IGCSE marine, ecosystem models

Today we are bulding a small ecosystem model.

What we need is.

A glass that can be closed (big jam jars are great)
A local pond

a small net to capture some life

Fill a glass about 2/3 with water

Put a bit of mud from the pod at the bottom (so we have some of the local microorganisms)

Add some water plants (Pond weed works great)

Add a few invertebrates (snails work well)


Close them up and see what happens.

What I am trying to show here is a model system of a closed ecosystem.,

The sunlight provides energy for photosynthesis

This makes the plants grow and release oxygen

The invertebrates eat plant material and algae and releases CO2

The microorganisms at the bottom helps recycle nutrients.

So, a closed system in good balance can live for years without any other outside influence than the sunlight.

But a system off balance will collapse quite fast.

Use it to talk about phososynthesis, respiration and cycling of nutrients. 

here is the same systems 1 week later: