Speciation: Definition, Examples & Role in Evolution

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  • 0:00 What Are Species?
  • 1:05 Natural Selection and…
  • 2:40 Real Life Examples of…
  • 4:08 Lesson Summary
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Lesson Transcript
Instructor: Laura Nappi
Can you believe that over two million species have been identified on Earth? Have you ever wondered how so many species formed on Earth? Learn more about how new species form and test your knowledge with a quiz.

What Are Species?

Did you know there is a lizard that squirts blood out of its eye to deter predators? And, there is a fish that can breathe air on land for several days? There are some bizarre species out there, that's for sure. The diversity of species on Earth is simply astounding. Scientists have identified about two million species and still do not know how many species inhabit Earth. Scientists estimate as many as 30 million species may inhabit Earth. So, the big question is how did so many species form?

A species is a group of individuals that are genetically able to mate in nature and produce fertile offspring. The process of evolution has given rise to the diversity of species we see on Earth. Evolution is a process that explains how organisms have diversified and descended from earlier forms of organisms over time. Essentially that means all species living on earth have derived from a common ancestor. Speciation is an evolutionary process that leads to the formation of a new species.

Natural Selection and Speciation

For a new species to form, individuals of a population need to be reproductively isolated from one another. This isolation can occur in many ways, such as the separation of a population by a mountain range or body of water. This separation isolates individuals to a new environment. Over time, traits that are best suited to this different environment become dominant in this isolated population. This is called natural selection. Natural selection is a mechanism of evolution where individuals with traits best suited for their environment will survive and pass on their genes to the next generation. Over many generations, the isolated population can undergo enough genetic changes that it would no longer be able to breed with the original population. Let's look at an example.

Imagine a hypothetical species of rabbit living in a coastal forest. There were thousands of rabbits living in this coastal area. Then, an intense storm charged through, trapping a few rabbits on a floating log. For days this log floated in the ocean and eventually landed on an island. These castaway rabbits took refuge on this island and started breeding in this new environment. The temperature and food resources were very different than their original coastal surroundings. Over time, different traits that helped with survival, like short fur and smaller mouth size, became dominant in this isolated population. Over many generations, the island rabbits became genetically different than the original coastal rabbit population. If the rabbits from the coastal area were to meet rabbits from the island area, they would no longer be able to successfully reproduce.

Now let's look at some real life examples of speciation.

Real Life Examples of Speciation

Galapagos Finches

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