CHAPTER 6HUMANS IN THE BIOSPHERE

SECTION 1 A CHANGING LANDSCAPE

Key Concept Question:

• What types of human activities can affect the biosphere?

What is carrying capacity?

• the largest number of individuals that an environment can support

What do you think would be the

consequences of exceeding Earth’s

carrying capacity?

• overcrowding, shortage of food and water, shortage of fuel, malnutrition, increased disease

Humans and the Environment

• Humans now live in almost every kind of ecosystem on Earth.

• As human population increases, the impact of humans on the environment increases.

• Humans are a part of the environment and can affect the resilience of the environment. The more that the human population grows, the more resources from the environment we will need to survive.

• Earth is an interconnected planet: we depend on the environment, and the environment is affected by our actions.

• Learning about this connectedness helps us care for the environment and ensures that the environment will continue to support us and other species on Earth.

Visual Concept: Human Population

What types of human activities can affect the biosphere?

• hunting and gathering

• agriculture

• industry

• urban development

*According to a recent study, human activity uses as much energy as all of Earth’s other multicellular species*

Let’s think about how humans have changed throughout history.

MONOCULTURE

• large fields were cleared, plowed, and planted with a single crop year-after-year.

• needed irrigation

• chemical fertilizers

• pesticides needed

• human and animal power replaced by machines

What are the advantages of using agricultural machines such as tractors and harvesting combines?• Vast acreages can be plowed, sown, and

harvested in less time and with fewer people enabling farmers to produce large crops

What are the disadvantages?

• initial cost, and cost of repairs and maintenance

• increased energy resources are used

• release of exhaust gas into the air

• noise pollution

Results of the Industrial Revolution during 1800’s

• reliance on fossil fuels

• increased use of mineral resources

• large-scale production of manufactured goods

Suburban sprawl

• The spread of suburban communities across America

Problems

• large amounts of waste that needs to be disposed of

• consumes farmland

• consumes natural habitats

• places stress on native plants and animals

Key Concept Question:

• What types of human activities can affect the biosphere?

– hunting and gathering

– agriculture

– industry

– urban development

SECTION 2 RENEWABLE AND NONRENEWABLE

RESOURCES

Key Concept Questions:

• How are environmental resources classified?

• What effects do human activities have on natural resources

Resources

• Earth’s resources are described as renewable or nonrenewable.

• Renewable resources are natural resources that can be replaced at the same rate at which they are consumed.

• A renewable resource’s supply is either so large or so constantly renewed that it will never be used up.

RENEWABLE RESOURCES

• Trees

• Water

• Air

• Nonrenewable resources are resources that form at a rate that is much slower than the rate at which they are consumed.

• Most of our energy today comes from fossil fuels.

• Fossil fuels are nonrenewable energy resources that formed from the remains of organisms that lived long ago.

• Fossil fuels such as coal, oil, and natural gas, are nonrenewable resources because it takes millions of years for them to form.

• We use fossil fuels at a rate that is faster than the rate at which they form. So, when these resources are gone, millions of years will pass before more have formed.

How can people be sure that renewable resources will be available for future generations?

SUSTAINABLE USE

• a way of using natural resources at a rate that does not deplete them

• use of biological pest control instead of pesticides

• rotating animal grazing grounds

• planting trees after others have been cut down

Sustainable development manages resources for present and future generations.• Sustainable development meets needs without hurting

future generations.

– resources meet current needs

– resources will still be available for future use

• The timber industry has started to adopt sustainable practices.

• Global fisheries have adopted several sustainable practices.

– rotation of catches

– fishing gear review

– harvest reduction

– fishing bans

What effect do human activities have on natural resources?

• Human activities affect the supply and the quality of renewable resources

Land Resources• space for cities and industry

• supplies raw materials

• soil for crops

Soil Damage• Fertile soil allows agriculture to supply the

world with food.

• Fertile soil forms from rock that is broken down by weathering.

• Nutrients that make soil fertile come from the weathered rock as well as from bacteria, fungi and the remains of plants and animals.

• The processes that form just a few centimeters of fertile soil can take thousands of years.

• The greatest threat to soil is soil erosion. –Erosion is a process in which the

materials of Earth’s surface are worn away by wind, gravity, or water.

DESERTIFICATION

• In certain parts of the world with dry climates, a combination of farming, overgrazing, and drought has turned once productive areas into deserts

• Sustainable agricultural practices can prevent erosion

Terracing

Crop Rotation

Cover Crop

Contour Plowing

Ecosystem Disruption• Ecosystem disruptions can result in loss of

biodiversity, food supplies, potential cures for diseases, and the balance of ecosystems that supports all life on Earth.

