131-575: Cannibalism is the act of consuming another individual of the same species as food . Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well documented, both in ancient and in recent times. The rate of cannibalism increases in nutritionally poor environments as individuals turn to members of their own species as an additional food source. Cannibalism regulates population numbers, whereby resources such as food, shelter and territory become more readily available with
262-919: A flagellum to assist in hunting for food, and some protozoa travel via infectious spores to act as parasites. Many protists are mixotrophic, having both phototrophic and heterotrophic characteristics. Mixotrophic protists will typically depend on one source of nutrients while using the other as a supplemental source or a temporary alternative when its primary source is unavailable. Prokaryotes , including bacteria and archaea , vary greatly in how they obtain nutrients across nutritional groups. Prokaryotes can only transport soluble compounds across their cell envelopes, but they can break down chemical components around them. Some lithotrophic prokaryotes are extremophiles that can survive in nutrient-deprived environments by breaking down inorganic matter. Phototrophic prokaryotes, such as cyanobacteria and Chloroflexia , can engage in photosynthesis to obtain energy from sunlight. This
393-423: A mutation–selection balance . It is predicted that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit, "the quasispecies effect" or the "survival of the flattest". There is no suggestion that a viral quasispecies resembles
524-515: A taxonomic rank of an organism, as well as a unit of biodiversity . Other ways of defining species include their karyotype , DNA sequence, morphology , behaviour, or ecological niche . In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses ) are given
655-542: A two-part name , called a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature , also sometimes in zoological nomenclature ). For example, Boa constrictor is one of the species of the genus Boa , with constrictor being the species' epithet. While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example,
786-400: A "classical" method of determining species, such as with Linnaeus, early in evolutionary theory. However, different phenotypes are not necessarily different species (e.g. a four-winged Drosophila born to a two-winged mother is not a different species). Species named in this manner are called morphospecies . In the 1970s, Robert R. Sokal , Theodore J. Crovello and Peter Sneath proposed
917-424: A 'smallest clade' idea" (a phylogenetic species concept). Mishler and Wilkins and others concur with this approach, even though this would raise difficulties in biological nomenclature. Wilkins cited the ichthyologist Charles Tate Regan 's early 20th century remark that "a species is whatever a suitably qualified biologist chooses to call a species". Wilkins noted that the philosopher Philip Kitcher called this
1048-441: A by-product of cuckoldry in fish . Males consume broods, which may include their own offspring, when they believe a certain percentage of the brood contains genetic material that is not theirs. It is not always the parent that cannibalizes the offspring; in some spiders, mothers have been observed to feed themselves to their brood as the ultimate provision from mother to children, known as matriphagy . The dinosaur Coelophysis
1179-428: A connected series of neighbouring populations, each of which can sexually interbreed with adjacent related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene flow between each "linked" population. Such non-breeding, though genetically connected, "end" populations may co-exist in the same region thus closing
1310-459: A conspecific diet into reusable resources than a fully herbaceous diet; as herbaceous diets may consist of excess elements which the animal has to expend energy to get rid of. This facilitates faster development; however, a trade-off may occur as there may be less time to ingest these acquired resources. Studies have shown that there is a noticeable size difference between animals fed on a high conspecific diet which were smaller compared to those fed on
1441-432: A different species from its ancestors. Viruses have enormous populations, are doubtfully living since they consist of little more than a string of DNA or RNA in a protein coat, and mutate rapidly. All of these factors make conventional species concepts largely inapplicable. A viral quasispecies is a group of genotypes related by similar mutations, competing within a highly mutagenic environment, and hence governed by
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#17328486958861572-442: A fish species are low on energy, it might sometimes be beneficial for them to feed on their own offspring to survive and invest in future reproductive success. Another hypothesis as to the adaptive value of filial cannibalism in teleosts is that it increases density-dependent egg survivorship. In other words, filial cannibalism simply increases overall reproductive success by helping the other eggs make it to maturity by thinning out
1703-508: A genetic boundary suitable for defining a species concept is present. DNA barcoding has been proposed as a way to distinguish species suitable even for non-specialists to use. One of the barcodes is a region of mitochondrial DNA within the gene for cytochrome c oxidase . A database, Barcode of Life Data System , contains DNA barcode sequences from over 190,000 species. However, scientists such as Rob DeSalle have expressed concern that classical taxonomy and DNA barcoding, which they consider
1834-447: A greater risk of injury and expend more energy foraging for suitable prey as compared to non-cannibalistic species. Predators often target younger or more vulnerable prey. However, the time necessitated by such selective predation could result in a failure to meet the predator's self-set nutritional requirements . In addition, the consumption of conspecific prey may also involve the ingestion of defense compounds and hormones , which have
