Students who demonstrate understanding can:
Students who demonstrate understanding can:
Support an argument that plants get the materials they need for growth chiefly from air and water.
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. 5-PS3-1
Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment. 5-LS2-1
Review the teacher background section and the Alaskan intertidal and ocean food web models (links in the Resource section). NOTE: Not all of these models include the recycling of nutrients through decomposers.
Make field trip arrangements - buses, lunches, permission slips, life jackets (if applicable), volunteers, etc.
Gather nonfiction books, web links, and other resources for student research and/or schedule library time.
See the Resources section below and the Field Trip Resources page for links to online sources for student research.
Ask the students: Where do plankton get their food? Guide them in a discussion about the differences between phytoplankton and zooplankton. (Phytoplankton uses the sun to make its own food through photosynthesis. Zooplankton eat phytoplankton.) You can also review the differences between meroplankton and holoplankton that were described in the video, using barnacle and crab larvae as examples of holoplankton that eventually settle on the beach.
On a large piece of chart paper or a whiteboard, draw the sun and plankton and use arrows to show the flow of energy from the sun to the phytoplankton, to the zooplankton. (The arrows that show the flow of energy should begin at the sun and move out in order to describe the correct flow of energy in the web. The arrows that also show the movement of matter should point in the direction that matter is moving rather than in the direction from “who” is eating a plant or animal to the “whom” they are eating. Students often draw the arrows the other way in food webs.)
Add seaweeds as producers to the base of the food web. Ask students: What other types of matter are needed for phytoplankton and seaweeds to make their own food? (light and air in the form of gas dissolved into the water) Discuss the reason why seaweeds are only found in shallow water (They have to be able to grow tall enough that their leaf-like blades can float near or at the surface of the water and capture enough light for photosynthesis.) and why phytoplankton are only found in the top layer of the ocean (where there’s enough light for photosynthesis at least part of the year in northern waters).
Ask students what eats plankton and seaweeds. Distinguish between animals that eat phytoplankton and those that eat zooplankton or both. Allow students time to think and share their ideas. Remind them that many types of plankton are one-celled organisms that can be filtered out of the water as a way to capture them for food.
Guide this discussion and add the names of fish, marine birds, and marine animals to the chart. Distinguish between animals that eat plants (herbivores), animals that eat other animals (carnivores), and animals that eat both animals and plants (omnivores). Have students tell you where to add the arrows to show the direction of flow of energy and the recycling of matter). Include humans in the food web if they don’t think of it. Always start them back at the sun to describe the origin of energy in food webs.
Add dead plankton, seaweeds, and animals, at least one animal that eats dead things (a detrivore – examples: crabs, ravens, gulls) and a decomposer (example: bacteria).
Show the flow of matter into the phytoplankton and seaweeds after decomposition. (Students often leave the flow of energy and matter that happens through the process of decomposition out of food webs. This way of doing it demonstrates the cycling of matter that occurs after decomposition is completed.)
After you have provided students an orientation to the field trip site and reviewed beach etiquette and safety rules, provide them with 20-30 minutes to explore within boundaries. Their focus questions are: Who eats whom? What evidence can you find of animals feeding or being eaten? Where on the beach and in the water do you find seaweeds? In what types of places are seaweeds absent?
Chaperones can help the students find evidence that might include:
Bring the group back together and have them share their evidence.
Intertidal/Beach Food Chains: Divide the class into groups of three or four. Their task is to move from the lower intertidal zone to the upper intertidal zone (Use a band of mussels or rockweed as an indicator of the middle intertidal if there is one on the beach or kelps as an indicator of the lower zone.) and try to construct at least one food chain in each zone. The food chain needs to include a producer, an herbivore, a carnivore, and a detrivore (that feeds on dead things). They should use the species name if they know it, but if not, they can make a drawing and write a description (e.g., a green film on a rock, a brown kelp with holes in the blades).
Plankton Tow: Plankton sample can be collected in shallow water offshore of the beach, from a dock,
or at another predetermined water source.
Make sure the samples are put into a container with a lid for safe transport back to the classroom. If your net is constructed with a bottle that has a cap, you can simply put the cap on the bottle. If there is no cap, students can pour contents into a clean plastic container with a lid.
Provide website links or book for students to use to identify their plankton to a species group (Identification to species is difficult.). (See the Resources section for links.)
