Survivor! The Intertidal Zone Challenge
Students make close observations of the characteristics of intertidal seaweeds and animals to support an argument that external and internal structures are parts of a system that function to support the survival, growth, behavior and/or reproduction of an organisms as a living system. After a beach field trip, they extend their learning about the interactions of components of a system by constructing and explaining a model of the internal and external anatomy of one intertidal animal.
Essential Question(s)
How do the internal and external structures of plants and animals function to sustain organisms as living systems?
How do intertidal animals use their external and internal parts and senses to survive?
PDF Investigation
Time Required
3 1-hour class periods + Field Trip
Life Sciences
Investigation Type
Field Trip, Classroom
Grade Level
NGSS Performance Expectations
Materials Needed

Backpack Activity
Marine Biologist Backpack:
Magnifying glass or hand lens, notebook, clipboard/Rite in the Rain paper, pencil, camera, tide book, identification field guide, field guide book (marine or freshwater), measuring tape or ruler, warm clothes, thermometer, maps, aerial photo, sampling jars, first-aid kit, flashlight, water bottle, snack, cell phone or VHF radio).

Backpack of subsistence/recreational harvester: Tide book, flashlight, pail, gloves, hat, raincoat, piece of net, knife (pretend), fishing pole, berry-picker, map, identification chart, water bottle, snack, cell phone or VHF radio.

Backpack for students going on a beach field trip: Whatever is needed for your students to stay dry, warm, and safe during the field trip. (e.g., water bottle, rain gear, warm hat, gloves, etc.)

Field Trip

Shallow observation trays
Field guides
Identification charts
Quadrats (See How to Make a Quadrat)
Science notebooks (one for each student)
Survey tape to mark out “one small square”
Class Ipads or digital camera
Field microscopes (optional)

NGSS Performance Expectation

Students who demonstrate understanding can:

Construct an argument that plants and animals have internal and external structures that function to support survival, growth, behavior, and reproduction. 4-LS1-1

Use a model to describe that animals receive different types of information through their senses, process the information in their brain, and respond to the information in different ways. 4-LS1-2


Knowledge - Students will know that:
  • intertidal seaweeds and animals have internal and external structures that serve various functions in growth, survival, behavior, and reproduction.
  • different sense receptors are specialized for particular kinds of information, which may be then processed by the animal’s brain. Animals are able to use their perceptions and memories to guide their actions.
Skills - Students will be able to:
  • identify different internal and external structures of an organism and construct an argument based on evidence about how the structures support life functions.
  • use a model (drawing) to explain how a specialized sense receptor is used by an intertidal animal to gather a particular type of information that can result in behavioral responses.
Local and Cultural Connections
Invite people who harvest seaweeds and marine invertebrates from local beach to your classroom to tell or show students what parts (external and internal) of food plants and animals they eat or use for medicine and discuss reasons why they don’t eat other parts.
Teacher Preparation

Make copies of the Intertidal Challenge for hand-outs

Prepare a template on Google Slides for students to create their presentation.

For field trip:

See guidance for planning field trips.Gather equipment and supplies needed for the field session.

Cut up survey tape into 1 foot long pieces so students can make their “one small square.” (4 pieces/student)

Make copies of the Intertidal Zone Sensory Experiments for each student to glue into their science notebook the day before the field trip.

Learning Experiences


(45 mins.)

Present students with the Intertidal Challenge.

Brainstorm a list of plants and animals they have seen on the beach during field trips or other visits to the beach. Tell them the focus question for their beach field trip will be: How do different plants and animals do the things they need to do to survive, grow, and reproduce despite the intertidal challenge?

Show videos (See links in Resources section) so students can observe the external structures of different marine invertebrates and how they function and behaviors of marine invertebrates in response to chemical and tactile clues.


1.  Revisit the word “function” and discuss what functions happen every day for the animals like the ones they just saw in the videos and for seaweeds.

2.  Write them on the board as sentences, using the sentence starter: “All plants (or animals) . . .” or “All plants (or animals) have to . . . “

3.  If they don’t think of these functions, add these to the list:

All plants have to take in light, air (carbon dioxide), water, and minerals to make their own

All animals move.

All animals sense the world around them in different ways.

