Species Relationships

In an ecosystem, many species coexist, and there is bound to be some interaction between them sooner or later. There are different types of relationships that occur between species, each with different effects on the organisms and the environment. Symbiotic relationships are known as two organisms living in close proximity to each other and interacting in some way. The main types of symbiotic relationships include mutualism, commensalism, parasitism, amensalism, predation, and competition.

A bumble bee (Bombus spp.) collecting nectar from a flower, its body covered in pollen. Photo credits: National Geographic

1. Mutualism

Mutualism is a win-win interaction where both species benefit. A classic example of this is the relationship between bees and flowering plants (aka angiosperms). Bees pollinate flowers while collecting nectar for food, thereby aiding in plant reproduction. This symbiotic relationship not only sustains bee populations but also promotes biodiversity through plant reproduction.

A gray whale (Eschrichtius robustus) emerging from the ocean, its skin partially covered in barnacles. Photo Credits: Noyo Center for Marine Science 

2. Commensalism

In commensalism, one species benefits, while the other is neither helped nor harmed. One example of this is barnacles attaching to whales. The barnacles benefit by gaining access to nutrient-rich waters through the whale’s movement, while the whale remains unaffected. This subtle balance illustrates how some species can exploit resources without impacting their hosts.

Roundworm (Baylisascaris procyonis) next to a penny for size comparison. Photo Credits: Rousserre et al.

3. Parasitism

Parasitism represents a harmful interaction where one organism (the parasite) benefits at the expense of the other (the host). One example of this relationship that can be found in the wild is the roundworm, more specifically Baylisascaris procyonis, which is known to infect a large amount of the racoon population in North America. The raccoon acts as the host while the roundworm stays in the digestive tract absorbing nutrients from the host.

Noticeable algae blooms on a water source. Photo Credits: Joe Raedle

4. Amensalism

Amensalism occurs when one species is inhibited or destroyed while the other remains unaffected. One great example of this are algal blooms, which are the rapid accumulation of algae in a freshwater or marine environment. Algal blooms may occur naturally but are also known to be human-caused due to the runoff of fertilizers into ponds and streams. This process is called eutrophication and occurs when the water receives too many nutrients. Eutrophication has no effect on the algae itself but it is harmful to other organisms that may come in contact with the algae or rely on the water that houses it. It can disrupt and kill aquatic life because as the algae begins to die and decompose it uses oxygen depleting the supply for other organisms that reside in the same water source.

Red Tailed Hawk (Buteo jamaicensis) gliding in the air in search of food. Photo Credits: Hawk Creek Wildlife Center

5. Predation

Predation involves one organism (the predator) feeding on another (the prey). This interaction plays a critical role in maintaining ecosystem balance. In some ecosystems the predators regulate prey populations, which is actually a good thing because an overabundance of one organism can cause drastic changes to the environment.. The red-tailed hawk is a prime example of this. Some of its prey, such as rabbits, squirrels and other rodents, are known herbivores. If red-tailed hawks were to vanish from the ecosystem, there would need to be another predator to regulate the population of rodents in the area or rodents would run rampant decimating the plant diversity and population.

Bald Eagle (Haliaeetus leucocephalus) scanning the area as it glides over a water source. Photo Credits: National Geographic Kids

6. Competition

Competition arises when species vie for the same resources, such as food, space, or mates. This can occur within a species (intraspecific) or between different species (interspecific). An example is the interspecific competition between different raptor birds such as the bald eagle and the red tailed hawk as they have a similar diet of rodents. Competition between one bald eagle and another would be considered intraspecific, as it occurs within the same species.

Conclusion

The relationships between species are essential for understanding ecological dynamics. Each interaction—whether beneficial, harmful, or neutral—contributes to the balance of ecosystems. By studying these relationships, we can appreciate the complexity of life on Earth and the interconnectedness of all living beings. Understanding these interactions is vital for conservation efforts and maintaining biodiversity in our changing world. Local examples of these relationships are discussed by OC Habitats during our presentations or guided hikes and we work to preserve or bring back the natural balance of these interactions in our restoration projects.