Question

How do organisms obtain energy?

Answer 1

Hint: All the living organisms require energy for their- growth, development, reproduction, functioning, metabolic reactions, maintenance of their environment, and all the chemical processes that help them to live.

Complete answer:
All living organisms need energy for their survival, growth, and development. Energy is the ability to do work or perform various functions or chemical reactions. It can neither be created nor be destroyed and thus can only transfer from one form to another. For living organisms, the Sun is considered the ultimate source of energy.

All living organisms are not capable of utilizing the sun’s energy directly. Based on their mode of utilization of energy, the organisms can be divided into several categories.
Autotrophs or Producers- These organisms are capable of utilizing the sun’s energy directly. They use sunlight to perform photosynthesis through which they can form their own food. A significant amount of energy is stored in the sugar molecule formed, and the rest is utilized in the process. It is an endothermic reaction that combines inorganic compounds like carbon dioxide and water to release oxygen and sugar molecules. The food formed is an energy-rich compound and can be used by the plants for their functioning.
These organisms are primary producers and occupy the first trophic level in the food chain. Examples of autotrophic organisms are- all green plants and few other bacteria like Cyanobacteria.

Heterotrophs or Consumers- These organisms are incapable of utilizing the sun’s energy directly. They cannot synthesize their own food and depend on autotrophs for their food and energy requirements. They feed on the complex organic molecules prepared by the autotrophs. They generate energy through the process of respiration and release carbon dioxide in that process. Based on their source of food, heterotrophs can be divided into various categories like- Herbivores, Omnivores, Carnivores, Detritivores, Scavengers, and Decomposers.
The energy from the sun is passed to the heterotrophs through autotrophs. They occupy the higher trophic levels of the food chain and are mostly the primary, secondary or tertiary consumers.

Note: The flow of energy in a living ecosystem is always unidirectional and passes from one organism of a trophic level to another. The energy is trapped by the plants or producers and given to other organisms in the- form of food. Some amount of energy is always dissipated through this process in the form of heat.