Organisms are traditionally classified into three domains and further subdivided into one of six kingdoms of life. Show
Organisms are placed into these categories based on similarities or common characteristics. Some of the characteristics that are used to determine placement are cell type, nutrient acquisition, and reproduction. The two main cell types are prokaryotic and eukaryotic cells. Common types of nutrient acquisition include photosynthesis, absorption, and ingestion. Types of reproduction include asexual reproduction and sexual reproduction. Some more modern classifications abandon the term "kingdom." These classifications are based on cladistics, which notes that kingdoms in the traditional sense are not monophyletic; that is, they do not all have a common ancestor. Moelyn Photos/Getty ImagesArchaebacteria are single-celled prokaryotes originally thought to be bacteria. They are in the Archaea domain and have a unique ribosomal RNA type. The cell wall composition of these extreme organisms allows them to live in some very inhospitable places, such as hot springs and hydrothermal vents. Archaea of the methanogen species can also be found in the guts of animals and humans.
These organisms are considered to be true bacteria and are classified under the Bacteria domain. Bacteria live in almost every type of environment and are often associated with disease. Most bacteria, however, do not cause disease. Bacteria are the main microscopic organisms that compose the human microbiota. There are more bacteria in the human gut, for instance, than there are body cells. Bacteria ensure that our bodies function normally. These microbes reproduce at an alarming rate under the right conditions. Most reproduce asexually by binary fission. Bacteria have varied and distinct bacterial cell shapes including round, spiral, and rod shapes.
The protista kingdom includes a very diverse group of organisms. Some have characteristics of animals (protozoa), while others resemble plants (algae) or fungi (slime molds). These eukaryotic organisms have a nucleus that is enclosed within a membrane. Some protists have organelles that are found in animal cells (mitochondria), while others have organelles that are found in plant cells (chloroplasts). Protists that are similar to plants are capable of photosynthesis. Many protists are parasitic pathogens that cause disease in animals and humans. Others exist in commensalistic or mutualistic relationships with their host.
Fungi include both unicellular (yeast and molds) and multicellular (mushrooms) organisms. Unlike plants, fungi are not capable of photosynthesis. Fungi are important for the recycling of nutrients back into the environment. They decompose organic matter and acquire nutrients through absorption. While some fungal species contain toxins that are deadly to animals and humans, others have beneficial uses, such as for the production of penicillin and related antibiotics.
Plants are extremely important to all life on earth as they provide oxygen, shelter, clothing, food, and medicine for other living organisms. This diverse group contains vascular and nonvascular plants, flowering and nonflowering plants, as well as seed-bearing and non-seed bearing plants. As is true of most photosynthetic organisms, plants are primary producers and support life for most food chains in the planet's major biomes. Doug Allan / Getty ImagesThis kingdom includes animal organisms. These multicellular eukaryotes depend on plants and other organisms for nutrition. Most animals live in aquatic environments and range in size from tiny tardigrades to the extremely large blue whale. Most animals reproduce by sexual reproduction, which involves fertilization (the union of male and female gametes).
#nature Millions of living things inhabit our planet, but did you know that they are divided into five separate kingdoms? Some, like animals and plants, are visible to the naked eye; but others, like bacteria, can only be seen under a microscope. Let's delve into the world of the five kingdoms of nature and find out a bit more about them.
Living things are divided into five kingdoms: animal, plant, fungi, protist and monera.
Living things are divided into five kingdoms: animal, plant, fungi, protist and monera.
Living things are divided into five kingdoms: animal, plant, fungi, protist and monera.
Living things are divided into five kingdoms: animal, plant, fungi, protist and monera.
Living things are divided into five kingdoms: animal, plant, fungi, protist and monera.
Nobody knows for certain when, how or why life began on Earth, but Aristotle observed 2,400 years ago that all the planet's biodiversity was of animal or plant origin. This initial observation by the Greek philosopher was expanded in the 19th and 20th centuries by the discovery of new kingdoms, finally arriving at today's widely-recognised five, which cover the 8.7 million species that live on Earth, according to estimates by the United Nations Environment Programme (UNEP). WHAT IS A KINGDOM IN BIOLOGYThe system of biological kingdoms is the way in which science classifies living things according to their ancestry over the course of evolution. This means that all the species that make up these five large groups - some recent theories split them further into six or even seven - have common ancestors and therefore share some of their genes and belong to the same family tree. As well as the kingdoms of living things there are other taxonomic categories within the same classification system such as, for instance, domain, phylum, class, order, family, genus and species. They all follow a hierarchical order and are dependent on each other, so some divisions include others. In this way, the domain includes the kingdom, the kingdom the phylum, the phylum the class, and so on. CHARACTERISTICS OF THE FIVE KINGDOMS OF LIVING THINGSAll the species in a particular kingdom have similar characteristics in terms of their growth and the way they function. Now let's look at where the family relationships that define nature's kingdoms come from: Nutrition. Autotrophic (makes its own food) or heterotrophic (feeds on other living things). Cell organisation. Unicellular (having only one cell) or multicellular (having two or more cells). Cell type. Eukaryotes (the genetic material is surrounded by a membrane) or prokaryotes (lacking a membrane). Respiration. Aerobic (needs oxygen) or anaerobic (does not use oxygen). Reproduction. Sexual, asexual or through spores. Movement. Self-moving or static. THE CLASSIFICATION OF LIVING THINGS INTO FIVE KINGDOMSThe first person to divide living things into five broad kingdoms was North American ecologist Robert Whittaker. This researcher proved in 1959 that fungi were not plant organisms - previously it was thought that they were - and a decade later he proposed the creation of the fungi kingdom to differentiate them from plants. Whittaker's theory was widely accepted and the scientific community thereby added a new group to the previous four-kingdom system, established by the American biologist Herbert Copeland in 1956. Animal kingdomThe kingdom Animalia is the most evolved and is divided into two large groups - vertebrates and invertebrates. These animals are multi-celled, heterotrophic eukaryotes with aerobic respiration, sexual reproduction and the ability to move. This kingdom is one of the most diverse and comprises mammals, fish, birds, reptiles, amphibians, insects, molluscs and annelids, among others. Plant kingdomTrees, 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.
SEE INFOGRAPHIC: The kingdoms of living things and their species at a glance [PDF] External link, opens in new window. Fungi kingdomThis 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. Protista kingdomThis 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. Monera kingdomThis 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 1977 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. |
What characteristics of each kingdom are identified in the table?
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