Earthworm in the context of Angling

Due to climate change in the Arctic, this polar region is expected to become "profoundly different" by 2050. The speed of change is "among the highest in the world", with warming occurring at 3-4 times faster than the global average. This warming has already resulted in the profound Arctic sea ice decline, the accelerating melting of the Greenland ice sheet and the thawing of the permafrost landscape. These ongoing transformations are expected to be irreversible for centuries or even millennia.

Natural life in the Arctic is affected greatly. As the tundra warms, its soil becomes more hospitable to earthworms and larger plants, and the boreal forests spread to the north - yet this also makes the landscape more prone to wildfires, which take longer to recover from than in the other regions. Beavers also take advantage of this warming to colonize the Arctic rivers, and their dams contributing to methane emissions due to the increase in stagnant waters. The Arctic Ocean has experienced a large increase in the marine primary production as warmer waters and less shade from sea ice benefit phytoplankton. At the same time, it is already less alkaline than the rest of the global ocean, so ocean acidification caused by the increasing CO₂ concentrations is more severe, threatening some forms of zooplankton such as pteropods.

Soil biology is the study of microbial and faunal activity and ecology in soil.Soil life, soil biota, soil fauna, or edaphon is a collective term that encompasses all organisms that spend a significant portion of their life cycle within a soil profile, or at the soil-litter interface.These organisms include earthworms, nematodes, protozoa, fungi, bacteria, different arthropods, as well as some reptiles (such as snakes), and species of burrowing mammals like gophers, moles and prairie dogs. Soil biology plays a vital role in determining many soil characteristics. The decomposition of organic matter by soil organisms has an immense influence on soil fertility, plant growth, soil structure, and carbon storage. As a relatively new science, much remains unknown about soil biology and its effect on soil ecosystems.

Decomposition is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere. Bodies of living organisms begin to decompose shortly after death. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. Decomposition can be a gradual process for organisms that have extended periods of dormancy.

One can differentiate abiotic decomposition from biotic decomposition (biodegradation); the former means "the degradation of a substance by chemical or physical processes", e.g., hydrolysis; the latter means "the metabolic breakdown of materials into simpler components by living organisms", typically by microorganisms. Animals, such as earthworms, also help decompose the organic materials on and in soil through their activities. Organisms that do this are known as decomposers or detritivores.

A food chain is a linear network of links in a food web, often beginning with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as earthworms and woodlice), or decomposer (such as fungi or bacteria). A food web is distinct from a food chain. A food chain illustrates the associations between organisms according to the energy sources they consume in trophic levels, and the most common way to quantify them is in length: the number of links between a trophic consumer and the base of the chain.

Studies of food chains are essential to many biological studies.

Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases.

At the simplest level, composting requires gathering a mix of green waste (nitrogen-rich materials such as leaves, grass, and food scraps) and brown waste (woody materials rich in carbon, such as stalks, paper, and wood chips). The materials break down into humus in a process taking months. Composting can be a multistep, closely monitored process with measured inputs of water, air, and carbon- and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water, and ensuring proper aeration by regularly turning the mixture in a process using open piles or windrows. Fungi, earthworms, and other detritivores further break up the organic material. Aerobic bacteria and fungi manage the chemical process by converting the inputs into heat, carbon dioxide, and ammonium ions.

The annelids (/ˈænəlɪdz/), also known as the segmented worms, are animals that comprise the phylum Annelida (/əˈnɛlɪdə/; from Latin anellus 'little ring'). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments.

The annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into Polychaetes (almost all marine), Oligochaetes (which include earthworms) and Hirudinea (leech-like species). Cladistic research since 1997 has radically changed this scheme, viewing leeches as a sub-group of oligochaetes and oligochaetes as a sub-group of polychaetes. In addition, the Pogonophora, Echiura and Sipuncula, previously regarded as separate phyla, are now regarded as sub-groups of polychaetes. Annelids are considered members of the Lophotrochozoa, a "super-phylum" of protostomes that also includes molluscs, brachiopods, and nemerteans.

Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodies that can lengthen and contract. Both groups are hermaphrodites and have a clitellum, but leeches typically differ from the oligochaetes in having suckers at both ends and ring markings that do not correspond with their internal segmentation. The body is muscular and relatively solid; the coelom, the spacious body cavity found in other annelids, is reduced to small channels.

The majority of leeches live in freshwater habitats, while some species can be found in terrestrial or marine environments. The best-known species, such as the medicinal leech, Hirudo medicinalis, are hematophagous, attaching themselves to a host with a sucker and feeding on blood, having first secreted the peptide hirudin to prevent the blood from clotting. The jaws used to pierce the skin are replaced in other species by a proboscis which is pushed into the skin. A minority of leech species are predatory, mostly preying on small invertebrates.

Fishing bait is any luring substance used specifically to attract and catch fish, typically when angling with a hook and line. There are generally two types of baits used in angling: hookbaits, which are directly mounted onto fish hooks and are what the term "fishing bait" typically refers to; and groundbaits, which are scattered separately into the water as an "appetizer" to attract the fish nearer to the hook. Despite the bait's sole importance is to provoke a feeding response out of the target fish, the way how fish react to different baits is quite poorly understood.