All animals have to find food. They eat plants, other animals, or both.

All animals have to protect themselves from getting injured or eaten by other animals.

4.  Unpack what it means to “sense the world.”

5.  Ask students to draw two animals they predict they will see on their field trip and what they might see if they use a magnifying glass to get a closer view at some part or parts of the animal’s bodies that are used for on the functions on the list in an interesting or unique way.

6.  Students draw and write their predictions in their science notebooks. For the close-up view, they may use a Closer and Closer page that has been glued into their notebook.

7.  Students share their thinking, drawing, and writing with each other. This can be done in partners, small groups, or in the large group taking turns. After students have shared with each other, brainstorm about where they will look for the animals they have predicted they will see. Encourage students to explain their thinking by asking questions such s:

Why would you look there?
What do we know about this plant or animal? 
What kinds of structures do you think plants need? 
What structures have you seen on animals at the beach that function in these ways?

EXTENSION: Do the activity How Do Whales Hear? (See Resources section.)

Field Trip Preparation in the Classroom


See the activity Using Backpacks in Learning Centers

1.  While you are pulling things out of the harvester backpack, increase the focus on the cultural importance of beach food resources asking:

Why would I need to take this if I’m going to the beach to find some food?
How will I use it? (In other words,) what is its function?

Accept all reasonable answers. After you have emptied this pack, explain that when someone goes to the beach to harvest plants or animals for food, they are a predator like all other animals that eat plants, animals, or both. As a human, you take things, or tools, with you to use in harvesting. Reinforce the idea that some of the plants and animals they will be studying as scientists when they go on their beach field trip are also eaten and some are very important to subsistence users who have depended on these animals for foods for thousands of years. This is also a good lead-in to beach etiquette rule

2.  Ask: What do other predators use to capture their food? Help them come to the conclusion that every animal has some body parts it uses to get its food and has other body parts that are inside its body that digest the food and move the energy from the food through its body so it can survive and grow.When you are taking items out of the biologist backpack, one by one, ask:

Why would I take this to the beach if I’m going as a scientist?
How could I use it? (In other words,) what is its function?
What’s different about these tools compared to the ones I showed you for my subsistence harvest trip?

3.  After you’ve have emptied the pack, ask students what other scientific equipment they would like to take to the beach as tools. Review some of the “scientific tools” that we will have to assist their research. The students likely suggested microscopes, shovels and buckets as tools. Bring them out and share with students why we’ll be using trays vs. buckets for this trip.

4.  Finally, show them items that you will want them to bring on the field trip by unpacking the student backpack. Discuss the expected weather and what they, as human animals, will need to bring as their “external structures” (e.g., rain gear, warm clothes) to “survive” and be comfortable and safe. Make connections to their internal structures (e.g., they’ll be drinking water and eating snacks which will go into their stomach, they’ll be using their brain to remember the names of the plants and animals they see, etc.)

5.  Give them the intertidal zone experiments to glue into their science notebook or hand them out on the field trip if the students will have clipboards.

Describe how long the field trip will be and explain there will be boundaries set for where they may explore and that those will be pointed out when they arrive at the field site. Explain that there will be boundaries set for where they may explore and that those will be pointed out when they arrive at the field site.

Field Trip


(20-30 mins.)

After you arrive at the field trip site, keep students together to go over safety rules:

  • Have a partner
  • Stay within boundaries
  • Watch where you step
  • Be able to see the “gathering area” from wherever you are

Describe the boundaries of the area students should stay within and the signal you will use to bring them back together after 20 minutes. Review the focus question for the exploration time:  What can I observe plants and animals doing (staying wet, feeding, moving, hiding, etc.) and what kind of structures are they using to do it?

Remind them of the sensory experiments they can do with animals to find out what kind of senses different animals have and where they’re located.

Encourage students to use all their experiences and knowledge from the previous investigations and beach field trips to explore the local area and look, share, and identify plants and animals and look closely at their structures and how they do the things they do.

If elders or community partners are in attendance, ask them to share their discoveries with students out loud.


(1 hour)

1.  Gather the students together to being a structured exploration. Each student will explore “one small square” of the beach by marking it out with survey tape. Remind them to focus on structures of plants and animals and how they function.

