Unit B: Cells and Systems Topic 2: The Microscope and Microscopic Organisms

History First microscopes invented by Anton van Leewonhoek, in 1600s Holland, using small magnifying lenses. Leewonhoek’s microscopes could see up to 300X. He used his microscopes to study single celled organisms. He called these organisms animalcules.

Robert Hooke Lived at same time as Leeuwenhoek. English Studied the cells of cork trees. He called them cellulae, which meant little rooms. This is where we get the term cells.

Cell Theory Is a theory made up of two points: 1. All living things are either cells (eg. bacteria), or made up of cells (eg. mushrooms). 2. Cells are the basic units of structure and function of life.

Microscopes Today Two main types of microscopes today: 1. Compound light microscopes: made up of two lenses. Have a max. magnification of 2000X. Cannot see the smaller structures in cells. 2. Electron Microscopes – bounces beams of electrons off sample. The beam is then sent to a TV or photo plate providing a greatly magnified image. The max. magnification is X. The downside with electron microscopes is that they kill living specimens so dead ones are used.

Field of View Amount of area you can see with a microscope at a set magnification. Calculated in two parts: 1. Measure actual field of view on low power. 2. FoV = Low Power FoV*LowPower Mag/ High Power Mag

Microscopic Organisms and How They Move Example: Paramecium and Cilia Paramecia move by having hair-like projections around the cell wave in the same direction, propelling it forward like little oars. Example: Chlamydomonas and flagella Chlamydomonas have two tails that they whip around to help them move. Sperm cells in animals also have flagella to help them move.

Amoeba and the False Foot The amoeba is a single-celled predator which preys on other unicellular organisms. It moves by changing its shape and pushing part of its membrane forward and letting the rest of the cell catch up.