• We cannot avoid disrupting ecosystems as we try to meet the needs of a growing human population.

• We can learn about how our actions affect the environment so that we can create ways to conserve it.

• Over the last 50 years, about half of the world’s tropical rain forests have been cut down or burned for timber, pastureland, or farmland. This process of clearing forests is called deforestation.

• The problem with deforestation is that as the rain forests and other habitats disappear, so do their inhabitants.

• Habitat destruction and damage cause more extinction and loss of biodiversity than any other human activities do.

How We Can Help

• replant trees

• new tree varieties are being created to grow faster

Ocean Resources• food

Problem

• over fishing stresses ecosystems

How We Can Help

• limits on numbers of fish caught

AQUACULTURE

• Farming of aquatic ecosystems

Air Resources

• Fossil fuel emissions affect the biosphere.

Pollutants accumulate in the air.

• Pollution is any undesirable factor added to the air, water, or soil.

• Smog is one type of air pollution.

– sunlight interacts with pollutants in the air

– pollutants produced by fossil fuel emissions

– made of particulates and ground-level ozone

• microscopic particles of ash and dust that can enter the nose, mouth, and lungs, causing health problems over a long term

• Smog can be harmful to human health.

• Acid rain is caused by fossil fuel emissions.

– produced when pollutants in the water cycle cause rain pH to drop

– can lower the pH of a lake or stream

– can harm trees

• McDougall video – Air Pollution

How We Can Help

• strict automobile emission standards

• technology to reduce emissions from smokestacks of factories

Water Resources

• drinking

• washing

• watering crops

Water pollution affects ecosystems. • Pollution can put entire freshwater

ecosystems at risk.

Water Pollution• Water pollution can come from fertilizers

and pesticides used in agriculture, livestock farms, industrial waste, oil runoff from roads, septic tanks, and unlined landfills.

• Pollution enters groundwater when polluted surface water percolates down through the soil.

• Landfills and leaking underground septic tanks are also major sources of groundwater pollution.

• When pollutants run off land and into rivers, both aquatic habitats and public water sources may be contaminated.

• Fertilizers from farms, lawns, and golf courses can run off into a body of water, which increases the amount of nutrients in the water leading to an excessive growth of algae.

• Algal blooms can deplete the dissolved oxygen in a body of water. Fish and other organisms then suffocate in the oxygen-depleted water.

Water Pollution

How We Can Help

• protect wetlands such as swamps – they help purify through the water cycle

• conserve use

• cleaning water – sewage treatment plants

Key Concept Questions:

• How are environmental resources classified?

– Renewable or nonrenewable

• What effects do human activities have on natural resources?

– Human activities affect the supply and the quality of renewable resources

SECTION 3 BIODIVERSITY

Key Concept Questions:

• What is the value of biodiversity?

• What are the current threats to biodiversity?

• What is the goal of conservation biology?

BIODIVERSITY

• Is the sum total of the genetically based variety of all organisms in the biosphere

Biodiversity

Insects

BacteriaFungi

Plants

ProtistsOther Animals

54.4%

4.2%

18%

3.4%0.3%

19.7%

Species Diversity

Preserving biodiversity is important to the future of the biosphere.

• The loss of biodiversity has long-term effects.

– loss of medical and technological advances

– extinction of species

– loss of ecosystem stability

• Ecosystem disruption decreases the number of Earth’s species.

• Biodiversity affects the stability of ecosystems and the sustainability of populations.

• Every species plays an important role in the cycling of energy and nutrients in an ecosystem. Each species either depends on or is depended on by at least one other species.

• Indicator species provide a sign of an ecosystem’s health.

– Amphibians

– top predators

EXTINCTION

• occurs when a species disappears from all or part of its range

ENDANGERED SPECIES

• a species whose population size is declining in a way that places it in danger of extinction

This baby Slender Loris is a member of the shy, nocturnal primate species

• As the population of an endangered species declines, the species loses genetic diversity-an effect that can make it even more vulnerable to extinction

• Once a species becomes extinct, will it ever reappear?

• NO

Loss of habitat eliminates species.

• Habitat fragmentation prevents an organism from accessing its entire home range.– occurs when a barrier forms within the habitat– often caused by human development

• Habitat corridors are a solution to the problem.

