Beach Explorations:
A Curriculum for Grades 5-10

Tidal Pool Populations

A population is a group of plants and animals of the same kind that live and reproduce in a particular area. Generally, smalll organisms have huge populations, while large organisms have small populations. For the students to see this, have them make a second chart and arrange the plants and animals in order, from those that have the largest populations to those that have the smallest populations:

Tidal Pool Number
Plant or Animal
Class Totals
Checkered Periwinkles
Hermit Crabs
Shore Crabs
Tidepool Sculpins
Sea Lettuce

Discuss the Following Questions
  1. Which organisms have the largest populations? The smallest populations?
  2. How does the population of each kind of organism compare with its size? (Compared to large organisms, tiny organisms have huge populations to sustain their species because they are the food of countless larger organisms.)
  3. How might the population of each organism change with what it eats?
  4. Is it surprising to see so many organisms living in one tidal pool?
  5. Why is a tidal pool called a community?
Comparing Two Tidal Pools

Map a tidal pool high on the shore and a tidal pool low on the shore. Discuss the following questions:

  1. How are the two tidal pools similar? How are they different?
  2. Why is the water temperature lower in the low pool?
  3. Which pool has the greatest variety of life? Why is this so?
Brain-Buster Questions
  1. Does a tidal pool contain predators, scavengers, filter feeders, grazers? If so, what are they? (See "Getting Food," pages 125-130)
  2. How did the seawees, barnacles, and mussels in the tidal pool get there? (They settled out of the plankton, attached and began to live out their adult lives.) How did the crabs, sea stars, and sea urchins get there? (They likely moved into the tidal pool as adults.) (See the chapter on "Plankton Soup," page 91, and the lesson "The Life Cycle of a Crab," page 106.)
  3. What predator-prey relationships exist in a tidal pool? How could you find out?
  4. Why is a tidal pool called a community?
Preview Pages


overview of each chapter
page 13, 14

sample lesson, tidal pools
page 182, 183, 184, 185, 186, 187, 188, 189

sample lesson, adaptations of surf-dwelling rocky shore animals,
page 222, 223, 224, 225

sample lesson, vertical zonation,
page 202, 203