Why biologists classify living things

The first division of living things in the classification system is to put them into one of five kingdoms. The five kingdoms are:. Living things can then be ranked according to:. Phylum follows Kingdoms and has many different organisms, including three examples below:. Class is an additional sub-division, which for example, results in the Chordata phylum being divided into:.

Order follows class and as an example, mammals can be further sub-divide into a variety of different groups such as:. Orders are broken down into families. Here are a few examples of which carnivores can be divided into:. Genus, the Felidae family can be further sub-divided into four genus examples:. Species is the final classification stage, and the genus Panthera can be divided into:. As an example, the complete breakdown of the classification of lions :.

Trees, plants and other species of vegetation make up part of the Plantae kingdom - one of the oldest, and characterised by its immobile, multicellular and eukaryotic nature. These autotrophic things, whose cells contain cellulose and chlorophyll are essential for life on Earth since they release oxygen through photosynthesis.

As regards their method of reproduction, this may be either sexual or asexual. The kingdoms of living things and their species at a glance. This name is used to designate the fungi kingdom which includes yeasts, moulds and all species of mushrooms and toadstools. These multicellular aerobic heterotrophic eukaryotes have chitin in their cell walls, feed off other living things, and reproduce through spores. This group is the most primitive of the eukaryotics and all the others are descendants of it.

The Protista kingdom is paraphyletic - it contains the common ancestor but not all its descendants - and it includes those eukaryotic organisms that are not deemed to be animals, plants or fungi such as protozoa.

As it is so heterogeneous it is difficult to categorise it, since its members have very little in common. This is the kingdom of microscopic living things and groups together the prokaryotes archaea and bacteria.

This group is present in all habitats and is made up of single-cell things with no defined nucleus. Most bacteria are aerobic and heterotrophic, while the archaea are usually anaerobic and their metabolism is chemosynthetic. The classification of the five kingdoms of nature remains the most accepted today, although the latest advances in genetic research have suggested new revisions and reopened the debate among experts.

Such is the case for the sixth kingdom of Carl Woese and George Fox, who in divided bacteria into two types Archaea and Bacteria , and the seventh kingdom of Cavalier-Smith, who added a new group to the previous six for algae called Chromista. Skip to main content.

You are in Sustainability The kingdoms of living things. Share in Twitter. Share in Facebook. Whatsapp Whatsapp. Some species may look very similar to each other, so it is important for scientists to establish specific criteria for what distinguishes one species from another.

Scientists still use this Linnean system to classify living things. A hierarchical system, it works like a series of nesting boxes Fig. The largest box is the domain, and all the other levels of classification fit within the domains. There are three domains that include all the living things on Earth. The domains are Bacteria, Archaea, and Eukarya.

Bacteria and Archaea are all single-celled microorganisms that do not have DNA contained within a nucleus. Most of the Archaea live in extreme environments. The Bacteria and Archaea were once grouped together as a single kingdom called Monera , but scientists later discovered that the Archaea were distinctly different. Archaea are more similar to Eukarya than to Bacteria. The domain Eukarya includes all organisms that have DNA contained within a nucleus. Organisms with similar characteristics are grouped within these broad kingdoms.

Organisms are usually grouped together based on their unique characteristics. The classification of an organism often provides useful information about its evolutionary history and which other organisms are related to it.

At each level of hierarchy listed in Table 1. All organisms in Eukarya often referred to as eukaryotes have DNA contained in a nucleus rather than in the cytoplasm like the domains Prokarya and Archaea.

Next is the kingdom Animalia box. Everything in this box must consume other organisms to survive. Other kingdoms within Eukarya, like the kingdom Plantae, have organisms that can make their own food. Within the kingdom Animalia box, there are several other boxes, each labeled as a different phylum.

One is the phylum Chordata box. This box contains everything that has a notochord, gill slits, and a dorsal nerve cord. The phylum Chordata box contains many classes, one of which is the class Aves. Aves are the birds, with feathers and hollow bones. The class Aves box includes the box labeled order Anseriformes, the waterfowl that are grouped together due to their webbed front toes.

The order Anseriformes box contains two family boxes. One of these is the family Anatidae—the swans, ducks, and geese that have a broad bill, a keeled sternum, and other unique features. The family Anatida box contains the genus Branta. Geese in the genus Branta are noted for bold plumage and legs and bills that are black in color. The genus box Branta holds the species sandvicensis.

By examining each level of classification, it becomes clear that Branta sandvicensis is a Hawaiian goose with a black broad bill, legs, webbed toes, feathers, hollow bones, and a notochord. It must also eat other things. However, no other organism on earth is given the genus Branta and the species sandvicensis. The classification system tells something about the evolutionary relationships among species.

Moving down through each level of classification, the number of species in the group decreases Table 1. Two species within the same genus likely share a recent common ancestor in their evolutionary history.

These two species would be more closely related to each other than two species classified into different families. The levels of classification might also provide information on the evolutionary history of a species or other taxonomic group. Such is the case with the coelocanths Latimera spp. West Indian ocean coelacanth Latimeria chalumnae ; Fig. They are also the only living members of their family Latimeriidae and of their order Coelacanthiformes. All other species belonging to these levels of classification are now extinct.

Coelacanths are also some of the very few surviving fish species within the class Sarcopterygii, a group known as the lobe-finned fishes. All four-limbed vertebrate animals—amphibians, reptiles, birds, and mammals—also belong to class Sarcopterygii. The coelacanths, and the six species of lung fish, are more closely related to each other and to the four-limed vertebrates than to other fishes.

For this reason, the coelacanth offers a rare glimpse into the evolutionary history of vertebrate animals and their limb-development. Classification systems are used in many ways. Compare the classifications shown in Fig. Most people know something about water vehicles, so it is not necessary to say that a speedboat has a motor.

In the same way, there is general knowledge that a tuna is classified as a fish. So, a tuna can be described without needing to say that it is a fish because. Thus, if we make the statement that a skipjack tuna is caught while fishing in a speedboat, many details can be left out of the description because there is general, underlying knowledge of the classification of boats and tuna. This use of italics is part of the rules that the scientific community has developed for the naming of organisms.

There are three main codes that govern the naming of organisms. Scientific names are useful outside of science. Common names vary from place to place, and the scientific nomenclature system helps eliminate confusion.

This example also brings up another problem with common names. Notice that one of the common names for this fish uses the word dolphin, which is also the common name of a marine mammal. Scientific names are also valuable in navigating the classification system. The classification system provides great deal of information about the characteristics of organisms. Using scientific names can therefore act as a shorthand method for describing a plant or animal. For example, following a whale stranding along the Maui coastline, an observer might record this information:.

This is all information needed to identify the organism and avoid mixing it up with other similar organisms. Of course, when reporting the mammal stranding to her supervisor, the observer will report stranding of a Megaptera novaeangliae , which is the species name that describes the humpback whale.

The scientific name Megaptera novaeangliae encompasses all of the described features. Most binomial names are Latin terms. However, some binomial names are Greek, and some are derived from the names of their discoverers or other scientists. When Carl Linneaus developed his classification system, almost all educated people were trained in Latin and Greek. No matter what country they came from, people could communicate with one another using these languages.

Because Latin and Greek were the common languages of scientists, Latin and Greek were used to develop a universal classification system. Even today, the English language has many words that were originally Latin or Greek in origin. Latin and Greek terminology is also useful because it tends to be very descriptive of the species in question Table 1. For example, consider the great white shark.