Ecology: Net Primary Productivity & Biogeochemical Cycles

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Questions and Answers

What is primarily responsible for creating dead zones in lakes and rivers?

Eutrophication and human activities (correct)

Overfishing and pollution

Natural climate changes

Invasive species and habitat loss

How many dead zones were reported as of 2008?

600

800

200

400 (correct)

Which area is known to have one of the largest dead zones?

Gulf of Mexico (correct)

Great Lakes

Chesapeake Bay

San Francisco Bay

What substances from fertilizers contribute to the formation of dead zones?

Phosphates and nitrates Signup and view all the answers

Which of the following activities is NOT a cause of dead zones?

Natural weathering of rocks Signup and view all the answers

What is permafrost?

A layer of soil that remains frozen throughout the year Signup and view all the answers

Which process describes the movement of water vapor to clouds in the water cycle?

Condensation Signup and view all the answers

Which of the following elements is NOT commonly associated with organic molecules?

Iron Signup and view all the answers

Which term describes the amount of time that chemicals spend in a reservoir?

Residence time Signup and view all the answers

How much of Earth's water is freshwater found in lakes and rivers?

1% Signup and view all the answers

What process occurs when water moves from plants back into the atmosphere?

Transpiration Signup and view all the answers

Which of the following is primarily driven by the Sun's energy?

The water cycle Signup and view all the answers

Which of these statements accurately describes the role of groundwater?

It eventually contributes to surface water bodies. Signup and view all the answers

Which cycle is described as having both rapid and slow processes of nutrient movement?

Biogeochemical cycle Signup and view all the answers

What is the significance of evapotranspiration in ecosystem dynamics?

It returns water to the atmosphere from both soil and plants. Signup and view all the answers

What is net primary productivity (NPP)?

The energy remaining in producers after accounting for respiration and heat loss. Signup and view all the answers

Which biome is known to have the highest net primary productivity?

Estuaries Signup and view all the answers

Which factor is primarily responsible for higher NPP in swamps and tropical rainforests?

High moisture and warm temperatures Signup and view all the answers

How is net primary productivity commonly measured?

By calculating the biomass of organisms in an area. Signup and view all the answers

Which terrestrial biomes typically have the lowest net primary productivity?

Tundra and deserts Signup and view all the answers

What role do autotrophs play in ecosystems?

They convert solar energy into chemical energy for the ecosystem. Signup and view all the answers

Which of the following biogeochemical cycles is NOT mentioned as being impacted by human activities?

Oxygen cycle Signup and view all the answers

Why do grasslands and temperate forests have moderate NPP levels?

They benefit from mild temperatures and seasonal rainfall. Signup and view all the answers

What is a major method through which minerals are cycled from land to water?

Rain and surface runoff Signup and view all the answers

Which carbon compound is produced by cattle as a byproduct of digestion?

Methane (CH4) Signup and view all the answers

What percentage of the atmosphere's oxygen content is maintained by photosynthetic organisms?

21 percent Signup and view all the answers

How do heterotrophs primarily obtain their carbon compounds?

By consuming autotrophs Signup and view all the answers

What is the primary component of the shells of marine organisms formed from carbon ions?

Calcium carbonate (CaCO3) Signup and view all the answers

What type of respiration do autotrophs use when consuming the organic molecules they form?

Aerobic respiration Signup and view all the answers

What component of the atmosphere is a significant reservoir of carbon essential for photosynthesis?

Carbon dioxide (CO2) Signup and view all the answers

Which process directly contributes to the increase in atmospheric carbon dioxide levels due to human activity?

Deforestation for agriculture Signup and view all the answers

What is a significant impact of fossil fuel use since the Industrial Revolution?

Increase in carbon dioxide levels Signup and view all the answers

Which of the following best describes the biological carbon cycle?

It depicts rapid exchange of carbon among living organisms. Signup and view all the answers

What primarily causes the formation of fossil fuels?

Decomposition of living organisms Signup and view all the answers

Which process converts organic nitrogen back into nitrogen gas?

Denitrification Signup and view all the answers

Which source is primarily responsible for nitrogen re-entering the atmosphere?

Decomposition of aquatic organisms Signup and view all the answers

Why is phosphorus considered a limiting nutrient in freshwater ecosystems?

Its crucial role in plant growth Signup and view all the answers

What forms the phosphate ion (PO43-) found in nature?

Weathering of phosphate rocks Signup and view all the answers

What is a significant consequence of nitrogen and phosphorus runoff into aquatic ecosystems?

Excessive growth of algae Signup and view all the answers

Which group of bacteria plays a key role in nitrogen fixation in terrestrial systems?

Rhizobium Signup and view all the answers

What does ammonification convert into ammonium (NH4+)?

Organic nitrogen from waste Signup and view all the answers

How does phosphorus typically move from land to the ocean?

Through river runoff from phosphate-containing rocks Signup and view all the answers

Which process is NOT part of the nitrogen cycle?

Acidification Signup and view all the answers

Study Notes

Net Primary Productivity

Autotrophs are the energy base of most ecosystems, including plants, algae, and photosynthetic bacteria.
Autotrophs use solar energy to transform it into chemical energy in the form of ATP, which is used to create complex organic molecules.
Gross primary productivity is the rate at which producers incorporate energy from the Sun.
Net primary productivity (NPP) is the energy leftover in producers after accounting for their respiration and heat loss.
NPP is available to primary consumers at the next trophic level.
Estuaries have the highest NPP on Earth due to constant nutrient supply from rivers.
Swamps and tropical rain forests have high NPP due to ample moisture and warm temperatures.
Grasslands and temperate forests have moderate NPP.
Deserts and tundras have the lowest NPP due to limited water in deserts and cold temperatures in tundras.

