a. A fundamental category of taxonomic classification, ranking below a genus or subgenus and consisting of related organisms capable of interbreeding.
That’s just part of the dictionary definition
- no wonder people get confused. And in normal-person terms? A species is a group of organisms which can interbreed to produce fertile young. They tend to share common physical and mental traits, and have a common gene pool and chromosome complement.
Thankfully biology is one of my school subjects, and I know a little about evolution and speciation. I’ll outline that first- as simply as I can- so that we have a firm footing from which to approach the “new species declaration” question.
Speciation is the formation of new species- it’s brought about by evolution and involves changes in the genotype (selection of genes within an organism) of a population. These changes are adaptive, meaning that they’re made to allow the organism to better adapt to their environment. Here’s the down-low on how these changes occur:
1. Members of the same species occupy an area, share a gene pool, interbreed- generally, all is merry-happy for this population.
2. The population is split in two (or more, of course), by certain “isolating mechanisms”. These can be reproductive problems, ecological problems such as a change in temperature, or geographical changes like the emergence of a desert or body of water. This causes a barrier which prevents the species from having babies together (aww).
3. Mutations occur at random- these are changes in the genes or chromosomes of an organism which cause them to change and vary. This happens within both groups, but seperately- the mutations in each group are different.
4. The selection pressures on each group are different. These pressures vary depending on their -relatively- new environment, and can be factors such as climate, predators, disease and food source. As well as a zillion other things. This is when natural selection takes place (can I mention Darwin? Yay Darwin
!). This means, in simple terms, that the organisms which are good at taking advantage of their environment live and pass on their genes, and the ones which aren’t so good die out.
5. Over a long period of time the gene pools of the two seperated groups become so different that they become genetically isolated- basically just super varied from the original.
6. *Drum roll, please*- and if the groups were reintroduced, would they interbreed? No, no they wouldn’t. They would laugh at the weird animals you expected them to get all down-n-dirty with. They would no longer be genetically similar enough to breed and have babies.
Technically, this is when a new species is formed- shouldn’t that be when a new species is declared? Well, that was an extremely simplified version, and it’s easy to forget that the timescales involved in speciation are huuuuuge. So that’s where the problem seems to arise- at what point are they a new species, and at what point are the two groups just-a-little-different?
Well, when I checked this on trusty ‘ole Wiki and found that this whole species thing has been called the “species problem” even by biologists, I suspected finding the answer may not be easy. It wasn’t- in fact, I don’t have an exact one. There are so many exceptions to rules that finding the clear-cut point at which a group has seperated into two distinct species is extremely hard.
A species is supposed to be able to interbreed and produce young naturally, but there are many different -but closely related- species which can produce hybrids. Hybrids such as ligers
aren’t fertile, but they were still produced by natural, sexual reproduction.
Then there are so-called “ring species”. They can reproduce with adjacent populations, but not with non-adjacent populations. Yeah, that sounds super-simple… Right, imagine a big clock- for all you kl kids out there, not a digital phone-esque clock. A good ‘ole round clock. Imagine that the 12 and the 1 could have babies. And imagine that the 1 and the 2 could have babies. But the 12 and the 2 can’t. I hope that makes sense like it did in my brain- but that’s the down-low on ring species, which are just some exceptions to the whole “species” rule.
I’m sorry if you’re coming out of this more confused than before you read it, but I’m hoping that it helped more than hindered. The bare bones of the thing is that if a population becomes isolated, over time it’ll break into seperate species. Sometimes there will be exceptions to the favourite definition of “species” because it changes all the time, but it doesn’t differ too massively. As far as I can tell, scientists make the definition regarding lots of different factors, but there’s no exact, blanket time that can be cited as when a group breaks into two distinct species.
Are you a scientist working in the field, or do you know something I missed? Comment and let us know!
Image Credit: Wikimedia Commons