How Plants Reproduce

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Objective

SWBAT describe the process of reproduction for both flowering and nonflowering plants.

Big Idea

Students use observation skills to dissect a flowering plant, identifying and labeling each part and its role in reproduction.

Preparation and Rationale

The Why Behind Teaching This: 

Unit 3 addresses standards related to the transfer of energy and matter between organisms in an ecosystem.  The unit begins with identifying what solar energy is and what two forms of energy solar energy provides life on Earth.  This is an important foundation for understanding standard 5-PS3-1: Use models to describe that energy in animals' food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun.  We build on this knowledge throughout the unit in other lessons related to photosynthesis and how animals use the energy they get from food.  In this unit students will also be conducting experiments to gather evidence to support their belief that plants get the materials they need for growth from either water, air, or the soil.  This is covered in standard 5-LS1-1: Support an argument that plants get the materials they need for growth chiefly from air and water. Students will also be creating food chains and food webs to describe the movement of matter among organisms in an ecosystem.  This is covered in standard 5-LS2-1: Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.

I combined these three standards all into unit 3 because teaching them together allows students to see how they are all connected.  The energy that plants get from the sun is stored in their parts until animals consume them.  Plants cannot absorb this energy and reproduce without other materials from the environment such as carbon dioxide from the air, and water and nutrients from the soil.  The animals that consume the plants, use part of the energy for growth, reproduction, etc. but they also store some of the energy.  That energy is then passed on to other animals when they are eaten by other animals.  All of the energy that is available in an ecosystem can ultimately be traced back to the sun.  Teaching all of these standards together, instead of in isolation of each other, makes that connection easier to see.    

This specific lesson is building the foundation to dive deeper into standard 5-PS3-1: Use models to describe that energy in animals' food (used for body repair, growth, motion, and to maintain body warmth) was once energy from the sun.  One thing that plants use energy for is reproduction.  Flowering and nonflowering plants reproduce in two different ways.  Students will learn about both as a connection to the precious two lessons on the process of photosynthesis and parts of a plant.   

Lesson Goal: 

The goal of this lesson is for students to be able to identify the steps in the life cycle of flowering plants, identify the role of the male and female reproductive parts of a flower related to pollination and fertilization, and to be able to differentiate between flowering and nonflowering plants.   

Success Criteria:

Students will demonstrate success by answering the five review questions at the end of the lesson correctly. 

Preparing for Lesson:

Warm Up: 

  • Pine cone and flower for students to compare 
  • whiteboards and markers
  • Notebooks for notes 
  • Nonflowering Plant Photos to show the class 

Guided Practice: 

Explore: 

  • A flower with well defined reproductive parts for each group. (I used Liliums) 
  • Forceps and hand lens for each group 
  • A tray for dissecting on 
  • Whiteboard and marker for lab chart 

Wrap Up: 

Warm Up

10 minutes

Types of Plants 

I have a pine cone and a flower that I show the class.  I ask students to discuss with their table group similarities between the two.  I have them record their ideas on a whiteboard.  After about 2 minutes of discussion I have all groups hold up their boards and I read off the ideas they recorded.  Groups have things such as both are from plants, animals eat them, found on trees, etc.  I do this activity to lead into the reproduction of plants.  I explain to the class that one similarity they did not mention is that plants that produce flowers, and those that produce cones, both reproduce with seeds.  This is something that needs to be reiterated many times throughout the lesson because students often struggle to remember that cones, although they are nonflowering plants, still reproduce by seeds.  

Students have their science notebooks out ready for today's lesson.  I have my notebook on the overhead as a visual for students.  This helps ESE and ELL students, as well as any regular education student who struggles with writing or spelling.  It is also helpful to visual learners who learn better from seeing information as opposed to just hearing it.  

We title the page Types of Plants and begin a graphic organizer together.  At the top of the page we write Plants.  I explain that there are two main types of plants, flowering plants and nonflowering plants.  I refer back to the pine cone and flower.  I ask them which category they think the flower belongs in.  They tell me flowering.  I ask them which category they believe the pine cone fits in.  They tell me, nonflowering.  

Under the Flowering heading, I record Plants that produce flowers and reproduce by seed. Under the Nonflowering heading, I record Plants that produce cones and reproduce by seed.  I inform students that not all plants reproduce by seeds.  I show them the Nonflowering Plant Photos and ask them if they know what the plants are.  They are able to tell me the first photo is a fern but cannot tell me the second is moss.  After naming both plants I ask them which category they believe ferns and mosses would fit in, flowering or nonflowering.  They tell me nonflowering.  I show them the last picture which shows a fern with spores on it.  I tell them that the little black circles on the bottom of the leaf are called spores.  Ferns and mosses reproduce with this structure. Under the Nonflowering heading, I record Ferns and Mosses Reproduce by spores.    

                                                  

How Reproduction Occurs with Spores

I ask students how they believe spores are spread so that new plants can grow.  They tell me by the wind and getting stuck on animals that carry them.  They leave out water, so I discuss that briefly.  We add this information to the flow chart.   

The main focus of the lesson is on the life cycle of flowering plants so we do not get into great detail about spores.  Students only need to know that ferns and mosses reproduce by spores and that those spores are spread by wind, water, and animals. 