1965-459: A high stress environment where cannibalism between tadpoles and more developed individuals were present. Shifting their morphology plays a key role in their survival, creating bulkier bodies when put into environments where more developed tadpoles were present, to make it difficult for the individuals to swallow them whole. Diet shifts between different stages of development have also evolved to decrease competition between each stage, thereby increasing
2096-401: A higher requirement of energy in comparison to plants. The macronutrients essential to animal life are carbohydrates, amino acids , and fatty acids . All macronutrients except water are required by the body for energy, however, this is not their sole physiological function. The energy provided by macronutrients in food is measured in kilocalories, usually called Calories, where 1 Calorie is
2227-465: A lineage should be divided into multiple chronospecies , or when populations have diverged to have enough distinct character states to be described as cladistic species. Species and higher taxa were seen from the time of Aristotle until the 18th century as categories that could be arranged in a hierarchy, the great chain of being . In the 19th century, biologists grasped that species could evolve given sufficient time. Charles Darwin 's 1859 book On
2358-424: A low conspecific diet. Hence, individual fitness could only be increased if the balance between developmental rate and size is balanced out, with studies showing that this is achieved in low conspecific diets. In some insects, cannibalism is used to control population. In confused flour beetles , population density is lowered by cannibalism when crowding occurs. Cannibalism regulates population numbers and benefits
2489-492: A misnomer, need to be reconciled, as they delimit species differently. Genetic introgression mediated by endosymbionts and other vectors can further make barcodes ineffective in the identification of species. A phylogenetic or cladistic species is "the smallest aggregation of populations (sexual) or lineages (asexual) diagnosable by a unique combination of character states in comparable individuals (semaphoronts)". The empirical basis – observed character states – provides
2620-553: A nutrient deficiency. Early human nutrition consisted of foraging for nutrients, like other animals, but it diverged at the beginning of the Holocene with the Neolithic Revolution , in which humans developed agriculture to produce food. The Chemical Revolution in the 18th century allowed humans to study the nutrients in foods and develop more advanced methods of food preparation . Major advances in economics and technology during
2751-449: A particular species, including which genus (and higher taxa) it is placed in, is a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be corroborated or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as
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#17328486958862882-400: A perfect model of life, it is still a useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties. If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that
3013-432: A rate of about 0.3% and is considered to be an abnormal behavior. However, consumption by the sow of already dead piglets that were stillborn or accidentally crushed occurs at a much higher rate and is considered normal. Filial cannibalism is particularly common in teleost fishes, appearing in at least seventeen different families of teleosts. Within this diverse group of fish, there have been many, variable explanations of
3144-420: A result of extreme food shortage or of artificial/unnatural conditions, but may also occur under natural conditions in a variety of species. At the ecosystem level, cannibalism is most common in aquatic settings , with a cannibalism rate of up to 0.3% amongst fish. Cannibalism is not restricted to carnivorous species: it also occurs in herbivores and in detritivores . Sexual cannibalism normally involves
3275-400: A short way of saying that something applies to many species within a genus, but not to all. If scientists mean that something applies to all species within a genus, they use the genus name without the specific name or epithet. The names of genera and species are usually printed in italics . However, abbreviations such as "sp." should not be italicised. When a species' identity is not clear,
3406-481: A significant increase in human intake of fats and oils. Humans have developed advanced methods of food processing that prevent contamination of pathogenic microorganisms and simplify the production of food. These include drying, freezing, heating, milling, pressing, packaging, refrigeration, and irradiation. Most cultures add herbs and spices to foods before eating to add flavor, though most do not significantly affect nutrition. Other additives are also used to improve
3537-404: A specialist may use "cf." before the epithet to indicate that confirmation is required. The abbreviations "nr." (near) or "aff." (affine) may be used when the identity is unclear but when the species appears to be similar to the species mentioned after. With the rise of online databases, codes have been devised to provide identifiers for species that are already defined, including: The naming of
3668-523: A species as groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups. It has been argued that this definition is a natural consequence of the effect of sexual reproduction on the dynamics of natural selection. Mayr's use of the adjective "potentially" has been a point of debate; some interpretations exclude unusual or artificial matings that occur only in captivity, or that involve animals capable of mating but that do not normally do so in
3799-400: A species as determined by a taxonomist. A typological species is a group of organisms in which individuals conform to certain fixed properties (a type), so that even pre-literate people often recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens (such as longer or shorter tails) would differentiate the species. This method was used as
