Seed Dispersal
Lesson created by: UTeach Outreach Date of lesson: Week of March 3rd, 2014 Length of lesson: 50 minutes Description of the class: 2nd Grade Resources Used: UTeach Outreach TEKS addressed: 2.10: Organisms and environments. The student knows that organisms resemble their parents and have structures and processes that help them survive within their environments. The student is expected to: (B) observe, record, and compare how the physical characteristics of plants help them meet their basic needs such as stems carry water throughout the plant. I. Overview Seeds have many ways of dispersing. Some of these methods include animal transport, wind transport, water transport, and mechanical release. Seeds have adaptations, which aid their dispersal. By investigating external seed structure, students hypothesize their method of transport and test their predictions using models with limitations. II. Objectives 1. Students will predict and examine the structures that aid in seed dispersal. 2. Students will compare and contrast seeds to organize them into groups by their characteristics. 3. Students will categorize provided seed samples into groups based on their primary method of dispersal, which helps them survive in their environments. III. Resources, materials and supplies (per bin, student or teaching pair) Engagement: Seeds in bag (1 seed per kid) Exploration Per pair: Felt square Cup of water Rye grass seed Sticky burr Acorn seed Sunflower seed Elaboration: Picture of pea and Coconut 1
IV. Advanced Preparation: None V. Supplementary materials, handouts. Seed Dispersal worksheet Picture of peas in a pod and coconut Enlarged pictures of the 4 seeds used for the exploration activity VI. Background information College Level Most of the plants we’re familiar with start out as seeds. Seeds are alive, but are in a dormant state in which they do not grow or develop until certain environmental conditions are met. At that point the seeds germinate, or sprout. A typical seed is made up of three parts: a protective outer shell called the seed coat, a small embryonic plant called the embryo, and a food packet that will sustain the growing sprout until it reaches sunlight and is able to begin photosynthesis. This food packet is called the endosperm. Seeds typically remain dormant through the winter and germinate in the spring, when the two main conditions for germination, namely warmth and moisture, are met. However, if a seed is stored in cool, dry conditions, it can remain viable for decades or even centuries. Some seeds have additional criteria before germination can occur, such as heat treatment or scorching, or scratching the outer seed coat, but for the seeds of most familiar plants, warmth and moisture are all that is required. Plants are immobile, but it is to the plant specie’s advantage to spread its seeds widely. A plant population that exists solely within a limited geographic area can be wiped out by things like drought, disease or a harsh winter. In addition, tall plants such as trees require that their seeds be moved away from the parent plant in order to have enough room and sunlight to grow to maturity. But since the plants themselves are unable to move, they are forced to rely on some mechanism for moving the seeds away from themselves. We call this movement of seeds away from the parent seed dispersal. There are three main types of seed dispersal: animal, wind, and water. Seeds can be dispersed by animals in a variety of ways. Many plants develop their seeds inside a fruit of some kind. When the animal eats the fruit, it also eats the seeds. The seed coat protects the seed from being digested. The seed passes through the animal’s digestive system unharmed, and ends up being deposited with the animal’s feces. Since animal feces makes good fertilizer for plants, the seed has been moved to another place and then deposited with fertilizer to help it grow. Other seeds, like the sticker burrs common in Texas, have tiny spikes or hooks on them. These catch on the feathers and fur of animals and are carried away from the parent plant before falling off. Seeds can also be dispersed by animals such as squirrels, who bury so many acorns that they never find them all. Some seeds are specifically designed to be carried on the wind. The gray-­‐white fluffy “parachutes” of dandelion seeds are a common example. These can be easily blown right off the plant and carried away by the wind. Eventually the seeds land somewhere and start a new 2
dandelion plant. Maple seeds are another type of seed that is easily carried on the wind. Their “propeller wing” design helps keep them in the air longer when they fall from the tree, giving the wind more time to carry them away. Seeds with hair-­‐like or wing-­‐like structures are adapted for dispersal by wind. Plants that grow near water often rely on moving water to disperse their seeds. Coconuts are one example – coconuts float in water, so a coconut that has fallen from the tree and rolled into the water might be carried some distance before washing up on land again and taking root. You can often tell something about how a plant’s seeds are usually dispersed in nature simply by looking at the seed itself. There are two additional, less common, means of seed dispersal: gravity and ballistic. Some plants, such as apple trees, drop their fruit to the ground to facilitate removal by wind, water, or animals. Other plants, including geraniums, have a mechanism for throwing their seeds a short distance from the parent plant. Like a simple gravity release, this facilitates further dispersal by animals, wind, or water. Flowering plants rely on seeds for reproduction, but more primitive plants like mosses, ferns and liverworts, do not have seeds and use other means to propagate themselves. Elementary Level Most of the plants we’re familiar with start out as seeds in the ground. Sometimes people plant the seeds, like a farmer sowing crops or someone growing a vegetable garden or flower garden in their back yard, but how do seeds get