Unit A Lesson 3: Symbiosis

 Learning Targets

Inquiry Question: What kind of relationship does a clownfish and a sea anemone have?
Living things often have very important relationships with other living things that helps at least one of them to survive.

At the end of this inquiry, you should be able to answer the following questions:

  • What is symbiosis?
  • What is mutualism?
  • What is parasitism?
  • What is commensalism?
Pages 16 and 17 in your textbook will help you answer these questions about symbiosis.


Introduction


Mutualism – a wrasse cleans an eel's mouth. Photo by Silke Baron.

Why would a small fish swim into an eel's mouth? What do tapeworms and humans, sea anemones and clownfish, oxpeckers and rhinoceroses have in common? They all exist in a unique relationship that either benefits or harms each other. These relationships are called symbiotic relationships.

Symbiosis is made up of two words:

Sym (meaning together)  +  Bios (meaning life)

The root words describe symbiosis exactly.  It is a relationship between two organisms.  There are three types of symbiotic relationships:

  • Mutualism
  • Parasitism
  • Commensalism

Interactive


Ants and aphids. Bees and flowers. Squirrel and acorns. All of the symbiotic organism pairs have a special relationship because each species has a direct impact on the survival of the other.

The BrainPOP video "Symbiosis"  introduces the three types of symbiotic relationships: mutualism, commensalism, and parasitism. After you watch the video, explore some of the other activities on this web page.

You will need a username and password to access the video.

  • Username: 0099
  • Password: students







Mutualism is a relationship wherein both species benefit from the relationship.  An example is the oxpecker (a bird) and the rhinoceros.  The oxpecker rides on the back of rhinoceros and eats the debris on the rhino’s back, which benefits the rhino.  The oxpecker benefits by feeding and having a free ride on a rhino.  In this relationship, both species benefit.
Parasitism is a relationship where one species benefits and the other is harmed.  In the aphid – plant relationship, the aphids feed from the plants, but that feeding causes leaf curling, wilting, and even dieback of shoots and buds.  The aphid benefits from this relationship, but the plant is harmed.
Commensalism is a relationship where one species benefits and the other is not harmed nor does it benefit.  A lesser-known example of this is the barnacle and the whale.  The barnacle benefits greatly from having a place to live, and the whale is not harmed although sometimes the barnacles can become itchy and annoying.

Figure 1 - A symbiotic relationship?

Think about the following questions as relating to the cartoon in Figure 1.

  • Does the cat benefit from its relationship with its owner? 
  • Does the owner benefit from having the cat? 
  • What symbiotic relationship exists between the cat and the owner?

This relationship can be classified as mutualism because the human provides the basic needs of the cat and the cat provides the human with affection and companionship.

Interactive


Symbiotic Relationships

Take the BrainPOP quiz for Symbiosis to see how you do in your understanding of symbiotic relationships.

You will need a username and password to access the quiz.

  • Username: 0099
  • Password: students