BFE - Relationships Between Species (Lesson)

Relationships Between Species

Populations are composed of all individuals in a species within a defined area. All populations interacting within a particular area, make up a community. Community interactions, such as competition, predation, and various forms of symbiosis, can powerfully affect an ecosystem. Let's begin with a video review of community ecology... click below.

 

 

Competition

Friendly female koala imageCompetition occurs when the organisms of the same or different species attempt to use an ecology resource in the same place at the same time. For example, two different species of mountain lions may compete for the same prey, or weeds and grass may compete for the same nutrients available in the soil. Regardless of the species involved, both organisms are negatively impacted. In some cases, one species may have a competitive advantage over the other species, and may over time result in the complete elimination of the species. This is referred to as competitive exclusion.

Another way to respond to competition between species is to separate resources in a niche. An ecological niche is the sum of a species' use of biotic and abiotic resources in its environment. This is different from where the organism lives, that is the habitat. A niche is more so how the organism specifically interacts or fits in within the environment. This specifically includes the range of conditions that the species can tolerate, the methods by which it obtains needed resources, the number of offspring it has, its time of reproduction, and all its other interaction with its environment.

Two species cannot coexist permanently in a community if their niches are identical. If competitive exclusion does not lead to the extinction of the other organism, the niche of one species becomes modified. This leads to the development of the fundamental niche and the realized niche. The fundamental niche is the range of conditions that a species can potentially tolerate and the range of resources it can potentially use. The realized niche of a species is the range of resources it actually uses for that particular environment. Generalists are species with broad niches; they can tolerate a range of conditions and use a variety of resources. Opossums are generalists. Species that have narrow niches, such as the koala, are called specialists.

Predation

Predation is an interaction in which one organism captures and feeds on another organism. The organism doing the capturing is called the predator and the organism being captured is called the prey. This is probably an obvious review, so we will go into a little more depth as to why this is important to the study of ecology.

The predator-prey relationship is one of the primary influences of animal adaptations. Most predators have adaptations such as claws, teeth, fangs, stingers, or poison to help them capture and subdue their prey. Additionally, predators have acute sensory adaptations which allow them to locate and identify potential prey. Likewise, prey have adaptations that help them avoid attack and capture. While some defensive adaptations include behavioral patterns, others include morphological and physiological defense mechanisms. Review the interactivity below to review some of these adaptations.

 

Click through the following slides on special adaptations.

 

Symbiosis

Symbiosis is any relationship where two or more species live in direct and intimate contact. There are three categories of symbiosis, mutualism, commensalism, and parasitism. Mutualism is a symbiotic relationship in which both species benefit. One example we discussed previously was that of lichen. Both the algae and the fungi work together in a mutually beneficial relationship. Commensalism is an interaction between species in which one benefits and the other is not affected. Parasitism is a symbiotic interaction in which one organism benefits at the expense of the other organism. The benefiting organism is called the parasite and the organism harmed is called the host.

Self-Assignment: Species Interactions

These video-enhanced lessons from PBS focus on symbiosis, ecological relationships, and the human impact on ecosystems, using sharks and marine species as examples.

Please watch these short video clips below and then test your knowledge with the following questions. 

Clip 1: Shark and Turtle Links to an external site.

  1. How does the turtle protect itself?
  2. What relationship is held between the tiger shark and the loggerhead turtle?

Clip 2: Unlikely Travel Companions Links to an external site.

  1. List three ways in which being near a shark might be beneficial to a fish.
  2. What is one way that a shark might benefit from a fish (other than as prey)? 
  3. Classify each shark-fish relationship shown in this clip as commensalism or mutualism.

Clip 3: Collapse of Sharks Links to an external site.

  1. Why are shark populations in danger of collapse? 
  2. How has the relationship between sharks and humans changed over time? 
  3. What might happen if the shark fin trade continues unchecked? 

Clip 4: Sharks in our Future Links to an external site.  

  1. Describe the type of tourism seen in this clip. 
  2. What benefit do these businesses provide to sharks? To local populations? To tourists? 
  3. How might these businesses help prevent the collapse of shark populations?

Click here to download the Self-Check answers. Links to an external site.

 

RESOURCES IN THIS MODULE ARE OPEN EDUCATIONAL RESOURCES (OER) OR CREATED BY GAVS UNLESS OTHERWISE NOTED. SOME IMAGES USED UNDER SUBSCRIPTION.