2.  Tell them to take notes in their science notebook with as much detail as possible so they will remember what they observed. If they know the type of plant or animal (green seaweed or snail) inside their square, they should use that and if they know the name of that type of animal, they should write that down (sea lettuce, periwinkle snail). If they don’t know either one, they should create a descriptive name (small, red worm).

3.  After they have completed their drawing of what’s inside the square and taken notes about structures and their functions, Students can come back together to share what they’ve learned in a variety of ways. You could divide them into pairs to share their findings or each student could first share with one other student and then find two more partners with whom to share findings. You could also bring the whole group back together and then have students pair up. Students can also send photos to the teacher from a phone for a compiled Google slideshow later.

4.  Encourage children to discuss the different external structures that students discovered on plants and animals with each other and how they think they function.

5.  Are you able to sort them by function? Did you discover external structures that were new or surprising? If you were able to adopt a structure onto their own body, which would they choose?

6.  The goal is to have students share their thinking and understanding of what they have found. Ask some students with detailed drawings to share their entries as a way to model how to add details, labels, and explanations for local plants and animals.


If you are able to visit more than one type of habitat during the field trip (e.g. low intertidal and upper intertidal or river bank and river’s edge) students can make their “one small square” observations in both habitats and then compare and contrast what they observed. This is a very important concept when learning animal-habitat associations in coastal marine and freshwater environments.

Back in the Classroom


(30 mins.)

Guide a debrief session of the field trip.
What did we find out?
How can we share this information?
How did we gather information?
What kind of ways can we use this information to inform others?
What else could be done with this information?
How will we continue to learn about the local aquatic plants and animals in our area?

Assign each student one animal or seaweed that the class observed on their field trip or let them choose one. Their task is to find out about the digestive and nervous systems of animals and the function of internal structures in seaweeds. They will make models of their plant or animal, labeling the different internal and external parts. Give students choices for the media they want to use to create their models.

Drawing: Students can use colored pencils to draw and label external views of the animal from observations in their science notebook or from a digital photo and an internal view from a diagram in a reference book or online image.

Digital model: Students can use a photo of one of the plants or animals from their field photos to create an external anatomy poster. They will also need to find a diagram online that shows the internal anatomy of the digestive and nervous systems, add a title and labels for structures and their functions on slides in a Google Slide show.

Clay model: Students can use modeling clay to create a plant or animal of their choice with post-it tabs added to label the structures and their function. They will need to create a model of the digestive and nervous systems or make a drawing with labels.

Using their animal models, students will then make a class presentation that argues from evidence they either recorded on their field trip or found during their research that specific parts of their animal function differently or the same as structures with a similar function in humans. They will develop arguments for:

  1. one internal structure (e.g, stomach, nerves, brain)
  2. one external structure (e.g., arm, leg, head), and
  3. one sensory structure (e.g., light-sensing structure, a structure that can detect odors.

Using their seaweed models, students will make a class presentation that argues from evidence they either recorded on their field trip or found during their research that specific parts of the seaweed function differently or the same as structures with a similar function in green (land) plants.


Formative assessments:

  1. Peer review of prediction. Is it detailed enough that another student can identify the plant or animal they hope to see?
  2. Review the quality and quantity of work in science notebooks: inclusion of the date for observations, picture, labels, what student considers their best work, usability and quality of the data they collected, reflections on their field experience

Summative Assessment: Evaluate models on their quality as models and the accuracy of the labels. Evaluate the presentations on the quality of the arguments, the extent to which the arguments are supported by evidence, and a demonstration of understanding about the relationships of individual structures as parts that function to support the survival of the organism as a living system.

#res58Intertidal Challenge Hand-out  
#res59Intertidal Zone Sensory Experiments  
#res44Life of the Beach: Among Friends and Anemones

DVD with beach etiquette messages and an introduction and footage of animals typically found in different intertidal zones on Alaska’s rocky beaches.

#res61Intertidal Biome

Introduction to tidal cycles and life in the “washing machine” of the intertidal zone

#res62Mollusk Diets

Slide show illustrates mollusk anatomy and the function of feeding structures

#res63Spiky Sight

How sea urchins see with their spines over their entire body.

