For each group of four students:
- Science notebook
- Laminated field guide to local plants (See Resources section)
- Plot sampling equipment (an embroidery hoops, metal clothes hanger shaped into circles, or quadrat)
- How to make a Quadrat (out of PVC pipe)
Optional: Cameras or camera phones for each group
NGSS Performance Expectation
Students who demonstrate understanding can:
- four distinct zones (habitats) exist on rocky beaches.
- there are many different kinds of living things in any area, and they exist in different places on land and in water.
- tidal cycles determine how long plants and animals on the beach are exposed to air and submerged in salt water.
- predict which zone (habitat) specific animals live.
- make observations to collect data and use it to make comparisons of the diversity in four intertidal zones (habitats).
- make observations to compare the physical characteristics of the zones (habitats).
- set up plots and collect data about diversity within the plot.
- analyze data to look for patterns and order based on their observations about the world.
- Collect the equipment and supplies for the field trip.
- Arrange for chaperones to help with groups.
- If possible, visit the beach at low tide before the field trip to see how distinct the four zones are.
- Check the tide schedule to decide if students need to begin their surveys in the splash zone or lowest intertidal zone that will be exposed during your field trip.
Before the Field Trip
- Go over the beach etiquette rules with students. They will be observing and counting animals but should handle them as little as possible and keep them wet.
- Show students the sampling equipment they are going to use and explain what a study plot is and how it is used to sample scientifically (selecting a small part of an area that is typical that can be used to characterize a larger area). Tell them they will be scientists on their field trip and will observe, sample, and count (survey) the animals in study plots in each of the four intertidal zones.
- If you think it is needed, give students an opportunity to practice setting up a study plot or plots in your classroom using the hoop, coat hanger circle, or quadrat. You can set out different combinations of “animals” represented by different types of objects (paper clips, marbles, small toys, etc.) to sample. (This also works well with different kinds of candy.) This practice sampling can be combined with student predictions about where they will find particular species.
- When you arrive on the beach, help students recall their prior learning about the intertidal zones and animals they would predict they would find in each zone in the classroom.
- Point out the four intertidal zones, using the rockweed/mussel zone to define the middle intertidal zone and the presence of lichens and only scattered limpets, periwinkle snail, and barnacles as the splash zone.
- Divide the class into teams of four. Give each team a hoop, circle, or quadrat, two field guides, pencils, and a science notebook for recording their observations and data.
- Remind them they are scientists who will be observing and counting (surveying) animals in their plot. Demonstrate them how they are going to lay their plot sampling equipment in the splash zone. Ask them to take turns selecting where to place their plot which should be somewhere in the zone that is somewhat “typical” in terms of how many animals might fall within the plot. (They can avoid dense mussel or barnacle patches if that’s not typical and they should not choose a place with very few animals if that’s not typical.)
- Tell them to record the following in their science notebooks a) the name of the zone, observations about the zone...wet, dry, rocky, flat, etc. b) a simple drawing of the shape of the plot and what they observe inside the plot, and c) a list of animals they see inside. They will then count and add a tally mark for each individual of each different kind of animal inside (Example: 1 tally mark for each barnacle they see inside the plot, so the tally for 4 barnacles = llll ). Since it’s likely they won’t know or recall the name of every plant or animal they see, ask them to use the field guides or come up with their own name for a type of animal they don’t know the name of. (Examples: “red worm,” “big brown snail,” “little pink snail”)
- Explain that they will have 15 minutes in each of the four zones to set up their plot and complete their survey and counts. Establish the signal your will make (whistle, etc.) that tells them it’s time to move to the next zone. Check for understanding of the task by asking students to “share with a friend” the first step (then 2nd, 3rd, etc) they should do in each intertidal zone. Dismiss groups with their materials after you check for understanding. (An adult volunteer for each team would be beneficial to keep students focused during their fifteen-minute surveys, help children with naming and spelling the names of species they know, helping them use the field guide to look up names of animals or seaweeds they don’t know, and creating tally marks.)
If they finish their survey before the 15 minutes is up, invite them to add details to their drawing and make more observations about the zone in their Science Notebook. If cameras or camera phones are available, ask the chaperones to take a picture of the plot for use back in the classroom and keep track of which zone the photo was taken in.
Depending upon the low tide/high tide cycle, students should start either with the splash zone or with the lowest zone that will be exposed during the time you will be at the beach.
Students carry out their sampling and surveys in each of the four zones with the teacher or a chaperone keeping track of the track of time and making the signal to move to the next zone.
At the conclusion of the intertidal zone survey, bring the groups back together. Ask students in each group to share their findings with another group.
After they have talked with one another, ask: In what zone did you find the most mussels, the fewest anemones, the most fish? Which zone was underwater? Which zone was dry? Which zone had grasses? Seaweeds?
