In this lesson, we’re going to discuss some of the methods that scientist use to name and identify species. We’ll begin with a brief review of the hierarchical classification system introduced by Carl Linnaeus. Next, we’ll talk about what scientific species names are and the correct way to write them in scientific work. We’ll look at the advantages and disadvantages of scientific names. Next, we’ll look at the process a scientist needs to go through in order to have a scientific name accepted if they are lucky enough to find a new species. We’ll finish with a brief look at the ways in which scientists identify species.
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Added on: 30th Sep 2018
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In this presentation, we’re going to discuss some of the methods that scientist use to name and identify species.
We’ll begin with a brief review of the hierarchical classification system introduced by Carl Linnaeus. Next, we’ll talk about what scientific species names are and the correct way to write them in scientific work. We’ll look at the advantages and disadvantages of scientific names. Next, we’ll look at the process a scientist needs to go through in order to have a scientific name accepted if they are lucky enough to find a new species. We’ll finish with a brief look at the ways in which scientists identify species.
Scientists are very interested in sorting objects, based on their similarities and differences. This is particularly true of living things, which they sort on the basis of their biological characteristics: plants and animals, animals with backbones and animals without, animals with fur, scales or feathers and so on.
(click) The Swedish scientist, Carl Linnaeus developed a hierarchical classification system for organisms in the 18th Century. We still use an extension of this classification system today. Consequently, he is sometimes called the father of taxonomy. Taxonomy is a word that means a system of classifying and naming organisms. His system has the aims of representing evolutionary relationships between organisms and providing a system for the identification and comparison of different organisms.
(click) Linnaeus’ system is hierarchical. It begins with enormous groups, and splits these up into progressively smaller groups. As organisms are split up into smaller groups, they begin to share more and more characteristics.
(click) The hierarchy has 8 levels. These are domain, kingdom, phylum, class, order, family, genus and species. In this presentation, we’re going to be most interested in the genus and species of an organism.
(click) Scientists say that two organisms have the same species if they have many characteristics in common and are capable of producing offspring that are fertile. In other words, their offspring are able to reproduce.
For example, all domestic dogs are in the same species, but horses and donkeys are not because their offspring is unable to reproduce.
(click) Each genus is made up of a number of species. The different species in the same genus are closely related, but like the donkey and horse, or the lion and the tiger, their offspring will not be fertile.
Scientific names can be given to all species that have ever lived on the Earth – living or extinct. Scientists assign each new species they discover a two-part (or binomial) name.
(click) The first word of this binomial name corresponds to the genus of the organisms, and the second one specifies its species.
(click) A scientific name that we’ve all heard of is Tyrannosaurus rex. This scary dinosaur is part of the genus Tyrannosaurus, and a member of the species rex.
(click) You’ve probably heard a number of scientific names before. Like Tyrannosaurus rex, they are always written in Latin. This is because Latin was the international language of science back when Linnaeus developed his classification system.
(click) There are a few rules surrounding the use of scientific names in scientific reports. The first word (or genus) must always begin with a capital letter. The second word (or the species) has to begin with a lower case letter. Both words are written in italics if the report is typed, or underlined if the report is handwritten.
OK, well these Latin names look complicated. Why on earth do scientists use them?
Well, have a look at the two birds on the right. They both have the common name of “magpie”, but you can see that they’re different birds. How did this happen?
The one at the top is a European magpie. When the Europeans came to Australia, they saw our black and white friend down the bottom and thought that he looked like a magpie, so they called him a magpie. That sounds fair enough, doesn’t it?
However, there’s a bit of a problem. Suppose a scientist in Australia and another scientist in England were discussing magpies. They might very well be talking about totally different birds. It could get very confusing. The solution is to come up with a scientific name for each species. A name no other species shares, so that each scientist knows exactly what the other scientist is talking about. Let’s see: The European magpie has the very creative scientific name of Pica pica, and the Australian magpie has the scientific name of Cracticus tibicen, which is completely different. Now the Australian and English scientists will each precisely know what the other scientist is talking about.
(click) So, scientific names are standardised. They aren’t shared, and each species has a unique scientific name. There is no possibility for confusion.