Making a technical drawing of plankton
Start with a practice sketch of a familiar item. This lets students practice the detail in which they are sketching. Bring in a fish, apple, plant, soccer ball, or class pet and model the detail in which the students should sketch. This is also a great time to introduce scale as a math extension.
It may be a challenge for some students to find and focus in on live, moving plankton. You can complete this activity in two days; the first day, students can sketch plankton from examples in Zoom Gallery (species shown are pond plankton) and the second day, they can sketch live plankton.
Select four different varieties of plankton and do the activity again. If you are feeling ambitious, have students sketch ALL the varieties of plankton in the Zoom Gallery and arrange them from the smallest to largest!
(Adapted from Catch & Sketch Plankton, Arizona State University School of Life Sciences https://askabiologist.asu.edu/experiments/sketch-plankton/for-teachers)
Harmful Algal Bloom Monitoring
Involve your students in learning about harmful algal blooms and becoming citizen scientists who monitor phytoplankton in either fresh water or salt water. For more information and training, see https://products.coastalscience.noaa.gov/pmn/. This website also has a downloadable mobile app for identifying the most common saltwater phytoplankton and pronouncing their Latin species names correctly: https://coastalscience.noaa.gov/exit/?url=http://www.gano.name/shawn/phyto/
Other lesson plan and worksheets are available at It’s a Plankton Eat Plankton World Packet.
Refer back to the food web the class constructed before the field trip. Ask: What evidence did you find at the beach about who eats whom? Compile the answers on a whiteboard.
Ask: How do we know what animals eat if we can’t observe them often enough to know everything they eat? Call on students to share their answers and lead the discussion to how scientists look in the stomachs to determine diet or help them recall what they learned about the feeding structures and digestion systems of specific animals they may have observed in animals on previous field trips (e.g., filter-feeders, feeding structure of a sea urchin, clam siphon).
Have students select one local animal they observed on the beach to find out what they eat and what eats them using the evidence listed on the whiteboard, books and/or the Internet to create a food chain poster for their animal.
Students present their food chain posters to the class.
When students are finished presenting, facilitate making the creation of a diagram or mural of a food web involving more than one food chain.
After the food webs are completed, ask the students: Where do all of the food chains start? Are there other ways some of these organisms are connected? What is the difference between a food chain and a web?
Adaptations and Variations:
Students can cut and paste pictures, rather than draw.
Students can create a Google Slide or Web Poster instead of a drawn/colored poster.
Students can play a food web game, using the information they have collected to make connections with other species using yarn or string.
EXTENSION: The Alaska Seas and Watersheds unit The Case of the Missing Sea Otters provides an opportunity to explore what happens when a species is removed from the ecosystem and when people and other predators compete for the same prey species.
Use the student posters, class presentations, and participation in the development of a food web diagram to assess student understanding of the following concepts:
|#res116||Building a Plankton Net|
|#res117||The Invisible Watery World of Plankton|
|#res138||The Power of Plankton|
|#res118||The Secret Life of Plankton|
|Images of Alaska plankton and other marine species|
|#res114||Phytoplankton Line Drawings|
|#res115||Zooplankton Line Drawings|
|#res119||The Kachemak Bay Research Reserve Plankton Coloring Book|
|#res120||Images of marine organisms including fish and marine invertebrate larvae|
NOAA Auke Bay Laboratory, NOAA Fisheries
|#res121||Photographs of phytoplankton|
|#res122||Plankton Identification Cards and Dichotomous Key|
Alaska SeaLife Center
|Images of Alaskan species with information about food web connections|
|#res76||Food Web Cards: Rocky Intertidal Habitat|
|#res74||Food Web Cards: Mudflats|
|#res81||Mudflat food web||Kachemak Bay. Dennis Lees.|
|#res139||Ocean Food Web Cards|
|#res110||Arctic Ocean Food Web Cards|
|#res21||Ocean plastic smells like food to marine animals|
|Species Profiles on Alaska Department of Fish and Game|
|#res123||Invertebrates - Species Profile|
|#res124||Fish - Species Profile|
|#res125||Birds - Species Profile|
|#res126||Mammals - Species Profile|
|Alaska Intertidal and Ocean Food Web Models|
|#res112||North Pacific Food Web|
|#res111||Gulf of Alaska Food Web|
|#res113||Marine Food Web|
|#res128||Arctic Ocean Food Web|
Arctic Ocean Food Web includes phytoplankton, zooplankton, and sea ice algae as producers.
