3.3 Species Interaction
Completion requirements
Unit B
Module 3 ~ Lesson 3
Biotic Limiting Factors
Many biotic factors limit the growth of populations. If the number of births in a population is greater than the number of deaths, the population is growing. If the number of deaths is greater, the population will decrease.
Competition
When a population reaches a size where individuals must compete for space, food, mates, shelter, or water, intraspecific competition ensues. Intraspecific competition is where members of the same population and species compete with each other. Interspecific competition occurs when individuals from different species compete for resources. When species living in the same habitat have different niches, the chance for competition decreases.
Intraspecific competition
Male elk compete for mates. The winner is a desirable mate since its characteristics are likely to to be passed on to its young.
Male elk compete for mates. The winner is a desirable mate since its characteristics are likely to to be passed on to its young.
Courtesy of U.S. Dept of the Interior, Bureau of Land Management
Interspecific competition
Zebras and oryx compete for the same water and food resources.
Zebras and oryx compete for the same water and food resources.
Image by Richard Whomersley from Pixabay
Predator-Prey Relationships
Predators and prey can have impacts on each other's populations. For example, perhaps the number of prey is reduced due to a food shortage; this would decrease the food supply for predators. An increase in the number of predators or the introduction of an invasive predator will cause fewer prey.
Wolves are fierce predators affecting many populations, including the elk pictured here.
Courtesy of U.S. National Park Service
Parasites
Parasites get food and protection from their host. This relationship is different from a predator-prey relationship because the host is not consumed, but their survival or ability to reproduce is harmed.
Ticks are a common and widespread parasite that feeds on the blood of their host. If they are unable to find a host, they eventually perish. Ticks are known to cause Lyme disease. In Alberta, ticks are common in ungulate populations such as deer, elk, and moose.
By Nicoografe[Public Domian], via Pixabay
By Photo Credit: James GathanyContent Providers(s): CDC/ Dr. Amanda Loftis, Dr. William Nicholson, Dr. Will Reeves, Dr. Chris Paddock [Public domain], via Wikimedia Commons