Of Moths and Sloths

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Students will be able to apply information from a scientific text in order to categorize different types of symbiotic relationships.

Big Idea

Symbiotic relationships are complex and often involve more than two organisms


This lesson is a follow-up to the previous lesson on niches, and asks students to further explore the topic of symbiotic relationships by reading an article summarizing recent research on sloths and moths.


The article describes the complex interrelationships between sloths, seemingly parasitic moths, and a host of other organisms in a rainforest ecosystem.  In this lesson, students carefully read the article, identifying vocabulary words from class, as well as academic vocabulary with which they may be unfamiliar and will need to define to fully understand the article.  They then answer questions of varying levels of complexity, before finally categorizing the types of symbiosis occurring in the article.  As an extension, students are given the option to complete an extra credit assignment to describe another complex symbiotic relationship involving more than two organisms and produce a poster that diagrams and categorizes the relationships.


Although I prefer to hand out a hard copy of the article (which I modify to fit onto the front and back of one paper), you may prefer to send your students directly to the article from its original source at io9.com.


Connection to Standard:

In this lesson, students read an article aimed at general adult audiences and determine the central idea of the text, identify and define unfamiliar vocabulary to determine the meaning of key terms, use domain-specific vocabulary to adequately describe relationships between organisms, and cite specific text passages to answer questions about the article.

Warm Up

10 minutes

I begin this lesson asking if students know what sloths are.  I allow for a student or two to describe them, and once students have done so, I show this undeniably cute picture with an overhead projector.  After the "awww... so cute!" comments die down, I ask my largely Spanish speaking population if they know the Spanish word for sloths.  Some students may offer the answer if they know, but if not, I let them know that a sloth is called a perezoso in Spanish.  I then ask students what else the word perezoso means and they tend to quickly reply, "lazy".  I then let them know that the word sloth can also mean lazy in English too. 

I then ask students to reflect on what they know about sloths and why they may be called by names synonymous with laziness in more than one language.  Answers will vary, but most students will offer that sloths are slow moving animals that tend to spend most of their time up in trees. 

I build on this prior knowledge to set up the lesson by saying, "Yes, sloths are pretty lazy... so lazy, in fact, that they only come down from the trees to use the bathroom once per week." I then tell them that one possible explanation of why they come down so infrequently is that they are more exposed to dangerous predators on the ground and are much safer in the trees.  I then ask students if this is the case, why would they ever come down?  Why not just do like birds do and let gravity take care of their business? 

I allow students to offer a few potential explanations before I show them this considerably less cute picture of a sloth on one of its weekly trips to the restroom.  Students usually ask, "what's wrong with it?", but if they don't offer a question, I'll guide them with, "what's different about this sloth?"  They tend to point out that it's fur looks kind of nasty and has green stuff in it.  I assure them that nothing's wrong with this sloth, it's engaging in behavior that helps it survive, but that the answer to why it comes out of the trees so infrequently (and at all, considering it's more vulnerable to predators on the ground), and why it's fur looks kind of green depend on understanding the web of symbiotic relationships that sloths find themselves enmeshed with other species.

I let the students know that we're going to answer these questions by reading an article, but that first we'll need to review some of the different types of symbiotic relationships we discussed in the previous lesson. 

I ask students to get out their notesheet from the niches lesson, and then ask for students to volunteer definitions to the following terms:

Symbiotic relationship: a physically close relationship between two organisms where at least one benefits.

Mutualism: a symbiotic relationship where both species involved benefit (+/+)

Commensalism: a symbiotic relationship where one species benefits and the other is not affected positively or negatively (+/0)

Parasitism: a symbiotic relationship where one species benefits and the other species is negatively affected (+/-)

After we go over those terms, I ask for a student volunteer to distribute the article and we move on to the close reading section of the lesson.



Close Reading

30 minutes

After we have warmed up and the article and instructions have been distributed, I quickly go over the instructions to complete the assignment.


