All questions of Darwin’s Theory of Evolution by Natural Selection for Grade 9 Exam

Understanding Evolutionary Mechanisms
The fundamental views on evolutionary mechanisms between Darwin's theory of natural selection and de Vries' mutation theory highlight significant differences, particularly in their perspectives on variation.
Darwin's Theory of Natural Selection
- Darwin proposed that evolution occurs through natural selection, where variations in traits arise from small, incremental changes.
- These variations are usually minor and directional, enhancing the survival and reproductive success of organisms better adapted to their environment.
- The process is gradual, emphasizing a slow accumulation of changes over time leading to new species.
de Vries' Mutation Theory
- In contrast, de Vries introduced the concept of mutations as a primary source of variation.
- He argued that these mutations can be large and random, resulting in significant changes in an organism's traits.
- This theory posits that such abrupt changes can lead to the emergence of new species relatively quickly, rather than through gradual modifications.
Key Differences
- Darwin's variations are small, favoring gradual adaptations, while de Vries' mutations can be substantial and unpredictable.
- This distinction underscores the different mechanisms each theorist believed drove evolutionary change—natural selection for Darwin, and mutation for de Vries.
In summary, option 'B' correctly captures the essence of the differences between these two evolutionary theories, emphasizing the nature and scale of variations as central to their respective explanations of evolution.

Darwin's Gradual Evolution
Darwin's theory of evolution, primarily presented in his work "On the Origin of Species," is based on the idea of gradualism. He proposed that species evolve over long periods through small, incremental changes. Key aspects include:

• Natural Selection: Darwin emphasized that individuals with advantageous traits are more likely to survive and reproduce, leading to gradual adaptations in populations.
• Continuous Process: Evolution is viewed as a slow, continuous process rather than abrupt changes.
• Fossil Record: Darwin supported his theory with evidence from the fossil record, showing transitional forms and gradual changes over time.

de Vries' Mutation Theory
Hugo de Vries introduced a contrasting perspective with his mutation theory, which emerged in the early 20th century. His key ideas include:

• Sudden Mutations: de Vries argued that new species could arise from sudden large mutations, not just gradual changes.
• Variation Sources: He believed that significant genetic variations could occur in a single generation, leading to rapid evolutionary changes.
• Mutation and Evolution: De Vries's work emphasized the role of mutations as a primary source of evolutionary change, in contrast to Darwin's gradualism.

Conclusion
In summary, the fundamental difference lies in the pace and mechanism of evolution. Darwin viewed evolution as a slow, gradual process driven by natural selection, while de Vries emphasized the role of sudden mutations leading to rapid evolutionary changes. This distinction highlights the diversity of thought in the early understanding of evolutionary biology.