Ask students to brainstorm explanations for their results and observations. Did different zones have the same species or was there a different diversity of species in the four intertidal zones? Why do you think there was more or less diversity in some zones than in others? What challenges to survival did animals need to meet in each zone? (The class discussion will support those who may have had difficulty understanding the concept of diversity. Sharing observations will also help to teach those who may need more guidance.)
EXTENSIONS: (60 mins.) This activity (using plots, sketching, surveying) can be done in other habitats to find the diversity of life, such as those they walk through getting to the beach (forest, meadow) or in other types of habitats (streamside habitat, freshwater wetlands).
Back in the classroom give students a 12” x 18” inch piece of construction paper. As a review of the class discussion at the end of the field trip, ask students to describe the pattern they observed over the four zones in terms of “most” and “least” number of different types of seaweeds and animals on one side of the paper. Guide them to fold the paper long-way twice into four equal parts. On the other side of the paper, have them label the intertidal zones at the top of each of four columns. Give students the option to write about, draw or cut out line drawings of intertidal animals (See Resources section for links to line drawings.) and place them in their zones. If you have pictures of their study plots, allow them to look at the pictures as they fill in their columns.
You can also provide a bonus question that they can also answer on the back of their tide zone model:
Why do you think you would find many barnacles in the splash zone and no nudibranchs or sea stars?
Note to teacher: Additional tasks will be needed to fully assess student performance for the ELA, Math, and cultural standards.
The variety, or diversity, of life on Alaska beaches often is distributed in distinct bands, or zones, of biological communities that parallel the shoreline. Shoreline zonation is most distinct on rocky beaches, particularly on the faces of large boulders or bedrock outcrops where the plants and animals that are adapted to life on the rocky substrate also are adapted to different levels of exposure to the tides. Where the tidal range is large, the zones are spread out and can provide excellent opportunities for students to observe a diversity of seaweeds and animals in each zone. In places where the tidal range is smaller, the zones will be compressed. The presence of large boulders and the type of rock that forms tide pools provides other opportunities to observe diversity over small areas.
The communities on these rock habitats are very different from those adapted to live in soft-bottom substrates of sand or mud. Some beaches are mixtures of rock outcrops, boulders, cobbles, and areas where sand and mud are deposited. Beaches with this mixture of substrate types support the largest number of different species, and therefore the highest biodiversity. Although this activity was developed for rocky beaches where the zonation is distinct, the same approach can be used on other types of beaches with more than one type of substrate (e.g., boulders, large and small rocks, sand, and/or mud or to compare and contrast the diversity in different types of habitats.
In Alaska, the tidal cycle is semi-diurnal, with two cycles of high and low tides approximately every day. (Approximately, because the timing of the tides is a result of lunar cycle of the “tug” of the moon on the Earth, and the lunar day is slightly longer than 24 hours). In some locations in Alaska, tides have a large range between the highest high tides and the lowest low tides because the shape of inlets and channels “squeeze” the incoming water and cause it to pile up along the shoreline.
Who or What Lives Where, and Why
Alaskaʼs beaches are dynamic and often harsh environments for plants and animals. However, many species are uniquely adapted to live “between the tides.” This section of shoreline, which is the area uncovered by the lowest tides and covered by the highest tides, is known as the intertidal zone. The distribution of plants and animals in the intertidal zone appears to be dictated by a combination of biological adaptations to physical conditions and to inter- and intra-species competition and predation.
Upper limits for plants and sessile (fixed) animals are generally set by their tolerance to physical factors, while the lower limits are often set by biological interactions.
The intertidal zone is progressively more crowded at the lower tidal levels where complex dramas are played out in competition for space and food and the avoidance of becoming food. For mobile animals, behavior often provides important adaptations that influence where they can survive.
The most important factors that determine the suitability of the different tidal zones as habitat for each plant and animal species are tidal dynamics, exposure to waves, substrate type, and ecological interactions.
- Tidal Dynamics. The range and timing of tides are the primary controlling factors that dictate what kinds of organisms inhabit each zone. The action of the tides moves the salt waterʼs edge up and down the land in a predictable and regular sequence. When the tide is out, plants and animals in the higher part of the zone are exposed to drying (dessication) and extremes of heat and cold. But organisms that have adapted to survive these periods are again bathed in the rich “soup” of the ocean, or made buoyant when the tide returns.
Lower down in the intertidal zone, exposure to drying and temperature extremes occurs less frequently and for shorter periods. A greater number of species is adapted to these less stressful conditions.
- Exposure to Waves. Wave action can extend the intertidal zone even higher up on the land, and strong wave action on open coasts can sweep away whatever is not clinging or firmly attached.
- Substrate Type: Rock, Sand, and Mud. Rocks of various sizes, from cobbles to boulders, provide plants and animals with a variety of niches (under rocks, in crevices and tide pools, on sides and tops of boulders) for potential attachment where the organisms can withstand the force of tides and waves and be sheltered from drying out and from temperature extremes. Animals that live on sandy beaches and mudflats must be adapted to burial by shifting sediments.
