HOT Competition: Bacteria and archaea, collectively known as prokaryot

GMATWhiz Explanation

Step 1 – Analysing the stimulus and question stem

Bacteria and archaea, collectively known as prokaryotes, are present on every continent and make up around half of global biomass -- the total weight of all organisms on Earth.

• Bacteria and archaea – together known as prokaryotes.
• They are found on every continent.
• They comprise half of the total weight of all organisms living on the earth.

Most prokaryotes perform respiration that uses energy and releases carbon dioxide, contributing to climate warming.

• Majority of the prokaryotes display respiration.
• Respiration takes in energy and gives out carbon dioxide.
• Such respiration adds to climate warming.

o Inference: Carbon dioxide released into the atmosphere adds to climate warming.

Therefore, as global temperatures rise, prokaryotes could increase climate warming at a faster rate than current models suggest.

• Conclusion: With temperatures rising globally, climate warming could also increase at a faster speed than that indicated by current models. And prokaryotes would be responsible for this increase at a faster speed.

Step 2 – Pre-thinking

1. The conclusion to be evaluated is - . prokaryotes could increase climate warming at a faster rate than currently believed. Why? The conclusion contains information about “rising global temperatures”. Thus, the “rising temperatures” and “faster rate of increase in climate warming” are definitely correlated. And if the “prokaryotes” are somehow responsible for upping the climate warming rate, then, the prokaryotes and the “rising temperatures” must also be correlated.

2. Missing link

a. We know the respiration carried out by the prokaryotes adds to climate warming by adding carbon dioxide to the air.
b. Perhaps faster respiration = more carbon dioxide = faster climate warming. For that to be true, we need to know two things?

i. Evaluate question:

1. Whether respiration rate increases with increase in global temperatures?
2. Whether the amount of carbon dioxide released increases with an increase in the respiration rate ?

Step 3 – Answer Choice Elimination

Option A Analysis
“Inversely proportional” means if one entity increases by a certain amount, then the other entity decreases by that same amount. So, if the temperature increases then the carbon output decreases. That should lead to less addition to climate warming and that cannot certainly lead to a faster rate of climate warming. This choice actually casts a doubt on the conclusion.
Incorrect Choice.

Option B Analysis
The prokaryotes make up half the biomass weight. Thus, the carbon dioxide realesed would be according to that at any given point. This does not explain why the climate warming rate would be faster. The total weight of the prokaryotes is not changing here. This choice is just a distortion of the given information.
Incorrect Choice.

Option C Analysis
“Positively correlated” means if one entity increases, the other entity also increases.
Per this choice,

• Increase in temperature = increase in respiration rate

o And
• increase in respiration rate = increase in carbon output.

This choice is the answer to both the evaluate questions that we framed during pre-thinking. This choice would make us believe more in the conclusion.
Correct Choice.

Option D Analysis
“Some” could be a very small number or could be a huge number – anything from 1-99 in a population of 100. Thus, the impact of this choice will be ambiguous. Too small a number then, the choice does not make us believe more in the conclusion. Only a high number would do that. Because of the ambiguous impact, this choice has to be ruled out.
Incorrect Choice.

Option E Analysis
If the temperature increases then the respiration rate decreases. Ideally, although we do not know, a decrease in respiration rate should lead to a decrease in the amount of carbon dioxide released. That should lead to less addition to climate warming and that cannot certainly lead to a faster rate of climate warming. This choice actually casts a doubt on the conclusion.
Incorrect Choice.