ingridscience

The sponge, corn kernels and corn meal model different kinds of food of different sizes (different sized foam pieces are also pictured). The utensils represent different kinds of ways that fish catch food.
What is the easiest “food” to catch with each kind of mouth?
Students can use the worksheet to record what they find.

Results and discussion:
Some fish feed by biting pieces off their prey e.g. sharks, piranha, adult salmon. The tongs and clothes pegs grabbing onto large pieces of foam model this kind of feeding behaviour.

Fish use suction feeding. Food that is smaller than the mouth is sucked into it by a pressure difference when the mouth is opened. Most bony fish feed in this way. The baster or pipette sucking up medium and small pieces of food models this kind of feeding behaviour.
For a video of suction feeding try Wikipedia webpage “Aquatic feeding mechanisms”: https://en.wikipedia.org/wiki/Aquatic_feeding_mechanisms.

Some animals, instead of sucking water (and prey) into their mouths, move forward to engulf prey their mouths - called ram feeding.
The prey is trapped in the gill raker (a mesh). Tuna and whale shark eat this way.
Baleen whales use a specialized form of ram feeding called lunge feeding. They move forward fast to take a huge gulp of water and food, then expel the water through their baleen, which trap the krill in its mesh. Humpback whales lunge feeding video - try this link: https://www.youtube.com/watch?v=euYTbsjTJyo
Ram feeding modelled by the slotted spoon or spatula.

When tiny animals are caught by a mesh or filter, it is called filter feeding. Water and food can be brought into the mouth by either suction or ram feeding, then the water is expelled.
Baleen whales technically filter feed, as do fish with specialized gill rakers that catch tiny particles (e.g. some sharks and herring).
Barnacles, mussels, oysters and other shelled animals catch tiny animals from seawater in their filters.
Filter feeding of tiny particles is modelled by the tea strainer and sieve.
Watch real barnacles feeding as an example of filter feeding.

Discussion related to salmon:
Young Atlantic salmon (alevins) start feeding using the ram feeding method, moving their body forwards to capture small animals. After a week or so of feeding that way, they switch to suction feeding, to pull prey into their mouth from a distance. https://www.nrcresearchpress.com/doi/abs/10.1139/f91-225#.XK-IgC3MzdQ
Adult salmon use their teeth for eating (though sockeye don't have big teeth and continue to eat krill).

See animal eating methods for a similar activity.

Set up:

Cut a piece of fishing line a little longer than the tray.
Remove one arm (handle) from a mini binder clip, tie one end of the line to its remaining arm, and wrap modelling clay around the body of the binder clip. (Left of first photo.)
Thread the fishing line through the arms of the medium binder clip, then tie the free end to the other mini binder clip.
Attach a little pot to this mini binder clip.
See the first image for the result of these steps. Make two of these for one tray.

Half fill the tray with water, then attach the fishing line/clay unit at one end with its medium binder clip.
Allow the pot of marbles to hang down so that its weight pulls the clay up to the medium binder clip.
See the second image.
Attach the second unit next to the first.

Experiment:

Make two different shapes from two pieces of clay in the same tray.
Pull them both to the end of the tray and release at the same time.
Do several times, to see which shape moves through the water fastest.

Discussion:

In general, in the activity, wider shapes move more slowly than narrower longer "streamlined" shapes.
Compare to fish shapes (an image of fish shapes in silhouette is useful for reference). The fish that can move the fastest (e.g. fish that hunt live prey, like salmon) have longer, narrower shapes than those that do not move as fast (e.g. fish that feed on plants or algae).

Optional: give local fish examples and how their shape is an adaptation for how they eat and move. Examples of British Columbia fish:
herring (streamlined to escape predators - larger fish. eat tiny animals)
salmon (streamlined to swim through fast moving water, escape predators and to catch smaller fish)
sole (not streamlined - do not move fast; flattened to hide from larger fish that eat it. eat worms clams)
sculpin (not streamlined - do not move much; camouflaged to hide from predator fish. eat insects)

Optional: Watch a video showing various fish shapes moving through the water e.g. Planet Earth video of fish in the ocean of various shapes. Try this link: https://www.youtube.com/watch?v=4XXJs6vCTzc&list=PL8B8EDD0D02DA14B7

Cover the end of the paper towel tube with duct tape.
Cut a small hole in the duct tape the same diameter as lighter nozzle, push the lighter through so about 6cm extends inside the tube. Tape over any gaps and secure the lighter.
Bridge the ruler between the paper towel tube and the lighter, to strengthen the device.

