Final answer:
New species are formed through the process of speciation, which occurs when populations of the same species become reproductively isolated, often due to habitat isolation. Over time, genetic differences accrue due to natural selection, mutations, and genetic drift, ultimately leading to the emergence of a new species that cannot interbreed with the original population.
Step-by-step explanation:
To understand how new species, or speciation, arises, it is pivotal to grasp the concept of a species. A species is a collective of organisms that can breed and yield fertile offspring in nature. An organism is considered a new species if it cannot interbreed successfully with organisms that are like it. If a population is isolated from other populations of the same species for a sufficient length of time, they may develop significant genetic differences that make reproduction impossible with the originating population.
Reproductive isolation is a key mechanism driving this process. For example, geographic separation—also referred to as habitat isolation—often leads to reproductive isolation. This separation can occur due to natural events like floods, which may divide a population and limit their interaction with each other. Over extensive periods, usually thousands of years, processes such as natural selection, mutations, and genetic drift can lead these isolated populations to diverge significantly, ultimately resulting in the evolution of new species.
A species’ ability to reproduce is central to this concept. When isolated populations can no longer produce fertile offspring with their parent species, they are considered distinct species. This reproductive inability signifies the culmination of speciation and underscores the transformation from population variance to the birth of a new species.