4.2 Ecology Study Guide

Question 1

Define Nitrogen fixation.

Answer 1

The process of converting atmospheric nitrogen (N2) into a form usable by living organisms, primarily ammonia (NH3)

Nitrogen fixation is essential for the synthesis of amino acids and nucleotides.

Question 2

Define Nitrification.

Answer 2

The process by which ammonia (NH3) is converted into nitrites (NO2-) and then into nitrates (NO3-)

Nitrification is a key step in the nitrogen cycle, facilitating the uptake of nitrogen by plants.

Question 3

Define Denitrification.

Answer 3

The process of converting nitrates (NO3-) back into nitrogen gas (N2), releasing it into the atmosphere

Denitrification helps to complete the nitrogen cycle and reduce nitrogen levels in the soil.

Question 4

Define Assimilation.

Answer 4

The process by which plants and animals incorporate nutrients from the environment into their own tissues

Assimilation is crucial for growth and development in living organisms.

Question 5

List the inputs and outputs of photosynthesis.

Answer 5

• Inputs: Carbon dioxide (CO2), water (H2O), sunlight
• Outputs: Glucose (C6H12O6), oxygen (O2)

Photosynthesis occurs in chloroplasts of plant cells.

Question 6

List the inputs and outputs of cellular respiration.

Answer 6

• Inputs: Glucose (C6H12O6), oxygen (O2)
• Outputs: Carbon dioxide (CO2), water (H2O), energy (ATP)

Cellular respiration occurs in the mitochondria of cells.

Question 7

What type of organisms perform the processes of photosynthesis and cellular respiration?

Answer 7

• Photosynthesis: Plants, algae, some bacteria
• Cellular Respiration: All living organisms

Photosynthesis is primarily associated with autotrophs, while cellular respiration occurs in both autotrophs and heterotrophs.

Question 8

What are the major abiotic reservoirs of carbon, nitrogen, and phosphorus?

Answer 8

• Carbon: Atmosphere, oceans, sedimentary rocks
• Nitrogen: Atmosphere, soil, water bodies
• Phosphorus: Soil, rocks, water bodies

These reservoirs play critical roles in the biogeochemical cycles.

Question 9

How do carbon, nitrogen, and phosphorus enter the food chain and how do they return to abiotic reservoirs?

Answer 9

• Carbon: Enters via photosynthesis; returns through respiration and decomposition
• Nitrogen: Enters via nitrogen fixation; returns through denitrification and decomposition
• Phosphorus: Enters through weathering of rocks; returns through sedimentation

These processes ensure the cycling of essential nutrients in ecosystems.

Question 10

How do humans affect the carbon and nitrogen cycles?

Answer 10

• Carbon: Increased CO2 emissions from fossil fuels, deforestation
• Nitrogen: Fertilizer runoff, industrial nitrogen fixation

Human activities significantly alter the natural cycles, leading to environmental issues such as climate change and eutrophication.

Question 11

Differentiate between how energy and how carbon flow through a food chain.

Answer 11

• Energy: Flows in one direction (from producers to consumers)
• Carbon: Cycles through the ecosystem (from producers to consumers and back to the environment)

Energy is lost as heat at each trophic level, while carbon is reused in various forms.

Question 12

Compare and contrast the pathways of the carbon, nitrogen, and phosphorus cycles.

Answer 12

• Carbon Cycle: Involves photosynthesis and respiration; atmospheric and geological reservoirs
• Nitrogen Cycle: Involves fixation, nitrification, and denitrification; atmospheric and soil reservoirs
• Phosphorus Cycle: Involves weathering and sedimentation; primarily terrestrial and aquatic reservoirs

Each cycle has unique processes and reservoirs but is interconnected within ecosystems.