How Living Things Obtain Food and Energy

Energy Requirements

• Energy is required to maintain a state of order in our body, even when we are not doing any apparent activity.
• Energy is also needed to grow, develop, synthesize protein, and other substances needed in the body.

Food as the Source of Energy and Materials

• The source of energy and materials is the food we eat.
• Food provides energy and materials for the upkeep and growth of the body.

Autotrophic Nutrition

• Autotrophs, including green plants and some bacteria, use simple food materials obtained from inorganic sources.
• Autotrophs obtain carbon dioxide and water from the environment and convert them into stored forms of energy through photosynthesis.
• Photosynthesis occurs in the presence of sunlight and chlorophyll, producing carbohydrates that provide energy to the plant.
• Excess carbohydrates are stored in the form of starch, serving as the internal energy reserve.
• Plants obtain carbon dioxide through stomata, tiny pores on the surface of leaves, which can be closed when not needed.

Autotrophic Nutrition (Continued)

• Autotrophs also need other raw materials for building their body, such as water, nitrogen, phosphorus, iron, and magnesium.
• Water is taken up from the soil by the roots in terrestrial plants.
• Nitrogen is an essential element used in the synthesis of proteins and other compounds, taken up in the form of inorganic nitrates or nitrites, or as organic compounds prepared by bacteria from atmospheric nitrogen.

Heterotrophic Nutrition

• Heterotrophs, including animals and fungi, utilize complex substances that need to be broken down into simpler ones before they can be used for the upkeep and growth of the body.
• Heterotrophs use bio-catalysts called enzymes to break down complex substances.
• The survival of heterotrophs depends directly or indirectly on autotrophs.
• Different organisms have adapted to their environment, using various strategies to obtain and use food, such as breaking down food material outside the body or using specific nutritive apparatus.