|Nonfiction Children’s Books|
|#res129||Ocean Sunlight: How Tiny Plants Feed the Sea|
By Molly Bang and Shirley Chisholm with an accompanying science/ELA lesson plan
|#res130||Sea Soup: Phytoplankton|
By Mary M. Cerullo
|#res131||Sea Soup: Zooplankton|
By Mary M. Cerullo
|#res132||This is the Sea that Feeds Us|
By Robert F. Baldwin
|#res133||A Whale’s Tale from the Supper Sea|
By C.J. and Ba Rea (written about the Kenai Fjords area)
|Resources for Extensions|
|#res134||Catch & Sketch Plankton|
ASU School of Life Sciences
|#res135||PLOSABLE Are Plankton Super Stars|
|#res136||Whale Jenga Food Web Game|
|#res137||Meroplankton vs. Holoplankton||Video|
In 5th grade, the emphasis in the NGSS Life Science disciplinary core ideas related to food webs is on tracing the food of animals back to plants and tracing the movement of energy in the food web back to the sun. Students should gain the understanding that plants take in matter that is not food (water, air, and what’s left at the end of the decomposition process) and turn it into food and extend their understanding about “who eats whom” to interconnections within food webs that facilitate the cyclical pattern of movement of matter through ecosystems.
For a brief (approx. 2 minute-long) overview of how scientific thinking has changed about food webs over the last 50 years and the importance of understanding ocean food webs and the role of humans in them, watch this video about marine food webs.
Beach field trips provide opportunities to watch food webs in action, with sea stars feeding on mussels or clams, submerged barnacles in tide pools using their cirri to filter the water like the baleen plates of whales, and clams squirting out their waste water after filtering sea water through their body. Many consumers in the intertidal zone graze on producers in the form of seaweeds and algal films on rocks; others filter sea water for both live prey and detritus. Many intertidal invertebrate and fish species are, in turn, prey for larger, more pelagic predators such as larger fish and marine birds and mammals which can also often be observed feeding nearshore.
While plankton are too small to be observed with the naked eye as other than stationary or moving specks, net tows can be taken in shallow water near shore or from docks to provide students the opportunity to view plankton under a field microscope or using microscopes back in the classroom. Green or brown chloroplasts can often be observed within transparent phytoplankton as well as movements of zooplankton seeking prey and moving their food through their digestive system.
The word “plankton” is derived from the Greek word “planktos” and means to drift or wander. Phytoplankton, microscopic, one-celled plankton that are capable of photosynthesis, are the base of the ocean food web. They use the energy from the sun to make their own food and, in the process, produce most of Earth’s oxygen in the ocean, the largest ecosystem on Earth covering 70% of Earth.
One-celled zooplankton eat phytoplankton; multi-cellular drifting animals like jellyfishes eat a variety of zooplankton. Zooplankton can be divided into two categories - meroplankton and holoplankton. Holoplankton spend their whole lives drifting and meroplankton, which include many marine invertebrates, spend the first part of their lives drifting and settle down on the bottom of the ocean or in the intertidal zone when they mature.
Plankton nets are used to collect plankton samples in either coastal waters or aquatic field trip sites like streams and ponds by plankton can also be sampled in the ocean using either nets or continuous plankton recording devices mounted on moving ships.
See the examples of Alaskan intertidal and ocean food web models. (Links in the Resources section.)
Students should have a basic understanding that plants use the energy from the sun and need air and water to make their own food through the process of photosynthesis. They should also know some intertidal ecosystem food chain connections if they have gone on beach field trips in previous years. The emphasis in 3rd grade is on relationships between external and internal structures and their functions so students should have some knowledge of how marine invertebrates capture prey and feed as a basis for thinking about which species they graze on or prey on and which species scavenge dead matter or feed on detritus on the beach.
Learner Preconception/Misconception: The producers in food webs are always plants. Plankton are plants at the base of marine food webs.
