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CHAPTER 6 HUMANS IN THE BIOSPHERE

All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

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Page 1: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

CHAPTER 6HUMANS IN THE

BIOSPHERE

Page 2: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

6-1 A CHANGING LANDSCAPE

Page 3: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things.

Page 4: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Human Activities Industry and technology give humans a

strong advantage in competing with other species for limited resources such as food, energy, and space. Humans are the most important source of environmental change on the planet.

Human activities can change the flow of energy in an ecosystem and reduce the ability of ecosystems to recycle nutrients. Human activities that have that have changed the biosphere are hunting and gathering, agriculture, industry, and urban development.

Page 5: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Hunting and Gathering

For most of human history, hunting and gathering was the primary means of survival. Early humans hunted birds and other animals and fished. They gathered seeds, fruits, and nuts. Some people were nomadic, which means they traveled to take advantage of movements and cycles of natural plant and animal populations.

Page 6: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Hunters and gatherers lived in small groups. They often changed the environment. They built dams to divert water and burned grasslands to encourage the growth of certain plants. Some scientists believe early human hunters caused one of the major mass extinctions of large animals (etc: woolly mammoths, giant ground sloths, sabertooth cats)

Page 7: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Today, groups of people in different parts of the world still follow the hunting and gathering way of life. They supplement their diet with the meat of wild animals through subsistence hunting. Subsistence hunters make few demands on the environment but use some form of technology, such as guns, snowmobiles, or tools.

Page 8: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Agriculture Early hunter-gatherers planted seeds

near human settlements. About 11,000 years ago, humans began farming, or agriculture. Agriculture spread in many directions as people planted other varieties of seeds. Acriculture gave people a dependable supply of food. People settled around regions of agricultural growth, creating town and cities, leading to the development of elements of civilizations such as government, laws, and writing.

Page 9: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Domestication of Animals

As crops improved and farming methods became more reliable, farmers began to keep herds of domesticated animals, like sheep, goats, cows, pigs, horses, and dogs. They supplied milk, meat, wool, companionship, and did work. Overgrazing by goats, cows, and others changed grassland ecosystems to eroded soils and put large demands on water supplies.

Page 10: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

From Traditional to Modern Agriculture

Between 1450 and 1700, an exchange of foods began. In the 1800s, advancements in science and technology led to a change in agriculture. Large-scale watering (irrigation), new crop varieties, and the invention of farm machines for plowing, planting, and harvesting helped farmers to increase their yields tremendously.

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The Green Revolution

By the 1950s, there was not enough food to keep up with the growing population. In a global effort to increase food production, governments and scientists developed new, intensive farming practices that greatly increased yields of rice, wheat, and other crops. This is now known as the green revolution.

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The green revolution needed a few things to increase crop production. The main strategy was the development of new, highly productive varieties of major food crops. Crop breeders developed new plant varieties called “miracle strains” that improved harvests. Another strategy was a method called monoculture. Monoculture calls for large fields to be cleared, plowed, and planted with a single crop every year. Irrigation, chemical fertilizers, and pesticides are used. Farmers also replaced human and animal power with machines

Page 13: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

The green revolution increased food production and helped prevent food shortages.

Disadvantages: water supplies and energy depleted, pesticides carry potentially harmful chemicals, fertilizer can interfere with food webs and biogeochemical cycles.

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Industrial Growth and Urban Development

Many ecologists are concerned about the effects of human activity on the environment. Some industrial processes pollute air, water, and soil.

 

Page 15: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

6-2 Renewable and Nonrenewable Resources

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Resource – something that can be taken when needed

Common Resource – environmental resource owned by many people in common

Two types or resources: renewable and nonrenewable

Renewable resource – can regenerate and is therefore replaceable

Not necessarily unlimited (fresh water can become limited by drought or overuse)

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Nonrenewable resource – Can’t be replenished naturally

Ex – Fossil fuels (coal, oil, gas)When these fuels are gone, they

are gone forever Sustainable use is a way of using natural

resources at a rate that does not deplete them

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Land Resources Plants need fertile topsoil to grow.

