It may seem silly, but in order to make sense of the natural world we have to actually define what a species is. What kinds of requirements are there? For this section you will stay on this page to gather the information you need in order to answer the questions in the handout.
In case you are wondering the image on the left is real. This spider lives in Hawaii and is suitably called the Happy Face Spider!
In case you are wondering the image on the left is real. This spider lives in Hawaii and is suitably called the Happy Face Spider!
Once people started trying to organize the vast diversity that is life on Earth into different species, the debate of what a species is began and is still happening today. We will focus on the two leading species concepts used by biologists to define a species: Morphological and Biological.
If you were to guess, would you say that all of the images above are from the same species as the Hawaiian Happy Face Spider or a mix of related species? Write your answer down on your handout (you will be given the real answer later). If you were to use the morphological species concept you would do so by using comparative anatomy to say whether or not the spiders above are from the same species. If one were to use this approach they would most likely label them as different species.
On the other hand if one were to use the biological species concept, they would see if the spiders could interbreed and produce viable offspring. That is the offspring they produce must be fertile and and able to reproduce themselves. If they could, they would be considered the same species.
On the other hand if one were to use the biological species concept, they would see if the spiders could interbreed and produce viable offspring. That is the offspring they produce must be fertile and and able to reproduce themselves. If they could, they would be considered the same species.
Those of you who have watched Napoleon Dynamite remember him talking about the liger. The liger is a cross between a male lion and a female tigress. The liger is a great example for how the biological species concept works. Despite the fact that two different species (lion = Panthera leo, tiger = Panthera tigris) can produce offspring, these offspring, such as the liger are sterile and are essentially the end of the line. We call these crosses hybrids. Other examples would be the cross of a donkey and a horse to produce a mule or the cross between a grizzly and a polar bear, which is called a grolar bear. The biological species concept works great with most species we can observe alive today. For instance, all of the spiders above are from the same species! Think of them as the crazy variety we see in dog breeds. The spiders in that image can all produce viable offspring with one another.
So you may be wondering why we should even bother with the morphological species concept. The answer is two-fold: We use it when studying fossils and with many asexually reproducing organisms such as bacteria. ThiThink about it, how in the world could a paleontologist use the biological species concept on fossils of extinct species? There is no way to breed them and see if the offspring are fertile. With organisms that reproduce asexually it is pretty hard to use the biological species concept seeing how we cannot test the offspring of two organisms at all! As you can see it is not always so cut-and-dry when it comes to identifying a species.