(click) The common names of organisms vary from place to place. For example, the plant with scientific name Stellaria media is variously called chickweed, starwort, adder’s mouth, winterweed and chicken-weed. If scientists used the common names, they might think they were talking about different species, when in fact, they all refer to Stellaria media.
(click) Scientific names have inbuilt parts that help scientists to quickly determine how closely species are related. For example,
The scientific name of the lion is Panthera leo, and the scientific name of the tiger is Panthera tigris. When scientists look at these two names, they automatically know that the lion and tiger are in the same genus, but are not in the same species.
(click) Finally, everything has to have a disadvantage. The disadvantage of scientific names is that they are long and complicated and in Latin, so they’re difficult to remember. However, they do follow patterns, and working with them frequently makes them much easier to remember.
Now, let’s pretend for a little while that we’re scientists and we’ve discovered a new species (or at least we think we have) like the bizarre looking Wunderpus photogenicus in the photo on the right. How do we come up with a name for it? There are a number of steps that need to be followed.
(click) First, we need to find what we call a ‘type’ specimen. For extinct animals, we need a ‘type fossil’. This is an example of the species that all other candidates can be compared to to make sure they are part of the same species. That is, to make sure they share the same biological characteristics.
(click) Next, we’ll need to come up with a complete description of the species. This will include its behaviour, its anatomy and its genetic characteristics. We’ll need to describe the ways it is different from other species that we know about and to argue why it isn’t just a natural variation of a species that already exists.
(click) Now, it’s time to come up with the name. As you can see from our friend the octopus, there aren’t a lot of rules for this, but it needs to be in Latin. IT can’t have already been used, it can’t be offensive, and it is bad form to include your own name in the scientific name. That’s for someone else to do later.
(click) Once we’ve done all this, we’ll need to publish the description and name. We have to make sure that it is accessible to international scientists, so, at the very least, the publication needs to be available through international publication archives.
Let’s finish the presentation by talking about the ways that scientists identify organisms. Nowadays, they often use genetic techniques like DNA testing to identify the species of an organism, but there are times when this is not possible or practical. In these situations we still use classification keys. Classification keys are checklists which describe the characteristics that an organism might possess. Scientists are able to use the combination of characteristics possessed by the organism to identify its species (or any of the other classification groups described by Linnaeus).
(click) One type of classification key is the dichotomous key. It provides a list of alternatives in an order that lets you determine which group an organism belongs to. Perhaps it could help you to track down the family of the organism, its genus and then the name of the species itself.
This slide shows a simple dichotomous key that helps us to track down the class of an organism. We start by answering the question at the top of the diagram. Is our creature a plant or an animal? Well, it looks suspiciously animal-like to me, so we’ll choose the right branch and move to the next question which asks whether it is water or land dwelling. The answer is Land dwelling, so we move to the right again. The next question is does it have hair or feathers? In this case the answer is feathers, so we move to the left branch and find that our organism is in the class of mammals. The scientific name of this class is mammalia.
Why don’t you have a go at working through this key with another organism? You could also have a go at constructing your own dichotomous key. Perhaps you might like to construct one that will allow you to distinguish between a wombat and an elephant. Divide your group of organisms up into two on the basis of a single difference. Make sure that every member of the group has one of these two characteristics. Then proceed to divide each subgroup up into two on the basis of a single characteristic. Continue on in this manner until you have a dichotomous key like the one shown in the diagram on this slide.
Let’s finish by summarising the main points from this presentation. Scientists use binomial species names so that they can communicate with scientists from other countries and regions without becoming confused. Common names can vary from region to region, and different species can share the same common name.
Scientists can assign scientific names to organisms that are alive today and to organisms that are extinct.
The scientific name of a species uniquely identifies it. Species do not share scientific names.
Each scientific name is made up of two Latin words. The first represents the genus of the organism, and the second tells us its species.
We can use biological keys to identify organisms.
We looked at an example of a dichotomous key. This is a checklist of alternative characteristics which can be used to identify the classes an organism belongs to. Two alternatives are provided at each step.