Semester 2 Final Review Part 2

Carbohydrates, Photosynthesis & Respiration and Ecology

CYCLESWaterCarbon Nitrogen

• Energy transfer through an ecosystem is ONE WAY

– Most energy is lost as heat

• Nutrients such as nitrogen, water and carbon are able to cycle through an ecosystem and be reused.

NUTRIENT CYCLES

Evaporation:Liquid water rising

converting to water vaporand rising to the

atmosphere.

Condensation:

The changing of

water from a

vapor to a liquid

Precipitation: Any form of water

falling from the sky such as rain, sleet,

snow, and hail

Transpiration:

Release of water throughthe leaves of plantsinto the atmosphere

THE CARBON CYCLE

Plants acquire CO2 thru stomata in their leaves and incorporate it in to organic molecules of their own biomass photosynthesis

Link between Atmosphere and Terrestrial:

Link between Atmosphere and Terrestrial:

Carbon is cycled quickly because of high demand from plants

Some of this organic material becomes a carbon source for consumers

• All organisms return CO2 to the atmosphere thru respiration

• Decomposition recycles carbon to the soil and back to atmosphere

• Fires oxidize organic materialto CO2 (burning)

Link to animation

Link between Atmosphere and Terrestrial:

Carbon is also stored on land:

• Carbon is accumulated in wood and other durable organic material

• Organic detritus, under intense pressure, changes into coal and petroleum in rock.

• Nitrogen gas (N2) makes up 79% of our atmosphere

• Nitrogen is needed by plants and animals to make proteins and DNA– It ranks fourth behind oxygen, carbon, and hydrogen as

the most common chemical element in living tissues.

• Most organisms CAN NOT obtain nitrogen through the atmosphere!

The Nitrogen Cycle

The Nitrogen Cycle• Since animals cannot

get nitrogen directly from the atmosphere they must eat it through plants.

• Certain plants can pull atmospheric nitrogen into their roots and make NO3

– Legumes, Red Alder trees

Rhizomes

The Nitrogen Cycle

• Animals then eat the plants that contain NO3 and incorporate it into their body– DNA– Proteins

Cycles Vocabulary

Evaporation Fossil FuelsCondensation NitratePrecipitation Nitrogen FixingTranspiration DenitrificationStomataCarbon SourceCarbon SinkDecompositionCombustion

Climate Change

Greenhouse Effect

Light energy from the sun (solar radiation) is either reflected or absorbed by the Earth.

When it is absorbed it is converted into heat energy (infrared radiation).

That heat energy either escapes the Earth through the atmosphere, or gets absorbed by greenhouse gases and reflected back down.

This is how heat is trapped within the troposphere and how the Earth stays warm.

Greenhouse Effect

Greenhouse gasses include: Water (H2O)Methane (CH4)Carbon Dioxide (CO2)Nitrous Oxide (N2O)

The first 3 are very natural, and infact necessary to keep the Earthwarm.

Global WarmingThe greenhouse effect is natural and necessary for most life here on Earth.Without the greenhouses gases in our atmosphere the Earth’s average temperature would be -160C ! This happened to Mars which lost its atmosphere.

If a planet has extremely high concentrations of greenhouse gases in its atmosphere however it can have a runaway greenhouse effect.This is the case with Venus, whose high concentrations of carbon dioxide give it an average surface temperature of 4250C!!!

Effects of Climate Change

High global temperatures

(Heat Waves)

Increased drought, extreme weather.

Raising sea levels caused by melting ice.

Acidification of the ocean.

Positive FeedbackWe call this a positive

feedback loop where:

A produces more of B, which then in turn produces more of A.

Melting sea ice creates a lower albedo, which then in turn causes more ice to melt.

Negative FeedbackOf course there is also negative feedback as well.You are probably most familiar with this in

homeostasis.With negative feedback: A produces B, which then

stops or lowers the production of A

Negative FeedbackWith climate change there are many more examples

of positive rather than negative feedback.Here is one example of negative feedback in the

climate:

Global warming is expected to intensify rates of land degradation and desertification, which in turn results in more windblown dust. Dust acts to cool the surface (by raising albedo), thus lowering the temperature of the Earth.

Positive vs. Negative Feedback.

Positive feedback tends to promote instability in systems (think spiraling out of control).

Negative feedback tends to promote stability in systems (think again about homeostasis).

Climate Change Vocabulary

Positive FeedbackNegative FeedbackGreenhouse EffectGreenhouse GasesClimate Change