planted in nature? There are whole forests of trees all around the world that nobody planted. Even the grass in an open field came from seeds. And Texas wildflowers really are wild – nobody planted them, so how did the seeds end up there? Sometimes seeds simply fall from the parent plant and grow where they’ve fallen, but far more often the seeds get moved somewhere away from the parent. We call this movement of seeds away from the parent seed dispersal. (“Dispersal” means spreading out over a wide area.) There are three main types of seed dispersal: animal, wind, and water. Seeds can be dispersed by animals in a variety of ways. Many plants develop their seeds inside a fruit of some kind. When the animal eats the fruit, it also eats the seeds. But each seed has a protective shell called the seed coat that protects the seed from being digested. The seed passes through the animal’s digestive system unharmed, and ends up coming out the back end when the animal poops. Since animal poop makes good fertilizer for plants, the seed has been moved to another place and then deposited with fertilizer to help it grow. Other seeds, like the sticker burrs common in Texas, have tiny spikes or hooks on them. These catch on the feathers and fur of animals (and on socks and pant legs and shoelaces of people), and are carried away from the parent plant before falling off. Seeds can also be dispersed by animals such as squirrels, who bury so many acorns that they never find them all. 3
Some seeds are specifically designed to be carried on the wind. You may have played with a dandelion that has gone to seed. The gray-­‐white fluffy “parachutes” can be easily blown right off the plant and carried away by the wind. Eventually the seeds land somewhere and start a new dandelion plant. Maple seeds are another type of seed that is easily carried on the wind. Their one “propeller wing” helps keep them in the air longer when they fall from the tree, giving the wind more time to carry them away. Plants that grow near water often rely on moving water to disperse their seeds. Coconuts are one example – coconuts float in water, so a coconut that has fallen from the tree and rolled into the water might be carried some distance before washing up on land again and taking root. The seeds of different plants are specifically designed for dispersal by one means or another. Seeds inside fruit and seeds with tiny hooks are specifically adapted to being dispersed by animals. Lightweight seeds with parachutes, sails, or propeller blades are specifically adapted for dispersal by wind. And thick-­‐shelled seeds that float are perfect for dispersal by moving water. You can often tell something about how a plant’s seeds are usually dispersed in nature simply by looking at the seed itself. In each case, the seed is deposited in a new site, ready to germinate and grow into a new plant as soon as the conditions are right. Normally the conditions required before a seed begins to grow are a warm, moist environment. Since seeds are often deposited in autumn when the air and ground are cooling off, the seeds usually remain dormant through the winter and begin to sprout in spring when warmer temperatures and spring rains provide the right conditions for growth. Seed dispersal is important for a plant species’ survival. Without seed dispersal, the seeds from a tall tree, for example, would fall in the shade of the parent tree and wouldn’t get enough sunlight to become tall trees themselves. Dispersal also helps spread out a plant species over a wider area. If a plant species is limited to a small area, then a single hard freeze or a root disease could kill off the entire species. By spreading its seeds over a wider area, a plant species has a greater chance of maintaining long-­‐term survival. VII. Possible Misconceptions Big seeds do not float. The size of seeds do not determine if they float or not. Big seeds like coconuts can float. Small seeds can also sink. Seeds that travel by wind needs wings. Seeds that travel by wind does not need to have wings like dandelions but can also be light enough so the wind can pick it up like rye seeds. Fruits are seeds. Fruits contain seeds but are not the source in which another fruit can grow from; it is the seed within the fruit like orange/apple seeds that a new plant can grow and give fruits. Fruit produces seeds. As we learned fruits aren’t seed and they don’t produce seeds fruits are produce in a consequence of seeds to protect them. 4
VIII. Vocabulary and Definitions College Level: Seed Dispersal: the method by which a plant scatters its offspring away from the parent plant to reduce competition Wind: Blows seeds with hair-­‐like or wing-­‐like structures to a new place Water: Carries seeds that are able to float on water going downstream Animal: Animals’ fur can carry the seeds or animals can eat the seeds and it would come out in their feces. Dormant: Not active or developing Elementary Level: Seed Dispersal: Ways seeds are carried away from the parent plant Wind: Blows seeds with hair-­‐like or wing-­‐like structures to a new place Water: Carries seeds that are able to float and washes them onto a different shore Animal: Seeds are carried by animal’s fur or eaten by animals and then digested out Dormant: Seeds that are alive, but not growing IX. Safety Considerations: -­‐Do not eat the seeds -­‐Do not spill the water X. Question of the Day: How does the structure of seeds affect its dispersal? Five-­‐E Organization ENGAGEMENT What the Teacher Will Say or Do We are back for another lesson! Today we will begin by passing out different seeds to each person. As you get your seed, I want you to observe your seed and think about where it came from and where it could grow. Take out the bag of different seeds and give out one seed per student making sure no one has the same seed within the group. Remember our rules: Be safe and think like a scientist, so don’t eat the seeds or put them in your mouth. Look at your seed and then look at your partner’s seed. Probing Questions 1.