Identifying Vocabulary

First of all, this assignment requires students to identify both content-specific vocabulary from class and academic vocabulary with which they may not be familiar.  I ask students to underline class vocabulary and highlight unfamiliar academic vocabulary.  I ask students to identify class vocabulary so that they can see connections to the course content aimed at a general audience, hopefully reinforcing the impression that what they're learning is valuable knowledge that adults are expected to have reasonable familiarity with.  I ask them to identify unfamiliar academic vocabulary because I believe that reading always offers opportunities to learn new expressions and terms to broaden a student's vocabulary and basic knowledge.  Additionally, much of the academic vocabulary that native speakers of English may take for granted is absolutely necessary for my largely ELL students to learn so that they can comprehend the content of the article.

I ask students to make lists of the words they identified in both categories, but only ask that they write definitions for 5 words of their choice.  The reason I don't have them define all the words they identified is that would incentivize making a smaller list of unfamiliar words.  In this way, students have a small number of words to define but are encouraged to identify all the words they find unfamiliar, which is a great resource to me when looking over their work and seeing which words are consistently highlighted.


Text Based Questions

After students have completed reading the article and identified and defined vocabulary, there are several text-based questions to answer.  I arranged the questions in order of ascending complexity.  There are essentially 3 levels of text-based questions.

Level 1- "Point to the answer": This is a question that a student can point to a specific line of text to find the answer.

Level 2- "Synthesize Information": This is a question that asks students to gather information and evidence from multiple sections of the text to create an understanding from which they can generate an answer.

Level 3- "Text and Prior Knowledge": This is a question that asks students to integrate what they've learned in the text with prior knowledge to think more critically and generate an answer that communicates a new level of understanding.

I do not give any explicit instruction on these multiple levels of questions during this lesson because the multilevel text-based questioning is a strategy that is employed across disciplines and grade levels at my school (alas, I can not claim to be the teacher that came up with the 3 tiers).  Because my students are already familiar with the 3 levels of questions, I simply let them know to be on the lookout for questions at all 3 levels during this assignment.  Later, as students are working on the assignment, if there are any students struggling, I may be more explicit and ask them, "is this something that you can find in just one place in the text?", or, "That sounds like you need to know something else not discussed in the article to answer that, that's a level 3 question... so what did we learn last time?". 

Once students begin working, I let them have about 15 minutes uninterrupted quiet time with the article and then begin to walk around the room to check on students one on one and see if they need my assistance with anything.  After 30 minutes, we move on to the wrap up and extension.


Wrap Up and Extension

20 minutes

After students have had time to read the article once or twice and answer the questions, I announce that I would like them to discuss their answers to the questions with their group members.  During this time, I move around from group to ensure that students are actively engaged and not having one student dominate all the air time and essentially "gift" the other group members with the answers to the questions.  If need be, I'll ask individual students what they wrote, or ask if anyone disagrees or has a different interpretation of the answer. 

After about 10-15 minutes of this, I bring the attention of the entire class back and quickly go over answers to the questions in a short discussion (see this key for answers to the questions).  If students are shy about offering answers, or again, if one student or group is dominating the airtime, I'll call out specific students to share what I heard them discuss in their smaller groups.  To do this, I try to offer a bit of encouragement by saying something like, "You know, Teresa really had an interesting thing to say about this question... Teresa, can you share what you told me with the whole class please?".


If students are not finished with any part of the assignment after our short discussion, I let them know that it should be completed as homework.  I then use the last few minutes to introduce the extension extra credit.



As an extension to this reading activity, I ask students to make a graphic representation of a symbiotic relationship similar to the graphic provided in the original article.

Essentially, I ask students to research a symbiotic relationship and make a kind of illustrated concept map.  As we look at the article's graphic, I show them how arrows point to feeding relationships, actions, or transfers of energy.  I ask my students to do similar "action arrows", but to go a step further and:

  1. Put a +,-, or 0 at each end of the arrow to show who is benefiting, being negatively affected, or not being affected by the action.
  2. Add a written explanation next to the arrow of whether this particular action is an example of commensalism, mututalism, or parasitism and why.

Since this extension is extra credit, I don't tend to spend too much time in class on this aspect of the lesson.  Instead, I encourage students to engage in independent research and see me during homeroom or after school if they need more guidance.  Examples of symbiotic relationships abound, but I recommend to my students to at least check out this article at Cosmos magazine.