Tidepool Island Biogeography

Lesson Plan by Tania Kim

General Information

Location:  This can be conducted anyplace with tidepools.  It was originally planned for execution at The Scripps Coastal Reserve.

Duration:  Field: one day (2 hours out in the tidepools is more than enough)
Class: one intro lesson, and a data analysis lesson and discussion minimum. May be expanded before field and after field-with reports and more background given.

Grade Level:  7-12, adaptable
This lesson can be used directly or modified to satisfy any of the standards having to do with diversity, biomes, adaptation and form and function as well as the scientific method and scientific investigation techniques.


Intellectual: Students will get hands on experience and test island biogeography ideas by comparing diversity and abundance of rocky inter-tidal patches. Depending on the grade level and time in depth background lessons of inter-tidal species can be added before the students come out to the tidepools.

Social: Students will work in groups of three, each student will have a task and the tasks will be rotated throughout the activity. This will enable students to get to know classmates in an out-of classroom experience, also they will interact socially with students they otherwise would not get to know. This will promote better classroom dynamics and an environment of cooperative learning and mutual support.

Personal: The tasks and trust that develops in the teams helps build self-esteem and promotes the development of personal interests by expanding the opportunity for discovery and personal inquiry in the field (even if not directly related to the academic lesson at hand).

Lesson Development

This lesson was designed as a cooperative learning and field experience in which students are individually assessed by writing their conclusions. This can be easily modified to group or other types of assessment. The concept of island biogeography can be tested in a standard test, the main objective is to reinforce the concept but most importantly to expose students to a local habitat and one way science is done through observation and record keeping. It is important to allow students to do each task whenever possible and to allow them to explore and to foster their own curiosity. One of the possible extensions listed below would allow students to design their own project and be really engaged in the process of science (a California State Standard).


The teacher should have good command of what is in the tidepools, or have a field guide and be willing to learn along with the students.  Teacher may want to contact and inquire for information from reserve manager-who should be notified of trip BEFORE it takes place-in many cases the manager may be willing to interpret for the class. If you are taking your students to tidepools in a park or managed area contact the ranger first. If you are going to public unmanaged beaches and would like information contact any aquarium near you-they always have an education department and may be able to help you in your planning.

Make sure you have your transportation arranged and that you have checked the tide-tables-a low tide is must of course. Check with number of required chaperones-if not by the school then by the park or facilities you will be using.

Background Information

The amount of background information the students or teacher needs for this activity is variable and depends on the time given for the activity. If it is to be part of an in-depth unit on tidepools or ecology, then more background will be needed. The teacher must be familiar with the tidepools, be aware of low tides. The teacher would benefit from going out to the site and exploring on their own (plus it is fun!). This will enable the teacher to become acquainted with some of the organisms the students will be encountering and identifying on their outings. There are many guides and pamphlets available on tidepool creatures that the teacher can use with the students or even get an inexpensive class-set (waterproof if possible-also they are working in groups only one guide per group is required). A nice, waterproof visual guide is Mac’s Field Guide to California Coastal Invertebrates. 

Regardless of the level of background your students (or you) have, please make sure you do teach (and do the following):

  • When turning rocks over, do so with care-and put them back with care.
  • Watch where you step! Some of the “rocks” are animals!!! (Tube worms, barnacles, Anemones) And even if you’re not stepping on an animal, the rocks tend to be slick, as you are probably standing on algae.
  • If you pick anything up, put it back exactly where you found it. (Encourage students to not pick anything up)
  • If you pick anything up, put it back exactly where you found it. (Encourage students to not pick anything up)
  • Explain to students that tidepools are fragile and care must be taken when enjoying them.

This lesson can be used in a tidepool (habitat unit) or Island biogeography unit. Depending on your teaching style, it can be used at the beginning, middle or end of a unit. As an introduction students would be allowed to discover more on their own. In the middle will keep the momentum of the unit, and at the end it will be a nice review and bring closure to the concepts.

If the emphasis is island biogeography, it is up to you whether you assign reading from the text before the students venture out to record and measure in the field.

If the emphasis is on tidepools or diversity then there are lots of videos on the topic or on specific species-such as sea stars. Students can prepare reports on tidepool creatures and then present their finding in the field.


  • note: lessons discussing island biogeography using text may precede the field-concept: larger islands have greater diversity and abundance than smaller islands.
  • Lesson 1-preparing your students for the field
  • What is a tidepool or the rocky inter-tidal?-ask students-initiate a discussion.
  • After students all know what habitat you will be visiting, make sure they are aware of proper behavior/treatment of area-see above.
  • If you have slides or props to demonstrate the following methods great-otherwise-you’ll have a chance to demonstrate to the students in the field.

