Explore Related Concepts

definition of competition in biology and examples

Best Results From Wikipedia Yahoo Answers Youtube

From Wikipedia

Biological agent

A biological agent is a bacterium, virus, prion, fungus, or biological toxin that can be used in bioterrorism or biological warfare. More than 1200 different kinds of biological agents have been described and studied to date. Applying a slightly broader definition, some eukaryotes (for example parasites) and their associated toxins can be considered as biological agents.

Biological agents have the ability to adversely affect human health in a variety of ways, ranging from relatively mild allergic reactions to serious medical conditions, even death. These organisms are ubiquitous in the natural environment; they are found in water, soil, plants, and animals. Because many biological agents reproduce rapidly and require minimal resources for preservation, they are a potential danger in a wide variety of occupational settings.

Biological and toxin agents of military importance

Bacterial Biological Agents

Chlamydial Biological Agents

Rickettsial Biological Agents

Viral Biological Agents

Mycotic Biological Agents

Biological Toxins

Biological Vectors


  • MR - molasis residium
  • BG - Bacillus globigii
  • BS - Bacillus globigii
  • U - Bacillus globigii
  • SM - Serratia marescens
  • P - Serratia marescens
  • AF - Aspergillus fumigatus mutant C-2
  • EC - E. coli
  • BT - Bacillus thursidius
  • EH - Erwinia hebicola
  • FP - fluorescent particle

Homology (biology)

A homologous trait is any characteristic of organisms that is derived from a common ancestor. This is contrasted to analogous traits: similarities between organisms that were not in the last common ancestor of the taxa being considered but rather evolved separately. As defined by Owen (1843), a homology is a "structural correspondence", whereas an analogy is a "non-correspondent similarity".

Whether or not a trait is homologous depends on both the taxonomic and anatomical level at which the trait is examined. For example, the bird and bat wing are homologous as forearms in tetrapods. However, they are not homologous as wings, because the organ served as a forearm (not a wing) in the last common ancestor of tetrapods. By definition, any homologous trait defines a clade—a monophyletictaxon in which all the members have the trait (or have lost it secondarily); and all non-members lack it.

A homologous trait may be homoplasious – that is, it has evolved independently, but from the same ancestral structure – plesiomorphic – that is, present in a common ancestor but secondarily lost in some of its descendants – or (syn)apomorphic – present in an ancestor and all of its descendants.

A homologous trait is often called a homolog (also spelled homologue). In genetics, the term "homolog" is used both to refer to a homologous protein, and to the gene (DNA sequence) encoding it.

Homology of structures

Shared ancestry can be evolutionary or developmental. Evolutionary ancestry means that structures evolved from some structure in a common ancestor; for example, the wings of bats and the arms of primates are homologous in this sense. Developmental ancestry means that structures arose from the same tissue in embryonal development; the ovaries of female humans and the testicles of male humans are homologous in this sense.

Homology is different from analogy, which describes the relation between characters that are apparently similar yet phylogenetically independent. The wings of a maple seed and the wings of an albatross are analogous but not homologous (they both allow the organism to travel on the wind, but they didn't both develop from the same structure). Analogy is commonly also referred to as homoplasy, which is further distinguished into parallelism, reversal, and convergence.

From the point of view of evolutionary developmental biology (evo-devo) where evolution is seen as the evolution of the development of organisms, Rolf Sattler emphasized that homology can also be partial. New structures can evolve through the combination of developmental pathways or parts of them. As a result hybrid or mosaic structures can evolve that exhibit partial homologies. For example, certain compound leaves of flowering plants are partially homologous both to leaves and shoots because they combine some traits of leaves and shoots.

Homology of sequences in genetics

Homology among proteins and DNA is often concluded on the basis of sequence similarity, especially in bioinformatics. For example, in general, if two or more genes have highly similar DNA sequences, it is likely that they are homologous. But sequence similarity may also arise without common ancestry: short sequences may be similar by chance, and sequences may be similar because both were selected to bind to a particular protein, such as a transcription factor. Such sequences are similar but not homologous. Sequence regions that are homologous are also called conserved. This is not to be confused with conservation in amino acid sequences in which the amino acid at a specific position has been substituted with a different one with functionally equivalent physicochemical properties.

