Introduction:
Life on Earth is sustained by various carbon-based molecules, which play a crucial role in the functioning of organisms. These molecules are not only essential for the survival of living organisms but also serve as the primary source of energy and nutrients. Consequently, most of the food sources available to organisms are carbon-based.

Explanation:

1. Dependence of life on carbon-based molecules:
Life as we know it is based on carbon chemistry. Carbon atoms have unique properties that allow them to form long chains and complex structures, making them ideal building blocks for biological molecules. Carbon-based molecules, such as carbohydrates, lipids, proteins, and nucleic acids, are fundamental to the functioning of living organisms. They participate in various biological processes, including energy production, metabolism, growth, and reproduction.

2. Carbon-based food sources:
Since carbon-based molecules are crucial for life, organisms require a constant supply of these molecules to meet their energy and nutritional needs. Consequently, most of the food sources available to organisms are composed of carbon-based molecules. These food sources include both plant and animal matter.

3. Plant-based food sources:
Plants are primary producers that convert light energy into chemical energy through photosynthesis. They utilize carbon dioxide from the atmosphere and water from the soil to synthesize glucose, a simple sugar and a vital source of carbon. Glucose serves as the building block for more complex carbohydrates, such as starch and cellulose, which form the structural components of plants. Additionally, plants produce other carbon-based molecules like proteins, lipids, and vitamins.

4. Animal-based food sources:
Animals, including humans, obtain their carbon-based molecules by consuming plant-based and other animal-based food sources. When animals consume plants, they break down the complex carbohydrates, proteins, and lipids present in plant cells and convert them into energy and nutrients needed for their own survival. Animals also produce their own carbon-based molecules, such as proteins and lipids, which are essential for their growth, repair, and various physiological processes. These molecules can be obtained by consuming animal-based food sources.

Conclusion:
The dependence of life on carbon-based molecules is a fundamental aspect of biology. Since these molecules are essential for the functioning of organisms, the majority of the food sources available to support life on Earth are also carbon-based. Plants, as primary producers, synthesize carbon-based molecules through photosynthesis, while animals obtain these molecules by consuming plant-based and other animal-based food sources. Understanding the significance of carbon-based molecules in sustaining life helps us appreciate the intricate web of ecological relationships and the importance of a balanced diet for the well-being of organisms.