Lesson: Non-fiction Text Structures: Author's Purpose: Main Idea Paragraphs (Lesson 18)

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Lesson Objective

Paragraphs have purposes. Their purpose should be clear from their main idea. In non-fiction, there is always a paragraph that introduces the main idea of the entire article.

Lesson Plan

Lesson 18:

Standard: Identify the purpose of common textual features (for example, title, headings, key words, paragraphs, topic sentences, table of contents, indices, glossary,  captions accompanying illustrations or photographs).

Identify topic sentences, supporting details, and elaboration in paragraphs. 

Determine the purpose of individual sentences and paragraphs and how they contribute to the text as a whole. 

Big Idea:  Writers use lots of evidence to support the main idea or theme.  These supporting details fill the text; they are found in every paragraph, all textual features, and all graphic features. 


Teaching Point: Paragraphs have purposes.  In NF, there is always a paragraph that introduces the main idea of the entire article.


Reading Workshop: Reading binders, pencils, copies of “Loggerhead,” “Boys and Girls in the Primate World,” “Masters of Verse,” “Splitting Up,” “Fear on the Brain,” and “Poop Power,” small post-its.

Note: All articles have been used in previous lessons from this unit. Students should have copies in their reading binders.

RA: Reader binders, copy of Exploding Ants, small post-its


Reading Workshop Lesson:

  • Readers, we have been learning about how authors organize paragraphs. We learned that every paragraph has one purpose – one topic that it is about. If an author tries to have too many purposes in one paragraph, then they will confuse the reader!
  • As readers, when we see a new paragraph, it is our job to notice that the author is moving on to a new topic. It is also our job to understand what that new topic is. Last time, we learned that the purpose of some paragraphs is to “hook” the reader and catch our attention. Usually these paragraphs are in the introduction, or beginning, of the text. Today, I am going to teach you that in non-fiction, the purpose of some paragraphs is to tell the reader what the main idea is. We already know this from when we learned about non-fiction text structure – we can make a pretty good main idea prediction just from reading the first couple of paragraphs. Today we’re going to read through some of our old non-fiction texts to see if we can find some paragraphs whose purpose is to tell the reader the main idea.
  • Open your binder to your “Non-Fiction” tab to “Life of the Loggerhead.” Let’s read until we find the paragraph that tells us the main idea. [Stop at the end of the second paragraph. Did anyone notice where the author tells us the main idea?  [Re-read the last two sentences of the paragraph – we can put those together to come up with the main idea that female loggerheads use navigational tools to return to the beaches where they were born.] If I know that the purpose of this paragraph is to teach us the main idea, then I will understand the article much more clearly – I will read knowing what the main idea is! Let’s annotate that paragraph by writing “main idea” in the margins.
  • Let’s turn to “Boys and Girls in the Primate World.” Remember, this was a compare/contrast article that taught us why boys and girls act differently. [Read to the second paragraph and stop. T&T to share what the main idea is, then share out – it should be pretty clear that it is the last sentence of the paragraph. Annotate.]
  • [Do the same with “Masters of Verse” – the main idea is in the first paragraph. Annotate.]
  • [Repeat with “Splitting Up.” The main idea can be found in the subtitle and also in the second paragraph. Annotate.]
  •  [Repeat with “Fear on the Brain” – the main idea is in the first paragraph, where is says, “Fear is your brian’s defensive response to danger.” Even though there are many more details in this paragraph, the purpose of the paragraph is to help us understand the main idea. Annotate.]
  • [Repeat with “Poop Power” – the main idea is found in the first paragraph. Annotate.]
  • Readers, it is important to think about the purpose of each paragraph because if you don’t know why an author included a paragraph, then you must be confused about the text overall.  Today and every day, you should notice when the purpose of a paragraph is to hook the reader and when the purpose of a paragraph is to teach you the main idea.
  • Today when you read, if you find that the beginning paragraph in your story or article catches the reader’s attention, or if you find a paragraph that teaches the reader the main idea, then you may get a small post-it note and mark that.


Read Aloud Lesson:

  • Readers, we have been learning that in all texts we read, every paragraph has a purpose, and good readers always know what the purpose of each paragraph is. Today, we are going to continue looking at the text structure and the purpose of the paragraphs in “Exploding Ants.” We should stop every time we see a paragraph that hooks the reader or a paragraph that tells the reader the main idea of that section.
  •  [Start reading “Swelling, Expanding, and Exploding Bodies.” Make predictions based on headings and pictures before starting each section. Notice that much like last time, most of the first paragraphs are meant to catch the reader’s attention, to make us more interested in the disgusting thing this animal does. T&T after the first or second paragraph of each section to discuss where the author tells us the main idea for that section. Mark each hook or main idea paragraph with a post-it.]
  • [Stop at the end of page 19. We will read “Dog Mucus and Other Tasty Treats” next time.]


Lesson Resources

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