Instructional Clarification: There are many different kinds of plankton because the word plankton means that the organism is of a size, shape, and density that it drifts with ocean or stream currents. At this grade level, students can think of phytoplankton as “plant plankton,” although algae and cyanobacteria are both considered phytoplankton. Many zooplankton are one-celled but since the only criterion for being plankton is one of drifting in the currents, large multi-celled animals like jellies are also considered plankton.
The main producers in marine and intertidal food webs are phytoplankton and seaweeds. Their classification is confusing. Even scientists don’t always agree on which kingdom or kingdoms to put them into. Because phytoplankton (phyto – plant-like) are one-celled, they are often classified with one-celled zooplankton (zoo = animal) and other types of one-celled animals as protists in the Kingdom Protista. The instructional emphasis at this grade should be on where different planktonic organisms fit into food webs in terms of making their own food or consuming other plankton.
Learner Preconception/Misconception: Seaweeds are plants.
Instructional Clarification: As fifth graders explore marine food webs which have at their base producers that aren’t classified as members of the Plant Kingdom, it’s a good time to help them understand more about the complexity of grouping organisms and build on their knowledge about what plants need to survive and aspects of plant structure and function from earlier grades.
Seaweeds are macroalgae (macro = big, but there is no agreed-upon definition for algae.) All seaweeds are photosynthesizers and they lack structures that other members of the plant kingdom have. Still, some algologists (scientists who study seaweeds and other algae) place green and red seaweeds in the plant kingdom while they place brown seaweeds, which include the kelps, in a separate kingdom with one-celled diatoms and dinoflagellates. Given the complexity of the science and the lack of agreement, it’s probably best in upper elementary to allow your students to think of seaweeds as “the plants of the sea,” and phytoplankton as the “plant plankton.”
Learner Preconception/Misconception: Seaweeds aren’t plants because they don’t grow in soil.
Instructional Clarification: While it’s true that seaweeds lack roots which means they can grow on the beach or on the ocean bottom in shallow water, that doesn’t mean plants need soil to get what they need to photosynthesize. Plant matter actually comes mostly from air and water, not soil, and phytoplankton and seaweeds are also able to obtain what they need for photosynthesis from water and air. They can also obtain some of the carbon dioxide they need in the form of gas dissolved into the water. You can ask students about their experience with hydroponic gardening as evidence that plants can grow in water.
Learner Preconception/Misconception: All animals that eat dead plants and animals or detritus are decomposers.
Instructional Clarification: Scavenges like crabs, ravens, and bottom fish are scavengers. They are consumers of organic matter in large lumps which aren’t broken down into inorganic minerals and nutrients that plants can recycle in photosynthesis. Detrivores like some marine worms consume much smaller clumps of detritus much like earthworms on land as do sea slugs. All of these detrivores speed up the decay process. Decomposers like bacteria and fungi complete the process by metabolizing detritus on a microscopic scale. Detritus feeders and decomposers can thus both be considered decomposers in marine food webs but scavengers are not decomposers.
The assessment probe Ecosystem Cycles developed by Page Keely can be used as pre-assessment of student understanding of these concepts.
Developing and Using Models
Use models to describe phenomena. (5-PS3-1)
Engaging in Argu-ment from Evidence
Support an argument with evidence, data, or a model. (5-LS1-1)
Developing and Using Models
Develop a model to describe phenomena. (5-LS2-1)
PS3.D: Energy in Chemical Processes and Everyday Life: The energy released [from] food was once energy from the sun that was captured by plants in the chemical process that forms plant matter (from air and water). (5-PS3-1)
LS1.C: Organization for Matter and Energy Flow in Organisms: Food provides animals with the materials they need for body repair and growth and the energy they need to maintain body warmth and for motion. (secondary to 5-PS3-1)
Plants acquire their material for growth chiefly from air and water. (5-LS1-1)
LS2.A: Interdependent Relationships in Ecosystems: The food of almost any kind of animal can be traced back to plants. Organisms are related in food webs in which some animals eat plants for food and other animals eat the animals that eat plants. Some organisms, such as fungi and bacteria, break down dead organisms (both plants or plants parts and animals) and therefore operate as “decomposers.” Decomposition eventually restores (recycles) some materials back to the soil. Organisms can survive only in environments in which their particular needs are met. A healthy ecosystem is one in which multiple species of different types are each able to meet their needs in a relatively stable web of life. Newly introduced species can damage the balance of an ecosystem. (5-LS2-1)