Matter and Energy in Organisms and Ecosystems
Microorganisms around us
Name the main groups of microorganisms and say what they do for soil, food and crops.
Leave a lemon out for a week and something powdery grows on it. Bury vegetable peels in a pot of soil and three weeks later they are dark crumbly manure. Warm some milk, stir in a spoonful of curd, and by morning the whole bowl has set. Nobody did any of that. Something too small to see did.
Who the microbes are
Microorganisms, or microbes, are the living things too small to see with the naked eye — and viruses, which sit at the edge of that description. Bacteria and protozoa such as Amoeba are made of a single cell. Fungi may be one cell, as yeast is, or many, as mold is. Algae are the group that carry a green pigment and make their own food. Viruses are different again: they are acellular, and multiply after entering a living cell.
Worked example
Bowl A gets lukewarm milk and a spoonful of curd; bowl B gets cold milk and the same spoonful. In the morning bowl A has set and bowl B has not. What has happened?
Notice what the spoonful of curd brought with it: bacteria, one of them Lactobacillus.
The curd is not an ingredient so much as a delivery of living things. Without it neither bowl would set.
Try it together
Flour, a pinch of sugar and warm water are kneaded in two bowls. Yeast powder goes into bowl A but not into bowl B. Five hours later bowl A's dough has risen and bowl B's has not.
A word or two for each answer.
1.Yeast belongs to one of the groups of microorganisms. Which group is it?
Have a go
Have a go on your own. Breaking down dead plant and animal matter into simpler, nutrient-rich substances has a one-word name. What is it?
Ready to practice?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.