Which concept suggests that all current organisms descended from a single-celled ancestor?

The concept that suggests all current organisms descended from a single-celled ancestor is rooted in the idea of macroevolution. Macroevolution refers to large-scale evolutionary changes that happen over long periods, including the emergence of new species and major evolutionary transitions. It encompasses the grand evolutionary patterns and processes that can be observed in the fossil record and evolutionary lineage tracing.

This concept underscores the belief that all life on Earth is interconnected through a common ancestry, tracing back to simpler, single-celled organisms. By examining the relationships between different species and their evolutionary histories, scientists can infer how diverse forms of life evolved over millions of years from this common origin.

Microevolution, on the other hand, deals with small-scale changes within a species over relatively short time frames, often involving variations in traits due to environmental pressures. Phyletic gradualism and punctuated equilibrium are theories about the tempo and mode of evolution but do not encapsulate the broader idea of descent from a single ancestor in the same general terms that macroevolution does.