Multicellular organism facts for kids
Multicellular organisms are living things made up of more than one cell. This includes animals, plants, and most fungi. In these organisms, cells usually have special jobs. Cells that do the same job work together in groups called tissues.
Multicellular organisms also have special cells for reproduction. These are called sex cells. In males, these are sperm cells. In females, they are ovum (or egg) cells. If an organism has both types of sex cells, it is called a hermaphrodite.
How Multicellular Life Evolved
Scientists can tell from how cells are built that multicellularity (having many cells) has developed many times in Earth's history. This happened separately in different groups like plants and animals.
The very first signs of life in fossils are tiny cyanobacteria. These are found in rocks from about 3.5 billion years ago. They were single cells but lived together in large groups called stromatolites.
The first true multicellular fossils were found in rocks from 2.1 billion years ago in Gabon, Africa. These were eukaryotic cells (cells with a nucleus) that lived in colonies. These fossils were big enough to see without a microscope, much larger than bacteria. Scientists think that being multicellular helped these organisms grow bigger. They also believe that enough oxygen in the air was needed for this type of life to develop.
Reproduction and Development
For multicellular organisms to reproduce, they need to be able to create a whole new organism from just a few germ cells (like sperm and egg cells). How this happens is studied in a field called developmental biology. It's amazing how a single fertilized egg can grow into a complex animal or plant!
Long-living multicellular animals also face a challenge called cancer. This happens when some cells in the body start to grow out of control and don't follow the normal rules for development.
Related Pages
See also
In Spanish: Organismo pluricelular para niños
