Question

DARWIN & NATURAL SELECTION
Develop a definition for each of the following words.
Word Definition
Evolution
Natural Selection
Adapation
Variety
Overproduction
Competition
Reproductive Isolation
Genetic Diversity
Mutation

1. Darwin’s theory is sometimes called “survival of the fittest.” In this context, fittest
doesn’t necessarily only mean “fastest” or “most muscular.” Based on your reading,
what do you think “fittest” means here?
2. Darwin did not call his theory “evolution.” Instead, he called it “descent with
modification.” Why do you think he called it that?

Answer 1

Word definitions

- Evolution: Change in the inherited traits of a population over successive generations; a process that can lead to the formation of new species.
- Natural selection: The process by which individuals with traits better suited to their environment tend to survive and reproduce more, causing those traits to become more common in a population.
- Adaptation: A trait (structure, behavior, or physiology) that increases an organism’s chances of survival and reproduction in a particular environment.
- Variety (variation): Differences among individuals in a population in traits such as size, color, or behavior.
- Overproduction: When organisms produce more offspring than can survive given the available resources, creating pressure for selection.
- Competition: The struggle between individuals or species for limited resources (food, space, mates), which influences which individuals survive and reproduce.
- Reproductive isolation: Any barrier (behavioral, geographic, temporal, genetic, etc.) that prevents different populations from interbreeding and exchanging genes, promoting the formation of separate species.
- Genetic diversity: The range of different genes and alleles present in a population; higher diversity gives populations more capacity to adapt to changing conditions.
- Mutation: A change in an organism’s DNA sequence; mutations are a source of new genetic variation and can be harmful, neutral, or beneficial.

Short answers

1) “Fittest” means those individuals best suited to their environment in a way that increases their reproductive success — not simply the strongest or fastest, but those that leave the most surviving offspring.

2) Darwin called his idea “descent with modification” because it emphasizes that species are connected by common ancestry (descent) and that their traits change gradually over generations (modification), producing the diversity of life rather than abrupt, unrelated replacements.