Final answer:
b. The time required varies considerably The time it takes for new species to form on Earth varies considerably, influenced by a multitude of factors. Scientists recognize two main models of speciation:
Step-by-step explanation:
The question of how long it takes for new species to form on Earth can be quite complex. The answer is (b) the time required varies considerably. Speciation is a process that occurs over evolutionary time scales, and it can happen through different mechanisms such as geographic isolation or reproductive isolation. Scientists study these processes through observational evidence and the fossil record and have proposed two primary models: the gradual speciation model and the punctuated equilibrium model.
In the gradual speciation model, species slowly change over long periods of time, while the punctuated equilibrium model suggests that species remain relatively stable for long periods, with significant changes occurring in relatively short, abrupt bursts usually associated with a significant and sudden environmental change. The biodiversity of an area is determined by the balance between speciation and extinction rates. This balance has shifted throughout Earth's history, sometimes causing dramatic fluctuations in the number of species.
It is also important to note that speciation is an ongoing process, and the time it takes for new species to fully emerge can vary broadly, from thousands to millions of years, depending on numerous factors including environmental conditions and genetic variations. Therefore, the process of speciation continues to contribute to the biodiversity change through geological time.