Fitness

Definition

Fitness refers to an organism's ability to survive and reproduce in its environment, ultimately contributing to the gene pool of the next generation. It encompasses not only the physical health of an individual but also how well it can attract mates and raise offspring, impacting evolutionary success. Understanding fitness is crucial because it helps explain how certain traits become more common in populations over time due to reproductive advantages.

5 Must Know Facts For Your Next Test

1. Fitness is often measured by the number of offspring an individual can produce that survive to reproductive age, known as 'reproductive success.'
2. An individual's fitness can be influenced by various factors including environmental conditions, availability of resources, and competition for mates.
3. Not all traits that enhance survival directly correlate with increased fitness; some may improve reproductive success without necessarily aiding survival.
4. Fitness can change over generations as environmental conditions shift, causing certain traits to become more or less advantageous.
5. The concept of fitness also encompasses the idea of trade-offs; for example, a trait that enhances mating success might decrease survival odds in other contexts.

Review Questions

• How does fitness influence the process of natural selection within a population?
  • Fitness plays a crucial role in natural selection by determining which individuals are more likely to survive and reproduce. Those with higher fitness levels have traits that enhance their survival or reproductive success, allowing them to pass those advantageous traits to the next generation. This process leads to the gradual adaptation of the population to its environment as favorable traits become more prevalent.
• Compare and contrast natural selection and sexual selection in terms of their impact on fitness.
  • Natural selection focuses on traits that improve an organism's overall survival and ability to reproduce in its environment, while sexual selection emphasizes traits that increase an individual's attractiveness to potential mates. Both processes affect fitness but do so in different ways. For instance, a peacock's elaborate feathers may not directly improve survival but enhance its mating opportunities, demonstrating how sexual selection can impact fitness distinctly from natural selection.
• Evaluate how the concept of inclusive fitness expands our understanding of reproductive success and fitness beyond individual organisms.
  • Inclusive fitness broadens the definition of fitness by considering not only an individual's direct reproductive success but also the reproductive success of its relatives. This means that helping relatives can increase the overall genetic contribution to future generations, enhancing the inclusive fitness of an individual. For example, an animal might forego its own reproduction to assist siblings, thus ensuring that shared genes are passed on, illustrating a more comprehensive view of how social behaviors can impact evolutionary success.

Related terms

natural selection: A process where individuals with favorable traits are more likely to survive and reproduce, leading to the gradual evolution of species.

sexual selection:

A type of natural selection where certain traits increase an individual's chances of attracting mates and reproducing.

inclusive fitness:

A concept that expands the idea of fitness to include the reproductive success of an organism's relatives, not just its own offspring.