Final answer:
The reproductive success of an individual, known as fitness, is crucial for natural selection and evolutionary change. Adaptations for reproductive success vary depending on whether a species uses external or internal fertilization. Fitness determines how dominant certain traits become within a population over time. The correct option is 3) fitness
Step-by-step explanation:
The reproductive success of an individual is known as fitness. The concept of fitness is central to natural selection, which is the greater relative survival and reproduction of individuals in a population that have favorable heritable traits, leading to evolutionary change.
In the context of external fertilization, adaptations that might increase male reproductive success could include the production of large quantities of sperm to increase the chances of fertilization, or behaviors that improve the alignment with female gamete release.
With internal fertilization, adaptations might include behaviors or morphological features that increase the likelihood of successful mating, as well as sperm that are more competitive in reaching and fertilizing the egg.
Natural selection operates on populations based on their genetic variations and the resulting phenotypic expressions that influence fitness.
Microevolution refers to changes within a population's genetic structure (i.e., allele frequency), while macroevolution entails evolutionary changes on a broader scale, potentially resulting in new species over paleontological time.
In both cases, individuals with higher fitness pass their traits to subsequent generations, influencing the gene pool and overall direction of evolution. The correct option is 3) fitness