3.4 LESSON Matter in Ecosystems

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• Elements and compounds that make up nutrients move

continually through air, water, soil, rocks, and living organisms within ecosystems via nutrient cycles.

3.4 What Happens To Matter in an Ecosystem?

Multiple Choice

What is it called when elements and compounds that make up nutrients move continually through the four spheres?

• nutrification

• nutrient cycles

• nutrient reactions

• nutrient balancing

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• Nutrient cycles, or biogeochemical cycles, are

driven directly or indirectly by incoming solar
radiation and Earth’s gravity.

– Nutrient cycles include the hydrologic (water),

carbon, nitrogen, and phosphorus cycles.

– Human activities are disrupting these cycles.

– Certain nutrients may accumulate in temporary

reservoirs, including the atmosphere, the oceans
and other bodies of water, underground deposits,
and living organisms.

Nutrients Cycle Within and Among Ecosystems

Multiple Select

Which two of these are responsible for driving nutrient cycles?

• gravity

• geothermal energy

• solar radiation

• human activities

Multiple Choice

What are the places called that may temporarily store nutrients?

• cupboards

• closets

• reservoirs

• sheds

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• The hydrologic cycle collects, purifies, and

distributes Earth’s fixed supply of water.

• Incoming solar radiation causes evaporation

(conversion of liquid water to water vapor).

– Most water vapor rises into the atmosphere,

condenses in clouds

– 90% water vapor above land contributed by

transpiration (evaporation from plant surfaces)

• Gravity draws water back to Earth as

precipitation (rain, snow, sleet).

The Hydrologic Cycle—Evaporation and Precipitation

Multiple Choice

Which stage of the water cycle is solar powered?

• precipitation

• condensation

• evaporation

• runoff

Multiple Select

Where does most (~90%) evaporated water in the atmosphere come from?

• oceans

• plants

• transpiration

• deserts

• lakes and rivers

Multiple Choice

Most atmospheric water vapor

• falls as precipitation

• condenses into clouds

• flows across the surface

• sinks into the ground

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• Most precipitation falling on land ecosystems

becomes surface runoff.

– Flows over land into streams, rivers, lakes,

wetlands, the ocean, where it can evaporate

• Some precipitation seeps into the soil.

– May evaporate or be used by plants, organisms

– May seep deeper into soil as groundwater that

collects in aquifers (underground layers of sand, gravel, water-bearing rock)

The Hydrologic Cycle—Surface Runoff and Groundwater

Multiple Choice

Most precipitation becomes

• groundwater

• oceanwater

• clouds

• surface runoff

Multiple Choice

Some precipitation sinks into the ground and collects in underground layers of sand, gravel and water-bearing rock. These layers are called

• water sinks

• aquifers

• parfaits

• watersheds

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The Hydrologic Cycle

Labelling

Label the steps of the water cycle in order, starting with the solar powered step.

Drag labels to their correct position on the image

4

3

1

2

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• By draining and filling in wetlands, which

disturbs natural flood control

• By withdrawing freshwater resources faster

than natural processes replenish it (aquifer
depletion, reduced river flow)

• By replacing forests/vegetation with urban

development—reducing infiltration and
increasing runoff

How Do Humans Alter the Water Cycle?

Match

Match the following human activities with their consequences

• draining and filling in wetlands

• withdrawing too much freshwater

• replacing forests with urban areas

disturbs natural flood control

aquifer depletion, reduced river flow

reduces infiltration & increases runoff

• disturbs natural flood control

• aquifer depletion, reduced river flow

• reduces infiltration & increases runoff

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• Carbon dioxide gas, a key component of the

carbon cycle, significantly affects global
temperatures (due to the greenhouse effect).

• How does carbon cycle through the

biosphere?

– Photosynthesis by producers

– Aerobic respiration by producers, consumers, and

decomposers

– Marine sediments (Earth’s largest store of carbon)

The Carbon Cycle

Multiple Select

How does carbon cycle through the biosphere?

• photosynthesis

• respiration

• marine sediment

• volcanic activity

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The Global Carbon Cycle

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• By adding large amounts of CO₂ to the atmosphere

– Extracting and burning fossil fuels at a much higher rate than they

are naturally formed

• By clear-cutting forests faster than they re-grow

– Destroys carbon-absorbing vegetation

How Do Humans Alter the Carbon Cycle?

Multiple Select

How do humans affect the carbon cycle?

• adding large amounts of carbon dioxide to the atmosphere

• extracting and burning fossil fuels

• clear-cutting forests

• destroying carbon-absorbing vegetation

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• Atmospheric nitrogen cannot be absorbed

and used directly by organisms.

– Bacterial action makes nitrate ions available to

plants.

• Plant roots take up nitrate ions

• Animals eat plants, get nitrogen-containing compounds

• Organisms return nitrogen-rich organic compounds to

environment via waste, cast-off particles, dead remains

• Bacteria break down organic material, which eventually

releases nitrogen gas back to atmosphere

The Nitrogen Cycle

Multiple Choice

Which organism is responsible for converting atmospheric nitrogen into a form usable in the biosphere?

• plants

• bacteria

• animals

• fungi

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The Nitrogen Cycle

Reorder

Reorder the following - starting with nitrogen in the atmosphere.

• bacteria convert nitrogen into nitrate ions

• plants roots soak up nitrate ions

• animals eat plants

• dead organisms decompose putting nitrogen in the soil

• decomposing bacteria return nitrogen to the air

1

2

3

4

5

• 1
• 2
• 3
• 4
• 5

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• By burning fossil fuels that add nitric oxide to the atmosphere

– Nitric oxide can be converted to nitrogen dioxide gas and nitric acid

vapor, which fall as acid rain.

• By removing atmospheric nitrogen to make fertilizer

– Excess nitrates in runoff from farm fields and sewage discharge

contaminate bodies of water and cause excessive algal growth.

How Do Humans Alter the Nitrogen Cycle?

Multiple Select

How do humans alter the natural nitrogen cycle?

• burning fossil fuels produces acid rain

• contaminating bodies of water with nitrates causing algal blooms

• removing atmospheric nitrogen to make fertilizer

• decomposing bodies release nitrogen gas into the atmosphere

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• Phosphorus cycles through soils, rocks, water

and plants, but not through the atmosphere.

– Water flows over rock, eroding inorganic

compounds containing phosphate ions

– Phosphate ions wash into soil, are absorbed by

producers

– Phosphate compounds transfer from producers to

consumers

– May wash into oceans, get trapped in marine

sediments for millions of years

The Phosphorus Cycle

Multiple Choice

The phosphorus cycle is different from the water, carbon and nitrogen cycles because phosphorus doesn't enter the

• hydrosphere

• biosphere

• atmosphere

• geosphere

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• By mining phosphorus deposits to make

fertilizer

• By clearing tropical forests, which increases

erosion and reduces phosphorus in topsoil

• By adding large quantities of phosphate ions

to streams, lakes, and oceans as a result of
fertilizer runoff and topsoil erosion

– Excess phosphates stimulate algal growth

How Do Humans Alter the Phosphorus Cycle?

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The Phosphorus Cycle

Categorize

Options (6)

runoff from mining waste

runoff from sewage

fertilizer runoff

animals eating plants

decomposition

erosion

Which phosphorous pathways are natural and which have been affected by humans?

Affected by Human

Natural