Humans in the Biosphere

Chapter 6

VIII. Humans in the Biosphere

A. Earth as an Island-

1. all organisms that live on Earth share limited resource base

2. Understanding how humans interact is crucial to protecting resources

The iiwi (Hawaiian honeycreeper), a native species in Hawaii is becoming scarce due to disease, habitat loss, and predation by introduced species

1. Industry and Technology give humans advantage in competing with other species for limited resources such as food, energy, and space2. Today, humans most important source for environmental change

B. Human Activities

a. Hunting and Gathering-have changed environment since pre-historic times

Human hunters arrived in North America about 12,000 years ago. They caused one of major mass extinctions of large animals (woolly mammoths, giant ground sloths, sabertooth cats, cheetahs, zebras, etc.)

b. Agriculture- humans began practicing farming 11,000 years ago (after last ice

age)

2). Modern Agriculture- In 1800’s, advancement in science led to remarkable changes in agriculture

and increased yields (irrigation, new crop varieties, invention of farm machines

1). Domestication of Animals- sheep, goats, cows, pigs, horses, dogs (led to overgrazing, eroded soils, large demands on water

3). Green Revolution- global effort to increase food production for fast-

growing world population (new, intensive farming practices that increase yields)

C.Renewable and Nonrenewable Resources

a. Renewable- can regenerate (are replaceable) not necessarily

unlimited b. nonrenewable- one that cannot be replenished by natural processes (eg. Fossil fuels, oil and natural gas

1. Two types of environmental resources

2. Sustainable use- using natural resources so that you don’t deplete them (based on principles of ecology and economics)

This proud, tall tree is no match for a huge chainsaw. Once cut, it will be used to make many consumer products

A tiny tree will be placed in its stead. Varieties of trees that reach harvesting size in fewer years have been developed

3. Land Resources- provides space for cities, materials for industry, soils in which crops are grown.

desertification- in certain parts of the world with dry climates, a combination of farming, overgrazing, and drought have turned once productive areas into deserts

4. Forest Resources- provides products, habitats and food for organisms,

moderates climate, limits soil erosion, protects freshwater supplies, “lungs” of the Earth”

deforestation- loss of forest. Can lead to severe erosion. Sustainable-use strategies include selective harvesting and replanting.

What are two ways in which reforestation might affect the biosphere?

5. Ocean Resources- provides valuable food resources.

How do you explain graph #2 (fish catch per person remains the same despite steady increase in world fish catch)?

6. Air Resources- Air is common resource. Preserving air quality remains a challenge for modern society.

a. Smog- common pollutant in large cities. (pollutant- harmful material that can enter the biosphere through land, air, or water)

b. Acid rain- acidic gasses released into air and combine with water vapor forming drops of nitric and surfuric acid. Can kill plants, change chemistry of soils and standing water ecosystems

Photomicrograph of drop of acid rain. Serious threat to environment

7. Water Resources- water is renewable resource but must be protected because supply is limited.

a. Water pollution- threatened by chemicals, domestic sewage, wastes discarded on land- all can seep into underground water supplies.

City sewage must be treated in sewage-treatment plants. Organic wastes are broken down by bacteria and then chemicals are added to kill harmful microorganisms.

Where does all of your trash end up?

Why do we have to be careful about what goes into our garbage landfills?

Trawlers clean up an oil spill caused by a disaster at sea. A system of floats called booms helps keep the oil from spreading during the cleanup process.

b. Domestic sewage, which is the wastewater from sinks and toilets, contains nitrogen and phosphorous compounds that can encourage the growth of algae and bacteria in aquatic habitats

Algae bloom

D. Biodiversity- sum total of the genetically based variety of all organisms in the biosphere

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

b. Species diversity- number of different species in the biosphere

c. Genetic diversity- sum total of all the different forms of genetic information carried by all living organisms

1. Forms of diversity

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

3. 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 into new environments

a. Pollution- many forms of pollution can affect biodiversity.

Biological magnification- concentrations of harmful substances increase in organisms at higher trophic levels. Affects all levels, but top-level carnivore are at highest risk

By what number is the concentration of DDT multiplied at each successive trophic level?

b. Introduced Species- one of most important threats. Introduced either intentionally or unintentionally they have destroyed habitats of species native to those ecosystems.

Fire ants were accidentally imported from Brazil about 45 years ago. Now found in San Clemente

Zebra mussels were introduced into Great Lakes from ballast of ships. Fast-growing mussels filter food from the water, blocking many food chains

Kudzu was introduced into the U.S. from Russia and Japas as an ornamental and to reduce soil erosion. It grows and reproduces rapidly, smothering areas of native plants

Can you name any introduced species that have created problems locally?

4. Conserving Biodiversity- many conservation efforts focusing on entire ecosystems as well as single species

D. Charting a Course for the Future- two major concerns

1. Ozone depletion- naturally occurring ozone gas (20-50 km above Earth’s surface) absorbs good deal of harmful ultraviolet radiation from sunlight before it reaches Earth’s surface.

a. Beginning in 1970’s scientists found evidence showing ozone “hole” over Antarctica

b. Problem caused by compounds called chlorofluorocarbons (CFCs)

(CFCs act as catalysts that enable UV light to break apart ozone

2. Global Warming- an increase in average temperature of the biosphere.

a. Hypothesize that human activities have added carbon dioxide and other greenhouse gasses (methane, H20) into the atmosphere

b. Scientific models suggest that could cause polar ice caps to melt and raise sea level. This could also cause more severe weather disturbances

D. The Value of a Healthy Biosphere

1. Human society depends on healthy, diverse, and productive ecosystems because of the environmental and economic benefits they provide

2. People need to make wise choices in use of resources and disposal or recycling of materials

Chapter 6Chapter 6Humans in the Humans in the

BiosphereBiosphere

Review

In the very distant past, most people

a. lived in small groups.

b. lived in permanent settlements.

c. did not gather plants.

d. did not hunt animals.

In the very distant past, most people

a. lived in small groups.

b. lived in permanent settlements.

c. did not gather plants.

d. did not hunt animals.

The arrival of Europeans in the Hawaiian Islands changed the islands by introducing

a. ranching.

b. predators.

c. disease.

d. all of the above

The arrival of Europeans in the Hawaiian Islands changed the islands by introducing

a. ranching.

b. predators.

c. disease.

d. all of the above