Species concept

\( \newcommand\) • • • • • • Quantifying species diversity requires developing a definition of a species. We would not expect all members of a species to be identical, so we must consider what magnitude and types of differences between individuals would lead us to consider them members of different species. A species concept is, therefore, a working definition of a species and/or a methodology for determining whether or not two organisms are members of the same species. In this section, we will consider three species concepts that are commonly used by scientists. All species concepts have limitations and work better for some organismal groups than others. Each section below considers the definition of the species concept, its assumptions and limitations, and examples of groups for which that species concept does, and does not, easily apply. The Biological Species Concept By far the most well-known species concept is the biological species concept, which was proposed by evolutionary biologist Ernst Mayr. The biological species concept states that a species is a group of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. Reproductive isolation can occur in several ways (which we will discuss in detail later in the quarter); individuals of different groups may not mate with each other, their mating may not produce offspring, or the offspring produced may not be viable (able to survive) or fertile (able to reprod...

Most people have a basic idea of what species are, even if they are not sure of the best way to define the word species. Quite simply, species are kinds, or types, of organisms. For example, humans all belong to one species (the scientific name of our species is Homo sapiens), and we differ from other species, such as gorillas or dogs or dandelions. But defining, identifying, and distinguishing between species really isn't that simple. In fact, it is often a complex and difficult process-especially in cases of new or previously unknown species. Biologists frequently disagree about species, and even argue over how best to define the word species. This disagreement is so well known, and so much discussed, that it is sometimes referred to by biologists as the "species problem" (Hey 2001). This article explores the idea of species, including both the meaning of the word species, and how biologists think species can be identified in nature. It also examines why an understanding of species is important, both for the study of biology and for our society. The central difficulty when studying species is that, even though all species are kinds of organisms, all kinds of organisms are not species. For example, birds are a kind of organism, but birds are not a species --there are many thousands of species of birds. For scientific purposes, it is not enough to identify a kind of organism. As a biologist you must also determine what level or rank of kind to assign to an organism. If you...

Menu • Home • Evolution 101 • An introduction to evolution: what is evolution and how does it work? • The history of life: looking at the patterns – Change over time and shared ancestors • Mechanisms: the processes of evolution – Selection, mutation, migration, and more • Microevolution – Evolution within a population • Speciation – How new species arise • Macroevolution – Evolution above the species level • The big issues – Pacing, diversity, complexity, and trends • Teach Evolution • Lessons and teaching tools • Teaching Resources • Image Library • Using research profiles with students • Active-learning slides for instruction • Using Evo in the News with students • Guide to Evo 101 and Digging Data • Conceptual framework • Alignment with the Next Generation Science Standards • • Teaching guides • K-2 teaching guide • 3-5 teaching guide • 6-8 teaching guide • 9-12 teaching guide • Undergraduate teaching guide • • Misconceptions about evolution • • Dealing with objections to evolution • Information on controversies in the public arena relating to evolution • Learn Evolution A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator. Happy face spider photos courtesy of Rosemary Gillespie, UC Berkeley. Streptococcus micrograph courtesy of Dr. Vincent...

Formation of New Species Although all life on earth shares various genetic similarities, only certain organisms combine genetic information by sexual reproduction and have offspring that can then successfully reproduce. Scientists call such organisms members of the same biological species. Species Concepts It turns out that scientists don’t always agree on the definition of a species. The different ideas about what does and does not constitute a species are referred to as species concepts. There are around twenty-six different species concepts, but four are the most accepted. The biological species concept​ states that if two organisms are able to successfully breed and produce viable, fertile offspring, then they are the same species. When populations of organisms cease to successfully breed (called reproductive isolation) they are then considered separate species. ​The biological species concept​ works well for scientists studying living creatures that have regular breeding patterns, such as insects or mammals. ​The morphological species concept​ states that if two organisms are morphologically similar enough, then they are the same species. There is no guideline about how similar counts as similar enough, so it is up to the researcher to make the judgment call. This concept works well for organisms that don’t breed regularly (such as fungi) or that are no longer living. ​ The genetic species concept​ states that if two organisms are genetically similar enough, then they...

