How to…explain biome distribution

Following on from @GeographyTom9‘s outline of how he teaches the Global Curculation Model, I thought i’d have a go at explaining how I teach about biome distribution.

Step One – Find a spare exercise book (or two)

I’ve found that when i’m drawing an explanation using my visualiser the best results always come from when I use an exercise book that is exactly the same size and those used by the class in front of my. This means I can guide their drawings and explanations and lay it out exactly as I have done. Ideally, two books are better than one as you can have your pre-planned drawings by your side as you re-draw them with the class in another book.

Step Two – Plan your drawings and explanations before delivering it in front of a class

This has been learnt from bitter experience. Drawing or writing down a half-baked explanation which requires continual editing and scrambles for rubbers (or a new page for those that never seem to use a pencil) will be avoided if your drawing and explanation (including edits) are planned in advance. In addition, it allows you the time and space to consider your explanations and whether they are clear and concise enough and whether your drawings need any more or less detail.

Pre-lesson

Step Three – Explaining latitude

With my pre-planned explanation in front of me I use a protractor and draw round the whole 180 degrees. I explicitly instruct students to draw their semi-circle with the 0 degree line on a line in their book so that this becomes the equator. The equator is then drawn on and labelled as 0 degrees and then 90 degrees north and south are also labelled as the most straightforward latitudes. After this, I then add on the Tropics of Cancer and Capricorn and Newcastle-upon-Tyne to show how north we are.

Explaining Latitude

Step Four – Insolation

After latitude, I explain insolation. Again, drawing the equator on a line in the book helps as I use one full line north and south of this to indicate insolation at the equator. I then instruct the students to draw a line of equal thickess at the top (the last two complete lines before the north pole). This allows me then to explain how the curvature of the Earth increases the surface area heated by the same amount of insolation and therefore how latitude affects temperatures. This is also a good time to check for the common misconception that distance from the sun affects temperatures.

Explaining Insolation

Step Five – Global Atmospheric Circulation

My explanation of rainfall explains global atmospheric circulation. This must come after latitude and temperatures as the main driver of the Hadley Cell is insolation at the equator. In order to explain global atmospheric circulation (not done that differently from @GeographyTom9) I start by looking at what happens to air heated by maximum insoaltion at the equator then take it from there to explain that rising warm air causes cooling and condensation that leads to rainfall and that sinking cold air doesn’t cause rainfall as there is no condensation. This allows me to then highlight that rainfall isn’t as straightforward as temperature and that it moves in bands of high and low rainfall from the equator to the poles. A small, but important, point here is that the size of each atmospheric cell is drawn to the size required to fit with the first drawing of latitude and the final drawing of biomes. This means that the descending cold air of the Hadley Cell aligns with the Tropics and the desert biome.

Explaining Global Atmospheric Circulation

Step Six – Latitude, Temperature, Rainfall and Biomes

The final drawing has the equator and the tropics drawn on it, but nothing beyond that. This is where a vivid array of colors come in handy to mark the biomes. As this is drawn and explained the two previous diagrams outlining temperature and rainfall and constantly referred to to explain biome distribution, e.g. the desert biome is located at the tropics where there is little rainfall due to descending cold air and not clouds. This means no rainfall and the ground being heated intensely due to limited cloud cover. I have, recently, added a side bar to the final diagram that gives an overview of temperature and rainfall by the side of biome distribution to aid the explanation and overall understanding.

Explaining Biome Distribution

After this, I do some short answer exam questions to check understanding. That’s it.

Next time: I’ll find my notes on explaining hurricane formation over a double page spread from Africa to the Caribbean.

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