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What do you observe about your seed? (What does it look like? What color is it? What shape?) Where do you think this seed Time: _5 minutes_______ Expected Student Responses / Potential Misconceptions 1.
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My seed is small. It’s orange. It’s brown. From the forest. Someone took 5
ENGAGEMENT What the Teacher Will Say or Do Now I want you to look at your shoulder partner’s seed and talk about similarities and differences between the two seeds. Hook ‘em… Go ahead and put all of your seeds in the middle of you table and we will come around and pick them up. Pick up the seeds. You may have noticed seeds can come in all different shapes, sizes, and colors. They all grow differently, but first they have to find a place to grow! Today we will observe different seeds and how they travel. Before we leave you will be able to answer the questions of the day: How do the structures of seeds affects its dispersal? Display Question of the Day on doc cam. Probing Questions came from? How do you think it got there? 3.
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What are some differences about the seeds? Similarities? Could both seeds have come from the same place or have gotten there the same way? How do you know? Time: _5 minutes_______ Expected Student Responses / Potential Misconceptions it there. Horns! 3. They are the same shape/color. They have different shapes/color. 4. Maybe. Once couldn’t fly in the wind like the other one. EXPLORATION What the Teacher Will Say or Do Pass out job cards and worksheets. Make sure you get a different job than you had last week and be sure to put your name on the top of your worksheet. Before we begin our activity, we will cover our first vocabulary word. Seeds travel throughout the world in many ways; this is called seed dispersal. Everyone say seed dispersal with me. SEED DISPERSAL. Write seed dispersal on the board. There are 3 main ways that seeds can be dispersed; one of them is by Probing Questions 1.
What are some ways seeds can 1.
disperse? Time: 30_ minutes___ Expected Student Responses / Potential Misconceptions They can fly in the wind. People can carry them to another place. 6
EXPLORATION What the Teacher Will Say or Do wind. Can everyone say wind? WIND Show wind on the vocabulary sheet. Right! Wind can help carry seeds away from their parent plant and it lands in a new place for it to grow. Another way seeds disperse is by water. Can everyone say water? WATER. Show water on the vocabulary sheet. Correct! Some seeds can float on water and wash up on a beach or shore far, far away from where it came from. Then it will plant at a new location. Animals are another way seeds can be dispersed. Can everyone say animal? ANIMAL. Show Animal on the vocabulary sheet. Great thinking everyone! Before we do any seed dispersal testing on the seeds, you will be making observations on each of the seeds you will be using. You will be working with your shoulder partner, and you will be getting four seeds to observe and test. The seeds we will be using today are (show pictures on doc cam) rye grass seed, sticker bur, sunflower seed, and an acorn. Pass out seeds. Go ahead and take a few minutes to make your observations for each seed with your shoulder partner. Make sure you record your observations on your worksheets. Walk around and monitor students. Make sure they are using descriptive and detailed observations on their worksheets. Probing Questions 2.
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How do you think wind helps with seed dispersal? How do you think water helps with seed dispersal? How do you think animals help with seed dispersal? What kinds of things can you write down as your observations? Time: 30_ minutes___ Expected Student Responses / Potential Misconceptions 2.
