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Title: Modes of Seed Dispersal
Principle(s) Investigated: Botany, ecology, evolution.
Standards:
HS-LS2-8 - Evaluate evidence for the role of group behavior on individual and species' chances to survive and reproduce.
HS-LS4-4 - Construct an explanation based on evidence for how natural selection leads to adaptation of populations.
Materials:
- Brown paper lunch bags with the following items:
1.) Explosive seed dispersal:
- balloon
- confetti
- ball pump
2.) Animal seed dispersal(1):
- "sticky seeds" found on front yard
3.) Animal seed dispersal (2):
- acorns or actual fruit
4.) Wind seed dispersal:
- soft fluffy seeds and/or seeds with wing- bought and found in front yard
5. ) Water seed dispersal:
- bought lotus seed pod
6.) Seed dispersal by gravity:
- pinecones found near pine tree
Procedure:
1.) Place the different seeds (1-6) in the brown paper bags numbered 1-6.
2.) Give students a brief introduction of seed dispersal and how seed shape may give clues of the type of dispersal they exhibit.
3.) Break students into small groups of maybe 3-4 students each.
4.) Give each group of students a brown bag with a specific type of seed in it. (Unless it is #1 this one is hard to decipher by seed phenotype this group will demonstrate the actual type of seed dispersal).
5.) Each student will be assigned a specific Google Slide from the presentation that pertains to their bag number.
6.) Students will then analyze the seeds contained in their bags and fill their corresponding slide with their Claim, Evidence and reasoning for why they came up with their mode of seed dispersal.
7.) Explain the adaptation of dormancy after dispersal and how some seeds wait for conditions to be advantageous to avoid competition and then germinate when conditions are favorable. Give relevant everyday example of how fires disrupt ecosystems but also give way to different species to come about in the same environment.
Student prior knowledge: Prior knowledge on structures of the flower such as: Pistil- (ovary, ovule, pollen tube, style, stigma), Stamen- (anther and filament), petals, sepals. Students should know the process of pollination and what pollinators are as well as how they are important to plants. Students may know ecological relationships between species such as commensalism, mutualism, parasitism, competition and predation. From evolution, natural selection and adaptation.
Explanation: Plants have developed a series of adaptations to be able to survive in our ever changing world. Some of these adaptations have included the ability to reproduce sexually to increase the plant's ability to survive in harsh environments. Some features significant to these evolutionary adaptations include the formation of "showy" structures that are flowers as well as certain ecological relationships with insects or animals that have helped the plant survive and further evolve for thousands of years. With sexual reproduction comes the production of seeds and offspring. Before the seed can germinate, the plant must disperse the seeds away from itself to ensure that its offspring may be successful. Although one plant can produce thousands of tiny seeds, it is not guaranteed that every single one of these seeds will germinate and grow a mature plant that will then produce seeds. Here is where plants have also developed adaptations for the dispersal of their seeds for the purposes of avoiding predators or pathogens that can appear on the parent plant, spreading seeds to different environments where some may be more successful than others, and to reduce competition near the parent plant.
Questions & Answers:
1.) The way we grow crops today to feed people relies heavily on the use of monocultures or the planting of one crop over a large area of land. This process is known to have serious implications on the reduction of biodiversity and linked to a decrease in pollinators such as bees. Could you propose a solution as to how we can still be able to continue to produce food (seeds) for human consumption and increase biodiversity?
Answer: One way in which we humans can keep growing food for ourselves but increase biodiversity and to increase the number of pollinators is to plant native and diverse flora in the area surrounding the monoculture crop. For example, humans could purposefully place plants that flower and attract pollinators around a monoculture crop of corn.
2.) Plants shape our everyday experiences. Think about an entire day of your life and list all the possible ways you carry a commensalistic relationship with plants.
Answer: Answers can vary but should include things such as food they eat, their homes or shelter, shade outside, the grass they run on during PE class, the clothes they wear... etc.
3.) Plants coevolved with animals to be able to disperse their seeds to far distances. What evolutionary principles were needed for two species to coevolve? How do characteristics of each species make it so that they both benefit from each other or does one benefit more than the other? Give a real life example and relate seed dispersal to a coevolutionary phenomenon.
Answer: One possible coevolutionary principle used to describe the relationship of one species to another in an ecological setting would be Darwin's finches. Here, through the process of natural selection, birds developed different size and shaped beaks to overcome competition. Furthermore, the finches reduced competition by selectively eating different seed types. Some seed types had harder outer shells so finches developed shorter and stronger beaks. Other finches chose diets of smaller and/softer seeds and hence their beaks evolved to specify the type of seed the finches consumed.
Applications to Everyday Life: We as humans have developed a relationship with plants and their seeds, fruits, wnd woody structures. We largely depend on seeds in agriculture for food consumption and this directly affects the way we consume food every day. As the world population grows we must come up with new ways to disperse seeds and grow crops that will be able to feed our growing population. We must do this also think of possible consequences on ecologies and other organisms we depend on for food production. Plants also provide us with the materials we need for shelter. In California, as well as many other parts of the world, we depend on the woody structures of plants to make our homes. Both, food production and the provision of shelter or housing, depend on how we use plants and hence their seeds. Furthermore, these ways in which we use plants have direct implications on the economy.
Videos:
<iframe width="560" height="315" src="https://www.youtube.com/embed/wOIHzl2h9a8" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
https://www.youtube.com/watch?v=wOIHzl2h9a8
Citations:
Youtube video by BBC earth
Fenner, Michael, and Ken Thompson. The Ecology of Seeds. Cambridge, UK ; New York, NY, USA: Cambridge University Press, 2005.
Herr, Norman. The Sourcebook for Teaching Science, Grades 6-12: Strategies, Activities, and Instructional Resources. 1st ed. Jossey-Bass Teacher. San Francisco, CA: Jossey-Bass, 2008.
Symposium on "Post-Primary Seed Fate: Predation Secondary Dispersal" Corporate Author, Symposium on "Post-Primary Seed Fate: Predation Secondary Dispersal", and Forget, Pierre-Michel. Seed Fate: Predation, Dispersal, and Seedling Establishment. Wallingford, Oxfordshire, UK ; Cambridge, MA: CABI Pub., 2005.
https://www.youtube.com/watch?v=wOIHzl2h9a8
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