Cells and Micro-organisms

Context
LIFE SKILLS// SCIENCE
In both subjects I often had to use the terms "micro-organisms", "germs", "bacteria" or "virus". The learners kept asking me "Madam, what is a micro-organism?". I was really unhappy with the quick answer "some very small creatures that make you sick". That´s why I dedicated an extra lesson to the topic. The 
classteacher was surprised, but happy about that lesson.

Jokers of interest
poster
drawing tasks (my learners loved drawing)
model of a cell

Materials
poster
Plasmodium-book from a Clinic, if possible

Model of a cell made of:

• a pumpkin shell to make the plasma membrane/body of the cell
• the inner stone of an avocado to make the nucleus

1)      Cells

• All living beings (= organisms) are made up of cells: humans, animals and plants
• 1 adult person consists of 100 000 000 000 000 cells
• Cells are usually between ten and a hundred micrometers long (1 millimetre = 1000 micrometers)
• Structure of cells:
• Cell- or plasma membrane around it controls what passes into and out of the cell
• cytoplasm is a watery jelly
• the nucleus controls what goes on in the cell and it also carries the nucleic acid (DNA) - the architect´s plan to make new cells
• every second, 50 Million of cells die in our body and have to be produced new
• different types of cells have different functions and jobs in our body and they have a different lifetime: the cells on our lips live 2 weeks, then die; but the cells in our bones can survive 30 years!

suggested extra-Activities:

If available, let the learners have a look through the microscope at the cells of an onion skin. (I brought a microscope from home). Or else, look some pictures of cells up in the interent and show the learners on your laptop.

2)      Bacteria, for example yoghurt, typhoid, cholera

o       bacteria are very simple organisms, made up of only one cell!

o       They don´t even have a nucleus, the nucleic acid (architect´s plan) is just spread throughout the cell

o       There are three basic shapes of bacteria:

o       Balls or spheres

o       Rods

o       Spirals or cork-screw shaped cells

o       bacteria can be linked together to form chains or clumps

o       some bacteria are able to move using whip-like structures called flagella

• Bacteria are found in/on almost everything: millions of them in the air, on our skin, in our bodies, in our food – most of them are harmless
• Bacteria can be grown or cultured on special food (like yoghurt) or in the laboratory in culture media
• Some bacteria can do us harm, they can be passed in the air or water or by one person touching another
• When a person sneezes or coughs their mouth should be covered
• If the faeces of an infected person are not disposed properly then the bacteria may spread to drinking water, a person drinking infected water will then pick up the disease (cholera!)

3)      Fungi

• Fungi include the yeasts (Hefe) which are used in brewing beer and making bread

4)      Plasmodium

In Malawi, Malaria is the most common disease. The Clinic laboratorys have some books with microscope-photographies of Plasmodia, which they use to compare when they analyse Malaria blood tests. I asked the nearest Clinic to borrow me one of this books for my lesson. They had no problem at all with it!

• Plasmodium are the micro-organisms that spread Malaria
• Also made up of only one cell, but this ones have their architect´s plan packed in a nucleus

5)      Viruses, for example Ebola

• Made up of nucleic acid, surrounded by a coat made of protein
• Can only live inside other (host) cells, cause disease and death in animals, plants and even bacteria – scientist cannot agree if they are living beeings or not!
• Only the centre part (nucleic acid) is passed into a new cell, once inside a cell it is quickly reproduced to give more viruses, a protein coat is developed around each new virus – after a while the cell dies and the viruses are released
• Some viruses attack only certain cells in the body of an organism

Drawing tasks:

• Copy an animal cell from the board into your exercise book – headline: “this is the material that I´m made of”
• Draw things made of cells (=humans, animals, plants)
• Draw a bacteria (copy from the poster)
• Draw a virus