3.2 ENERGY FLOW
Sunlight is the main energy source for life on Earth. Some types of organisms rely on the energy stored in inorganic chemical compounds. Autotrophs can capture energy from sunlight or chemicals and use that energy to produce food. Autotrophs can also be called producers due to them being able to make their own food. The most known autotrophs are the one that use solar energy through a process called photosynthesis. These autotrophs can use light power to chemical reactions that convert carbon dioxide and water into oxygen and energy rich carbohydrates such as sugars and starches. Without these autotrophs, we will not be able to live due to lack of oxygen. When organisms uses chemical energy to produce carbohydrates , the process is called chemosynthesis. This process is performed by certain types of bacteria that live in the ocean and some other places.
Organisms that rely on other organisms for their energy and food supplies are called heterothrophs. Heterothrophs are also called consumers. Herbivores obtain energy by eating only plants. Carnivores eat animals. Omnivores eat both plants and animals. Detritivores eat dead matter. Decomposers are also in the heterothrophs group. They break down organic matter.
When the energy stored by producers passed through an ecosystem by a series of steps in which organisms transfer energy by eating and being eaten is called the food chain.
In most ecosystems, feeding relationships are more complex that can be shown in the food chain. When the feeding relationship among the various organisms in an ecosystem form a network of complex interactions, ecologists describe these relationships as a food web. Each step in a food chain or food web is called a trophic level.
An ecological pyramid is a diagram that shows the relative amounts of energy or mater contained within each trophic level in a food chain or food web. Only about 10% of the energy available within one trophic level is transferred to organisms at the next trophic level. The total amount of living tissue within a given trophic level is called biomass. Ecological pyramids can also be based on the numbers of individuals organisms at each trophic level.
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