Biological species concept facts for kids

The biological species concept is a way to understand how new species form. It says that a species is a group of living things that can breed with each other. They can have healthy babies that can also breed.

However, members of one species usually cannot breed with members of other species. If they do, their offspring might not be healthy or able to have their own babies. This idea means that different species are "reproductively isolated" from each other.

The scientist Ernst Mayr explained that a new species often forms when an existing species splits. This happens a lot when groups of the same species get separated. For example, if a group of animals gets split by a new river or mountain range, they can't breed with each other anymore. This is called geographical isolation.

Over time, these separated groups change and develop different features. Eventually, even if they come back together, they might not be able to breed anymore. At that point, they have become two different species. This is the most common way new species form, and it's called allopatric speciation.

Sometimes, new species can form even if they live in the same area. This is much rarer and is called sympatric speciation.

Classifying Living Things

The biological species concept is very important for classifying living things. But it's not always easy to use in real life. Here's why:

• It's hard to test if two groups can breed if they live far apart.
• Some groups might not breed in a lab, but they could in nature.
• Some species, like bacteria, don't need a partner to have babies (they are asexual). This concept doesn't work for them.
• Sometimes, different species can still have babies together, but their offspring are not fertile (like a mule, which is a mix of a horse and a donkey).

Because of these challenges, scientists often use other ways to classify species too. It's a complex job, and there isn't one perfect way to classify every living thing.

How the Idea of Species Developed

Scientists have thought about what a "species" is for a long time.

Early Ideas

In 1686, a scientist named John Ray had an early idea about species. He thought that species always produced the same kind of offspring. He believed that species were fixed and didn't change much, even if there could be some differences within a group.

Later, Carl Linnaeus used a system to name and classify living things. He often looked at the physical features of organisms to decide if they were the same species. This is still useful today for people who study nature.

Charles Darwin's View

Charles Darwin, who wrote The Origin of Species, also thought about species. He said that the word "species" was just a convenient label. It helped scientists group together individuals that looked very similar.

However, even before his famous book, Darwin had a very modern idea. He thought that species were kept separate because they couldn't breed with other groups. He even noticed that some species could look almost identical but still be different species because they didn't breed together. He saw this with two types of leaf warbler birds.

Modern Discoveries

In the last 70 years, two main ideas have helped biologists understand species better:

• Gene Pools: This idea looks at a species as a group that shares a common "gene pool". This means they can all mate together, even if they have small differences. It's like all the genes in that group are mixed together.
• DNA Analysis: Scientists can now look at the DNA of different organisms. By comparing their DNA, they can see how closely related they are. This is very helpful when it's hard to do breeding experiments, especially for tiny organisms or those that live in hard-to-reach places.

Hidden Species

Sometimes, two groups of animals or plants look exactly the same, but they are actually different species. These are called sibling species or cryptic species (meaning "hidden" species). Their differences can only be seen by looking at their DNA.

• For example, a tiny sea animal called Celleporella hyalina was thought to be one species. But DNA analysis showed it was actually more than ten different species!
• Scientists also found that what was thought to be one species of giraffe is actually at least 11 different groups based on their DNA.
• The Amazonian frog Eleutherodactylus ockendeni is another example. DNA showed it's at least three different species that separated millions of years ago.

Finding these hidden species means that there are probably many more species on Earth than we once thought!