To fire: spray some hairspray into the paper towel tube, drop in a ping pong ball, then ignite the lighter.

The device works by a combustion reaction: the alcohol combines with the oxygen in air and is converted to CO2(gas) and water. The reaction is started by the energy of the lighter, and then can continue on its own. More and more gas is made in the confined space behind the ping pong ball, until the pressure of the gas is enough to shoot the ball forward.

Set up before lesson:
Cut recycled water bottles in half and discard cap.
Cut a square of panty hose/nylons and use a small elastic band to secure over the spout of the water bottle.
Ideally, make one filter per student.
Mix a cup of soil with water in several large tubs.

Introduction:
Where do we get our drinking water? [Tap.] Where does this water come from? [Reservoirs.] It is cleaned to be safe.
Indigenous people and others living off the land would get their water from natural water sources such as fast flowing streams. This is usually OK, if water is taken well away from toilets (most common source of dangerous microorganisms).

We will filter muddy water through some different materials to see how well they can clean it.
Show students the filter, how to pour and show them the materials selection (depending on age group):
e.g. coffee filter, moss, kleenex, wood chips, cotton balls, washed sand, washed gravel
e.g. Kindergarten: washed sand, cotton balls, filter paper and tissue
For older students, discuss setting up a control, where the filter has no material added.
Show students the worksheet, where they can record the colour of the emerging water (see worksheet attachments).

Encourage students to try one filter material at a time, before showing them how to layer filter materials, or stack up the filter units, to make the water cleaner.
Free play will happen naturally, but encourage note-taking so that students know what works best.
If students need encouragement: ask them to try different filter combinations that are all natural/one kind repeated to see if this cleans the water better.

Class discussion of results:
Ask how good each material was for filtering water when used alone, and make a class chart. (The results will vary widely, so use the chart to show the best that each material did.) Discuss how the materials filter the water: the dirt particles are trapped in the tiny spaces between the filter material. The water flows through, along with anything that can fit through the spaces. Different materials have different sized spaces, so are effective at filtering different sized dirt particles. Materials that clean the water better have smaller spaces in them, but the water takes longer to pass through them.
Then students will be keen to tell how their different combinations of materials worked.

Connect to water treatment plants:
For younger students they can be told that water treatment filtering systems that clean our water also use sand and gravel. They use several filters and use other membranes as well.
For older students discuss how sand and gravel are arranged in water treatment filtering systems, and that filtering is just one step that our water treatment facilities use. They use gravel and sand to remove larger particles, and meshes to remove smaller particles. Here is the multistep process:
1. aeration to remove gases from water
2. coagulation to clump together dirt (floc)
3. sedimentation allows floc to fall to bottom of settling beds
4. filtration to remove particles (several filters including meshes, sand and gravel)
5. disinfection with chlorine to kill remaining pathogens (ozone and UV treatment do not persist)
See http://www.agr.gc.ca/eng/science-and-innovation/agricultural-practices/…

More info on filtering water, naturally and by man:
https://sciencing.com/natural-materials-used-water-filtration-5371122.h…

Your classic rain gauge that you might have made from a water bottle is very simple, but fills up.

A tipping bucket rain gauge uses electronics to count the number of times a bucket fills and empties, so can be left to run for long periods.
A funnel above the tipping bucket directs rainfall into it. The volume of water in the bucket is known, so if you can count the number of times it tips, you can calculate the amount of water.
See a gif of a tipping bucket rain gauge here: https://www.yoctopuce.com/EN/article/how-to-build-an-usb-pluviometer

Students design their own tipping bucket mechanism with household materials, and use a marble dropped into the bucket to make it work.

Start like this: insert skewer in straw piece, tape onto spoon at the balance point, making sure it can rotate freely. Secure to cup with clay. It’s like a see saw. We have the rotation part. This pivot is one design element of a tipping bucket.
You are going to design the rest. You will be using a marble instead of water. It needs to start horizontally, tip down when the marble falls in the spoon to dump the marble out, then returns quickly to the horizontal position. (Demonstrate the steps.)
What other design elements will it need? Write up any that they come up with e.g. weight, stop - but do not add more than they can think of as they will discover more as they work.
Students can break the materials apart if they need, and take more of anything.

Once the students have made their designs, ask what other design elements are needed.
Complete the list of design elements:
pivot, weighted lever, stops to limit movement.

The tipping bucket rain gauge in a weather station is finely weighted, balanced and housed so that it works as your models do.
It uses a magnet to hold the bucket until it is heavy enough to tip. A circuit detects when the bucket tips, and counts the number of times, to calculate total rainfall over time.