Full Answer
Indeed, many primitive multicellular organisms probably experienced both unicellular and multicellular states, providing opportunities to forego a group lifestyle. For example, the bacterium Pseudomonas fluorescens rapidly evolves to generate multicellular mats on surfaces to gain better access to oxygen.
The transition from unicellular to multicellular life was one of the most momentous events in the evolution of life. Estimated to have first occurred more than 1.5 billion years ago, the shift to multicellularity gave rise to increasingly complex life forms on Earth, from ancient algae-like organisms to dinosaurs to human beings.
More complex forms of life took longer to evolve, with the first multicellular animals not appearing until about 600 million years ago. The evolution of multicellular life from simpler, unicellular microbes was a pivotal moment in the history of biology on Earth and has drastically reshaped the planet’s ecology.
From worms to insects, the dinosaurs, grasses, flowering plants, hadedas and humans, you just have to look around and see the extraordinary forms of multicellular existence," says Durand. "It has been difficult to explain how this occurred because it was not an easy thing to have happened.
A new study published in Nature Communications put that theory to the test. The researchers divided ten strains of Chlamydomonas reinhardtii, a unicellular green algae, into two groups. One group was subjected to a microscopic predator called Brachionus calyciflorus, a type of rotifer. The other group evolved without predators.
According to theory, once cell groups are established, cells can begin to serve specialized functions.
However, scientists have now completed a study of the complete DNA of one of the most important model organisms, Gonium pectorale, a simple green algae that comprises only 16 cells. This microscopic organism is helping to fill the evolutionary gap in our understanding.
Credit: The Volvocales Information Project by Aurora Nedelcu. Throughout the history of life on Earth, multicellular life evolved from single cells numerous times, but explaining how this happened is one of the major evolutionary puzzles of our time. However, scientists have now completed a study of the complete DNA of one ...
However, the volvocine green algae include a diverse variety of unicellular, colonial, and multicellular species," says Durand. There are many members of the volvocines with varying degrees of complexity, so it is possible to examine different stages on the road to multicellularity.