
30
Holes in the Ozone Layer
  • A layer of ozone exists far above the Earth in a
    part of the atmosphere called the stratosphere
    (10 30 miles above the Earths surface)
  • Protects the Earth from harmful ultraviolet
    radiation from the sun
  • Without the protection of this layer, few living
    things could survive

31
Holes in the Ozone Layer
  • Scientists have recently discovered that the
    ozone layer is becoming thinner in certain places
    around the poles
  • Holes in the ozone layer
  • The major cause of ozone depletion is a form of
    chemical air pollution that results from the
    addition of chlorofluorocarbons to the air
  • Scientists predict that if the amount of UV
    radiation that reaches the Earth increases, the
    frequency of certain diseasessuch as certain
    forms of skin cancerwill also increase

32
In this image, areas of low ozone concentration
are in black/blue. The hole in the ozone layer
extends over Antarctica and part of South
America.
33
Water Pollution
  • In the United States, billions of liters of fresh
    water are used daily
  • Drinking, cooking, bathing, cleaning
  • Although water is a renewable resource, there is
    a limited amount of fresh water
  • 75 of Earth is water
  • Only 3 is fresh water
  • Only a small portion is available for living
    things
  • The greater portion is locked up in ice, mainly
    in polar ice caps and glaciers
  • The most common sources of water pollution are
    chemical wastes, raw sewage, and high temperatures

34
In many places in the world, the supply of
drinkable water is severely limited. Here in
Malawi, people fill buckets with water that is
pumped from a communal well. These heavy buckets
of water must be carried to their home.
35
Chemical Contamination
  • Toxic chemicals can pollute water in two ways
  • The chemicals can enter into streams and rivers
  • Chemical wastes discarded on land can seep
    through the ground and enter the ground water
    supply

36
Sewage Contamination
  • Sewage consists of large quantities of wastes
    that contain nitrogen compounds
  • These compounds are used by bacteria in a process
    that requires oxygen
  • If untreated sewage is added to rivers and
    streams, the number of bacteria increases
    dramatically
  • These bacteria use up most of the available
    oxygen as they break down the nitrogen compounds
  • Other organisms that live in the water may
    suffocate because their supply of oxygen is
    depleted

37
Sewage Contamination
  • In rural areas, where homes are far apart, sewage
    is usually treated in septic systems
  • In a septic system, bacteria work on the sewage,
    reducing it to water that is nearly pure
  • This water seeps out of the septic system and
    into the ground

38
Sewage Contamination
  • In cities, sewage must be treated in sewage
    treatment plants
  • In special tanks, this sewage is broken down by
    bacteria
  • Once the bacteria have decomposed the organic
    matter, chemicals that kill harmful
    microorganisms are added to the sewage and the
    treated water is released

39
Sewage Contamination
  • Human sewage also contains many potentially
    harmful microorganisms bacteria, viruses, and
    protozoa
  • Filter-feeding organisms, such as clams and
    mussels, ingest the microorganisms and
    concentrate them in their tissues
  • When these shellfish are eaten, diseases such as
    hepatitis, typhoid, and certain forms of
    dysentery can spread

40
Although almost three quarters of the Earth is
covered by water, the supply of fresh water that
is available for human needs is limited. It is
extremely important to protect this water from
becoming polluted.
Many cities and towns have sewage-treatment
plants that process household waste water. In
huge outdoor tanks, water is treated by chemicals
and microorganisms.
41
Thermal Pollution
  • Many factories and power plants produce heat as a
    waste product
  • In the past, water from nearby rivers, lakes, or
    the ocean was used to cool such plants
  • The water was pumped through pipes in the cooling
    system, where it absorbed heat
  • The heated water was then pumped back into the
    environment

42
Thermal Pollution
  • In some cases, heated water has no harmful
    effects on the ecosystem
  • But often, heated water kills aquatic plants and
    animals
  • This kind of water pollution is called thermal
    pollution

43
Water is often used by industries as a coolant.
In this nuclear power plant, heated water is
returned to the river from which it was pumped,
causing a kind of pollution called thermal
pollution. Thermal pollution is a danger to some
forms of aquatic life.
44
Ocean Pollution
  • For centuries people have dumped their wastes
    into the oceans
  • Too many people produce too much waste, a great
    deal of which is nonbiodegradable
  • Plastics and other wastes dumped into the oceans
    may float around for months or even years
  • Large cities continue to dump so much sewage into
    the oceans that it cannot be degraded quickly
    enough
  • Often, some of this sewage washes up on beaches

45
Ocean Pollution
  • Pollution near the shore is a serious matter
  • Some wastes dumped into the oceanssuch as
    containers of disposable medical itemswash back
    onto shore, threatening the health of beach-goers
  • Other wastes remain at sea, posing a hazard to
    ocean life

46
The solid wastes produced by consumer societies
are often dumped into the oceans. This is
devastating not only to ocean life, but also to
beach-goers.
47
Oil Spills
  • Regardless of the cause, once oil is spilled, it
    is difficult to remove
  • Oil slicks are deadly to marine animals that
    swallow the toxic oil or become coated with it
  • Toxic chemicals in oil often accumulate in those
    animals that are not killed immediately
  • In most cases, these chemicals make the animal
    sterile
  • Some of the chemicals that accumulate in animal
    tissue are potent carcinogens that may cause
    cancer in the people who eat them

48
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49
Chapter 49 People and the Biosphere
  • Section 3 The Fate of the Earth

50
The Fate of the Earth
  • People have always relied upon plants and animals
    for food, clothing, and shelter
  • The survival of humans and human society depends
    upon the survival of other organisms in the
    biosphere
  • Today, the survival of many of these organisms is
    threatened

