7 ORGANISMS ARE ORGANIZED ON A CELLULAR BASIS AND HAVE A FINITE LIFE SPAN

Worksheet 7: Organisms consist of cells

WORKSHEET Workshop

Teaching aids:

  • Worksheet, microscope and accessories (tweezers, microscope slide, cover slip, dissecting needles, pipette), the epidermis of an onion

Procedure:

First, the students should prepare an epidermis of an onion for the observation with a microscope (see worksheet for students). Then the teacher gives the following instructions: “Use the microscope to look at the cells of the onion. Describe and draw what you see!“

This task can be difficult for younger students and they will need help with the preparation of the onion. If necessary, the preparation can be done in advance. Before starting the observation, the teacher explains the structure of the microscope and discusses the rules to be followed when using it.

The educational objective of this task is to observe the composition of life (and living creatures) from cells.

If the assignment is carried out as a group or in the whole class, the students need more support from the teacher. Younger and weaker primary school students may also need more help.

Pic 89: Microscope

Background information: Microscope

Microscope slide: A little glass plate on which you have to place the object you want to observe. It has to be covered with a drop of water and a (second) cover plate so that nothing can slip.

Coarse and fine adjustment: For focusing, the microscope stage hast to be moved up or down. In doing so you can first adjust the coarse adjustment, then the fine adjustment until the optimum acuity is achieved.

Object stage, lens tube and ocular, objective lenses, light

Observation: The epidermis consists of many small parts. This small parts are called “cells” and are separated from each other by visible cell walls. In addition, they have a nucleus, which may be visible as a dark rounded structure.

Pic 90: Onion cell 1

Explanation: The epidermis of the onion consists of many small parts, which are called cells. In addition, each cell has a small dark rounded structure - the nucleus. All genetic information is stored here. It also controls the individual processes inside the cell.