Answer & Solution
Answer: Option
D
Solution:
The correct answer is Option D: Stebbins.
This quote explains how living things change and evolve over long periods. Let's break it down:
1. Variations make evolution possible: Imagine a group of plants. Some might be taller, some shorter, some have different colored flowers. These differences are called variations. Evolution, which is the process of life changing over time, can only happen if there are these differences among individuals.
2. Intermediate basis: Genetic Segregation and Recombination: Think of it like shuffling a deck of cards. You're not creating new cards, but you're getting new combinations. Similarly, genetic segregation (when genes separate during reproduction) and recombination (when genes from parents mix to form new combinations in their offspring) create new mixes of existing genetic material. This is a very important way to create diversity, but it's like rearranging what's already there.
3. Ultimate source: Mutation: This is the key! While shuffling cards (recombination) creates new hands, what if a card itself suddenly changed, or a new card appeared in the deck? That's what a mutation is. A mutation is a sudden, permanent change in the genetic material (DNA). It's the only way to introduce truly *new* genetic information into a population. So, mutations are the ultimate source because they create the original raw material for variation, which can then be shuffled around by segregation and recombination.
Stebbins (G. Ledyard Stebbins) was a famous evolutionary biologist who was a key figure in developing the "Modern Synthesis" of evolution. This theory combined Charles Darwin's ideas of natural selection with Gregor Mendel's genetics and the understanding of mutations. His work emphasized the crucial role of mutation as the ultimate source of genetic variation upon which evolution acts.
So, in simple terms: Mutations create new traits, and then those traits get mixed and matched through genetic segregation and recombination, allowing evolution to happen!
