The Feeling is Mutual

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SWBAT identify and differentiate between symbiotic relationships among animals in an ecosystem, including symbiosis, commensalism, mutualism, parasitism, competition and predatory relationships.

Big Idea

Living things in an ecosystem rely on a web of interdependence. These relationships can take on many forms.


5 minutes

This lesson has been adapted from the original lesson entitled, "Good Buddies", from Project Wild.

I start not by giving any formal introduction, but rather by playing the National Geographic video Larva Removed from a Girl's Scalp. While I can never be sure whether students will react with fascination or disgust, I know this short video clip will definitely elicit everyone's attention and curiosity.


After watching the video*, I give the students a minute or two to process what they just saw, and then I pose the following question to the class:

You just witnessed a very natural interaction between two different organisms. Who benefited from the interaction - the maggot, the woman, or both?

I provide a minute or two of think time, then ask the students to discuss their ideas with their nose partners. Many students will be able to determine that the maggot was the one receiving the benefits, but some will not. Rather, they will believe that neither of the organisms received the benefit, as they will not see that the human scalp provided shelter, protection, and even nourishment from the human whom it burrowed inside. I ask for a few pairs to share their responses.  It is at this time that I explain during today's lesson, we will learn about how some organisms can provide many of the things that others need in order to survive.

*If this video makes you squeamish, you can always watch a milder video on fleas instead. It will still serve as an introduction to the topic, but with less of a "gross" factor.


15 minutes

Next, I pass out the Animal Relationships worksheet. While students watch the Untamed Science Symbiosis: Mutualism, Commensalism, and Parasitism video about the relationships that organisms use with others in order to survive, they should fill in the blanks on the first page. This will help them as we continue throughout the lesson.

After watching the video and filling in the blanks with the correct response, the students sketch a simple drawing that will serve as a symbol of each type of relationship. (For example, mutualism might be represented by links of a chain.) For more information on symbols and how to guide students through their creation, please read the reflection.


45 minutes

Next, I pair students up and have them read through the many (30, to be exact) examples of symbiotic relationships on their paper. I have them work together to determine which type of symbiosis each example represents. Student may need textbooks, reference materials, or technology devices available to them to look up some of the terminology presented in the examples. I always make sure they have these tools available. They will come across some content-related vocabulary they are not familiar with - by my design - and I want them to do the research, rather than just make a guess, as to the meaning. I am sure to direct them to do just that before we begin, and I question them throughout the activity as I monitor the room, to make sure they are making sense of what they are reading.

I also prep the activity by explaining that there are 10 "trick questions"* hidden within the 30 examples presented to them. I want them to be on the lookout for scenarios that don't "fit in" well with any type of symbiotic relationship.

As the students work, I move from group to group, asking them to justify their responses and to explain their thinking. I may ask questions such as:

  • What does it mean by...?
  • Why did you choose....?
  • Tell me why you answered this way...
  • Can you give me another example of...?
  • How come this could not be an example of...?

*What the students don't know is that the "trick questions" are actually examples of either competitive or predatory relationships. I will go through this with them later in the lesson, but for now, I hold off. These relationships are pretty easily explained and the terminology is not as new as the other types of relationships, so I choose to wait and let them focus on the newer material at first.


20 minutes

Once students have read through each of the examples and identified the type of relationship, we discuss as a class.  I make sure to choose random groups to identify each relationship, and to call on another random pair to explain why they agree or disagree, using evidence from the example and from what they learned in the video. I also ask the class to identify which were the "trick questions", explaining that these are examples of competitive and/or predatory relationships, and discussing the meaning of each. I call on volunteers to provide additional examples, not only to assess understanding but also to help students who may need additional support.

Next, I explain it is time to play a game. I have copied several decks of the "Good Buddy" cards from the Project Wild curriculum on cardstock prior to the lesson. Each deck should contain 31 cards (15 pairs showing symbiotic relationships and one blank good buddy card).  The purpose of the game will be for student to identify animals that form the relationship we have been learning about. This game also serves as a great review, because it calls upon students' knowledge of ecosystems, survival needs, and animal adaptations, in order to properly identify the animal pairs and their relationships.

I start by having students sort the cards, attempting to make pairs according to who they think would have some sort of symbiotic relationship. If students have a hard time, I prompt them to look for animals that may share an ecosystem in order to find pairs. Once the groups feel they have correctly identified pairs, I pass out the accompanying list that contains the descriptions of each animal relationship. The students should check their work to make sure they have adequately identified pairs, then sort each pair according to the type of relationship they have with their animal partner. When they are finished, I check their work and then direct them to shuffle their cards.

Next, I regroup the students into groups of 4. One student in each group combines two sets of cards, shuffles them again, and deals out all of the cards equally among the four students, including him/herself. Play starts to the left of the dealer and rotates clockwise. Each player randomly takes one card from the player to the left. After the player has drawn a card, that player may lay down all cards in his or her hand that form symbiotic, competitive, or predatory pairs.  The "Good Buddy" card serves as a wild card and can e used whenever the person holding that card needs it. Once the first player runs out of cards, the game is over. The player with the largest number of pairs at the end of the game is the winner.


10 minutes

After the students finish their game, they return to the Animal Relationships worksheet. I direct them to find the blank box in the middle of the second page. In that box, the students must draw and explain an example of one of the types of symbiotic relationships we have learned about, using specific animals within a shared ecosystem.  On the lines next to the box, each student must label the type of symbiotic relationship and explain why this pair of animals demonstrates the relationship they have selected.