Single-Celled Organisms
Explain how unicellular organisms such as bacteria and Amoeba carry out all the functions of life within a single cell
What a learner can do afterwards
- Names examples of unicellular organisms
- Lists the seven life processes (MRS NERG) and explains how a single cell performs each one
- Contrasts how unicellular organisms meet their needs compared to multicellular organisms
1 · Read
Most living things you know, like people, dogs, and trees, are built from trillions of cells working together. Some living things are different. A bacterium or an Amoeba is made of just one cell, and cells like these live in pond water and inside you. That single cell has to do every job a whole body does, all by itself. Scientists call the seven jobs MRS NERG: Movement, Respiration, Sensitivity, Nutrition, Excretion, Reproduction and Growth.
An Amoeba stretches part of itself out like a tiny arm to move toward a bacterium, then wraps around it and takes it in as food. Later, that same Amoeba splits itself into two new Amoebae. One cell just moved, fed itself, and reproduced.
In your body, a skin cell mostly protects and a muscle cell mostly moves you. A bacterium has no other cells to help, so its one cell must feed, sense, excrete, grow, and reproduce, and many can also move, all by itself.
A single cell, like a bacterium or an Amoeba, carries out every life process in MRS NERG completely alone, while your body shares those same jobs across many specialized cells.
The readings 'Two kinds of cells' and 'One cell dividing into two' were written for this dataset. 'Key points: Cells and organisms' is adapted from a Khan Academy article. This record does not establish that article's license terms.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.