ingridscience

Ask students to try each of the sorting activities (below), and to figure out how the materials are sorted in each case [by shape, size].
Review the different ways of sorting materials. (Optionally add in other ideas e.g. colour.)
Tell students that their kidney can remove poisons and other waste from our bodies by using sorting mechanisms.

Sorting by size
Make a mixture of marbles, gravel and sand.
Shake the mixture in a kitchen sieve and see what passes through the sieve.
The smallest items, which pass through the sieve (sand) represent the smaller blood molecules which pass through the kidney membrane into the kidney tubes (salts, water, urea, sugar, vitamins). The larger items held by the sieve (marbles and gravel) represent the blood cells and large protein molecules like albumin and antibodies, which stay in the blood.
Show image of kidney membrane that filters the blood, allowing smaller molecules into the kidney:
https://www.researchgate.net/profile/Jeffrey-Miner-3/publication/510761…
https://ars.els-cdn.com/content/image/3-s2.0-B9780123814623000732-f73-0…
Diagram:
https://cdn.kastatic.org/ka-perseus-images/1b9aacb6315df5f730565e23d7bb…
Did you get small gravel stuck in the mesh? The kidney actively cleans its filter, to stop it clogging up.

Sorting by shape
Special molecules in the kidney tube walls only let some molecules through back into the blood.
If the small molecules have the right shape to fit, they can pass through the membrane.
Diagram: https://i.ytimg.com/vi/j-9z_p9yly0/maxresdefault.jpg
Like a lock and key mechanism.
Students find the lock which opens with their key. Their key is numbered. The locks each have a letter.
Draw a string of numbered boxes on the board. Students add the letter on the lock they open in the box with the same number as their key. The boxes spell out the name of the molecule gates in the kidney tube walls: "transport protein" (also called "carrier protein").

Moving from high to low concentration by diffusion
Drip food dye onto wet tissue on a flat surface, and watch as it slowly spreads out away from the concentrated drip, and into areas where there is no food dye.
This models diffusion (although it is too fast to be actual diffusion). Diffusion is how molecules move across membranes the same way, from high to low concentration.
Water and salts are moved back into the blood by this mechanism.

The kidney sorts blood molecules using these three above mechanisms.
Show diagram of kidney ducts and blood image, to show where each happens:
https://o.quizlet.com/4OkPEUeiopsNE6JxIos4Mw_b.jpg
or https://thumbs.dreamstime.com/b/nephron-functional-unit-kidney-minute-m…
First, in the rounded glomerulus, all the small molecules are filtered into the kidney, while large molecules and cells stay in the blood (sorting by size).
Then along the kidney tubes water, salts, sugars, vitamins and other nutrients are move through transport proteins back into the blood. Urea does not go back into the blood. (sorting by shape).
Many small molecules diffuse from high concentration to low concentration, which does not need any energy.
Sometimes energy is used to pump molecules up their concentration gradient e.g salt.
Urea mostly stays in the kidney tubes - it is not taken back into the blood, also other toxins. They flow to the bladder, to be later excreted.

As well as removing urea from our blood, the kidney regulates how much salt and water are returned to the blood, and how much is excreted. This keeps the blood chemistry exactly right, so that our organs can function properly.
The kidney filters an enormous amount of blood: every heartbeat, ¼ of your blood goes through the kidneys (1.2L of nearly 5L total)!

This is an activity with wind on sand. Like in a desert.
A student pair shares a tray. Each student has sand, a bottle to puff wind and a rock.

Introduce materials and activities to try to the students gradually (suggested order below). The materials invite free play of many kinds, so initially guide the students through wind erosion-related activities before opening up to free play. Discussion can come after each activity, or all at the end.

First, use the paddle to make a pile of sand, then place the rock on top, like a rock in a desert.
Use the wind from puffing the bottle to move the sand (don't use hands!)
Can you move the rock by only using wind?
Discussion: yes, by eroding sand from under the rock with wind, gravity will pull the rock downwards bit by bit.
In a desert, larger rocks slowly move downwards as smaller sand is blown away.