- Ecological Interactions. In addition to physical factors, relationships between and among organisms also affect and often control survival at any specific site. These relationships are especially important in the lower intertidal zone where competition, grazing, and predation control the composition of the biological community.
For more information about marine invertebrates commonly observed on Alaska beaches, see Meet the Invertebrates.
Splash Zone: The places on a beach exposed to occasional wave surges or spray of salt water often during storms. Seaweeds and animals found here have to be hardy to survive long periods out of the water, exposure to sun, and fresh water from rain. Diversity is the lowest of all the zones.
Upper Intertidal/High Tide Zone: Wet during high tides. This is the part of the beach exposed to air most of the time, covered only during the higher tides in the cycle. Few types of plants, seaweeds, or animals can survive being dry most of the time when the tide is out, being submerged in salt water occasionally, the risk of being washed away by waves, and exposure to temperature extremes often on a daily basis. Diversity is low.
Middle Intertidal/Mid-Tide Zone: Wet and dry. These are the places on a beach closest to “land” that is usually covered and uncovered twice a day by the tides and where exposure to air lasts longer during periods of higher and lower tides and for a shorter amount of time during more moderate tides. Diversity is higher than further up the beach but only of organisms that can survive life both underwater and out-of-water. The diversity includes more animal predators and their abundance can limit whether or not their prey can survive in this zone.
Lower Intertidal/Low Tide Zone: Usually wet.These are the places on a beach exposed to air only during the lowest tides. The highest diversity of both seaweeds and animals are in this zone because they only have to tolerate short exposures to air that don’t occur every day. Some animals become stranded as the tide recedes but others can move up the beach to find food. Predator-prey relationships affect survival in this zone as do other relationships between species, especially competition.
In the primary grades, the NGSS emphasize observations of patterns and a foundational understanding of relationships between the external structures and their functions for plants and animals. The emphasis is not on classification for the sake of grouping and naming. The NGSS specifically exclude assessment of knowledge of animal species names in primary grades, however, learning Alaska Native names of culturally-important animals and animal groups receives emphasis in bilingual education in a number of Alaska school districts. Teachers should use their judgment in terms of the emphasis placed on assessing learning about the scientific or common names of different species or species groups.
Prior Student Knowledge: Students will have had prior experience observing plants and animals in different tidal zones on Sea Week field trips although they may not recognize the different zones. They will know how to group animals based on shared external structures (mollusks, crustaceans, echinoderms, bivalves, univalves) and have been introduced to variation in traits between parents and their offspring (plants and animals) and among individuals of the same type of plant or animal.
Students should also have foundational conceptual understandings in cross-cutting concepts of patterns, structure and function, and systems.
Possible learner preconceptions, misconceptions and instructional clarifications:
Learner Preconception/misconception: Plants and animals can live anywhere on the beach.
Instructional Clarification: Survival, and thus the pattern of distribution of plants and animals on a beach is related to many factors, as described in the Teacher Background section. The concept of adaptation (that in any given habitat, some organisms can survive well, some can survive less well, and some cannot survive at all) is a 4th grade Life Science concept but students at this developmental stage can observe and collect data that will allow them to infer patterns that demonstrate that plants and animals cannot live anywhere on the beach.
Learner Preconception/misconception: Animals that live in tide pools or other places in the lower intertidal zone can survive out of the water.
Instructional Clarification: Many animals that live in tide pools spend their entire life in the same tide pool. Animals like tidepool sculpins that aren’t able to breathe air very long, so are somewhat restricted to pools. Other animals in the lower intertidal zone can spend a limited amount of time out of the water but need to stay wet to survive. If they move too far up the beach when the tide is out, they can dry out and die before the tide comes back in.
Components of Next Generation Science Standards Addressed
Planning and Carrying Out Investigations
Make observations (firsthand or from media) to collect data which can be used to make comparisons. (2-LS4-1)
Science Knowledge Is Based on Empirical Evidence
Scientists look for patterns and order when making observations about the world. (2-LS4-1)
LS4.D:Biodiversity and Humans
There are many different kinds of living things in any area, and they exist in different places on land and in water. (2-LS4-1)
None are listed for this NGSS performance expectation.
Cause and Effect is a relevant cross-cutting concept emphasized in 2nd grade. Consideration of the relationship between the differences in physical environments and in diversity in each intertidal zone could address this concept.
The cross-cutting concept Patterns that is also emphasized in 2nd grade is also a relevant.
RI.2.4 Determine the meaning of words and phrases in a text relevant to a grade 2 topic or subject area.
RI.2.7 Explain how specific images (e.g., a diagram showing how a machine works) contribute to and clarify a text.
Field Trip learning experiences:
W.2.8 Recall information from experiences or gather information from provided sources to answer a question.
SL.2.1.a-c Participate in collaborative conversations with diverse partners about grade 2 topics and texts with peers and adults in small and larger groups
E2) Understand the ecology and geography of the bioregion they inhabit.