Density Independent Factors and Their Effects on Populations

Density independent factors can affect a population no matter what its density is. For example: natural disasters, temperature, sunlight, human activities, physical characteristics and behaviors of organisms affect any and all populations regardless of their densities.

such as droughts, floods, hurricanes and fires can be devastating to aquatic life. For example, a severe drought could lower the water levels of Lake Winnipeg and decrease its carrying capacity. Thus, the fish population would decrease.

Temperature influences the activity and growth of organisms. Temperature also determines which type of organisms can live in a lake. Usually, the higher the water temperature, the greater the activity in a lake. However, all aquatic species have a preferred temperature range. If temperatures vary too much out of this range the species will either die or move to a different location. Temperature also influences the chemical properties of water. The rate of chemical reactions in the water increases as temperature increases. For example, warm water holds less oxygen than cool water, so even though there is more activity in warm water there may not be enough oxygen for the activity to continue for long periods of time.

can only penetrate to a depth of 30 meters in water. Thus most photosynthesis in
aquatic environments occurs near the surface. This means that most plants cannot grow if they are at the bottom of a deep lake.

can also affect population dynamics. For instance, lake sturgeon spawn in fast water and sometimes use the "tailraces" of hydroelectric dams. However, the water level in this location often drops suddenly and the eggs die because they become exposed.

of organisms can affect their population. Many organisms have
adapted and evolved in order to increase their chance of survival. For example, some species of fish have colored markings to warn predators that they may be toxic. Or, some species use camouflage colors to help them hide and avoid being eaten.

Behaviors of organisms can also affect their population. For example, some species migrate to find new food sources or to mate. Some organisms create societies or feeding
territories. For instance, white bass live in schools and work together to drive emerald shiners to the surface for feeding. Some species may have mating or courtship behaviors that affect their population.