Next, give students a piece of cloth.
Show them how to fold the cloth to make layers, adding a thin layer of sand between each layer of cloth and also a thin layer of sand on top of the last cloth layer. Then place the rock on top. (See photo.)
Is it harder or easier to blow the sand away from under the rock with the cloth?
Discussion: it should be harder to blow away the sand with the cloth. (If it made no difference students may have had a lot of sand on top of the upper layer of cloth - the rock should be sitting on only a thin layer of sand over the top cloth layer.)
The cloth models plant roots, which hold sand (or soil) in place and slow down erosion by wind (or by water).

Next give students some counters.
Show how to make a layer of counters, then a layer of sand, then counters, then sand.
Use wind to blow away the sand between the counters.
Can you make a pile of counters, just by blowing away the sand?
Discuss: It takes a while, but by blowing away the sand, a pile of counters forms.
This models formation of a 'desert pavement'. In a desert, sand is blown away but larger rocks remain. The rocks gradually fall lower and lower as the sand between them is removed. Eventually a layer of rocks remain on top of a lowered ground, protecting against further erosion. The layer of rocks on top is called a desert pavement. The lowering of the land surface by wind erosion is called 'deflation'.

Free play.
Students use all the materials they have for free play.
Ideas for them:
Make your own structures e.g. a house, and see if you can make it fall using wind, or by blowing sand into it.
Combine materials with your partner or another tray and create together.

Wrap and more information:
Wind is formed by the Sun heating the Earth, which causes warm air to rise, which causes more air to move in from the side, which is wind.
Wind erosion happens when the surface of the ground is dry with few plants e.g deserts.
When sand is blown into rocks it wears them away - called 'abrasion'. Abrasion can make strangely-shaped rocks e.g. the Hoodoos in Alberta. See this link: https://upload.wikimedia.org/wikipedia/commons/9/9e/Close_up_of_the_Hoo…
Sand that is blown away can pile up into dunes. The shape of the dunes formed depends on the amount of sand and the direction of the wind(s). See second image in this link: https://www.nps.gov/subjects/geology/aeolian-landforms.htm or this link: https://www.researchgate.net/figure/Major-dune-types-as-defined-by-McKe…
Sometimes wind blows dust around the Earth! Dust from the Sahara desert in Africa is carried by winds around the Earth to the Americas! Some of the nutrients in the Amazon rainforest are from Sahara rocks (phosphorus). See this NASA link: https://earthobservatory.nasa.gov/images/146871/dust-traverses-the-atla…

Tell students that sediment layers at the bottom of the ocean show changes in Earth’s atmosphere millions of years ago.
Optionally show an image of how core samples are collected e.g. https://images.ctfassets.net/kzewhs8e6cvu/7GhngoRnVhczSssydtnh5Q/78daa1…

Distribute images of ocean sediment core. Demonstrate how core samples are collected. Younger at the top, older at the bottom.
What do you notice in the colours of the core samples?
The whiter parts are shells of ocean animals. When the animals died their shells fell to the ocean floor, layering and compressing into white rock (called limestone).
The red is clay. No shells fell to the bottom of the ocean where it is red.
The white-red boundary is from a huge burst of greenhouse gases in the atmosphere, 55 million years ago, when volcanoes released a huge amount of CO2 into the atmosphere. Called the Paleocene–Eocene Thermal Maximum.
This massive carbon release into the atmosphere lasted from 20,000 to 50,000 years. The entire warm period lasted for about 200,000 years. Global temperatures increased by 5–8 °C.
The change of CO2 in the atmosphere changed the ocean.
At our current rate of emissions, we are releasing CO2 into the air faster than the PETM.

BUT, see how the ocean sediments gradually recovered, turning white again as the atmospheric CO2 decreased, so decreasing CO2 in the ocean.
If we choose as a society to vastly reduce emissions, the oceans will recover.. The movement is growing to make it happen.

Students look through the 'insect eye' (also called 'fly eye'), and draw their own art to look at with it.
The insect eye partly models how an insect eye works, but is not completely accurate.

Bees and other insects, as well as crustaceans, have compound eyes: https://en.wikipedia.org/wiki/Compound_eye

The insect eye lens roughly models what information is collected by a compound eye, but not what the animal actually sees.
Each of the tiny lenses in a compound eye collect light from part of the scene in front of the animal. These images are combined in the animal's brain to make one image.
The images collected by the lenses in compound eye are actually very low resolution (each one just colour shade with no details), unlike the insect eye lens (which is high resolution). Compound eyes collect information that would look like a computer image made up of very few pixels.
See this link: https://askabiologist.asu.edu/content/bugvision-hollywood-misconception.
When students make their own art work, and look at it close-up, the fly eye does at least show that each image is a part of the whole picture (a better job than the "Hollywood" version in the link), but is still too high resolution. Students that use the insect eye to look around them at further-away objects will have an even less accurate model (so I ask them to look close-up at a drawing).