Biogeochemical Cycles

Energy flows one way through ecosystems, entering as sunlight and leaving as heat during trophic level transfers.
Matter is recycled.
The five common elements in organic molecules are carbon, nitrogen, hydrogen, oxygen, and phosphorus.
Biogeochemical cycles involve the recycling of these elements within and between the living and nonliving environment.
Reservoirs are locations where elements are stored, and residence time is the duration they spend in each reservoir.
Flux mechanisms move elements between reservoirs.

Water Cycle

Water movement and storage occurs in the hydrosphere.
The water cycle is driven by solar energy warming oceans and other surface waters, leading to evaporation and sublimation.
Water vapor condenses into clouds and falls as precipitation.
Precipitation can evaporate, flow over the surface, or infiltrate the ground.
Surface runoff occurs when the soil is saturated.
Plants absorb water through roots, use some for metabolism, and lose the rest through evapotranspiration.
Groundwater forms from water that percolates into the subsoil and bedrock.
Groundwater is a significant reservoir of fresh water, replenishing streams and lakes.
Aquifers are groundwater reservoirs that often provide drinking or irrigation water.

Carbon Cycle

Carbon is the fourth most abundant element in living organisms.
Carbon compounds store energy.
Fossil fuels are stored carbon from plants and algae.
The carbon cycle is divided into a biological subcycle (rapid exchange among organisms) and a geological subcycle (long-term cycling through Earth).
The biological carbon cycle involves the exchange of carbon between heterotrophs and autotrophs.
Autotrophs use carbon dioxide for photosynthesis, releasing oxygen as a byproduct.
Heterotrophs obtain carbon from consuming autotrophs and release carbon dioxide through respiration.
Agriculture contributes to increased atmospheric carbon dioxide through livestock production and deforestation.
The geological carbon cycle involves the long-term storage of carbon in reservoirs like the atmosphere, oceans, sediment, soil, rocks, and Earth's interior.
Carbon dioxide dissolves in water, forming carbonates and limestone, the largest carbon reservoir.
Volcanoes, geothermal systems, and subduction release carbon back into the environment.

Nitrogen Cycle

Nitrogen is a key component of nucleic acids and proteins.
Nitrogen enters the living world through nitrogen fixation by bacteria.
Nitrogen fixation converts atmospheric N2 into usable forms.
Nitrogen fixation is performed by cyanobacteria in aquatic ecosystems and Rhizobium bacteria in legume root nodules.
Organic nitrogen is a crucial limiting nutrient, impacting primary production and decomposition.
Nitrogen is returned to the atmosphere through ammonification, nitrification, and denitrification.
Ammonification converts nitrogenous waste into ammonium.
Nitrification converts ammonium to nitrites and nitrates.
Denitrification converts nitrates to nitrogen gas.
Human activities release nitrogen through fossil fuel combustion and fertilizer use.
Nitrogen oxides contribute to acid rain and greenhouse gas effects.
Fertilizer runoff causes eutrophication, leading to algal overgrowth and ecosystem imbalances.
The marine nitrogen cycle involves similar processes performed by marine bacteria and archaea.

Phosphorus Cycle

Phosphorus is vital for nucleic acids, phospholipids, and bone formation.
Phosphorus is often the limiting nutrient in aquatic ecosystems.
Phosphate is found primarily in rocks and is extracted for use in fertilizers and detergents.
Phosphate is released into water through weathering of phosphate-containing rocks and runoff from human activities.
Marine organisms play a significant role in phosphorus cycling, contributing to ocean sediment formation.
Uplift of Earth's surface brings phosphate-rich sediment back to land over geological time.
Phosphorus exchange between the ocean and marine organisms contributes to the cycle.
Phosphorus movement from the ocean to land is slow, with a long residence time in the ocean.

Excess Nutrients and Dead Zones

Fertilizer runoff and sewage discharge introduce excess phosphorus and nitrogen into aquatic ecosystems.
This nutrient overload triggers excessive algal growth, a process known as eutrophication.
The subsequent decay of dead algae depletes dissolved oxygen, leading to the death of aquatic organisms such as shellfish and finfish.
These oxygen-depleted areas are known as dead zones.
Dead zones are characterized by the absence of typical aquatic flora and fauna.
Their formation can be attributed to various factors including eutrophication, oil spills, toxic chemical dumping, and other human activities.
The prevalence of dead zones has significantly increased in recent years, with over 400 zones documented by 2008.
One of the most prominent dead zones is located in the Gulf of Mexico, covering an area exceeding 8,463 square miles.
This specific dead zone is primarily caused by fertilizer runoff from the Mississippi River basin.
The Chesapeake Bay in the eastern United States is another major ecosystem negatively impacted by phosphate and nitrate runoff from fertilizers.

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Description

Explore the concepts of net primary productivity (NPP) and biogeochemical cycles in this quiz. Understand how autotrophs convert solar energy into chemical energy and the importance of NPP in ecosystems. Test your knowledge on the factors affecting NPP across different ecosystems.