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Ch. 6 Humans in the Biosphere

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1 Ch. 6 Humans in the Biosphere
Unit 2 Ecology Ch. 6 Humans in the Biosphere

2 Earth as an Island Earth is an island, that all organisms, including humans, live on & share a limited resource base, & depend on for their long-term survival We all rely on the natural ecological processes that sustain these resources

3 Earth as an Island To protect these resources, we have to understand how humans interact with the biosphere We must also learn how to predict what will happen in the future

4 Human Activities Some human activities that affect the biosphere are hunting & gathering, agriculture, industry, & urban development

5 Human Activities Hunting & Gathering:
For most of human history, our ancestors got food by hunting & gathering Today, groups of people in different parts of the world follow the hunter-gatherer way of life As a result of overhunting, species have become extinct

6 Human Activities Agriculture: Agriculture - the practice of farming
People in different regions grow wheat, rice, & potatoes The development of agriculture included raising animals like sheep, goats, cows, pigs, etc.

7 Human Activities Agriculture:
Agriculture provides a stable & predictable food supply for humans Monoculture - large fields are planted with a single variety of crop, year after year Chemical fertilizers boosted plant growth & pesticides controlled crop damaging insects

8 Human Activities Agriculture:
Green revolution - period of time in the middle of the 20th century, when governments began a major push toward an increase in the world’s food supply Over the last 50 years, the green revolution has helped world food production double

9 Human Activities Agriculture:
While increasing food supply, modern agriculture has created ecological challenges Chemical pesticides have contaminated water supplies, usable water has declined, etc.

10 Human Activities Industrial Growth & Urban Development:
Cities have greatly contributed to pollution of air, water, & soil Human wastes have been dumped into habitats, polluting those habitats, etc.

11 Renewable & Nonrenewable Resources
Environmental goods & services may be either renewable or nonrenewable Renewable resources - can be replenished by biochemical cycles if they are nonliving Ex.) Water is a renewable resource that can become limited by drought or overuse

12 Renewable & Nonrenewable Resources
Nonrenewable resource - 1 that cannot be replenished by natural processes Ex.) Fossil fuels like coal, oil, & natural gas are nonrenewable resources Fossil fuels formed millions of years ago from deeply buried organic materials When they are depleted, they are gone forever

13 Renewable & Nonrenewable Resources
The classification of a resource as renewable or nonrenewable depends on its context A single tree is renewable, but a population of trees in an ecosystem, may not be renewable because the ecosystem may change forever once those trees are gone

14 Sustainable Development
Human activities can affect the quality and supply of renewable resources like land, forests, fisheries, air, & fresh water Sustainable development - a way of using natural resources without depleting them & of providing for human needs without causing long-term environmental harm

15 Land Resources Land is a resource that provides space for human communities & raw materials for industry It also includes the soils where crops are grown If managed properly, it is a renewable resource, but could become nonrenew.

16 Land Resources Plowing the land removes the roots that hold the soil in place, which increases soil erosion Soil erosion - the wearing away of surface soil by water & wind

17 Land Resources In dry climates, a combination of farming, overgrazing, & drought has turned once productive areas into deserts - Desertification

18 Forest Resources Deforestation - loss of forests
It can lead to severe erosion, can wash away nutrients, grazing after deforestation can deplete nutrients permanently

19 Fishery Resources Fishes & other animals that live in water are a valuable source of food for humanity Overfishing, or harvesting fish faster than they can be replaced by reproduction, has greatly reduced the amount of fish in the ocean’s

20 Fishery Resources People from several countries were taking advantage of a resource, fisheries Until recently, fisheries seemed to be a renewable resource, that could be harvested indefinitely Overfishing has destroyed that resource

21 Air Resources Air is a common resource that we use every time we breathe Large cities often have smog - mixture of chemicals that occurs as a grayish haze in the atmosphere It is primarily due to car exhausts & industrial emissions

22 Air Resources Pollutant - harmful material that can enter the biosphere through the land, air, or water Burning of fossil fuels can release pollutants that cause smog & other problems

23 Air Resources When chemical compounds combine with water vapor in the atmosphere, they form drops of nitric & sulfuric acid - Acid rain Acid rain can kill plants by damaging their leaves & change the chemistry of soils & standing-water ecosystems

24 Freshwater Resources Pollution threatens water supplies in the following ways: Wastes discarded on land can seep through soil & enter underground water Chemicals can enter streams & rivers Sewage can encourage the growth of algae & bacteria in aquatic habitats

25 The Value of Biodiversity
Biodiversity - the sum total of the genetically based variety of all organisms in the biosphere Ecosystem diversity - the variety of habitats, communities, & ecological processes in the living world

26 The Value of Biodiversity
Species diversity - the # of different species in the biosphere Genetic diversity - all the different forms of genetic information carried by all organisms living on Earth today

27 The Value of Biodiversity
Biodiversity is 1 of Earth’s greatest natural resources Species of many kinds have provided us with foods, industrial products, & medicines - including painkillers, antibiotics, heart drugs, antidepressants, & anticancer drugs

28 Threats to Biodiversity
Human activity can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic compounds into food webs, & introducing foreign species to new environments

29 Threats to Biodiversity
Extinction - 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

30 Habitat Alteration When land is developed, natural habitats may be destroyed As habitats disappear, species that lived in those habitats also vanish Development also splits ecosystems into pieces - habitat fragmentation Ex.) Central Park

31 Demand for Wildlife Products
Humans have pushed some animal species to extinction by hunting them for food & other products Today, endangered species are protected from hunting in the U.S. Hunting still threatens rare animals in other countries, however

32 Pollution Many forms of pollution can threaten biodiversity, especially when toxic compounds accumulate in the tissues of organisms Biological magnification - when concentrations of a harmful substance increase in organisms at higher trophic levels in a food chain/ food web

33 Pollution

34 Introduced Species 1 of the most important threats to biodiversity today comes from apparently harmless plants & animals that humans transport around the world either accidentally or intentionally

35 Introduced Species Introduced into new habitats, these organisms often become invasive species that reproduce rapidly Invasive species - increase their populations because their new habitat lacks the parasites & predators that control their popul. “back home”

36 Conserving Biodiversity
Conservation - describes the wise management of natural resources, including the preservation of habitats & wildlife Today, conservation efforts focus on protecting entire ecosystems as well as single species

37 Conserving Biodiversity
Protecting an ecosystem will ensure that the natural habitats & the interactions of many different species are preserved at the same time By focusing on protecting specific ecosystems, biologists hope to preserve global biodiversity

38 Charting a Course for the Future
Researchers are gathering data to monitor & evaluate the effects of human activities on important systems in the biosphere 2 of these systems are the ozone layer high in the atmosphere & the global climate system

39 Ozone Depletion Ozone layer Km above Earth’s surface, a layer of high concentration of ozone gas exists Ozone at ground level is a pollutant, but in the atmosphere, serves an important function

40 Ozone Depletion It absorbs a harmful UV radiation from sunlight before it reaches Earth

41 Global Climate Change Global warming - describes the increase in average temperature of the biosphere 1 sign is the melting polar ice cap

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