Field procedures

  1. In each assigned group of 3 there are three tasks: recorder, measure person, species counter.
  2. Recorder: will record the dimensions and general shape of the rock the measure person calls out on the data sheet. Will also record the information provided by the species counter.
  3. Measure person: will measure, using the meter stick the dimensions of the rock-before it is turned over. The student also will assess if the rock is more similar to a circle or a square and the appropriate dimensions will be taken to calculate area. (Circle-student measures diameter, square/rectangle-student measures length and width). This student will also aid the species counter once the rock is turned over or lifted)
  4. Species counter: will note how many different species are found on/under rock and the number of individuals in each species. The level of specificity here can vary: you can have your students classify all sea-stars together, all crabs, all snails, all anemones-or you can make sure you point out the differences between the species when you demonstrate the procedures in the field. Make sure students are quick-some species will immediately try to leave the area and they must be accounted for-plus the level and time the area is disturbed should be minimized.
  5. Each group will record data for three rocks-each time students will switch roles-enabling all three to take on all three tasks. If you have a very large group, or are in a small patch of rocky-inter-tidal consider having each group record data for just one island (rock).

Once you have gone over the field procedures in the class (again slides or props if available are helpful)-get the students into their groups and ask them to very briefly discuss what they expect to find in terms of the size of the rock and the number or species or abundance. Then have a class discussion.

Then each member of the team is to prepare a data sheet (one per rock)-these could be half-sheets to save paper. You can also prepare them ahead of time and photocopy them-but if you are limited on copies, have the students prepare their own-here you can let them design their own or have them copy it from an overhead-below is a suggested format.

When students are done with the data sheets, review proper behavior and attire for field trip. Students should wear shoes that they are willing to get wet and are safe to walk in while at the tidepools. In some cases they may go barefoot-check with your school, reserve manager or park ranger for what is best as well as liability (sad, isn’t it?). Students should bring water to drink, a snack if they want and sunscreen-if the weather is going to be cold-a jacket. If your class will be gone all day-then lunch and a backpack to carry all their stuff (including their trash out of the reserve). A towel is a great idea and possibly a bathing suit-but this will encourage your kids to go in and it may not be the best idea if you’ve got a big group and if you are in an unguarded area.

Lesson 2: In the Field

Once you get to the field, if you are lucky enough to have an interpreter-such as a park ranger or reserve manager-let them do their thing after a quick introduction and reminder to students of proper behavior. This will give the students a great chance to learn from someone who has a better base of knowledge in this area that you might.

Make sure you demonstrate the field methods in the field with some volunteers (or pick a student or two to help you). While you do this you can point out neat critters or facts about tidepools, beaches, oceans-whatever seems relevant at the moment. It is important that the students see the common things they will encounter with their groups, and they can identify them. Emphasize care with the habitat and with their feet-both for the sake of the plants and animals and their own safety. 

Allow student groups to collect their data and explore on their own. If time is a limiting factor-keep them on track!

Enjoy the tidepools with them, and enjoy them outside the classroom (or bus!).

If time permits you can picnic with your students-but make sure it is allowed first! Also do not have students seat at the base of cliffs or on the rocky inter-tidal zone. Move them to sandy beach or park area if available. Clean up is essential!

Lesson 3: Analysis and closure

Have each group calculate the area of the island they studied and record it on the board or overhead. Example below:

Area of island species diversity abundance of organisms

(# of different types) (exclude algae since not counted)

230cm 2 11 23

and so on-

Have students graph the data. If time is limited they can do this as homework-or you can do it as a class. x-axis: island size, y-axis species diversity. Other graph with abundance as the y-axis.

Discussion of results-Was it what students expected? Does it support the concept of larger islands having more species? If not, why?

Homework and assessment: Writing a discussion section of a paper based on the results obtained in the field and what we have learned about island biogeography with our text or supplemental materials.


  • Per group of three
  • meter stick
  • clipboard (or any writing surface)
  • data sheet
  • pencil/pen
  • field guide to tidepool organisms (optional).

Possible Extensions

Students are assigned or choose from a list of organisms selected by teacher (must be something that will be encountered in the field) and individual students research the organism. They will be presenting or teaching the rest of the group in the field during the demonstration by the teacher or just before the students work in their groups in the field. 

Student groups do the graphs and write the entire report together, peer editing between groups.

If access to tidepools is easy and time is available have students design their own projects (to be pre-approved by teacher) and carry them out in one or two more outings to the tidepools-for example: Is a certain species found only in islands of a certain size? This is time intensive and required lots of preparation and supervision. 

Students can also be asked to identify the different organisms as predators, prey, or if they are grazers and compare the composition between islands.

Downloads: Tidepool Island Biogeography data sheet