Biological interaction in the context of "Commensal"

In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, biological community, ecological community, or life assemblage. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place or time, for example, "the fish community of Lake Ontario before industrialization".

Community ecology or synecology is the study of the interactions between species in communities on many spatial and temporal scales, including the distribution, structure, abundance, demography, and interactions of coexisting populations. The primary focus of community ecology is on the interactions between populations as determined by specific genotypic and phenotypic characteristics. It is important to understand the origin, maintenance, and consequences of species diversity when evaluating community ecology.

Animals are multicellular, eukaryotic organisms comprising the biological kingdom Animalia (/ˌænɪˈmeɪliə/). With few exceptions, animals consume organic material, breathe oxygen, have myocytes and are able to move, can reproduce sexually, and grow from a hollow sphere of cells, the blastula, during embryonic development. Animals form a clade, meaning that they arose from a single common ancestor. Over 1.5 million living animal species have been described, of which around 1.05 million are insects, over 85,000 are molluscs, and around 65,000 are vertebrates. It has been estimated there are as many as 7.77 million animal species on Earth. Animal body lengths range from 8.5 μm (0.00033 in) to 33.6 m (110 ft). They have complex ecologies and interactions with each other and their environments, forming intricate food webs. The scientific study of animals is known as zoology, and the study of animal behaviour is known as ethology.

The animal kingdom is divided into five major clades, namely Porifera, Ctenophora, Placozoa, Cnidaria and Bilateria. Most living animal species belong to the clade Bilateria, a highly proliferative clade whose members have a bilaterally symmetric and significantly cephalised body plan, and the vast majority of bilaterians belong to two large clades: the protostomes, which includes organisms such as arthropods, molluscs, flatworms, annelids and nematodes; and the deuterostomes, which include echinoderms, hemichordates and chordates, the latter of which contains the vertebrates. The much smaller basal phylum Xenacoelomorpha have an uncertain position within Bilateria.

Competition is an interaction between organisms or species in which both require one or more resources that are in limited supply (such as food, water, or territory). Competition lowers the fitness of both organisms involved since the presence of one of the organisms always reduces the amount of the resource available to the other.

In the study of community ecology, competition within and between members of a species is an important biological interaction. Competition is one of many interacting biotic and abiotic factors that affect community structure, species diversity, and population dynamics (shifts in a population over time).

Symbiosis is any close and long-term biological interaction between two organisms of different species. In 1879, Heinrich Anton de Bary defined symbiosis as "the living together of unlike organisms". The term is sometimes more exclusively used in a restricted, mutualistic sense, where both symbionts contribute to each other's subsistence. This means that they benefit each other in some way.

Symbiosis is diverse and can be classified in multiple ways. It can be obligate, meaning that one or both of the organisms depend on each other for survival, or facultative, meaning that they can subsist independently. When one organism lives on the surface of another, such as head lice on humans, it is called ectosymbiosis; when one partner lives inside the tissues of another, such as Symbiodinium within coral, it is termed endosymbiosis. Where the interaction reduces both parties' fitness, it is called competition; where just one party's fitness is reduced, it is called amensalism. Where one benefits but the other is largely unaffected, this is termed commensalism. Where one benefits at the other's expense, it is called parasitism. Finally, where both parties benefit, the relationship is described as mutualistic.

Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the host) and parasitoidism (which always does, eventually). It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators.

Predation behaviour varies significantly depending on the organism. Many predators, especially carnivores, have evolved distinct hunting strategies. Pursuit predation involves the active search for and pursuit of prey, whilst ambush predators instead wait for prey to present an opportunity for capture, and often use stealth or aggressive mimicry. Other predators are opportunistic or omnivorous and only practice predation occasionally.

A biologist is a scientist who conducts research in biology. Biologists are interested in studying life on Earth, whether it is an individual cell, a multicellular organism, or a community of interacting populations. They usually specialize in a particular branch (e.g., molecular biology, zoology, and evolutionary biology) of biology and have a specific research focus (e.g., studying malaria or cancer).

Biologists who are involved in basic research have the aim of advancing knowledge about the natural world. They conduct their research using the scientific method, which is an empirical method for testing hypotheses. Their discoveries may have applications for some specific purpose such as in biotechnology, which has the goal of developing medically useful products for humans.

A biocenosis (UK English, biocoenosis, also biocenose, biocoenose, biotic community, biological community, ecological community, life assemblage), coined by Karl Möbius in 1877, describes the interacting organisms living together in a habitat (biotope). The use of this term has declined in the 21st сentury.

In the palaeontological literature, the term distinguishes "life assemblages", which reflect the original living community, living together at one place and time. In other words, it is an assemblage of fossils or a community of specific time, which is different from "death assemblages" (thanatocoenoses). No palaeontological assemblage will ever completely represent the original biological community (i.e. the biocoenosis, in the sense used by an ecologist); the term thus has somewhat different meanings in a palaeontological and an ecological context.