The biological species concept defines a species as members of populations that actually or potentially interbreed in nature, not according to similarity of appearance. Although appearance is helpful in identifying species, it does not define species. Appearance isn’t everything Organisms may appear to be alike and be different species. For example, Western meadowlarks ( Sturnella neglecta) and Eastern meadowlarks ( Sturnella magna) look almost identical to one another, yet do not interbreed with each other — thus, they are separate species according to this definition. The Western meadowlark (left) and the Eastern meadowlark (right) appear to be identical, and their ranges overlap, but their distinct songs prevent interbreeding. Western meadowlark photo by Kevin Cole Ant photo courtesy of Alex Wild. Organisms may look different and yet be the same species. For example, look at these ants. You might think that they are distantly related species. In fact, they are sisters—two ants of the species Pheidole barbata, fulfilling different roles in the same colony. Many characteristics can vary within a single species. For example, the plant hydrangea may have pink “flowers” — they’re actually modified leaves — or blue “flowers.” But that doesn’t mean that we should classify the two forms as different species. In fact, you could cause a blue-“flowered” plant to become a pink-“flowered” plant just by changing the pH of the soil and the amount of aluminum taken up by the plant. Add...

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Species Definition A species is a group of organisms that share a genetic heritage, are able to interbreed, and to create offspring that are also fertile. Different species are separated from each other by reproductive barriers. These barriers can be geographical, such as a mountain range separating two populations, or genetic barriers that do not allow for reproduction between the two populations. Scientists have changed their definition of a species several times throughout history. Species is one of the most specific classification that scientists use to describe animals. Scientists use a system of binomial nomenclature to describe animals without the confusion of common names. This system uses the genus as the first name, which is always capitalized, and the species name is the second name, always lower case. Thus, some animals like the Red fox, Vulpes vulpes, are both in the genus Vulpes and their species name is vulpes. Note the capitalization difference to distinguish between genus and species. Other foxes such as the swift fox, Vulpes velox, are also part of the Vulpes genus, but barriers exist that keep them from interbreeding with the Red foxes. In this way, they remain distinct species. Taxonomic Rank Graph Since the days of Carl Linnaeus, the creator of binomial nomenclature, animals have been constantly classified and reclassified into different groups, genre, species and subspecies. Linnaeus, classifying organisms in the 1700s, restricted his classifications ...

Biological Species Concept: Every day, news about the discovery of novel organisms and even endangered species is being reported. However, when one talks about a species, what do they pertain to? As it turns out, the answer to this simple question is very complex. More often than not, concepts about species (singular or plural) are very complicated. For example, even before Charles Darwin had launched his idea about how organisms could change through time, biologists have already struggled with questions about the definition of what a species is. Everything became even more complex when he showcased Several attempts have been made to define a species, and many explanations have been proposed. For example, some tried to delineate based on physical appearance, others on ancestry. However, this page will explore the most famous and widely accepted concept – the biological species concept. What is the Biological Species Concept? Ernst Mayr Statue in Berlin Museum (Source: Wikimedia) Apparently, the biological species concept is the most accepted and widely used concept that explains the concept of species. For instance, biologist Ernst Mayr (1940), has defined species as “ groups of interbreeding populations (both naturally and possibly), that are isolated from other groups in terms of their reproduction patterns“. In simpler terms, Mayr’s definition of a species is confined to interbreeding or reproduction with others of the same kind. • In addition to that, Mayr also claimed...

On some level, the idea of a species is pretty intuitive. You don't need to be a zoologist to classify organisms like humans, giant pandas, or sunflowers into groups based on their appearance. This method works well when the species in question look very different from one another. You probably wouldn’t mistake a panda for a sunflower—unless you really needed your glasses! If appearance doesn’t reliably define a species, then what does? For most eukaryotes—such as animals, plants, and fungi—scientists tend to define a species based on reproductive compatibility. That is, organisms are usually considered to be members of the same species if they can successfully reproduce with one another. In this definition, members of the same species must have the potential to interbreed. However, that doesn't mean they have to be part of the same interbreeding group in real life. For instance, a dog living in Australia and a dog living in Africa are unlikely to meet but could have puppies if they did. In order to be considered to be a single species in the biological species concept, a group of organisms must produce healthy, fertile offspring when they interbreed. In some case, organisms of different species can mate and produce healthy offspring, but the offspring are infertile, can’t reproduce. For example, when a female horse and a male donkey mate, they produce hybrid offspring called mules. Although a mule, pictured below, is perfectly healthy and can live to a ripe old age, it is...