3 - Ecosystems II

Question 1

What are the main features of the carbon cycle

Answer 1

Predominantly gaseous; CO₂ is the main atmospheric form

Question 2

What is the role of photosynthesis in the carbon cycle

Answer 2

Plants and algae fix CO₂ into organic carbon

Question 3

What happens during respiration in the carbon cycle

Answer 3

Respiration by plants, animals, and microbes returns CO₂ to the atmosphere

Question 4

What is the ocean-atmosphere exchange in the carbon cycle

Answer 4

Equilibrium between atmospheric CO₂ and dissolved CO₂/HCO₃⁻ in water

Question 5

How does decomposition contribute to the carbon cycle

Answer 5

Organic carbon is returned to the soil and air

Question 6

How does the combustion of fossil fuels impact the carbon cycle

Answer 6

Adds ancient carbon to the modern cycle

Question 7

What is methane release in the carbon cycle

Answer 7

Methane is released from anaerobic respiration (e.g., wetlands, livestock)

Question 8

How do autotrophs regulate the carbon cycle

Answer 8

Autotrophs (plants, algae) sequester carbon through photosynthesis

Question 9

How do heterotrophs regulate the carbon cycle

Answer 9

Heterotrophs return carbon via respiration and decomposition

Question 10

What role do microbes play in the carbon cycle

Answer 10

Microbes break down organic material and cycle carbon

Question 11

How do humans impact the carbon cycle

Answer 11

Fossil fuel combustion = excess CO₂

Deforestation reduces CO₂ uptake

Industrial agriculture contributes to methane emissions

Question 12

What are the ecological impacts of human actions on the carbon cycle

Answer 12

Climate change due to enhanced greenhouse effect

Ocean acidification harms marine life

Changes in carbon availability affect productivity and species distributions

Question 13

What are the main features of the nitrogen cycle

Answer 13

Atmospheric reservoir (N₂) is inert and biologically inaccessible

Question 14

What is nitrogen fixation in the nitrogen cycle

Answer 14

Cyanobacteria and root nodulating bacteria convert N₂ to NH₃

Question 15

What happens during nitrification in the nitrogen cycle

Answer 15

NH₃ → NO₂⁻ → NO₃⁻ (plant-available forms)

Question 16

What is assimilation in the nitrogen cycle

Answer 16

Plants incorporate nitrate into tissues

Question 17

What is ammonification in the nitrogen cycle

Answer 17

Decomposers convert organic nitrogen into NH₃

Question 18

What is denitrification in the nitrogen cycle

Answer 18

NO₃⁻ → N₂/N₂O, returning nitrogen to the atmosphere

Question 19

How do nitrogen-fixing microbes regulate the nitrogen cycle

Answer 19

They enable biological access to atmospheric nitrogen

Question 20

How do plants and consumers regulate the nitrogen cycle

Answer 20

Plants and consumers cycle nitrogen in food webs

Question 21

What is the role of decomposers and denitrifiers in the nitrogen cycle

Answer 21

They maintain soil nitrogen balance

Question 22

How do humans impact the nitrogen cycle

Answer 22

Synthetic fertilisers increase reactive nitrogen

Fossil fuel combustion releases NOx gases

Intensive farming and livestock excretion accelerate nitrogen loss

Question 23

What are the ecological impacts of human actions (N cycle)

Answer 23

Eutrophication (algal blooms, hypoxia, fish kills)

Soil acidification and altered microbial communities

Increased N₂O emissions contribute to global warming

Question 24

What are the main features of the phosphorus cycle

Answer 24

Sedimentary cycle; no atmospheric phase

Key reservoirs: rocks, soils, sediments

Question 25

What happens during weathering in the phosphorus cycle

Answer 25

Releases phosphate ions (PO₄³⁻)

Question 26

How do plants interact with phosphate in the phosphorus cycle

Answer 26

Plants take up phosphate through roots

Question 27

What happens during decomposition in the phosphorus cycle

Answer 27

Returns phosphate to the soil

Question 28

How does sedimentation impact the phosphorus cycle

Answer 28

Leads to long-term storage of phosphorus in aquatic systems

Question 29

How do plants and microbes regulate the phosphorus cycle

Answer 29

They mobilise phosphate for uptake

Question 30

How do humans impact the phosphorus cycle

Answer 30

Overuse of phosphate fertilisers Mining of phosphate rocks depletes natural stocks Phosphate-containing detergents (historically)

Question 31

What are the ecological impacts of human actions on the phosphorus cycle

Answer 31

Eutrophication in freshwater systems Disruption of aquatic food webs Long-term changes in soil nutrient availability

Question 32

What are the main features of the sulphur cycle

Answer 32

Moves through atmosphere, water, soil, and organisms

Question 33

How does volcanic activity impact the sulphur cycle

Answer 33

Volcanic emissions release H₂S

Question 34

What happens when H₂S oxidises in the sulphur cycle

Answer 34

H₂S oxidises to sulphate (SO₄²⁻) in atmosphere

Question 35

What is acid deposition in the sulphur cycle

Answer 35

Acid deposition returns sulphur to soils and water

Question 36

How do plants interact with sulphur in the sulphur cycle

Answer 36

Plants assimilate sulphate and incorporate it into proteins

Question 37

How does decomposition impact the sulphur cycle

Answer 37

Returns sulphur to the system

Question 38

How do sulphur-reducing bacteria regulate the sulphur cycle

Answer 38

They produce H₂S

Question 39

What role do decomposers play in the sulphur cycle

Answer 39

Recycle organic sulphur

Question 40

How do humans impact the sulphur cycle

Answer 40

Burning fossil fuels releases SO₂ Industrial activity increases atmospheric sulphur levels

Question 41

What are the ecological impacts of human actions on the sulphur cycle

Answer 41

Acid rain damages plants, leaches nutrients from soil Reduces buffering capacity of soils and water Alters microbial activity and reduces biodiversity

Question 42

How does agriculture affect nutrient cycles

Answer 42

Overuse of N and P fertilisers Increased livestock = more methane and nitrogenous waste Erosion and overgrazing reduce soil fertility

Question 43

What is eutrophication and its effects

Answer 43

Nutrient overload → excessive algal growth → oxygen depletion Fish kills and biodiversity loss Worsened by climate warming

Question 44

What are the impacts of greenhouse gas emissions

Answer 44

Accelerates climate change, sea level rise, polar ice melt

Question 45

What are the impacts of acid precipitation

Answer 45

Soil acidification, nutrient leaching, damaged aquatic systems Alters species composition and microbial functioning