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Blows them away! In a storm, the winds knock down branches and leaves, etc. It floats away! They eat them! They carry them away! etc. How big it is, the color, what it looks like. 7
EXPLORATION What the Teacher Will Say or Do Hook ‘em… Now that everyone has completed their observations, we are going to move on to our dispersal tests. For wind dispersal, you are going to lay them at the edge of your desk and blow lightly and see what happens. You will be blowing towards the middle of your desk, so the seeds don’t fall on the floor. Whichever goes the furthest is the best for wind dispersal. Demonstrate how to do this test. For the animal test, you will use a piece of this cloth, or felt. You will put the cloth on top of each seed to see if it would stick to an animal’s fur or even clothes. Whichever sticks to the cloth is the best for animal dispersal. Demonstrate how to do this test. For the water test, we will come around and pass out a cup of water. Right! So you will work with your partner and take turns to see which seed floats in the water. Before we begin any of these tests, I want you to go ahead and make your predictions for each test to see which seed you think could be dispersed that way. Once you have made your predictions, you may begin your first test, and we will come around with the cloth and the cup of water. Walk around and monitor students. Make sure students are recording their predictions then results. Pass out felt when they are ready for it, then pass out cup of water when they are at that point. Probing Questions 6.
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How will you blow the seeds? Which object went farther? How will you do the animal test? How could we use the cup of water to test the seeds? Time: 30_ minutes___ Expected Student Responses / Potential Misconceptions HORNS! 6. Lightly! 7. Feather 8. Use the cloth to see if it sticks. 9. See if they float! 8
EXPLORATION What the Teacher Will Say or Do Pick up all the materials. Pour out water and seeds into the sink, but take the marble back out. Probing Questions Time: 30_ minutes___ Expected Student Responses / Potential Misconceptions Probing Questions Time: _20 minutes___ Expected Student Responses / Potential Misconceptions EXPLANATION What the Teacher Will Say or Do These seeds are dormant. Can everyone say dormant? DORMANT Show dormant definition on the doc cam. This means the seeds are alive but not growing since they’re not in the right environment. Right! To grow these seeds, we would need a warm and moist environment, like in the spring! Right now, it’s not in a warm or moist environment, so it’s DORMANT and waiting to grow. Now, let’s go through our results together! That’s correct! Seeds that are dispersed by wind need to be lighter so the wind can pick it up. Many seeds can be dispersed by the wind, but the weight of the seed affects how far the wind can carry it. That’s correct the seeds need to be sticky and have hooks so they can 1.
What do seeds need to grow? 2.
What are three ways that seeds can be dispersed? 3.
Which seed was best dispersed by wind? 4.
What structures does this seed have that helps it be dispersed by wind easier? 5.
Why aren’t the other seeds easily dispersed by wind? 6.
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Which seed was best dispersed by animals? What structures does this seed have that makes it the best seed to be dispersed by animals? 1.
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Water! Wind, water, animals! Rye grass seed Lighter, flat, smallest, etc. They were too heavy, too big, etc. Sticky burr Pointy, they have hooks, sticky, etc. 9
EXPLANATION What the Teacher Will Say or Do hook onto the animals’ fur. This is how the animals can carry the seeds around wherever they go, but it’s not the only way! Animals can eat seeds, but since it has a really hard, protective shell, it doesn’t get broken down and comes out in the animals’ poop! That’s correct seeds that are carried by the water needs to be able to float. This way, streams can carry them and wash them onto the shore. Show a picture of a coconut seed. Floating is not dependent on the size of the seed. Small seeds can still stink and big seeds can still float. Remember the test of the ping pong ball and marble? The ping pong ball floated even though it was bigger than the marble. Probing Questions 8.
Which seed was best dispersed by water? Which seed floated more or stayed above water the most? 9.
What makes this seed better than the others? Time: _20 minutes___ Expected Student Responses / Potential Misconceptions 8.
