Question

Why don't the biggest and strongest individuals in a population always produce the most offspring? a. The biggest and strongest individuals always have higher fitness. b. In some environments, being big and strong lowers fitness. c. Sometimes the biggest and strongest individuals may choose to have fewer offspring. d. Sometimes the number of offspring is not related to fitness.

Short answer

The most accurate answer is option b: In some environments, being big and strong lowers fitness. This is because environmental factors can determine an individual's fitness and the number of offspring they produce.

Step-by-step solution

Understand Fitness in a Population

Fitness is the ability of an individual to survive and reproduce in its environment. It is an essential concept in understanding natural selection and evolution. In a population, individuals with higher fitness tend to produce more offspring and be more successful in passing on their genes.

Option a: The biggest and strongest always have higher fitness

This option suggests that bigger and stronger individuals in a population always establish higher fitness. However, this may not always be true because other factors, such as environmental conditions and mating preferences, may also affect an individual's fitness. Thus, option a is not correct.

Option b: In some environments, being big and strong lowers fitness

This option is correct. There could be situations where being big and strong may not be an advantage and could even be a disadvantage. For example, in an environment with limited resources, being big might mean higher energy requirements that cannot be met, reducing an individual's chances of survival and reproduction. Alternatively, a population's predators may be more likely to target bigger and stronger individuals. In these cases, the largest and strongest individuals might have lower fitness and produce fewer offspring.

Option c: Sometimes the biggest and strongest individuals may choose to have fewer offspring

This option implies that the biggest and strongest individuals' conscious choice leads them to have fewer offspring. This statement is anthropomorphic and does not accurately describe the processes that occur in nature related to offspring production. Therefore, option c is incorrect.

Option d: Sometimes the number of offspring is not related to fitness

This option proposes that there may be instances where offspring production is unrelated to an individual's fitness. Although there may be some circumstances where other factors influence offspring production, generally, higher fitness individuals produce more offspring, which is a key aspect of natural selection. Therefore, option d is not accurate.

Conclusion

The most accurate answer to the exercise is option b: In some environments, being big and strong lowers fitness. This option highlights the role of environmental factors in determining an individual's fitness and the number of offspring they produce.

Key concepts

Natural Selection

Natural selection is a fundamental concept in evolutionary biology. It describes the process by which certain traits become more common in a population over generations. Traits are favored when they enhance an individual's survival and reproduction. The key idea is that

• Individuals with traits that increase their fitness are more likely to survive and reproduce, passing those advantageous traits to their offspring.
• Over time, these traits become more prevalent in the population.

It's essential to understand that natural selection doesn't always favor the biggest or strongest individuals. Instead, it favors those whose traits best match the environment. For example, in an environment where food is scarce, smaller individuals might require less energy to survive, giving them a selective advantage over larger, stronger counterparts. Natural selection works over many generations to shape the characteristics of a population, responding to environmental pressures and changes.

Environmental Adaptation

Environmental adaptation refers to how organisms evolve traits that make them better suited to their surroundings. This process is driven by natural selection and involves changes in physical, behavioral, or physiological traits. Adaptations help increase an individual’s chances of survival and reproductive success.

• Different environments present different challenges and therefore require different adaptations.
• An adaptation that is beneficial in one environment might be a disadvantage in another.

For instance, an animal living in a cold climate might develop a thick fur coat to retain heat, while the same adaptation would be detrimental in a hot desert environment. Similarly, being big and strong might seem advantageous, but in an environment with limited resources, it could reduce survival chances. This underscores the importance of environmental context in shaping the traits favored by natural selection.

Reproductive Success

Reproductive success is a crucial component of an organism's fitness. It refers to the number of offspring an individual can produce that survive to reproduce themselves. High reproductive success means more of an individual’s genes are passed to the next generation.

• Factors influencing reproductive success include the individual's ability to find food, avoid predators, and successfully mate.
• It is also affected by the environment, which can change the benefits of certain traits.

Despite its importance, reproductive success is not just about having more offspring. It's about producing offspring that can survive and reproduce in their environment. In some cases, producing fewer offspring but investing more resources in their survival can lead to greater reproductive success. This complexity explains why the biggest and strongest individuals don’t always produce the most offspring: they need to be adapted not only for survival but also for efficient reproduction in their unique environment.