Fishing baits can be grouped into two broad categories: natural baits and artificial baits. Traditionally, fishing baits are natural food or prey items (live or dead) that are already present in the fish's normal diet (e.g. worms, insects, crustaceans and smaller bait fish), and such baits are both procured from and used within the same environment. Artificial baits, conversely, are not naturally acquired and must involve some kind of production process. These can be processed foods (e.g. bread, cheese, dough, cutlets, fish food or pet food pellets, etc.), commercially made feed mixtures (e.g. boilies), or imitative replica "fake foods" made of inedible materials known as lures (e.g plastic worm, swimbaits, spoons, stickbaits, hybrid spinners or even bionic robot fish). The variety of baits that a fisherman may choose is dictated mainly by the target species and by its habitat, as well as personal preference. Both natural and artificial baits frequently demonstrate similar efficiency if chosen adequately for the target fish. The overall bait type, size and techniques used will affect the efficiency and yield when fishing.

Saprotrophic nutrition /sæprəˈtrɒfɪk, -proʊ-/ or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs (organisms which feed on decaying organic matter), and is most often associated with fungi (e.g. Mucor) and with soil bacteria. Saprotrophic microscopic fungi are sometimes called saprobes. Saprotrophic plants or bacterial flora are called saprophytes (sapro- 'rotten material' + -phyte 'plant'), although it is now believed that all plants previously thought to be saprotrophic are in fact parasites of microscopic fungi or of other plants. In fungi, the saprotrophic process is most often facilitated through the active transport of such materials through endocytosis within the internal mycelium and its constituent hyphae.

Various word roots relating to decayed matter (detritus, sapro-, lyso-), to eating and nutrition (-vore, -phage, -troph), and to plants or life forms (-phyte, -obe) produce various terms, such as detritivore, detritophage, saprotroph, saprophyte, saprophage, and saprobe; their meanings overlap, although technical distinctions (based on physiologic mechanisms) narrow the senses. For example, biologists can make usage distinctions based on macroscopic swallowing of detritus (as in earthworms) versus microscopic lysis of detritus (as with mushrooms).

A hermaphrodite (/hərˈmæfrəˌdaɪt/) is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic.

The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants.

Caecilians (/sɪˈsɪliən/; New Latin for 'blind ones') are a group of limbless, worm-shaped or snake-shaped amphibians, with either small eyes or no eyes, comprising the order Gymnophiona. They mostly live hidden in soil or in streambeds, making them some of the least familiar amphibians. Modern caecilians live in the tropics of South and Central America, Africa, and southern Asia. Caecilians feed on small subterranean creatures, such as earthworms. The body is noodle-like and often dark in colour, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, such as fused skull and jaw bones, a two-part system of jaw muscles, and chemosensory tentacles between the eyes and nostrils. The skin is slimy, with ringlike markings or grooves, and in some species hides scales underneath.

Modern caecilians are a clade, the order Gymnophiona /ˌdʒɪmnəˈfaɪənə/ (or Apoda /ˈæpədə/), one of the three living amphibian groups alongside Anura (frogs) and Urodela (salamanders). Gymnophiona is a crown group, encompassing all modern caecilians and all descendants of their last common ancestor. There are more than 220 living species of caecilian classified in 10 families. Gymnophionomorpha is a recently coined name for the corresponding total group which includes Gymnophiona as well as a few extinct stem-group caecilians (extinct amphibians whose closest living relatives are caecilians but are not descended from any caecilian). Some palaeontologists have used the name Gymnophiona for the total group and the old name Apoda for the crown group. However, Apoda has other even older uses, including as the name of a genus of butterfly, making its use potentially confusing and best avoided. The clade's name 'Gymnophiona' comes from Ancient Greek γυμνος (gumnos), meaning "naked", and ὄφις (óphis), meaning "snake", as the caecilians were originally thought to be related to snakes and to lack scales.

The common blackbird (Turdus merula) is a species of true thrush. It is also called the Eurasian blackbird (especially in North America, to distinguish it from the unrelated New World blackbirds), or simply the blackbird. It breeds in Europe, western Asia, and North Africa, and has been introduced to Australia and New Zealand. It has a number of subspecies across its large range; a few former Asian subspecies are now widely treated as separate species. Depending on latitude, the common blackbird may be resident, partially migratory, or fully migratory.

The adult male of the common blackbird (Turdus merula merula, the nominate subspecies), which is found throughout most of Europe, is all black except for a yellow eye-ring and bill and has a rich, melodious song; the adult female and juvenile have mainly dark brown plumage. This species breeds in woods and gardens, building a neat, cup-shaped nest, bound together with mud. It is omnivorous, eating a wide range of insects, earthworms, berries, and fruits.

Detritivores (also known as detrivores, detritophages, detritus feeders or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, vertebrates, and plants that eat detritus or carry out coprophagy. By doing so, all these detritivores contribute to decomposition and the nutrient cycles. Detritivores should be distinguished from other decomposers, such as many species of bacteria, fungi and protists, which are unable to ingest discrete lumps of matter. Instead, these other decomposers live by absorbing and metabolizing on a molecular scale (saprotrophic nutrition). The terms detritivore and decomposer are often used interchangeably, but they describe different organisms. Detritivores are usually arthropods and help in the process of remineralization. Detritivores perform the first stage of remineralization, by fragmenting the dead plant matter, allowing decomposers to perform the second stage of remineralization.

Plant tissues are made up of resilient molecules (e.g. cellulose, lignin, xylan) that decay at a much lower rate than other organic molecules. The activity of detritivores is the reason why there is not an accumulation of plant litter in nature.