Plowing the land increases the rate of soil erosion – (wearing away of surface soil by water and wind)

Desertification – farming, overgrazing, and drought in dry climates turn once productive areas into deserts

Page 19: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Forest Resources Forests are an important resource for the

products they provide and functions they perform (wood, provide oxygen)

Deforestation – loss of forests Can lead to severe erosion of

soil Tree farms are a renewable resource

because when a tree is cut down, a new one is planted.

Page 20: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Ocean Resources People depend on sea life for food.

Overfishing can destroy a fishery. Aquaculture – the farming of aquatic

organisms-an efficient way to produce sea life

If not properly managed, can pollute water with fish waste and damage local aquatic ecosystems.

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Air Resources Air is a resource we use every time we

breathe. Smog – a mixture of chemicals that occurs

as a gray-brown haze in the atmosphere Pollutant – harmful material that can enter

the biosphere through land, air, or water Burning fossil fuels can release pollutants

that cause smog. Burning fossil fuels releases acidic gases into the air and form drops of nitric and sulfuric acids and fall as acid rain - can kill plants

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Water ResourcesAmericans use billions of gallons of fresh water daily for everything from drinking and washing to watering crops and making steel. Although water is renewable, the total supply of fresh water is limited. Protecting water supplies from pollution and managing society’s ever-growing demand for water are major priorities. As demand for water grows rapidly in many parts of the US, water conservation is becoming an increasingly important aspect of sustainable use.

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6-3 BIODIVERSITY

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Biodiversity – the sum total of the genetically based variety of all organisms in the biosphere

Ecosystem diversity - the variety of habitats, communities, and ecological processes in the living world

Species diversity – the number of different species in the biosphere

So far, biologists have identified and named about 1.5 million species and estimate that milllions more may be discovered in the future.

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Genetic diversity – the sum total of all the different forms of genetic information carried by all organisms living on the earth today.

Biodiversity is one of Earth’s greatest natural resources. Species of many kinds have provided us with foods, industrial products, and medicines

 

Page 26: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Threats to Biodiversity Human activity can reduce biodiversity

by altering habitats, hunting species to extinction, introducing toxic compounds into food webs, and introducing foreign species to new environments.

As human activities change ecosystems, this may lead to the extinction of species. (no longer exists)

Endangered species – a species whose population is declining in a way that places it in danger.

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Habitat Alteration and Fragmentation

When land is developed, natural habitats may be destroyed. As habitats disappear, the species that live in those habitats vanish. Development often splits ecosystems into pieces. This is called habitat fragmentation.

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Conserving Biodiversity Conservation – the wise management of

natural resources, including the preservation of habitats and wildlife

Today, conservation efforts focus on protecting entire ecosystems as well as single species. Protecting an ecosystem will ensure that the natural habitats and the interactions of many different species are preserved at the same time.

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6-4 CHARTING A COURSE FOR THE FUTURE

Page 30: All organisms rely on resources which are limited. Our growing population means increasing demands for Earth’s air, water, land, and living things

Many biologists are concerned about the biological effects of two types of global change: the thinning of the ozone layer and global warming

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Ozone Depletion Ozone layer – the concentration of ozone gas

that the atmosphere contains between 20 and 50 km above the Earth’s surface

In the 1970s, scientists found evidence that the ozone layer was in trouble. A hole was discovered in the ozone layer. Over the years, the hole has been growing larger. A second has also been found. These holes allow higher than normal levels of UV onto the Earth.

These holes were caused by CFCs, which were used in aerosol cans, Styrofoam, and coolants. The use of CFCs have been phased out.

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Global Warming Global warming – the increase in the average

temperature of the biosphere Over the past 120 years, global temperature have

risen 0.5 degrees Celsius. Temperatures are rising at a faster rate now than

they did during the previous 100 years. Some scientists believe that human activities have

caused global warming by adding carbon dioxide (from burning fossil fuels) and other greenhouse gases such as methane to the atmosphere. If global warming continues at its current rate, the polar ice caps will continue to melt and sea levels could rise enough to flood some low-lying coastal areas. Storms and other weather disturbances could become more frequent and more severe.