Week 21

Question 1

What is the nitrogen cycle?

Answer 1

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms, circulating through the atmosphere, soil, and living organisms.

Question 2

What is ammonification in the nitrogen cycle?

Answer 2

Ammonification is the process by which decomposer bacteria break down organic matter in dead organisms and waste, converting nitrogen compounds into ammonia (NH₃).

Question 3

What is nitrification?

Answer 3

Nitrification is a two-step aerobic process where ammonia is first oxidized to nitrites (NO₂⁻) by Nitrosomonas, then nitrites are oxidized to nitrates (NO₃⁻) by Nitrobacter.

Question 4

What is denitrification?

Answer 4

Denitrification is the anaerobic process by which bacteria like Pseudomonas convert nitrates (NO₃⁻) back into nitrogen gas (N₂), returning it to the atmosphere.

Question 5

What is nitrogen fixation?

Answer 5

Nitrogen fixation is the conversion of atmospheric nitrogen gas (N₂) into ammonia (NH₃) by nitrogen-fixing bacteria such as Rhizobium, often in symbiotic relationships with legume plants.

Question 6

What is the role of nitrogenase in nitrogen fixation?

Answer 6

Nitrogenase is the enzyme used by nitrogen-fixing bacteria to convert nitrogen gas into ammonia during nitrogen fixation.

Question 7

How does Rhizobium benefit from symbiosis with legumes?

Answer 7

Rhizobium bacteria gain carbohydrates and a protected environment inside root nodules of legume plants.

Question 8

How do plants benefit from symbiosis with Rhizobium?

Answer 8

Plants receive a usable form of nitrogen (ammonia) which is vital for building amino acids and proteins.

Question 9

What is the function of leghaemoglobin in root nodules?

Answer 9

Leghaemoglobin binds oxygen to maintain low oxygen levels in root nodules, allowing nitrogenase to function efficiently since it is inactivated by oxygen.

Question 10

Why is nitrogen recycling important for living organisms?

Answer 10

It provides essential nitrogen compounds like amino acids and nucleotides needed for growth and reproduction in plants and animals.

Question 11

How does nitrogen fixation benefit species beyond plants?

Answer 11

Animals and insects like stag beetles rely on plants or decomposers for nitrogen, which ultimately comes from nitrogen-fixing processes.

Question 12

What are the main types of carbon cycles?

Answer 12

The carbon cycle includes short, intermediate, and long cycles, depending on the timescale and storage of carbon.

Question 13

What are carbon reservoirs?

Answer 13

Carbon reservoirs are large storage areas of carbon such as the atmosphere, biosphere, oceans, sediments, and fossil fuels.

Question 14

How does photosynthesis contribute to the carbon cycle?

Answer 14

Photosynthesis by terrestrial plants absorbs atmospheric CO₂ and converts it into organic matter.

Question 15

What role does respiration play in the carbon cycle?

Answer 15

Respiration by plants and animals returns CO₂ to the atmosphere as they break down food for energy.

Question 16

What is decomposition in the context of the carbon cycle?

Answer 16

Decomposition breaks down dead organisms, releasing CO₂ and methane back into the environment.

Question 17

What is the fast carbon cycle?

Answer 17

The fast carbon cycle involves rapid exchange of carbon among living organisms, the atmosphere, and surface waters over days to decades.

Question 18

What is the slow carbon cycle?

Answer 18

The slow carbon cycle includes long-term geological processes like sedimentation, fossil fuel formation, and volcanic release of CO₂ over millions of years.

Question 19

What is marine snow and its role in the carbon cycle?

Answer 19

Marine snow consists of organic particles that sink to the ocean floor, helping transfer carbon from the surface to deep-sea sediments.

Question 20

How is carbon recycled in marine environments?

Answer 20

Carbon is cycled via marine food chains, surface CO₂ exchange, sedimentation, and deep ocean currents.

Question 21

What are anthropogenic effects on the carbon cycle?

Answer 21

Human activities such as fossil fuel burning, deforestation, and cement production increase atmospheric CO₂ and disrupt natural carbon flows.

Question 22

How does increased CO₂ affect the oceans?

Answer 22

CO₂ dissolves in ocean water forming carbonic acid, which can lower pH and affect marine organisms, especially shell-forming species.

Question 23

What is the importance of carbon fluxes in the marine environment?

Answer 23

They regulate the exchange of CO₂ between the ocean and atmosphere and affect global climate dynamics.

Question 24

How does the geological carbon cycle operate?

Answer 24

It involves long-term storage of carbon in rocks and sediments and its release through volcanic eruptions and weathering.

Question 25

Why is understanding carbon reservoirs important for climate change?

Answer 25

Knowing how carbon is stored and transferred helps predict how changes (like emissions) affect atmospheric CO₂ and climate systems.

Question 26

What is the hydrosphere?

Answer 26

The hydrosphere includes all water on Earth, including oceans, lakes, rivers, groundwater, and water vapor in the atmosphere.

Question 27

How did the hydrosphere form?

Answer 27

The hydrosphere formed from water vapor released by volcanic activity and from icy comets that delivered water to Earth during its formation.

Question 28

What is the water cycle?

Answer 28

The water cycle describes the continuous movement of water on, above, and below the surface of the Earth through processes like evaporation, condensation, precipitation, and collection.

Question 29

What is evaporation in the water cycle?

Answer 29

Evaporation is the process where water changes from liquid to vapor due to heat, primarily from the sun.

Question 30

What is condensation in the water cycle?

Answer 30

Condensation is the process where water vapor cools and changes back into liquid, forming clouds.

Question 31

What is precipitation in the water cycle?

Answer 31

Precipitation occurs when condensed water in clouds becomes too heavy and falls back to the Earth as rain, snow, sleet, or hail.

Question 32

What is the distribution of water on Earth?

Answer 32

About 97.5% of Earth's water is salt water, and only 2.5% is fresh water. Of that, most is trapped in glaciers and ice caps, with a small fraction available as surface or groundwater.

Question 33

What are water reservoirs and their residence times?

Answer 33

Water reservoirs include oceans, glaciers, groundwater, lakes, atmosphere, and biosphere. Residence time is how long water stays in a reservoir; oceans have long times (thousands of years), while atmosphere has short times (days).

Question 34

What is groundwater?

Answer 34

Groundwater is water that is stored in soil and rock underground, often feeding wells, springs, and contributing to rivers.

Question 35

What causes loss of atmospheric water?

Answer 35

Loss occurs through precipitation, condensation, and interactions with physical and biological surfaces.

Question 36

How do humans impact the water cycle?

Answer 36

Humans affect the water cycle by urbanization, deforestation, irrigation, damming rivers, and contributing to pollution and climate change.

Question 37

What is water cycle intensification?

Answer 37

Water cycle intensification is an increase in the rate of evaporation and precipitation caused by global warming.

Question 38

What are the projected effects of climate change on the water cycle?

Answer 38

Climate change is expected to increase the frequency and intensity of droughts and floods, alter precipitation patterns, and reduce snowpack and freshwater availability.

Question 39

What role do ocean currents play in the water cycle?

Answer 39

Ocean currents help redistribute heat and moisture around the globe, influencing climate and precipitation patterns.