Grouping Organisms: All organisms (living things) are classified into a number of different groups. The first, most broad group is a kingdom. The last, most selective group is a species there are fewer organisms in each group after a kingdom; this is because, as you approach the species fewer organisms appear in each group because they have more similarities. For example, for a tiger: Group Kingdom Phylum Class Order Family Genus Species Tiger Animalia (Animal) Chordata (Vertebrate) Mammalia (Mammal) Carnivora (Carnivore) Felidae (Cat) Panthera Panthera tigris (Tiger) There are two ways in which you can classify organisms: A Natural Selection based on the evolutionary relationship between organisms; generally these will be related via a common ancestor. Closely related animals are more likely to be in the same group. An Artificial Selection very easy way of identification; based on one or two similar characteristics. The sequencing of bases in DNA has meant that scientists now know more about how closely related organisms actually are MUCH re-classification has happened as a result. Species: By definition, a species is a group of organisms that can interbreed to produce fertile offspring. All species are named using the binomial system. This system works simply; the first part of the name is the genus and the second is the species of the organism; for example the tiger s species was Panthera tigris. The genus has to start with a capital letter, and the species has to start with a lower-case letter. Issues with Classifying: There are a number of issues presented when trying to classify organisms. For example, bacteria do not interbreed, they produce offspring asexually so the offspring will be genetically identical to the parent. This means that they cannot be classified into different species because of the fertile offspring idea.
Some organisms are hybrids; this means that they were produced when members of two species interbred. An example of a hybrid is a mule which is a produced when a donkey and a horse interbreed. Hybrids are NOT fertile so cannot be classed as a species. Furthermore, organisms are all at different stages of evolution, and new ones are discovered every day. This means it is difficult to place organisms into distinct groups. An example of such organism was the archaeopteryx which had characteristics which could place it into two different groups: - It had feathers, like a bird - BUT, it also had teeth and a long, bony tail like a reptile Classification and Evolution: Organisms that are grouped together are generally closely-related and share a recent common ancestor. However, they may have very different features if they live in different habitats. When we classify organisms, it s important to consider that similarities and differences between organisms may have different explanations. For example, dolphins and fish are similar because they both live in the same habitat (they are ecologically related). But dolphins are classified differently and are classed as mammals. Both dolphins and bats have evolved to their respective (very different) habitats, but both are still classed as mammals because they have an evolutionary relationship; they are related through evolution.
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