ingridscience

Please note that in a class of students it is likely that one of them is at least partially colourblind (1 in 12 males are colourblind). As this is an activity distinguishing colours, these students will not be able to tell some colours apart and perceive some colours differently. The common red/green colour blindness means reds and greens (or colours containing reds and greens such as browns) look similar. More information at colourblindawareness.org and colorblindguide.com/post/the-advantage-of-being-colorblind.

Activity 1: Stare at the red and green cross for 20 seconds, then look at some blank white paper. Try not to blink after you move your gaze.

Activity 2: Stare at the black spot in the centre of the red circle for 20 seconds. Then slowly move the image away from your eyes, still staring at the black spot. You will see the inverse colour (light blue, or cyan) appearing as a halo around red circle.

The cells sensitive to a particular colour get tired when you stare at one colour for along time and stop sending signals to the brain. When you put white into the same field of view (either by moving your gaze, or by moving the image away from you), all the colour cells are now stimulated. The tired cells send a weak signal and the other cells send a strong signal, so you see the inverse colour from the original colour stared at.
(Staring at green makes green cells tires. Red and blue cells give a strong signal, perceived as magenta; inverse of red is blue and green giving cyan. Inverse of blue is red and green giving yellow).

Activity 3: Try making your own shapes from one or two bold colours. Use the method in activity 1 or 2 to play with colour perception.

About colourblindness:
About 1 in 12 men (8%) and 1 in 200 women in the world are colourblind, though not all the cases are extreme, and someone might not even realise they have partial colourblindness. Colour blindness is usually from a genetic cause (in your DNA and inherited from parents). The most common kind is red/green colourblindness, and is partial or complete loss of sensitivity to red and green colours. In the more extreme cases (protanopia - loss of red, and deuteranopia - loss of green) colours containing red or green appear yellow or brown, and blues and purples are confused. Less extreme cases (deuteranomaly - partial loss of green) are most common, where reds appear browner and purples appear bluer. https://en.wikipedia.org/wiki/Color_blindness#/media/File:Color_blindne…
Find out what it is like to be colour blind: http://www.colourblindawareness.org

Look at the foods that a black bear eats, and unnatural foods that they should not eat. Draw one of the foods they eat on the worksheet.
Add bear food to a scale until there is enough for one black bear “meal” (5kg), and record the amount on the worksheet. Compare with a person’s lunch (e.g. bagel and cheese)
If time, look at a bear skull to see the kinds of teeth they have.

See a real bear pelt and feel real bear fur. Find the underfur that keeps them warm, and the guard hairs that keep off rain and dirt. Use a magnifier to look at the fur closely.
Compare to their own hair. Draw bear fur and their own hair.
Measure how long bear fur is and record.
What do we wear that does the same job as the different kinds of bear fur?
If time, talk about how much fat a bear has (4cm). Compare to our own layer of fat.
If time, talk about different colours of bear fur.

Use a metre stick to measure a template of a black bear, and find out how tall and how long a bear is. (It is on all fours, 2m long and 1m high). Record it on their worksheet.
Stand next to the bear template to compare its size to their own (are you taller/shorter, narrower/wider) and measure their own height if time and able.
Students fit their foot into a bear print, to compare sizes.
Students look at a model of bear claws and compare their size to their own nails.
They can use space on the worksheet to draw the bear paw or claws.

Students add a drop of methylene blue (or iodine to a slide).
Students scrape cheek cells from the inside of their cheeks with a toothpick, then wriggle them off in the drop on the glass slide.
Drop on a cover slip.
Look at the cheek cells under low power to start to find the cells.
Then increase the power, keeping a good-looking cell in the centre when moving up to the highest power.
Look for the nucleus in the centre of the cell.
With methylene blue, other cell organelles are also visible, and sometimes bacteria (dark blue spots outside the cheek cells).