DIVE DRY WITH DR. BILL #880: WE'RE NOT TALKING ABOUT COINS!
I often cringe when I search the Internet or peruse Facebook and find biological terms that are used incorrectly... or don't even exist at all! The example that initiated this column is the word "specie." People often use that for a single species of plant or animal, but they're wrong! The definition of the word "specie" is coin or other metallic money. In biology the word "species" applies both to a single type of life form, or a group of them. In other words, it is both singular and plural.
So what do we biologist mean by the word species? It is more complicated than you might imagine. Back in my Harvard daze, I used to walk past Ernst Mayr's office in the Museum of Comparative Zoology. Way back in 1942 he established a definition of species known as the biological species concept: "Species are groups of interbreeding natural populations that are reproductively isolated from other such groups." Most biologists in my early years used that definition.
If a raven could successfully mate with a crow, and produce viable offspring, then they might be considered the same species. They can't, even if they live in proximity to one another, so they are separate species. Anthropologists know that our species, Homo sapiens, could mate with Homo neaderthalensis. Both evolved from Homo erectus hundreds of thousands of years ago. Do you know if you have Neanderthal genes in your ancestry? This violates the definition of species that Mayr proposed.
I have also encountered examples of what we refer to as different species mating in nature. While diving the Caribbean I am often intrigued by the hamlets, a group of fairly small fish in the sea bass family Serranidae. It isn't simply because of their beautiful colors. Hamlets are synchronous hermaphrodites, both male and female at the same time. When mating, they take turns being the lady or the gent. Could be a bit confusing, eh?
Now add to this the fact that different "species" of hamlet can interbreed with one another to form hybrids! This either throws out Mayr's concept of species... or means that several of the existing species should be lumped together. If these hybrids are reproductively viable, I think taxonomists need to get busy and redefine the group.
Mayr's definition has some other drawbacks besides observed hybridization. Since it depends on reproduction between individuals, it cannot be tested with organisms that reproduce asexually such as single-celled bacteria. Extinct fossil species are another example since we don't know if they could interbreed when alive.
Molecular biology is giving us a better tool to assess species identity. While some species may exhibit wide variation in coloration and other physical features, an analysis of their genetic make-up can often be used to identify valid species. Unfortunately for old geezers like me who learned many of their species decades ago, this forces us into re-education camps to learn all the new names!
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: An example of specie and the butter hamlet species (singular) mating; several different species (plural) and my ancient relative and me.
I often cringe when I search the Internet or peruse Facebook and find biological terms that are used incorrectly... or don't even exist at all! The example that initiated this column is the word "specie." People often use that for a single species of plant or animal, but they're wrong! The definition of the word "specie" is coin or other metallic money. In biology the word "species" applies both to a single type of life form, or a group of them. In other words, it is both singular and plural.
So what do we biologist mean by the word species? It is more complicated than you might imagine. Back in my Harvard daze, I used to walk past Ernst Mayr's office in the Museum of Comparative Zoology. Way back in 1942 he established a definition of species known as the biological species concept: "Species are groups of interbreeding natural populations that are reproductively isolated from other such groups." Most biologists in my early years used that definition.
If a raven could successfully mate with a crow, and produce viable offspring, then they might be considered the same species. They can't, even if they live in proximity to one another, so they are separate species. Anthropologists know that our species, Homo sapiens, could mate with Homo neaderthalensis. Both evolved from Homo erectus hundreds of thousands of years ago. Do you know if you have Neanderthal genes in your ancestry? This violates the definition of species that Mayr proposed.
I have also encountered examples of what we refer to as different species mating in nature. While diving the Caribbean I am often intrigued by the hamlets, a group of fairly small fish in the sea bass family Serranidae. It isn't simply because of their beautiful colors. Hamlets are synchronous hermaphrodites, both male and female at the same time. When mating, they take turns being the lady or the gent. Could be a bit confusing, eh?
Now add to this the fact that different "species" of hamlet can interbreed with one another to form hybrids! This either throws out Mayr's concept of species... or means that several of the existing species should be lumped together. If these hybrids are reproductively viable, I think taxonomists need to get busy and redefine the group.
Mayr's definition has some other drawbacks besides observed hybridization. Since it depends on reproduction between individuals, it cannot be tested with organisms that reproduce asexually such as single-celled bacteria. Extinct fossil species are another example since we don't know if they could interbreed when alive.
Molecular biology is giving us a better tool to assess species identity. While some species may exhibit wide variation in coloration and other physical features, an analysis of their genetic make-up can often be used to identify valid species. Unfortunately for old geezers like me who learned many of their species decades ago, this forces us into re-education camps to learn all the new names!
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: An example of specie and the butter hamlet species (singular) mating; several different species (plural) and my ancient relative and me.