51
Forests
  • Wherever you live, your life is dependent upon
    forests in many ways
  • Trees provide us with many essential products
  • Wood is used to make everything from pencils to
    houses
  • Trees are a vital part of many ecosystems
  • The roots of trees keep the soil loose and at the
    same time hold it in place, allowing rainwater to
    penetrate the soil without washing it away

52
Forests
  • When forests are carelessly cut down, many
    important changes occur
  • Soil structure changes
  • Microorganisms die
  • Many small plants and animals can no longer
    survive
  • Heavy rains wash away topsoil
  • Water table drops

53
Forests
  • Many of our countrys few remaining old forests
    are being cut down at an alarming rate
  • In tropical countries, rain forests are being
    destroyed so rapidly that they may disappear
    completely in 60 years
  • Fortunately, government officials became aware of
    the problems associated with forest destruction

54
Forests
  • Programs that plant new trees when old trees are
    cut down are called reforestation programs
  • Vital to the health of the biosphere

55
These trees are no match for a chainsaw. Once
cut, they will be used to make many consumer
products. A tiny tree will be placed in its
place.
56
Endangered Species
  • When an animal or plant species becomes so rare
    that it is threatened with extinction, it is
    called an endangered species
  • Species become endangered in several ways
  • Hunting
  • Are able to live in only one type of habitat
  • Today, one plant or animal species becomes
    extinct every hour

57
Huge herds of bison roamed the Great Plains until
hunters brought these awesome animals to the
verge of extinction. Today, protected by strict
laws, herds of these animals once again roam.
58
Why Save Endangered Species?
  • Extinction is forever
  • Many people feel that we have no right to cause
    the extinction of other species
  • Scientists, biologists, activists, etc.
  • But human needs are great, as are the demands on
    the ecosystem

59
Other animals have not been as lucky as the
bison. The California condor is close to
extinction. Captive breeding programs aim to keep
this species alive. The black-footed ferret hunts
prairie dogs. The population of ferrets is so
small that their actual location in the wild is a
closely guarded secret. The desert pupfish lives
in small desert pools. If anything happens to its
delicate habitat, it too will be in real danger
of becoming extinct.
60
Useful Products
  • Many everyday foods, medicines, and industrial
    compounds come from wild plant and animal species
  • Antibiotics, heart drugs, anticancer medications,
    painkillers, and other important medicines are
    derived from plants

61
Useful Products
  • No one knows the benefits that might be hidden in
    yet unknown plants that grow in tropical rain
    forests
  • If these rain forests disappear, the potential
    contributions of their inhabitants to our society
    will also vanish
  • Many animal species produce compounds that may
    prove important to human health
  • Sponges
  • Sea cucumbers
  • Horseshoe crab

62
Food from Plants
  • Most of the worlds population obtains its food
    from crops grown on farms
  • The crop plants grown in the US today are the
    results of generations of selective breeding
  • When plant breeders develop a better variety, it
    is produced in enormous numbers and planted all
    over the country
  • But planting a single variety can prove dangerous

63
Food from Plants
  • Genetically similar plants are susceptible to the
    same diseases
  • In some cases, people maintain seeds of crop
    varieties that are no longer commercially grown
  • The genetic material in these seeds may become
    important if new crop varieties are wiped out by
    disease
  • In other cases, crop breeders are constantly at
    work developing new disease resistant strains of
    crop plants

64
Food from Plants
  • In many cases they cross crop plants with strains
    of wild plants that have more genetic variability
  • So far, wild plants related to crop plants have
    provided the necessary new genes crop breeders
    want to introduce into already developed strains
    of crop plants
  • Scientists all over the world regularly search
    for new wild species related to food crops
  • But they face one serious problem the
    destruction of natural habitats will destroy yet
    undiscovered wild plants

65
The tomato, eaten by many people, was once
thought to be poisonous. In the past, the tomato
grew in the wild. Today, the plant is commonly
grown in many gardens. Who can tell how many
other wild plants will be found in remote areas
and what uses these plants may serve?
66
Chapter 49 People and the Biosphere
  • Section 4 The Future of the Biosphere

67
The Future of the Biosphere
  • A lot of people agree that because Earth supplies
    us with all we need for life food, water, air,
    and natural resources we owe our planet the
    very best care possible
  • In the past, people have treated Earth with
    neglect
  • Today, attitudes are changing

68
Actions for Conservation
  • There are people in the world who love wild
    places, wild plants, and wild animals
  • There are also many people who understand how
    important the health of the biosphere is to the
    health of all species, including humans
  • These people work together to protect the
    environment in many different ways

69
Actions for Conservation
  • Towns, counties, states, the federal government,
    and conservancy groups have all purchased land
    that is to be set aside for conservation purposes
  • The preservation of land habitats is one of the
    most important responsibilities we shall assume
    in the years ahead
  • It is more difficult to conserve the resources in
    the ocean
  • To conserve ocean species, the countries of the
    world must join together to protect the oceans
    and their inhabitants

70
Actions for Conservation
  • Sometimes people work together to protect a
    single species
  • For example, sports fisherman on the east coast
    have formed a group called Stripers Unlimited
  • A group that works to protect habitats important
    to the striped bass
  • Larger organizations such as the Sierra Club,
    World Wildlife Fund, and Green peace work on a
    national and international level to protect the
    environment

71
Difficult Decisions
  • Cleaning up the environment and keeping it clean
    are not easy jobs
  • Solid-waste disposal
  • Sewage treatment plants
  • Toxic waste

72
Difficult Decisions
  • In overwhelming numbers, Americans are expressing
    their fears for the future of planet Earth
  • You must decide how important the environment is
    and whether you are willing to pay to keep it
    healthy
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