Ecosystem Dynamics: Biotic, Abiotic, and Energy Flow

Biotic and Abiotic Factors

An ecosystem consists of all the living and nonliving parts of an environment. Biotic factors are the living parts of an ecosystem, while abiotic factors are the nonliving parts.

Living things need nonliving things to survive. Without food, water, and air, living things die. Other essential elements for living things include:

• Sunlight: It provides energy that plants and certain bacteria absorb to make their own food.
• Shelter
• Soil

Trees are biotic elements which need water, an abiotic element. Without water, a tree would not produce oxygen; conversely, without trees, water would not complete the water cycle.

Changes in abiotic factors can result in extreme problems for some organisms. For example, if a plant is adapted to low temperatures and the specific area where it lives undergoes a change in temperature (due to global warming), this plant will die. Consequently, this area will no longer support life due to the change in an abiotic factor (temperature).

Energy Flows in the Environment

All energy originates from the sun. The solar energy captured during photosynthesis becomes chemical energy. This chemical energy can then become:

• Electrical energy needed for heat
• Mechanical energy stored in fats
• Free energy, which is released back into the environment

Plants are organisms that feed themselves through photosynthesis, whereas animals obtain their food by eating others. The trophic level of an organism is the number of steps it is from the start of the chain. On average, only about 10% of the available energy is passed from one trophic level to the next.

The Structure of Trophic Levels

A food web starts at trophic level 1 with primary producers, such as plants. It can move to herbivores at level 2, carnivores at level 3 or higher, and typically finishes with apex predators at level 4 or 5.

Energy decreases as it moves up trophic levels because energy is lost as metabolic heat when organisms from one level are consumed by those at the next. The level with the least amount is the secondary consumer. The population decreases significantly at each level. Additionally, the number of times an organism of a higher trophic level ingests food increases as you move up the food chain; therefore, more food must be available from the lower levels so that the required energy is available.