#res64My date with a Giant Pacific Octopus


#res65Color changes in octopuses and squids(video)  
#res66Experiments with octopuses(camouflage)  
#res67How Do Whales Hear?  
Anatomy Diagrams
#res69Sea star anatomy  
#res70Bivalve anatomy  
#res71Seaweed anatomy  
Teacher Background
#res147Structure and Function: Marine Animal Examples

Examples of a variety of internal and internal structures of Alaska marine invertebrates in relation to how they are used for different types of functions.

Teacher Background

Internal and external structures of marine invertebrates that support basic life functions are very different from those of humans and other vertebrates. For example, some marine invertebrates circulate water under pressure in structures that function as a hydrostatic skeleton to support the body instead of having a skeleton made out of bones. Others circulate fluids that function like blood in open systems instead of closed systems like veins and arteries, and they utilize a different pigment for carrying oxygen than hemoglobin so is not red when exposed to air. Sensory receptors are often distributed throughout the organism, rather than being concentrated in sensory structures like eyes, ears, and noses and the “brain” many also be distributed throughout the body. See the attached table of Structure and Function: Marine Animal Examples of specific structures and their functions as well as marine animal behaviors and the types of sensory stimuli that evoke them.

For more information about how function can be inferred from the structure of bivalve shells, see Reading Information from Empty Shells.

Prior Student Knowledge:

Students may be somewhat familiar with different seaweeds and animals that live in the intertidal zone if they have already gone on beach field trips in earlier grades. The NGSS emphasis in first grade is on making observations of external structures, such as shells, and making connections to their how they function to help plants and animals survive. The NGSS emphasis in 4th grade is on: 1) both external and internal structures and function in the organism as a whole or system of interacting parts and 2) the use of information from the environment received by sense receptors that result in behavioral responses by organisms with an information-processing brain.

Possible learner preconceptions, misconceptions and instructional clarifications:

Learner Preconception/misconception: Students may not think about plants or seaweeds and animals as systems made up of interactive parts that are both external and internal.

Instructional Clarification: Students can grasp the connections between external and internal parts with opportunities to view diagrams that display ways in which they are connected and function together.

Learner Preconception/misconception: Students may have a hard time understanding that although the internal and external structures of marine invertebrates are very different from those of humans and other vertebrates, they function in the same ways to support life.

Instructional Clarification: Function is a more abstract concept that structure so students will need multiple opportunities to make connections and be reinforced in their thinking about how something works, or functions, in the context of staying alive, growing, and reproducing. Emphasizing the challenges to survival that all plants and animals face in any environment and then the more specific challenges posed by the intertidal environment can help students focus on understanding the many different ways plants and animals have solved the same problems. The videos and simple experiments in this investigation can provide opportunities for students to observe behaviors and then infer sensory perception and the type and location of sensory receptors on animals.

Components of Next Generation Science Standards Addressed

Science & Engineering Practices

Engaging in Argument from Evidence
Construct an argument with evidence, data, and/or a model. (4-LS1-1 )

Developing and Using Models
Use a model to test interactions concerning the functioning of a natural system. (4-LS1-2)

Disciplinary Core Ideas

LS1.A: Structure and Function
Plants and animals have both internal and external structures that serve various functions in growth, survival, behavior, and reproduction. (4-LS1-1)

LS1.D: Information Processing
Different sense receptors are specialized for particular kinds of information, which may be then processed by the animal’s brain. Animals are able to use their perceptions and memories to guide their actions. (4-LS1-2)

Cross-Cutting Concepts

Systems and System Models
A system can be described in terms of its components and their interactions. (4-LS1-1), (4-LS1-2)


Common Core

SL.4.5 - Add audio recordings and visual displays to presentations when appropriate to enhance the development of main ideas or themes. (4-LS1-2)

W.4.1 - Write opinion pieces on topics or texts, supporting a point of view with reasons and information. (4-LS1-1)
Alaska Cultural Standards
A.4) Practice traditional responsibilities to the surrounding environment.

E.2) Understand the ecology and geography of the bioregion they inhabit.
Developed by Katie Pittman, Juneau School District. Adapted for Alaska Sea Grant by Marilyn Sigman.
Last Updated on
Last Updated by
Marilyn Sigman