ingridscience

Students are shown a marine snail egg case (e.g. knobbed whelk egg case containing tiny shells), found washed up on a beach (information and images).
An adult cuts baby shells out of the egg case. One shell is put in each student’s box magnifier.
Discussion of the shell shape: spiral, unlike the clams (and mussels) we have looked at before.
Students draw the spiral shell, filling a page of their notebook, to be as large as an adult shell. Tape the baby shell next to the adult, to compare the enormous size difference between baby and adult shells of this type.

Students each find a piece of rockweed. Discuss what it is, where it grows, and that it is an alga (not a plant).
Students look closely at the parts of the rockweed, draw it in their notebooks (draw around a small piece), then label the parts: holdfast, bladders and blades.

Optional with older students: predict of what the parts of the seaweed might be for (younger students just guess, and then feel bad if they are "wrong" distracting from the activity).
Test the function of each part of the seaweed by tearing the rockweed into pieces: pieces of the blade or a bladder on its own, then see if each float in a tray of water.
The blades should sink, and the bladders float (unless the air has been popped out of them). Do many pieces until a pattern is seen.

Discussion of the parts.
Bladders: they keep the tips of the seaweed floating up in the water, to maximally expose all parts of the seaweed to sunlight. The bladders can be torn open to find the gas bubbles among the jelly that make it float.
Holdfast: it keeps the seaweed anchored to a rock, so that it is not washed ashore.
Blades: wide to catch sunlight for photosynthesis.

Younger students can use their hands to show how rockweed grows: a balled fist is a rock, and use the other hand on top with the fingers ("blades") spreading upwards; the fingernails represent the "bladders".

Beach hoppers live under dried seaweed, and can be used for further discussion if there is time (information and images of beach hoppers, 6th image down).

If this activity is to be conducted in a classroom, collect small rocks with barnacles attached, and store in the fridge overnight out of water. Also collect containers of sea water, one kept in the fridge, one at room temperature. Return the barnacles to the same beach after the experiment.

At a beach, ask students to find barnacles themselves. Point out the young and old barnacles, and the scar where a barnacle used to be.
Live barnacles can be gently touched to make them shut their shells tight.

Watch barnacles feeding:
With the barnacle rocks in a jar each, add sea water to them.
Watch and wait. The barnacles will first release a bubble of air, then gradually open up and start to feed.
Their head is down attached to the rock. Their legs (called "cirri" in a barnacle) point upwards and beat back and forth to catch tiny particles of food in the water.
See half way down this page for a diagram: https://seahistory.org/sea-history-for-kids/barnacles/
or this page http://courses.washington.edu/mareco07/students/nina/barnacleshome.html
Barnacles at the beach start filter feeding when the tide comes in, and close up when the tide goes out.
Video of barnacles feeding: https://www.youtube.com/watch?v=-dgmV-tyUek Slow motion at minute 3:10

If you add room temperature water to the jar, the barnacles will start feeding very rapidly, but will die if the water is too warm for too long (i.e. 18 C, or so).
If you add cooler water, the barnacles will last for longer, but may not start feeding as rapidly.

Optional, though quite subtle: compare beat rates of barnacles at different temperatures. Temperatures need to be around 8C and 18C to really see a difference, and it is hard to maintain the sea water at these temperatures in a hot classroom. Also, different barnacles inherently beat at different rates, so it is an overall effect to be noticed: at the lower temperature they are overall beating more slowly than at the higher temperature.

Use barnacles feeding as a demonstration of how animals are dependent on the tides. As the Moon rotates around the Earth it pulls on the oceans back and forth, and causes tides. Animals live by these tides, the shelled animals feeding when the water comes in and closing up when the tide goes out. The crows, other birds, and wolves in more remote areas, wait until the tide is out, to feed on the shelled animals.

Great article on the great variety of places that barnacles live, and their place in the food web: https://outlifeexpert.com/barnacles-decomposers/

Barnacle larvae can travel 85Km before they attach to a rock as adults. (https://www.journals.uchicago.edu/doi/10.1086/BBLv216n3p373)

Filter feeding is a method of feeding used by clams, where water is filtered by tiny hairs to catch small food particles.

This activity is written as a demonstration with a student helper, but multiple versions can be set up so that all students can try it.

Teacher or student helper adds seeds/grain to a large tray of water, to represent food particles floating in the seawater.
The teacher shows the class the mesh stuffed into the cup, representing the hairs inside the clams body.
The teacher/student helper scoops the cup through the water and food particles, representing the clam taking in water with a siphon.
The teacher/student helper pours the water out of the cup again, representing the water leaving the clam’s body by the siphon.
The teacher shows the students the seeds/grain stuck in the mesh, representing the food particles stuck in the hairs in the clams body.

More information on filter feeding for the teacher at http://nathistoc.bio.uci.edu/Filter%20feeders.htm

Optional: precede this activity with finding clams on a beach.