Although compound eyes have very low resolution, they have a very large view angle, as well as the ability to detect very fast movement.
That is why it is almost impossible to catch a fly without a fly swatter or wide cloth.

We usually think of the orbit of a body in space to be fixed, but 'apsidal precession' of orbits (slow rotation of the orbit path) has been observed - see image here: https://en.wikipedia.org/wiki/Apsidal_precession#/media/File:Perihelion…

Most planets in the solar system have apsidal precession, but at a very slow rate, so their orbits are almost stationary.
https://en.wikipedia.org/wiki/Apsidal_precession

Show students orbit precession images. Note that drawings of precession are highly exaggerated - the actual shift on each orbit is very small and only observed after watching an orbiting body for many years.

Lunar precession of the Moon around Earth image: https://en.wikipedia.org/wiki/Lunar_precession#/media/File:Moon_apsidal…
Also animations of lunar precession at https://en.wikipedia.org/wiki/Lunar_precession

A star, called S2, orbiting Sagittarius A* (the black hole at the centre of the Milky Way) has been observed for 27 years to notice precession: https://newatlas.com/space/star-s2-spirograph-orbit-supermassive-black-…

Students make art with a spirograph to model the patterns made by precession of orbiting bodies.

Prepare the bottle and one balloon before the lesson:
Saw or cut the drink bottle so that the distance from neck to the cut is about the length of a deflated balloon. Sand the cut edge, so that it doesn't pierce a balloon later.
Tie a knot in the neck of one balloon, then cut the tip off the other end (the rounded part).

Distribute materials to each student: a cut bottle, one knotted and cut balloon, one whole balloon.
Have a partner hold the bottle, or stabilize it between the knees, with the bottle mouth pointing upwards.
Push the rounded main part of the intact balloon into the mouth of the bottle, then stretch the neck over the bottle mouth to secure it. The balloon should hang down in the bottle, with a hole into it at the mouth of the bottle.
Turn the bottle the other way up and stabilize, with the cut end of the bottle pointing upwards.
Stretch the open end of the knotted balloon over the cut end of the bottle, so that it is secure with the knot outwards.

Work the lung model:
The balloon hanging in the bottle is a lung (the physics is the same even though there are not two lungs).
The knotted ballon covering the cut end of the bottle is the diaphragm muscle.
Push the knot upwards so the diaphragm goes up into the bottle. This is the position of the diaphragm when it is relaxed. The lung should crumple and have no air in it.
Pull the knot downwards so the diaphragm ballon is pulled away from the bottle. This is the position of the diaphragm when it is contracted (it is actually straight across, not pulled down). The lung should inflate with air, fully or partially,

This model shows that we do not actively suck air into, or push air out of, our lungs (as it feels like). Air flows in and out of the lungs as the diaphragm muscle changes shape and the chest cavity changes size.
When the diaphragm contracts, it moves downwards, which increases the volume of the chest cavity, which decreases the air pressure in the chest cavity. Atmospheric air rushes into the lungs to equalize the pressure.
When the diaphragm relaxes again, it curves upwards, which decreases the volume of the chest cavity, so increasing the air pressure. Air leaves the lungs to equalize pressure.
In addition, when we breathe in, our rib muscles also move our rib cage up and outwards, further increasing the chest cavity, and making even more atmospheric air rush in.

Lung breathing gif:
Clear image of lungs and diaphragm only - https://upload.wikimedia.org/wikipedia/commons/9/9c/Diaphragmatic_breat… (but incorrect in that the same molecules enter and leave the lungs).
Shows diaphragm and ribs moving - https://www.luanamaso.com/wp-content/uploads/2019/09/AdolescentTastyFel…
Also shows heart and intestine - https://giphy.com/gifs/body-systems-organs-lckhIaarcbT20CXRDo

Go outside in the winter months, and look for buds on plants.
Buds are a protected flower, leaf or shoot, formed in the Fall. They protect delicate plant parts over the winter, and will open up in the Spring when it is warmer and sunnier.