Guided Practice

20 minutes

How Reproduction Occurs in Flowering Plants 

I explain to the students that the main focus of our lesson today will be on the life cycle of flowering plants.  We turn to the next page in our science notebook and title the page Life Cycle of Flowering Plants.  I ask students what would begin the life cycle of a plant and they tell me a seed.  We draw and label a seed in our notebooks.  I pass around a seed and ask students to describe how the seed feels.  They tell me it is smooth and hard.  I explain to students that the genetic material that grow into the actual plant is stored inside the shell of the seed.  The hard part they are feeling is a protective structure.  In order for the plant to grow, the seed cracks open and the plant begins to sprout out of it.  This is called germination and is the next step in the life cycle.  We draw this step in the diagram in our notebooks.  The plant continues to grow until it is mature enough to produce flowers which is where reproduction occurs.  We add in pollination and fertilization but do not discuss what they are yet.  

                                              

Diagramming the Reproductive Parts of Flowering Plants 

I show the class a video that summarizes the process of pollination and fertilization, two steps that students need to be able to differentiate between.  

  

As students watch the video, I pass out a copy of the Flower Structure Diagram to each student.  I drew the diagram and copied it for each student because it is a detailed picture that would take some students a long time to draw.  It also ensures that the structures look the same for every student.  We glue the flower diagram into the notebook at the bottom of the page.  

Questions I ask after watching the short video: 

  • What are some examples of pollinators that help in reproduction of flowering plants? (bees, birds, water, wind)
  • What attracts the bees and birds to the flowers to help with pollination?  (the color of the petals)
  • Does the male reproductive part or the female reproductive part produce the pollen? (male)

The questions above are fairly easy points for the students to remember from the video.  Asking these questions helps lead us into labeling the diagram.  I am teaching the process of pollination and fertilization as we diagram the reproductive parts.   

We begin with the sepal at the bottom.  We label it and add that it protects the flower until it is ready to open for pollination to occur.  I have a bouquet of flowers that will be used for the explore activity.  When selecting a bouquet, I purposely choose one that has a few flowers still closed so that students can see how the sepal protects it.  I walk around with one of these closed flowers and allow students to feel it.  They observe that it is hard, similar to the seed.  I explain that inside, the flower is still maturing, the pollen is being produced and the egg is getting ready for reproduction. Once the plant is ready for reproduction, the sepals open up and fall off.  

                                            

The next label that we add is the stamen.  I have students underline the last three letters MEN, and tell them that this is the male reproductive part of the flower which should be easy to remember because the end of the word spells men.  Pointing this out gives students an easy way to remember which is the male part.  I point out the top of the stamen and discuss how the pollen collects on this part and waits for a pollinator to help spread it.  

Next, we label the pistil which is the female reproductive part. I point out the little dots at the top of the pistil in the diagram and tell students that this part is sticky so once the pollen touches it, it gets stuck.  This ends the process known as pollination.  

I ask students what happens after pollination.  They tell me fertilization.  I ask them to explain fertilization.  They tell me the pollen moves down the tube of the pistil to the bottom where the egg is and fertilizes the egg.  I tell them that similar to the reproduction of animals, half of the chromosomes from the pollen (male) combine with half of the chromosomes from the egg (female), and a new seed is produced.  

                                                  

Spreading the Seeds

I remind students that spores are spread by wind, water, and by animals when they get stuck on them.  I ask them how seeds are spread so that new flowers can grow.  They tell me that wind can blow them, and water can carry them.  I ask them what we eat that has seeds in it and they tell me fruit.  I explain that fruits start out as flowers and once fertilization occurs, a fruit is produced that protects the seed.  Animals that eat those fruits also help spread seeds in their droppings.  

Explore

20 minutes

Dissecting a Flower

At this point in the lesson I give the students an opportunity to see each of the parts we just diagrammed and discussed in a real flower.  The goal of having them dissect the flower and separate it into the individual parts, is to see how all the parts look together in a real flower as opposed to our drawing, and to see the parts in isolation.  It also provides them with an opportunity to apply what they just learned while also giving them an activity to refer back to, to help them remember the information.   

I provide each group with a whiteboard and marker for recording the observations they make.  I draw a chart for recording their observations and have them copy it.  I provide each groups of students with a tray, hand lens, forceps, and a flower.  I circulate the room to ensure students remain on task and are completing the chart on their board while working. They dissect the flower by pulling off the petals, removing each stamen (there are usually at least 6 per flower),  and removing the pistil.  The chart has a place to draw a model of what each part looks like by itself, and also has a column for them to count how many there are of each part.  

  

This video of group dissecting a flower shows students working together to dissect, draw, and count each part of the flower.  They are labeling the parts on sticky notes as they work.  

 

Wrap Up

10 minutes

4 Corners Formative Assessment 

I have the corners of my room labeled A, B, C, and D.  This is an assessment strategy I use often, especially to check multiple choice homework quickly.  I place the 5 question flower reproduction review page on the overhead and provide each student with a sticky note to record their answers. 

As students are answering the questions independently, I collect materials from the dissection.   After materials are collected, I read off question one and tell students to go to the corner that matches their answer.  I have the students in each corner check each other's sticky notes to make sure they are in the correct corner.  I then tell them which answer is correct.  Any student who got the answer correct remains standing, all those who went to the incorrect corner return to their seats and continue checking their answers from their desk.  I was surprised that 5 students got knocked out on this question, I thought this was one that everyone would get correct.  2 students picked B and the other 3 picked C.  

I continue on by reading question two.  Students may not move to a new corner until I have finished reading the entire question and ask them to move.  Those who got it correct remain standing and those who went to the wrong corner return to their seat.  This question was a strength because everyone chose C which was the correct answer.  

We continue playing this game until all five questions have been checked.  Only a couple of students chose C for question 3 which was pistil instead of stamen.  Question four was answered correctly by all students.  There were 12 students remaining when I got to question five and all 12 answered it correctly.  I reward those who are remaining with tickets (our classroom incentive).