Biotic components are the living things that shape an ecosystem.
Biotic components usually include:
- Producers, i.e. autotrophs: e.g. plants, they convert the energy [from photosynthesis (the transfer of sunlight, water, and carbon dioxide into energy), or other sources such as hydrothermal vents] into food.
- Consumers, i.e. heterotrophs: e.g. animals, they depend upon producers (occasionally other consumers) for food.
- Decomposers, i.e. detritivores: e.g. fungi and bacteria, they break down chemicals from producers and consumers (usually dead) into simpler form which can be reused.
A biotic factor is any living component that affects the population of another organism, or the environment. This includes animals that consume the organism, and the living food that the organism consumes. Biotic factors also include human influence, pathogens and disease outbreaks. Each biotic factor needs energy to do work and food for proper growth.
All species are influenced by biotic factors in one way or another. For example, If the number of predators will increase, the whole food web will be affected (the population number of organisms that are lower in the food web will decrease). Similarly, when organisms have more food to eat, they will grow quicker and will be more likely to reproduce, so the population size will obviously increase. Pathogens and disease outbreaks, however, are most likely to cause a decrease in population size. Humans make the most sudden changes in an environment (e.g. building cities and factories, disposing of waste into the water). These changes are most likely to cause a decrease in the population of any species, due to the sudden appearance of pollutants.
Biotic components are contrasted to abiotic components, which are non-living components that influence population size and the environment. Examples of abiotic factors are: temperature, light intensity, moisture and water levels, air currents, carbon dioxide levels and the pH of water and soil.
The factors mentioned above may either cause an increase or a decrease in population size, depending on the organism. For example, rainfall may encourage the growth of new plants, but too much of it may cause flooding, which may drastically decrease the population size.