Question

to conclude the experiment, the students want to observe the effect of large - scale deforestation. they remove most of the plants in the greenhouse while keeping the same population of animals. predict any changes in the levels of photosynthesis and cellular respiration and how this would impact the atmosphere. what implications might this have for the global carbon cycle and humans?

Explanation:

1. Photosynthesis and Respiration Changes:

• Photosynthesis: Plants perform photosynthesis ($\ce{6CO_2 + 6H_2O \xrightarrow[\text{Chlorophyll}]{\text{Light}} C_6H_{12}O_6 + 6O_2}$). With most plants removed, the rate of photosynthesis will drastically decrease because there are fewer organisms capable of this process.
• Cellular Respiration: Animals (and remaining plants) perform cellular respiration ($\ce{C_6H_{12}O_6 + 6O_2

ightarrow 6CO_2 + 6H_2O + ATP}$). Since the animal population is the same, their respiration rate remains, and with fewer plants to take in $\ce{CO_2}$ and produce $\ce{O_2}$, the net production of $\ce{CO_2}$ will increase (because respiration output of $\ce{CO_2}$ is not balanced by photosynthesis input of $\ce{CO_2}$).

1. Atmosphere Impact:

• $\ce{O_2}$ levels: Decrease because less photosynthesis means less $\ce{O_2}$ production.
• $\ce{CO_2}$ levels: Increase because respiration (from animals and remaining plants) continues to produce $\ce{CO_2}$, but photosynthesis (which consumes $\ce{CO_2}$) is reduced. This creates an imbalance where $\ce{CO_2}$ accumulates.

1. Global Carbon Cycle Implications:

• The carbon cycle involves the movement of carbon between the biosphere, atmosphere, hydrosphere, and geosphere. Plants are a key part of the biosphere's carbon uptake (via photosynthesis, converting atmospheric $\ce{CO_2}$ to organic carbon). With deforestation (or large - scale plant removal), the amount of carbon taken out of the atmosphere by plants is reduced. Meanwhile, the release of carbon (as $\ce{CO_2}$) from respiration and decomposition (if plants die) continues. This leads to an increase in atmospheric carbon (as $\ce{CO_2}$), which can enhance the greenhouse effect.

1. Human Implications:

• Air Quality: Reduced $\ce{O_2}$ and increased $\ce{CO_2}$ can lead to respiratory issues for humans, especially in areas with poor air circulation.
• Climate Change: Increased $\ce{CO_2}$ is a greenhouse gas, so more $\ce{CO_2}$ in the atmosphere can lead to global warming. This causes changes in weather patterns (e.g., more extreme weather events like hurricanes, droughts), rising sea levels (due to melting ice caps), and impacts on agriculture (changes in growing seasons, crop yields, and increased pests).
• Ecosystem Services: Plants provide many ecosystem services like water purification, soil stability, and habitat for pollinators. Loss of plants can disrupt these services, which in turn affects human food security (e.g., reduced pollination leading to lower crop production) and access to clean water.

Answer:

Changes in Photosynthesis and Cellular Respiration:

• Photosynthesis: Decreases significantly due to the removal of most plants (the main organisms performing photosynthesis).
• Cellular Respiration: Remains relatively stable for animals (same population), but the net output of $\ce{CO_2}$ increases (since photosynthesis - driven $\ce{CO_2}$ uptake is reduced while respiration - driven $\ce{CO_2}$ release continues).

Atmosphere Impact:

• Oxygen ($\ce{O_2}$): Levels decrease (less photosynthetic $\ce{O_2}$ production).
• Carbon Dioxide ($\ce{CO_2}$): Levels increase (imbalance between $\ce{CO_2}$ release from respiration and $\ce{CO_2}$ uptake from photosynthesis).

Global Carbon Cycle Implications:

• Reduced carbon uptake by plants disrupts the carbon cycle, leading to increased atmospheric $\ce{CO_2}$ (a greenhouse gas). This enhances the greenhouse effect and can accelerate climate change.

Human Implications:

• Air Quality: Lower $\ce{O_2}$ and higher $\ce{CO_2}$ can cause respiratory problems.
• Climate Change: Leads to global warming, extreme weather, rising sea levels, and disrupted agriculture.
• Ecosystem Services: Loss of plant - related services (e.g., pollination, soil stability) threatens food security and access to clean water.