The clam has a muscle that keeps the shell tightly closed. The frozen clams will open up slightly, revealing this white adductor muscle.
Cut the muscle or simply pull open the clam to look at the internal organs.
Give students a photo of the inside of a clam to help them find the parts. (Photograph of the inside of a clam web archived at: http://web.archive.org/web/20070630042552/http://iweb.tntech.edu/mcapri…)
Clams and humans are both animals, but they are a mollusc and we are a mammal, so we might expect that some body parts are the same and some are different.
Students find each organ in the clam. The function of each part is discussed as they find them, or after all parts are found..
Optional: use the attached worksheet to compare the clam's body parts with ours.
1. The clam SHELL protects the clam. It is its shelter. We do not carry our shelter with us.
2. The MANTLE makes the shell. We do not have a mantle, as we do not have a shell.
3. The clam FOOT helps the clam dig into the sand. We move with our FEET too.
4. The clam GILLS take oxygen from the water (like fish). We have LUNGS for taking in oxygen. (Students may need a toothpick to gently lift up the gills to see them properly).
5. One of the clam SIPHONS sucks in water. Tiny food particles in the water get stuck in tiny hairs on the gills. Then the food gets washed towards the clam's mouth inside the body. The water goes back out the other siphon. We eat with our MOUTH. (Students may need to straighten out the siphons with a toothpick to see them properly.)

Note: a mussel has similar parts, but they are arranged a little differently. See http://faculty.orangecoastcollege.edu/mperkins/zoo-review/clam-mussel/c…

Video on restoration of clam gardens: https://www.youtube.com/watch?v=22Nytmxw2Z8

Hand each student a clam. Questions for discussion:
1. Close your eyes, and describe what you feel.
2. Is a plant or an animal? Do you know what animal it is? Where have you seen one before?
3. Point out that this clam is not alive.
4. You are an animal. Does it look like you? In what ways is it different? (This clam is a mollusc, an animal with a shell. You are a mammal).
5. What does the shell do? Discuss how the shell protects the clam from predators.

Ask students to compare their clam with the other sized empty clam shells on their desks.
Questions for discussion:
1. Which is the oldest shell and which is the youngest? How do you know?
2. Shells get larger as the animal inside them grows. The shell grows to fit the body.
3. Where is the new shell added? (on the outer edge - notice that this edge is soft).

It is a rocket powered by a chemical reaction.
Baking soda and vinegar react to make gas, which is trapped in the corked bottle. When the gas pressure is great enough to push the cork out, the rocket flies up in the air.

Pour 200ml vinegar into the bottle (if 1L; use half cup vinegar for a 710ml bottle).
Add a couple of teaspoons of baking soda to the tissue, and roll it up like a burrito, so the baking soda does not fall out and the package is narrow enough to fit through the mouth of the bottle.
Students can do these steps.

Make sure that you are away from the students, or with only a pair of students invited to come with their materials to the launch pad.
Students watch while the adult pushes the baking soda package into the bottle, corks the bottle, shakes the bottle once, then stands it up for take off.
Run away from the launch pad to a safe distance (30-50m). Even if it takes a little time, the tissue will disintegrate to mix the baking soda into the vinegar, the gas released will build up enough pressure to push the cork out, and shoot the rocket high into the air.
If you think gas is escaping more slowly (around the side of the cork, for example) and the rocket will not fly, kick it over with your foot before reaching down to take it apart (so the rocket does not go off in your face), and reset it.

A rocket nicely demonstrates Newton's 3rd Law - for every action there is an equal and opposite reaction. The gas and liquid shooting downwards out of the bottle (the 'action') pushes on the bottle ('reaction') sending it upwards.

For a dramatic demonstration of Newton's 2nd Law, set the bottle right-side-up for take off (with the cork pointing upwards), making sure there is a mound of gravel or something around the base of the bottle so that it will not tip over. With the same amount of baking soda and vinegar, the cork flies way higher than the bottle (be careful with set up - the cork shoots out of the bottle really fast). With the same force, the smaller mass of the cork accelerates more than the larger mass of the bottle.

With older students, model the chemical reaction that powers the rocket:
Give each student a model of HCO3 (baking soda) and H (the atom that makes vinegar acidic). We started with these in the rocket.
The baking soda and vinegar molecules react and rearrange to make two new molecules. Ask students to figure out what these molecules are, giving them the hint that one of them is water.
The products of the reaction are water (H2O) and carbon dioxide (CO2).
Carbon dioxide is a gas, and as more and more of it is made by the chemical reaction, the gas builds up in pressure until it blows the cork out of the bottle.
Once the cork is released, the gas can escape by shooting out of the bottom of the rocket. This force propels the rocket upwards.

A rocket that goes to space acts on the same principal of action and reaction: the exhaust is expelled out of the back of the rocket, and this force is countered by a force on the rocket that propels it upwards.

Purchase molecule models online at Indigo Instruments https://www.indigoinstruments.com