Problem 8 - Biology: The Unity and Diversity of Life

Question

Carbon is released into the atmosphere by ______________. a. photosynthesis c. burning fossil fuels b. aerobic respiration d. \(b\) and \(c\)

Step-by-Step Solution

Answer

d. b and c

Step 1: Understand the Processes

First, let's understand the processes involved: Photosynthesis uses carbon dioxide and does not release carbon into the atmosphere. Burning fossil fuels involves combustion, which releases carbon dioxide into the atmosphere. Aerobic respiration is the process where living organisms convert glucose and oxygen into energy, carbon dioxide, and water, thus releasing carbon dioxide.

Step 2: Analyze Each Option

- Option a: Photosynthesis - Incorrect because it consumes carbon. - Option b: Aerobic respiration - Correct because it releases carbon dioxide. - Option c: Burning fossil fuels - Correct because it releases carbon dioxide. - Option d: b and c - Examines if both options b and c release carbon.

Step 3: Select the Correct Answer

Since both aerobic respiration (b) and burning fossil fuels (c) release carbon into the atmosphere, the correct choice is d, which includes both b and c.

Key Concepts

photosynthesis

Photosynthesis is a fascinating process used by plants, algae, and some bacteria to convert light energy into chemical energy. This essential process happens in the chloroplasts within plant cells and uses sunlight to turn carbon dioxide (\(\text{CO}_2\)) and water into glucose and oxygen.

• Plants absorb carbon dioxide from the atmosphere through their leaves. They also take up water through their roots.
• Chlorophyll, the green pigment in plants, captures sunlight. This energy is used to split water molecules, releasing oxygen as a byproduct.
• In a series of reactions, carbon dioxide is combined with hydrogen (from the split water molecules) to form glucose, a type of sugar.

Glucose serves as food for the plant and is an energy source for cellular processes.
In summary, photosynthesis plays a fundamental role in the carbon cycle by using atmospheric carbon dioxide, thus reducing the amount of greenhouse gases in the atmosphere.

aerobic respiration

Aerobic respiration is a vital process in which cells of organisms use oxygen to break down glucose, releasing energy. This process is the opposite of photosynthesis and occurs in the mitochondria of cells.

• Glucose and oxygen are the primary inputs for aerobic respiration. Organisms obtain glucose from food and oxygen from breathing.
• The process involves multiple steps, including glycolysis, the citric acid cycle, and the electron transport chain.
• During these steps, glucose is broken down, resulting in the production of carbon dioxide, water, and adenosine triphosphate (ATP).

The carbon dioxide produced is then released back into the atmosphere with each exhalation, and ATP serves as an energy currency for cells.
Therefore, aerobic respiration is a key element of the carbon cycle, ensuring the continuous release of carbon dioxide into the atmosphere.

fossil fuels

Fossil fuels, including coal, oil, and natural gas, are energy-rich substances formed from the remains of ancient plants and animals. Over millions of years, these organic materials were subjected to intense heat and pressure.

• When fossil fuels are burned for energy, the carbon stored within them is released back into the atmosphere as carbon dioxide (\(\text{CO}_2\)).
• This combustion process is a major contributor to the greenhouse effect and climate change due to the increased levels of carbon dioxide.
• The use of fossil fuels is widespread, powering vehicles, generating electricity, and providing heat.

As a result, managing the use of fossil fuels is crucial to controlling atmospheric carbon levels. Reducing reliance on them can help mitigate adverse environmental impacts.