Q4. Which two questions did NCERT say remained open about the mechanism of evolution?
What is the origin of the variation, and how does speciation occur (NCERT page 119)?
Q5. Assertion: de Vries called his idea saltation. Reason: he believed a single-step large mutation caused speciation. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion (NCERT page 119).
Q6. In which period did de Vries bring forth the idea of mutations?
In the first decade of the twentieth century (NCERT page 119).