Mutation Theory of De Vries

• Proposed by: Hugo de Vries
• Experimental Organism: Evening primrose (Oenothera lamarckiana) observed in a field near Amsterdam.

Evolution and the origin of new species occur through mutations - sudden, large, and inheritable variations, rather than minor, gradual changes. De Vries coined the term saltation (single-step large mutation) for these sudden shifts.

1. Random Occurrence: Mutations appear spontaneously from time to time within naturally breeding populations.
2. Distinct & Heritable: Mutants are clearly distinct from their parents. Because these traits are genetic, they are passed directly to offspring, leading to the formation of new species.
3. Directionless: Mutations can occur in any direction (they are random).
4. Action of Natural Selection: Mutations are subject to natural selection. Nature eliminates unfavourable mutants and allows beneficial ones to survive and reproduce.

• Significance: While mutation alone doesn't drive all of evolution, it provides the essential raw material (genetic variation) upon which other evolutionary forces (like natural selection) can act.

• Major Criticism: It is highly unlikely that complex, specialised adaptations in nature (like the human eye or a bird's wing) could arise solely from sudden, random "jumps" or mutations.

• Evolution is driven by mutations, which are sudden, large, and inheritable genetic variations (saltations), rather than minor, gradual changes.
• These mutations emerge spontaneously and randomly in any direction within naturally breeding populations.
• Mutant traits are clearly distinct from parental characteristics and are directly inherited by offspring, facilitating the origin of new species.
• Natural selection operates on these directionless mutations by eliminating unfavourable variants and preserving beneficial ones.
• While mutations provide the essential raw material for evolution, it is highly unlikely they alone account for complex, specialised adaptations.