Caenorhabditis elegans (C. elegans) is a tiny worm that scientists use to learn about how cells develop and make decisions. Studying this little worm helps us understand important ideas in genetics.

Key Contributions:

1. Lineage Analysis:

   • C. elegans has a fully mapped out sequence of how its cells grow.
   • An adult worm has 959 body cells.
   • This helps scientists track how cells change from a single fertilized egg into a fully formed worm.

2. Cell Fate and Differentiation:

   • In C. elegans, certain early cells always turn into specific types of cells later on.
   • About 131 of the 959 cells die on purpose, a process called programmed cell death (apoptosis).
   • This shows how important these decisions are for cell development.

3. Genetic Tools:

   • C. elegans has a simple set of genes, about 20,000 in total.
   • Scientists can change or "turn off" these genes using a method called RNA interference (RNAi).
   • This has been used successfully on about 80% of the worm's genes.

4. Conserved Pathways:

   • Many processes that happen in C. elegans are similar to what occurs in more complex animals, including humans.
   • For example, the Notch signaling pathway, which helps decide what types of cells will become, works almost the same in mammals.

5. Quantitative Studies:

   • Scientists can use C. elegans to quickly study many different mutant worms that affect how cells develop.
   • This has helped them find and study over 500 mutants that change development.

C. elegans is vital for helping us understand how cells make choices during development. The knowledge gained from studying this little worm can also help us learn more about human biology and certain diseases.