Earth Science

22

Subject Area Standards Assessment Guide, Quarter 4 “Biogeochemical Cycles and Climate”

Std and No. of Items

What should be taught?

[According to the Science Frameworks]

KEY IDEAS/

VOCABULARY LIST

Sample Test Item

Biogeochemical Cycles

7a. Students know the carbon cycle of photosynthesis and respiration and the nitrogen cycle.

Carbon and nitrogen move through biogeo

chemical cycles. Th

e recycling of these

components in the environment is crucia

l to the maintenance of life. Through

photosynthesis, carbon is inco

rporated into the biosphe

re from the atmosphere.

It is then released back into the atmosphere

through respiration. Carbon dioxide in the

atmosphere is dissolved and stored in th

e ocean as carbonate and bicarbonate ions,

which organisms take in to make their shells. When these organisms die, their shells rain down to the ocean floor, where they may be dissolved if the water is not saturated in carbonate. Otherwise, the shells ar

e deposited on the ocean floor and become

incorporated into the sediment, eventually

turning into a bed of

carbonate rock, such

as limestone. Uplifted limestone may dissolve in acidic rain

to return carbon to the atmosphere as

carbon dioxide, sending calc

ium ions back into the ocea

n where they will precipitate

with carbon dioxide to form new carbonate

material. Carbonate rocks may also be

subducted, heated

to high temperatures, and deco

mposed, returning carbon to the

atmosphere as volcanic carbon dioxide gas. Ca

rbon is also stored in the solid earth as

graphite, methane gas, petroleum, or coal. Nitrogen, another element important to life,

also cycles through the biosphere and

environment. Nitrogen gas makes up most

of the atmosphere, but elemental nitrogen

is relatively inert, and multicellular pl

ants and animals cannot use it directly.

Nitrogen must be “fixed,” or converted to

ammonia, by specia

lized bacteria. Other

bacteria change ammonia to nitrite and then to nitrate, which plants can use as a nutrient. Eventually, decomposer bacteria

return nitrogen to

the atmosphere by

reversing this process.

CARBON CYCLE PHOTOSYNTHESIS ATMOSPHERE RESPIRATION CARBON DIOXIDE OXYGEN CARBONATES SEDIMENT LIMESTONE ACID RAIN METHANE PETROLEUM COAL FOSSIL FUELS GRAPHITE NITROGEN CYCLE MULTICELLULAR BIOSPHERE NITROGEN FIXATION AMMONIA NITROGEN-FIXING BACTERIA NITRATES NITRITES DECOMPOSERS

Which of the following processes in the

Carbon cycle removes CO2 gas from Earth’s

atmosphere?

From: Test Bank 2007-2008

A

weathering of carbpnate rocks

B

combustion of fossil fuels

C

respiration of marine organisms

D photosynthesis

7b. Students know the global carbon cycle: the different physical and chemical forms of carbon in the atmosphere, oceans, biomass, fossil fuels, and the movement of carbon among these reservoirs.

The global carbon cycle extends across phy

sical and biological Earth systems.

Carbon is held temporarily in a number of

reservoirs, such as in biomass, the

atmosphere, oceans, and in fossil fuels. Ca

rbon appears primarily as carbon dioxide

in the atmosphere. In oceans carbon takes

the form of dissolved carbon dioxide and

of bicarbonate and carbonate ions. In the

biosphere carbon takes

the form of sugar

and of many other organic molecules in

living organisms. Some movement of

carbon between reservoirs takes place throug

h biological means, such as respiration

and photosynthesis, or through physical me

ans, such as those related to plate

tectonics and the geologic cycle. Carbon fixed into the biosphere and then transformed into coal, oil, and gas deposits

within the solid earth has in recent years

been returning to the atmosphere through

the burning of fossil fuels to generate

energy. This release of car

bon has increased the concentr

ation of carbon dioxide in

the atmosphere. Carbon dioxid

e is a primary greenhouse ga

s, and its concentration

in the atmosphere is tied to climatic conditions.

GLOBAL CARBON CYCLE BIOMASS FOSSIL FUELS ATMOSPHERES AND OCEANS AS CARBON RESERVOIRS FORMS OF CARBON: CARBONATES, BICARBONATE IONS, CARBONIC ACID GEOLOGIC CYCLE CARBON FIXATION GREENHOUSE GAS GLOBAL WARMING

Which of these processes leads to

the formation of fossil fuels?

A photosynthesis C decomposition B respiration D industrial activities