Unit 5 Seminar

Carbon dioxide

The Carbon Cycle

• Carbon comes into the living world through the plants, algae, and bacteria that take in atmospheric carbon dioxide to perform photosynthesis.

• Animals obtain their carbon from these photosynthesizing organisms.

The Carbon Cycle

• The carbon cycle is completed when carbon moves back into the atmosphere in the form of carbon dioxide, which is produced naturally through two processes:– the respiration of living things– the decomposition of them following their

death

The Carbon Cycle

Figure 35.1

atmospheric CO2

photosynthesis

respiration

respiration

animalsplants

dead organismsfossil fuels

decompositionby bacteriaand fungi

burningof fossilfuels

The carbon cycle

Plants and otherphotosynthesizing organismstake in atmospheric carbondioxide (CO2) and convert or“fix” it into molecules thatbecome part of the plant.

The physical functioning orrespiration of organismsconverts the carbon in theirtissues back into CO2.

Plants and animals die andare decomposed by fungi andbacteria. Some CO2 results,which moves back into theatmosphere.

Some of the carbon in theremains of dead organismsbecomes locked up incarbon-based compoundssuch as coal or oil.

The burning of these fossilfuels puts this carbon into theatmosphere in the form ofCO2.

Source: Krogh, D. (2009). Biology: A Guide to the Natural World. Pearson Benjamin Cummings

The Carbon Cycle

• Carbon dioxide makes up a small but critical proportion of the Earth’s atmosphere.

• It is vital to life and greatly affects global temperature.

Global Warming

Global Warming

• The Earth’s atmospheric temperature is increasing through the phenomenon known as global warming.

• Scientists can now state with at least 90 percent certainty that most of the global warming seen since 1950 has come about because of human activities– deforestation – emission of such gases as carbon dioxide and methane into

the atmosphere.

Global Warming

• Global temperatures risen 0.74o C since 1906 to 2005

• Warming trend over last 50 years nearly twice that for the last 100 years

Growing Concentration of Atmospheric CO2

Beginning ofindustrialization

Carbon dioxide levels over the last 10,000 years A closer look at the last 250 years

Source: Krogh, D. (2009). Biology: A Guide to the Natural World. Pearson Benjamin Cummings

The Greenhouse Effect

• CO2 and methane are referred to as greenhouse gases – trap additional quantities of the heat that

comes to the Earth from the sun. – lower energy radiation (heat) cannot

penetrate layer of gases

The Greenhouse Effect

Figure 35.19

heat trapped

greenhouse gases

reflection oflow-energyradiation (heat)

high-energysun rays

Source: Krogh, D. (2009). Biology: A Guide to the Natural World. Pearson Benjamin Cummings

Global Warming

• Deforestation—today, primarily of tropical forests– puts CO2 into the atmosphere directly,

when trees are burned

– results in less CO2 being taken out of the atmosphere

• trees that are destroyed no longer take up CO2 to perform photosynthesis.

Global Warming

• The Earth appears to have warmed by 0.74°C or about 1.3°F in the 100 years that ended in 2005, according to our most authoritative source on global warming, the Intergovernmental Panel on Climate Change (IPCC).

Disappearing Glaciers

Figure 35.20

Source: Krogh, D. (2009). Biology: A Guide to the Natural World. Pearson Benjamin Cummings

Global Warming

• In 2007, the panel predicted that, over the course of the twenty-first century, the Earth is likely to warm by an addition 1.8°C to 4.0°C, depending on the additional quantity of greenhouse gases put into the atmosphere.

Global Warming

• The consequences of this warming– a rise in sea levels – more intense tropical storms– less snow cover globally– permafrost that thaws to increasing

depths.

Rise in Sea Level 6 meters (~20 ft) sea level rise

No greenhouse gases reduction

http://geology.com/sea-level-rise/florida.shtml

Habitat Changes: Disappearing Arctic Ice

Figure 35.21

Source: Krogh, D. (2009). Biology: A Guide to the Natural World. Pearson Benjamin Cummings

Australian Passerine Birds Body Size

• Australia average surface temp risen more than 1oF since 1900

• Passerine body size decreased by 3.6%

• Individuals within a species are larger the closer to a pole

• Smaller birds now live somewhat closer to the South Pole

• Nutritional deficiencies not found

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Jacky winter

Habitat Changes

• Alpine mountain regions– Native plants and animals driven to higher

elevations

Global Warming

• Global warming cannot be stopped, the IPCC said, but it can be lessened in accordance with future human activities.– Use less energy– Reduce fossil fuel use

– Store CO2

– Slow tropical rain forest destruction

Seminar Questions

• If there is strong evidence indicating that CO2 levels contribute to global warming, why is the United States opposed to any reductions?  

• Is there any science supporting those who do not wish to reduce fossil fuel CO2 emissions? 

• If we choose to reduce fossil fuel emissions significantly, how might we do so in a way that does not damage our economy? 

Seminar Questions

• Is there a fair method globally to reduce CO2 emissions? Support your answer. 

• If we decide to wait until the climate is clearly too warm for the human species, is there a technological quick fix? What can be done to monitor the situation? 

Questions?