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10. How about a coconut seed? Do you think that floats? The sunflower seed Light, floats, not sink, not heavy, etc. 9. Yes, no ELABORATION What the Teacher Will Say or Do Explain and set up as an extension Probing Questions So we studied 3 different ways of how seed is dispersed but there is one more way that they can be dispersed. Show picture of pea pods. That’s right! These pea pods burst when they get ripe and the seeds fall onto the ground. Then, other methods that we studied today, like wind, water, and even animals, can help it get dispersed even more. 1. How do you think these seeds get dispersed when they are ripe? 2. Do fruits have seeds in them? 3. What kinds of fruit have seeds in Time: __10 minutes____ Expected Student Responses / Potential Misconceptions 1. They burst out of their pods and fall to the floor, animals eat them, etc. 2. Yes 3. Apples, oranges, watermelon, 10
ELABORATION What the Teacher Will Say or Do Fruits have seeds in them but they are not considered a seed. The fruit is formed after the seed is produced to protect the seed. Yes, other animals like bees can disperse seeds from flowers when they fly around gathering pollen and it sticks onto their hairy legs. As humans we also pay a part in dispersing seeds. Explain and set up as an extension Probing Questions Time: __10 minutes____ Expected Student Responses / Potential Misconceptions etc. them? 4. Are fruits considered seeds then? 5. How do animals disperse seeds again? 6. Are there any other ways different animals can transfer seeds? Bees? Squirrels? 7. What are some ways that we disperse seeds? 4. Yes, no 5. With their fur; by eating and pooping them! etc. 6. Bees when going from flower to flower, squirrels hoarding acorns and burying them in different places, etc. 7. Planting them; eating fruits; when seeds stick to our socks; playing with dandelions; etc. EVALUATION What the Teacher Will Say or Do You guys did a great job finding out how each seed was dispersed and what structures are needed for each method of dispersal. Now it’s time to show off how much you learned today! Review the thumbs up and thumbs down method and the different letter answers. Put visuals onto doc cam and reveal one question at a time. Take out interactive journal if time permits or leave the journal prompt page with the teacher as a review for the following day. Journal prompt: Draw a picture of 3 different seeds. One that will be dispersed by water, one by wind, and another by an animal. Write one sentence explaining your picture and what structures your seed has that makes it really good at being dispersed that way. Time: __10 minutes____ Expected Student Responses/ Potential Misconceptions Probing Questions 11
Question of the Day: How does the structure of seeds affect its dispersal? Seed Dispersal: Ways seeds are carried away from the parent plant Wind: Blows seeds with hair-­‐like or wing-­‐
like structures to a new place Water: Carries seeds that are able to float and washes them onto a different shore Animal: Seeds are carried by animal’s fur or eaten by animals and then digested out Dormant: Seeds that are alive, but not growing 12
How are Seeds Dispersed? Name: ________________________________ ____________________: Ways seeds are carried away from the parent plant ____________________: Seeds that are alive, but not growing Seed Observations: Record your observations about each seed. Seed Observations: (How does it feel? What does it look like? What color is it?) Rye Grass Seed Sticky Burr Sunflower Seed Acorn WIND DISPERSAL 1. Which seed do you PREDICT will go the farthest when you gently blow them? Circle your prediction below. RYE GRASS SEED STICKY BURR ACORN SUNFLOWER SEED 2. Which seed went the FARTHEST when you blew them? Circle your result below. RYE GRASS SEED ACORN STICKY BURR SUNFLOWER SEED ANIMAL DISPERSAL 1. Which seed do you PREDICT will stick to the felt square? Circle your predicted seed below. RYE GRASS SEED ACORN STICKY BURR SUNFLOWER SEED 13
2. Which seed STUCK to the felt square? Circle your result below. RYE GRASS SEED ACORN STICKY BURR SUNFLOWER SEED WATER DISPERSAL 1. Which seed do you PREDICT will float? Circle your prediction below. RYE GRASS SEED STICKY BURR ACORN SUNFLOWER SEED 2. Which seed FLOATED? Circle your result below. RYE GRASS SEED ACORN STICKY BURR SUNFLOWER SEED Based on what you have learned, circle your prediction of how each seed is dispersed. Type of Seed How the seed is dispersed (circle one) Wind Water Animals Water Lily Wind Water Animals Acorn Wind Water Animals Dandelion Wind Water Animals Apple Wind Water Animals Cockle Burs
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Thinking Card Questions 1. What are some other ways seeds can be dispersed other than the main three (water, wind, animals)? 2. Name some fruits that have seeds in them 3. Name some animals that can carry seeds 4. Can you also eat the seeds? 1. What are some other ways seeds can be dispersed other than the main three (water, wind, animals)? 2. Name some fruits that have seeds in them 3. Name some animals that can carry seeds 4. Can you also eat the seeds?
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Journal prompt: Draw a picture of 3 different seeds: 1) A seed that will be dispersed by water. 2) A seed that will be dispersed by wind. 3) A seed that will be dispersed by an animal. Write at least 1 sentence explaining your picture and what structures your seed has that makes it really at being dispersed that way. 16
Show off what you know Evaluation Questions Thumbs Up or Down Questions 1. When a seed is dormant, they are alive but not growing. Thumbs up for yes Thumbs down for no 2. Only small seeds can float. Thumbs up for yes Thumbs down for no Multiple Choice Questions 3. What does seed dispersal mean? A. how seeds travel B. planting seeds C. how seeds grow 4. Which is not a type of seed dispersal? A. wind B. water C. sun 17
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Seed 1: Rye Grass Seed
Seed 2: Sticky Burr
Seed 3: Sunflower Seed
Seed 4: Acorn Seed
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