Species: Definition, Description, Distribution, & Fun Facts

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Species Definition

Species are a group of organisms that share a common genetic heritage, capable of interbreeding and producing equally fertile offspring. The different species are separated from each other by reproductive barriers and these barriers can be geographic, such as a mountain range separating two populations, or genetic barriers that prevent reproduction between two populations. Scientists have changed their definitions of species many times throughout history.

What are Species?

Species are one of the more specific classifications used by scientists to describe animals. Scientists use a binomial nomenclature system to describe animals without confusing common names.

This system uses the genus name as the first name, always in uppercase, and the species name as the second, always in lowercase. Therefore, some animals such as the red fox, Vulpes vulpes, all belong to the Vulpes genus and their specific name is vulpes.

Note the difference in capital letters to distinguish genus and species. Other foxes such as the fast fox, Vulpes velox, are also of the Vulpes genus, but there are barriers that prevent them from mating with the red fox.

In this way, they are always separate species. Since the time of Charles Linnaeus, the creator of binomial nomenclature, animals have been continually classified and reclassified into different groups, genera, species and subspecies.

Linnaeus, a taxonomy of organisms in the 1700s, limited its classification to the physical attributes of various organisms. Surprisingly, most of the organisms identified were related to each other. Others, however, could not have been more wrong.

Genetic engineering today has given us a much better chance of historical relationships between animals. For example, when Linnaeus first classified elephants in the early 1700s, he saw only one specimen. The specimen was an Asian elephant fetus, the smallest of all elephant species known today.

Without a better understanding, Linnaeus called the species Elephants maximus. Scientists today have been forced to reclassify the elephant over and over again. The first distinction is between Asian and African elephants, which vary greatly in size.

Scientists therefore had to distinguish between elephants that live in the grasslands and elephants that live in forests in Africa. Genetics show that populations do not intersect and are separated by a reproductive barrier.

In the following century, Charles Darwin and Alfred Wallace tailor-made the mechanism to generate multiple species from a single species. This process of natural selection applies the various adversities that organisms must overcome in order to reproduce.

Organisms better adapted to the environment can reproduce more and their offspring can also increase in number. In this way, different lines of the same species can be better or worse, depending on their genetics.

Eventually, the two successful lines can diverge, creating a reproductive barrier between the two populations. According to Darwin and Wallace, these populations are now considered separate species.

Since the dawn of time, this process has occurred and has divided organisms along a number of successful lineages. This theory has been confirmed by a lot of evidence. Fossil evidence provides clues that animal species have continuously changed over time, in response to changing environments.

When Linnaeus considered animals to be static and immutable entities, it is now widely accepted that species exist in a spectrum, with some species being closer to certain species than others. Therefore, animals can often interbreed or interbreed between species.

Examples of Species

i. Polar Bears and Grizzlies

Often the only obstacle to reproduction is geographic or based on the animal’s natural location. If that were to change, the animals could crossbreed and merge into one species. This is now seen in the wild in polar bears and grizzly bears. With climate change, polar bears are being pushed further south and must start exploiting different food sources.

Climate change is also allowing grizzly bears to venture further north, encountering polar bears along the way. Previously isolated populations now have the ability to reproduce and sometimes succeed.

Hybrids have been seen in the wild, but it is not yet clear whether they will be successful. There are many situations and examples of barriers to reproduction, but if the barrier can be removed, it is likely that two related species will be able to reproduce.

Unrelated species rarely have a chance to reproduce because they have become so different from each other. For example, a bat and a turtle have completely different genes.

The genes that control the development of turtles will not work in bats, and vice versa. In fact, they don’t even have the same number of chromosomes, which is necessary for the success of sexually reproducing organisms.

ii. Dogs and Wolves

Other animals, such as dogs and wolves, are technically still the same species. Although they have the same number of chromosomes and can technically reproduce, the domestic dog has come a long way compared to its wild breed.

Not only have dogs evolved to be more cuddly and kind, they are also more receptive to human social cues. Wolves operate in a very different social structure. So, these two things are very unlikely to happen again in the real world.

However, because they can produce fertile offspring, scientists consider them to be the same species. Dogs and wolves are a prime example of species brilliance, or of gradual change in a widely distributed population.

Think of a chihuahua. If Linnaeus had classified this animal, he certainly would not have placed it in the same category as the wolf. However, Chihuahuas can breed with a slightly larger dog, can breed with a large dog, can easily interbreed with wolves.

In this way, Chihuahuas and wolves have the same genetic basis, which is expressed in very different ways.

FAQ About Species

A hybrid is an organism created by crossing two distinct species.

Reproductive barriers are obstacles that prevent two species of animals from producing fertile offspring.

The binomial nomenclature is the naming system of the single species with two Latin names, the first relating to the genus, the second to the species.

A taxonomy is a system in which all organisms are placed to be classified.

Species Citations
  • Species Concepts: What about Ticks? Trends Parasitol . 2018 Dec;34(12):1017-1026.
  • Clostridium species as probiotics: potentials and challenges. J Anim Sci Biotechnol . 2020 Feb 20;11:24.
  • Demystifying dominant species. New Phytol . 2019 Aug;223(3):1106-1126.
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