Once Upon a Seashore:
A Curriculum for Grades K-6

At Low Tide, Seashore Animals Close Up Tight

Concepts
  1. At low tide the seashore is exposed to air, wind, rain, sun and freezing cold.
  2. To survive, seashore plants and animals must keep from drying out a low tide.
  3. Tidal pools, crevices, cobblestones and seaweeds provide protection for animals that cannot stand exposure to drying out during low tide periods.

Understandings
The children will be able to 1) describe the seashore plants and animals at low tide, 2) identify conditions at high tide and at low tide, 3) describe and dramatize how seashore plants and animals keep from drying out at low tide, and 4) draw pictures of seashore animals at high tide and at low tide.

Materials
Transparency: "Dock Piling at Low Tide"

Background Information
Twice each day the tide rises and falls. Twice each day the seashore is either covered with seawater or exposed to air. It's tough for animals to live in a place where sometimes they're under water, sometimes they're high and dry, sometimes fresh water rains down, sometimes salt water covers them, sometimes cold waves crash over them, sometimes the air is freezing cold, and sometimes they're left out in the hot sun.

At low tide (or when out of seawater) plants and animals must be able to retain moisture for long periods of time, especially those that live high on the shore. During periods of heavy rain they must tolerate rapid changes in the salt content of the water.

At low tide (or when out of seawater) barnacles close up their six hard crusty shell plates to create a moisture-filled shell. Mussels and clams close their twin shells and close their foot like a little trap door. Limpets and chitons pull their fleshy foot inside the shell and plaster themselves to the rocks with a very tight suction. Shore crabs hide among wet seaweeds or scurry into sheltered rock crevices, crawl under rocks or creep into tidal pools. Hermit crabs pull their soft curled bodies, the two long antennae, and the six pairs of walking legs deep into their mobile snail home. They use their large claws for blocking the entrance to the shell. Before the tide drops, sea stars take in seawater and firmly attach their tube feet to rocks or to whatever they happen to be eating. Sea anemones draw in their tentacles and close up their sac-like bodies, with their stomachs full of seawater. Sea urchins attach some of their tube feet to rocks and dig their long sharp spines into cracks and crevices. They keep a strong foothold and stay moist and cool inside their bristling water-filled shell. Tidepool sculpins either swim out to sea with the outgoing tide or become stranded in open pools of seawater. Blennies swim out to sea or hide in dark moist places among seaweeds, under rocks or in rock crevices.

At low tide seaweeds lie flat across the rocks or hang down in curtains, keeping the wetness in and under them. Rockweeds have floating gas-filled air bladders and thick fleshy stems and blades that keep the wetness in.

Procedures
  1. Who has been to the seashore when it was low tide? How did you know it was low tide?
  2. When the tide is low, what is life like for seashore animals? Allow an open-ended discussion.
  3. Review the concept of a tidal pool. How does life change (or does it change) for tidal pool animals when the tide goes out?
  4. When the tide goes out, how does life change for seashore plants and animals that are not in tidal pools? For animals on rocky shores or on dock pilings?
  5. What makes seashore animals dry out at low tide? (The hot sun, air, wind).
  6. How might animals that are attached, such as barnacles, keep from drying out? (The barnacle's shell is filled with moisture).
Preview Pages

cover

overview of each chapter
page 12, 13

sample lesson, hermit crabs
page 67, 68, 69

sample lesson, low tide
page 123, 124, 125

sample lesson, high tide
page 126, 127, 128

sample lesson, a trust walk
page 240