– corridors can be road overpasses or underpasses

– allow species to move between different areas of habitat

Many forms of pollution can threaten

biodiversity, but one of the most serious

problems occurs when toxic compounds

accumulate or build up in the tissues of

organisms

• Ex) DDT – cheap pesticide, long acting, and worked very well

• Problems – nonbiodegradeable and not eliminated from animals bodies

• One effect of DDT on eagles was to make their eggs too fragile to survive intact

DDT

BIOLOGICAL MAGNIFICATION (Biomagnification)(Bioaccumulation)

• concentrations of a harmful substance increase in organisms at higher trophic levels in a food chain or food web

Biomagnification causes accumulation of toxins in the food chain.

• Pollutants can move up the food chain.

– predators eat contaminated prey

– pollution accumulates at each stage of the food chain

• Top consumers, including humans, are most affected.

Which food level is at the highest risk for

biological magnification?

• Top-level carnivores

Bioaccumulation

Introduced species can disrupt stable relationships in an ecosystem.

• An introduced species is one that is brought to an ecosystem by humans.

– accidental

– purposeful

• Invasive species can have an environmentaland economic impact.

Invasive Species

Zebra Mussel Purple Loostrife

• Invasive species often push out native species.

– Burmese python (Florida Everglades)

– mice (Australia)

– kudzu (southeastern United States)

Conservation practices focus on a few species but benefit entire ecosystems.

• The Endangered Species Act works to protect individual species from extinction.

• A listed species is often called an umbrella species.– the habitat in which the species

lives must be protected– other species are protected

because they share the ecosystem

Protecting Earth’s resources helps protect our future.

• The Environmental Protection Agency (EPA) was created in 1970.

• The EPA develops policies and regulations to protect the environment.

• Legislation helps to protect the environment and endangered species.

– Clean Air Act

– Clean Water Act

– Endangered Species Act

• The National Park Service helps manage public lands.

• The park system includes over 390 areas, covering 84 million acres.

• There are several ways that people can help protect the environment.

– control population growth

– develop sustainable technology and practices

– protect and maintain ecosystems

Visual Concept: Conservation

Key Concept Questions:• What is the value of biodiversity?

– Species of many kinds have provided us with:• Foods• industrial products• Medicines

–Painkillers–Antibiotics–heart drugs–Antidepressants–anticancer drugs

Key Concept Questions:• What are the current threats to biodiversity?

– Habitat fragmentation

– invasive species

– endangered species

• What is the goal of conservation? –protecting existing natural habitats.

SECTION 4 CHARTING A COURSE FOR THE

FUTURE

Key Concept Question:

• What are two types of global change of concern to biologists?

WHAT ARE TWO TYPES OF GLOBAL

CHANGE OF CONCERN TO BIOLOGISTS?

• The thinning, or depletion, of the ozone layer

• Global warming

• Oxygen = O2

• Ozone = O3

OZONE LAYER

• between 20 and 50 kilometers above the Earth’s surface, the atmosphere contains a concentration of ozone gas

• Absorbs UV radiation before sunlight hits Earth

Visual Concept: Ozone and Ecosystems

Ozone “Hole” Over Antarctica

What happens if a person receives too much sun?

• Sunburn

• Cancer

• Damage eyes

• Decrease disease resistance

Too much UV radiation can have a harmful

effect on plants and phytoplankton in the

oceans

What is the cause of the holes in the ozone layer?• CFC’s = chlorofluorocarbons – they were

chemicals used in aerosol cans as the propellant, coolant in refrigerators, freezers, and air conditioners

What would happen to the temperature of

the atmosphere if the amount of

greenhouse gases increased?

• The atmosphere would become warmer = global warming

• The greenhouse effect slows the release of energy from Earth’s atmosphere.

– sunlight penetrates Earth’s atmosphere

– energy is absorbed and reradiated as heat

– greenhouse gases absorb longer wavelengths

– Greenhouse gas molecules rereleaseinfrared radiation

methane (CH4) water (H2O)

carbon dioxide(CO2)

• Global warming refers to the trend of increasing global temperatures.

North Pole

Air pollution is changing Earth’s biosphere.

• The levels of atmospheric carbon dioxide rise and fall over time.

• High levels of carbon dioxide are typical of Earth’s warmer periods.

• Scientists around the world are trying to make models of the effect of increasing global temperatures to predict what the future will be like

Visual Concept: Greenhouse Effect

Visual Concept: Global Warming

Key Concept Question:

• What are two types of global change of concern to biologists?

– Depletion of the ozone layer and Global Warming