Questions: Adaptation and Fitness

Question 1

A population of beetles lives in a forest with brown bark. Brown beetles survive to reproduce more often than green beetles. Which statement best describes the fitness of brown beetles in this scenario?

• A. Brown beetles are intrinsically stronger and healthier than green beetles
• B. Brown beetles have higher reproductive success relative to green beetles in this environment
• C. Brown beetles would have higher fitness in any environment regardless of background color
• D. Green beetles will evolve brown coloration through directed mutation over time

Answer: (B)

Fitness is always relative to the current environment and measured as reproductive success. Brown beetles are not 'better' in any absolute sense — in a green-foliaged environment, green coloration would have higher fitness. Fitness is context-dependent, not an intrinsic property of the organism.

Question 2

An adaptation is a trait that evolved because it will help an organism survive in future environments.

• T. True
• F. False

Answer: False

Adaptations reflect past natural selection, not future needs. A trait becomes prevalent because individuals with it had higher reproductive success in historical environments. Evolution has no foresight and cannot produce traits in anticipation of future conditions — this is a common misconception sometimes called the 'teleological fallacy.'

Question 3

What is a fitness trade-off, and why does it mean organisms are never 'perfectly' adapted?

Model answer: A fitness trade-off occurs when a trait that increases fitness in one dimension simultaneously decreases it in another. Because resources are finite, organisms cannot maximize all fitness components simultaneously, so all adaptations are compromises.

For example, large body size in male deer increases mating success but also increases predation risk and energy costs. Resources (time, energy, nutrients) available for reproduction, immune defense, and growth are limited, so selection produces trade-off solutions, not perfect organisms.