Relationships Between Organisms

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Students will be able to categorize relationships between organisms according to predator-prey, competition or symbiosis (mutualism, commensalism and parasitism).

Big Idea

All organisms interact with and depend upon each other and their environment to satisfy their basic needs.


5 minutes

To introduce the topic and catch the students attention I present the following video:


20 minutes

I tell the students that today we are going to learn about interactions between organisms. I explain that in order to make things easier, I have prepared a graphic organizer that can help them organize the information. Once they all have a copy of the organizer, I begin the slideshow.

On the second slide, I make sure to mention that even though the shipwreck survivor is "by himself", he is still interacting with the different organisms on the island, and elicit from the students examples of who might he be interacting with.

The "think about it" slide (3) is a way to make the lesson relevant to the students. Although middle-schoolers might think they in fact live in a bubble and do not interact with many organisms, it is important for them to realize how much they interact with and depend on other organisms around them. 

I continue the presentation, giving students time to write down the different concepts and examples in their graphic organizers (SW1SW2)

Identifying Relationships - Whole class

10 minutes

I tell the students that we will now watch some videos. Their job, as they watch the videos, is to identify the organisms and then identify the type of relationship being portrayed. They will be given a chance to confer with their table mates, and in the conversation they have to explain to each other why.

Note to teachers: The videos I am showing are part of a National Geographic "Ecological Relationships" lesson, and I have been unable to find them anywhere else (i.e. YouTube), so I cannot embed them here. However, they are all together at their site and can be accessed through this link.

I show the first video “Fish Thieves Take Rare Seals’ Prey”. I start the video at 0:49, and as we watch, I write the names of the different organisms mentioned on the board: monk seal, eels, octopus, jacks, sharks and trigger fish. As the video ends, I ask the question: "What is the relationship between the monk fish and the eels?", and model the thought process: "Well, they mentioned that the monk seal pulls the eels out of their hiding spot to feast on them. This means that the eels are being eaten, since predation is when an organism consumes all or part of another, that tells me that this is a predator-prey relationship." I continue by asking, "What is the relationship between the monk seal and the shark?" and again model the thought process by stating, "In the video they mentioned that the shark swoops in to steal the monk seal's meal. The seal did some of the work, but both animals need the same resource. This indicates that they are competing." I then ask the students to identify the rest of the relationships, indicating that in they need to give a complete response like what I just modeled.

After all relationships in the first video have been identified, I play the "Clownfish and Sea Anemone Partnership” (1.5 minutes—mutualism) to the class, and after table conversations where students have an opportunity to engage in argument from evidence (SP7), we discuss what it shows, formulating evidence from the information being provided by the video.

Identifying Relationships - Partnerships

15 minutes

I then ask the students to work with a partner on identifying relationships. The students analyze each sentence, collaborating with a peer to find the best explanation (SP 7), and then work together to provide the best explanation (SP8).

One of the fun things about this lesson is all of the assumptions that are made. Listen to some of them, then read what they actually wrote down (SW1SW2)


5 minutes

To close this lesson, I replay the video shown at the beginning of class, playing a mini-game of "Who can tell me", in which I ask the students to chorally respond to each of the pictures they see. This is just a fun activity since the assessment takes place in the "you do together" section.