Question

Which one of the given terms states that mutations caused speciation?

• A. Variation
• B. Genetic recombination
• C. Gene migration
• D. Saltation

Hint:

Comparison of Evolutionary Theories:
$\bullet$ Darwin: Small, gradual, continuous, directional variations.
$\bullet$ Hugo de Vries: Large, sudden, discontinuous, directionless mutations = Saltation (Single-step large mutation causing speciation).

Answer 1

The Correct Option is D

Concept:
Hugo de Vries formulated the Mutation Theory of Evolution based on his breeding experiments with the evening primrose (Oenothera lamarckiana), contrasting with Darwin's view of gradual evolution.

Step 1: Mechanism of Speciation according to Hugo de Vries:
Hugo de Vries believed that large, sudden, discontinuous, random, and directionless genetic changes called mutations are the primary cause of evolution and the origin of new species.
He proposed that mutation causes speciation in a single step, which he termed saltation (single-step large mutation).
This differed from Darwinian evolution, which emphasized minor, continuous, directional variations accumulating gradually over long periods.

Step 2: Evaluating the Other Terms:
- Variation: Morphological or physiological differences among individuals of a species, described by Darwin as small and continuous.
- Genetic recombination: Exchange of genetic material during crossing over in meiosis leading to new allelic combinations.
- Gene migration: The movement of alleles into or out of a population due to individual immigration or emigration.

Step 3: Final Answer:
The term that states that single-step large mutations cause speciation is Saltation (Option D).