The phrase "percent homology" is sometimes used but is incorrect. "Percent identity" or "percent similarity" should be used to quantify the similarity between the biomolecule sequences. For two naturally occurring sequences, percent identity is a factual measurement, whereas homology is a hypothesis supported by evidence. One can, however, refer to partial homology where a fraction of the sequences compared (are presumed to) share descent, while the rest does not. For example, partial homology may result from a gene fusion event.

Many algorithms exist to cluster protein sequences into sequence families, which are sets of mutually homologous sequences. (See sequence clustering and sequence alignment.) Some specialized biological databases collect homologous sequences in animal genomes: HOVERGEN, HOMOLENS, HOGENOM.

Homologous sequences are of two types: orthologous and paralogous.


Homologous sequences are orthologous if they were separated by a speciation event: when a species diverges into two separate species, the divergent copies of a single gene in the resulting species are said to be orthologous. Orthologs, or orthologous genes, are genes in different species that are similar to each other because they originated from a common ancestor. The term "ortholog" was coined in 1970 by Walter Fitch.

The strongest evidence that two similar genes are orthologous is the result of a phylogenetic analysis of the gene lineage. Genes that are found within one clade are orthologs, descended from a common ancestor. Orthologs often, but not always, have the same function.

Orthologous sequences provide useful in


In biology, a genus (plural: genera) is a low-level taxonomic rank (a taxon) used in the classification of living and fossilorganisms, which is an example of definition by genus and differentia. The term comes from Latin genus "descent, family, type, gender", cognate with γένος – genos, "race, stock, kin".

The composition of a genus is determined by a taxonomist. The standards for genus classification are not strictly codified, and hence different authorities often produce different classifications for genera. In the hierarchy of the binomial classification system, genus comes above species and below family.

Generic name

The scientific name of a genus may be called the generic name or generic epithet: it is always capitalized. It plays a pivotal role in binomial nomenclature, the system of biological nomenclature.

Binomial nomenclature

The rules for scientific names are laid down in the Nomenclature Codes; depending on the kind of organism and the Kingdom it belongs to, a different Code may apply, with different rules, laid down in a different terminology. The advantages of scientific over common names are that they are accepted by speakers of all languages, and that each species has only one name. This reduces the confusion that may arise from the use of a common name to designate different things in different places (example elk), or from the existence of several common names for a single species.

It is possible for a genus to be assigned to a kingdom governed by one particular Nomenclature Code by one taxonomist, while other taxonomists assign it to a kingdom governed by a different Code, but this is the exception, not the rule.

Pivotal in binomial nomenclature

The generic name often is a component of the names of taxa of lower rank. For example, Canis lupus is the scientific name of the Gray wolf, a species, with Canisthe generic name for thedog and its close relatives, and with lupus particular (specific) for the wolf (lupus is written in lower case). Similarly, Canis lupus familiaris is the scientific name for the domestic dog.

Taxonomic units in higher ranks often have a name that is based on a generic name, such as the family name Canidae, which is based on Canis. However, not all names in higher ranks are necessarily based on the name of a genus: for example, Carnivora is the name for the order to which the dog belongs.

The problem of identical names used for different genera

A genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different Nomenclature Code. Although this is discouraged by both the International Code of Zoological Nomenclature and the International Code of Botanical Nomenclature, there are some five thousand such names that are in use in more than one kingdom. For instance, Anurais the name of theorder of frogs but also is the name of a genus of plants (although not current: it is a synonym); Aotusis the genus ofgolden peas and night monkeys; Oenantheis the genus ofwheatears and water dropworts, Prunellais the genus ofaccentors and self-heal, and Proboscideais the order ofelephants and the genus of devil's claws.

Within the same kingdom one generic name can apply to only one genus. This explains why the platypus genus is named Ornithorhynchus—George Shaw named it Platypus in 1799, but the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. Names with the same form but applying to different taxa are called homonyms. Since beetles and platypuses are both members of the kingdom Animalia, the name Platypus could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800.

