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ⓘ Organisms




                                               

Organism

An organism is an individual living thing. It is easy to recognize a living thing, but not so easy to define it. Animals and plants are organisms, obviously. Organisms are a biotic, or living, part of the environment. Rocks and sunshine are parts of the non-living environment. Organisms usually have five basic needs to continue their metabolism. They need air, water, nutrient food, energy, and a place to live. However, not all living things need all these at the same time. Many organisms do not need access to air at all. A little thought is needed about viruses. There is no agreement as to ...

                                               

Unicellular organism

Unicellular organisms are organisms that have one cell. They are divided into two quite different types, from different classification kingdoms. Eukaryotes have a nucleus, and a more complex cell structure. The prokaryotes, bacteria and archaea, have cells with no nucleus and a simple cell structure. The differences between the prokaryota and eukaryota are significant. Eukaryotes possess a nucleus and various subcellular organs called organelles, and prokaryotes do not.

                                               

Multicellular organism

Multi-cellular organisms are organisms with more than one cell. This is the case for animals, plants and most fungi. In such organisms, cells are usually specialised. All the cells with the same function work together. Such a group of cells is then called a tissue. Multi-cellular organisms have a set of cells that specialize in reproduction. Reproduction in such organisms is usually sexual. The sex cells are either sperm or ovum also named "egg" cells. If they are sperm cells, the organism is male, if they are egg cells it is female. If both are present, the organism is a hermaphrodite.

                                               

Model organism

A model organism is a non-human species that is studied over many years, building up a lot of knowledge about it in order to understand fundamental biological phenomena. The hope is that discoveries made in the model will give insight into how other organisms work. In particular, model organisms are widely used in animal testing to explore potential causes and treatments for human disease when experimenting on humans would be impossible or less ethical. This strategy is made possible by the similarities of all living organisms. They are similar because of their common descent and the conse ...

                                               

Anaerobic organism

An anaerobic organism is any living thing that does not need oxygen for growth. Facultative anaerobes can use oxygen when it is present. Aerotolerant organisms can survive in the presence of oxygen, but they are anaerobic because they do not use oxygen as a terminal electron acceptor. Obligate anaerobes will die when exposed to atmospheric levels of oxygen. Microaerophiles are organisms that may use oxygen, but only at low concentrations low micromolar range; their growth is inhibited by normal oxygen concentrations approximately 200 micromolar. Nanaerobes are organisms that cannot grow in ...

                                               

Microorganism

A micro-organism or microbe is an organism which is microscopic, which means so small that people cannot see them with naked eye. The study of microorganisms is called microbiology. Micro-organisms include bacteria, fungi, archaea, protists and viruses, and are among the earliest known life forms. The first of these four types of micro-organisms may either be free-living or parasitic. Viruses can only be parasitic, since they always reproduce inside other living things. Most micro-organisms are unicellular organism with only one cell, but there are unicellular protists that are visible to ...

                                               

Genetically modified organism

A genetically modified organism is an organism whose genetic material has been altered using genetic engineering techniques. Organisms that have been genetically modified include micro-organisms such as bacteria and yeast, insects, plants, fish, and mammals. GMOs are the source of genetically modified foods, and are also widely used in scientific research and to produce goods other than food.

                                               

Cell

In biology, the cell is the basic structure of organisms. All cells are made by the division of other cells. The environment outside the cell is separated from the cytoplasm inside the cell by the cell membrane. Inside some cells, parts of the cell stay separate from other parts. These separate parts are called organelles like small organs. They each do different things in the cell. Examples are the nucleus where DNA is, and mitochondria where chemical energy is converted.

                                               

Body

A body is the physical material of a person or organism. It is only used for organisms which are in one part or whole. There are organisms which change from single cells to whole organisms: for example, slime moulds. For them the term body would mean the multicellular stage. Other uses: Plant body Cell body: here it may be used for cells like neurons which have long axons nerve fibres. The cell body is the part with the nucleus in it. The body of a dead person is also called a corpse or cadaver. The dead bodies of vertebrate animals and insects are sometimes called carcasses. The human bod ...

                                               

Reproduction

Reproduction is to create or recreate something, a new living thing, such as a baby. In biology, the two types of reproduction are sexual and asexual reproduction. Sexual reproduction involves two organisms of the same species, each supplying half the genes for the descendant. Asexual reproduction only involves a single organism; it works by division of the cell. Most bacteria reproduce by asexual reproduction. Some organisms can either reproduce sexually or asexually.

                                               

Robert Koch

Robert Koch was a German doctor. He won the 1905 Nobel Prize in Physiology or Medicine, for studying tuberculosis. The Royal Prussian Institute for Infectious Disease started in 1891, is now called the Robert Koch Institute.

                                               

Cladistics

Cladistics is the method of classifying organisms into groups called clades. A clade Greek = branch is a group of organisms with a common ancestor and all its descendants and nothing else. Such a clade is monophyletic. The term clade was coined by English biologist Julian Huxley.