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Sun: The Chief Source of Energy | Explanation

Aug 19, 2022

Key Concepts

  • Source of energy
  • Nuclear fusion
  • Photosynthesis
  • Transfer of energy
  • Transfer of matter


Graphing Motion 

We usually create a data table to present the numerical values of different physical quantities involved in the motion of a body. However, a data table makes it quite tedious to analyze the dependence of one physical quantity (such as velocity, displacement, etc.) on another (such as time). Plotting the same data in a graph sheet makes it much easier to analyze the dependence of a physical quantity on another. Thus, graphing is a convenient way of representing the motion of a body. 


Energy: Ability to do work. 

All organisms (plants, animals, and microbes) get energy from their food. Moreover, organisms need the energy to perform various activities and sustain life. Likewise, we humans require energy to perform the process of digestion, reproduction, locomotion, etc. In this chapter, we will be learning that this also requires energy.” 

Fig 1

Sun: The chief source of energy 

Energy is all around us, and it comes from many sources. One of the most important sources of energy is the sun. In fact, the energy of the sun is the original source of most of the energy found on the earth. Energy from the sun is called solar energy. 

Fig 2

The sun heats the earth’s surface, and the earth heats the air above it, causing wind. The sun generates energy from a process called nuclear fusion. During nuclear fusion, the high 

pressure and temperature in the sun’s core cause nuclei to separate from their electrons. 


Sun radiates light and heat, or solar energy, making it possible for life to exist on the earth. 

Plants need sunlight to grow. Animals, including humans, need plants for food and the oxygen they produce. Without heat from the sun, the earth would freeze. 

Fig 3

The energy in our food comes from the sun 

Nearly all our food comes from either plants or animals. After it enters our digestive system, our bodies break it down into essential materials. 

Fig 5

Flamingos are an excellent example of how food is used for growth. They like to eat algae which has a lot of beta-carotene, a natural chemical with a red color. The bird’s digestive system breaks down the algae, which releases the red chemical. The red chemical then gets deposited in the flamingo’s feathers as they grow, giving flamingos a pink color. 

Food also provides us with the energy to move and stay warm. The sun’s energy is transferred to plants, which use it to convert water and carbon dioxide into sugars. This process is called photosynthesis. Plants are then consumed by animals, which are eaten by larger animals. 

Fig 6

Although plants differ in their shapes and sizes, all plants are alike in one way. They make their own food in a process called photosynthesis. During photosynthesis, plants take in sunlight, water, and a gas in the air called carbon dioxide. Plants use these things to make sugar, which is a plant’s source of food and energy. 

Fig 7

Plants have a material called chlorophyll that helps them take in sunlight. Chlorophyll gives plants their green color. With the help of chlorophyll, plants take in energy from the sun and use it to produce sugar. Energy from the sun is called solar energy. 

Fig 8

Animals cannot make their food the way plants can. Instead, they must eat other organisms to obtain the energy they need. In contrast, plants provide energy that travels from one organism to another. After photosynthesis, they store some energy in their roots, stems, leaves, and other structures. When an animal, such as a grasshopper, eats a plant, stored energy passes from the plant to the animal. 

The animal uses most of this energy to grow and reproduce. It also stores some energy. When an animal, such as a bird, eats the grasshopper, stored energy passes to the bird. In this way, most animals depend on plants for energy.

To sum up, all living organisms get their energy through food, and the energy in food comes from the sun. We can say that all living organisms directly or indirectly depend on the sun for energy. After all, the sun is the main source of energy in the ecosystem. 


• Sun is the ultimate source of energy.

• All living organisms, directly and indirectly, depend on the sun to get energy.

• Plants, algae (including phytoplankton), and many microorganisms use the energy from light to make sugars (food matter) from carbon dioxide from the atmosphere and water through the process of photosynthesis,

• Plants produce their food by using simple inorganic compounds. Hence, they are also known as producers.

• Animals include humans eat plants as a food source to get energy.


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