Types and genera

Because of the rules of scientific naming, or "binomial nomenclature", each genus should have a designated type, although in practice there is a backlog of older names that may not yet have a type. In zoology this is the type species (see Type (zoology)); the generic name is permanently associated with the type specimen of its type species. Should this specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym, and the remaining taxa in the former genus need to be reas

From Yahoo Answers

Question:I need the definition of the following words! -Cellular Respiration -Photosynthesis -Intracellular digestion -Passive Transport -Facilitated Diffusion -Active Transport -Osmosis -Endocytosis -Excocytosis -Phagocytosis -Pinocytosis -Aerobic Respiration -Anaerobic Respiration

Answers:Don't ask much, do you?? Okay, Cellular Respiration: the process carried out in every living cell in which complex molecules are converted into energy for various metabolic processes. Photosynthesis: the process in which light from the sun is converted into oxygen and chemical energy in the chloroplasts of certain cells. Passive transport: transport that requires no expenditure of energy on the organism's part. Facilitated Diffusion: where certain molecules that would otherwise be too large or insoluble to pass through a cell membrane are transported across with the help of protein 'carriers'. This requires no energy. Active transport: molecules that would otherwise not be able to diffuse across the cell membrane (for example, if it is across a concentration gradient) are transported in at a cost to the plant - energy. Osmosis: diffusion across a selectively permeable membrane. Endocytosis: the process carried out by a cell in which it draws particles into itself. Exocytosis: the same, but out of the cell. Phagocytosis: a type of endocytosis. The cell stretches its membrane over a particle, effectively engulfing it. The membrane forms a vacuole around the particle and it is drawn into the cell. Pinocytosis: much the same as above, but involving liquids rather than particles. The cell forms a channel in the membrane and the liquid flows in. It is then 'pinched off' and drawn into the cell. Aerobic respiration: respiration that takes place in an oxygen rich environment Anaerobic: takes place with no oxygen.

Question:For example: No organism live alone I am not saying what is biology?. I just wanna ask is that what is life in terms of biology like organism, protoplasm to biosphere and the level organization of life.

Answers:1. Living things are made of cells. 2. Living things reproduce. 3. Living things are based upon the universal genetic code (DNA, RNA) 4. Living things grow and develop. 5. Living things obtain and use energy and materials. 6. Living things respond to their environment. 7. Living things maintain a stable internal environment. 8. As a group, living thing change over time (they evolve). You can organize life this way: Cell=>Tissues=>Organs=>Organ systems=>Organisms=>Population=> Ecosystems. I hope this helps!

Question:Also, after I pick a carrot, how long does it take for it to die? WTF, I don't think anyone knows so far... not everything alive has brains or anything like that.

Answers:Characteristics of Life 1. Movement. Example: change in position of the body or of a body part; motion of an internal organ. 2. Responsiveness. Example: Reaction to a change taking place inside or outside the body. 3. Growth. Example: Increase in body size without change in shape. 4. Reproduction. Example: Production of new organisms and new cells. 5. Respiration. Example: Obtaining oxygen, removing carbon dioxide, and releasing energy from foods (some forms of life do not use oxygen in respiration) 6. Digestion. Example: Breakdown of food substances into simpler forms that can be absorbed and used. 7. Absorption. Example: Passage of substances through membrane and into body fluids. 8. Circulation. Example: Movement of substances from place to place in body fluids. 9. Assimilation. Example: Changing of absorbed substances into chemically different forms. 10. Excretion. Example: Removal of wastes produced by metabolic reactions. These are all characteristics of life, whether you are a human, or a plant, or animal. You are right, plants do not have brains but they still have many of the characteristics of life, therefore are no less alive than we are.

Question:I am a 9th grader in Biology 1 accelerated so please dont make the answer too complex thanks :)

Answers:Active site: Simple definition --- a binding site. : ) More detailed definition: A specific region of an enzyme where a substrate binds and catalysis takes place (binding site). The part of an enzyme or antibody where the chemical reaction occurs.A structural element of protein that determines whether the protein is functional when undergoing a reaction from an enzyme. this structural element will be accordingly shaped to the structure of the enzyme at work on it. Retrieved from "http://www.biology-online.org/dictionary/Active_site" This page has been accessed 2,635 times. This page was last modified 23:43, 10 March 2007. Sources: http://www.biology-online.org/dictionary/Active_site BTW -- SAVE this link so you can access it again for future biology assignments : ) : )

From Youtube

Biological Control - A Natural Alternative :Department of Agriculture Animal and Plant Health Inspection Service Biological Control - A Natural Alternative AVA18029VNB1, 1989 This presentation deals with the practical and applied aspects of biocontrol by emphasizing strategies such as augmentation, recolonization and inundation. The program includes a definition and brief history of biocontrol along with examples of success.