3930-488: A species. All species definitions assume that an organism acquires its genes from one or two parents very like the "daughter" organism, but that is not what happens in HGT. There is strong evidence of HGT between very dissimilar groups of prokaryotes , and at least occasionally between dissimilar groups of eukaryotes , including some crustaceans and echinoderms . The evolutionary biologist James Mallet concludes that there
4061-685: A species. Generally the term includes the unknown element of a distinct act of creation. Many authors have argued that a simple textbook definition, following Mayr's concept, works well for most multi-celled organisms , but breaks down in several situations: Species identification is made difficult by discordance between molecular and morphological investigations; these can be categorised as two types: (i) one morphology, multiple lineages (e.g. morphological convergence , cryptic species ) and (ii) one lineage, multiple morphologies (e.g. phenotypic plasticity , multiple life-cycle stages). In addition, horizontal gene transfer (HGT) makes it difficult to define
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4192-519: A taxonomic decision at the discretion of cognizant specialists, is not governed by the Codes of Zoological or Botanical Nomenclature, in contrast to the PhyloCode , and contrary to what is done in several other fields, in which the definitions of technical terms, like geochronological units and geopolitical entities, are explicitly delimited. The nomenclatural codes that guide the naming of species, including
4323-506: A traditional biological species. The International Committee on Taxonomy of Viruses has since 1962 developed a universal taxonomic scheme for viruses; this has stabilised viral taxonomy. Most modern textbooks make use of Ernst Mayr 's 1942 definition, known as the Biological Species Concept as a basis for further discussion on the definition of species. It is also called a reproductive or isolation concept. This defines
4454-447: A variation on the morphological species concept, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms. It differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species
4585-566: A variety of foods. Cultivation of cereals and production of bread has made up a key component of human nutrition since the beginning of agriculture. Early humans hunted animals for meat, and modern humans domesticate animals to consume their meat and eggs. The development of animal husbandry has also allowed humans in some cultures to consume the milk of other animals and process it into foods such as cheese . Other foods eaten by humans include nuts, seeds, fruits, and vegetables. Access to domesticated animals as well as vegetable oils has caused
4716-515: A variety of reasons. Viruses are a special case, driven by a balance of mutation and selection , and can be treated as quasispecies . Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics . Early taxonomists such as Linnaeus had no option but to describe what they saw: this was later formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts,
4847-419: A vulnerable stage of their life cycle, increases the chances of cannibalism occurring due to the reduced risk of injury. A feedback loop occurs when increasing rates of cannibalism decreases population densities, leading to an increased abundance of alternative food sources; making it more beneficial to forage within the environment than for cannibalism to occur. When population numbers and foraging rates increase,
4978-438: Is "an entity composed of organisms which maintains its identity from other such entities through time and over space, and which has its own independent evolutionary fate and historical tendencies". This differs from the biological species concept in embodying persistence over time. Wiley and Mayden stated that they see the evolutionary species concept as "identical" to Willi Hennig 's species-as-lineages concept, and asserted that
5109-456: Is a cerebellar dysfunctional disease which has symptoms including a broad-based gait and decreased motor activity control; however, the disease has a long incubation period and symptoms may not appear until years later. Bovine spongiform encephalopathy , or mad cow disease is another prion disease which is usually caused by feeding contaminated bovine tissue to other cattle. It is a neurodegenerative disease and could be spread to humans if
5240-400: Is a group of sexually reproducing organisms that recognise one another as potential mates. Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms; no matter whether populations can hybridise successfully, they are still distinct cohesion species if
5371-458: Is a set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognise as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters. A genetic species as defined by Robert Baker and Robert Bradley is a set of genetically isolated interbreeding populations. This
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5502-414: Is called speciation . Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book The Origin of Species . Speciation depends on a measure of reproductive isolation , a reduced gene flow. This occurs most easily in allopatric speciation, where populations are separated geographically and can diverge gradually as mutations accumulate. Reproductive isolation
5633-482: Is common among bacteria that form in mats atop geothermal springs. Phototrophic prokaryotes typically obtain carbon from assimilating carbon dioxide through the Calvin cycle . Some prokaryotes, such as Bdellovibrio and Ensifer , are predatory and feed on other single-celled organisms. Predatory prokaryotes seek out other organisms through chemotaxis or random collision, merge with the organism, degrade it, and absorb
5764-403: Is described formally, in a publication that assigns it a unique scientific name. The description typically provides means for identifying the new species, which may not be based solely on morphology (see cryptic species ), differentiating it from other previously described and related or confusable species and provides a validly published name (in botany) or an available name (in zoology) when
5895-671: Is further weakened by the existence of microspecies , groups of organisms, including many plants, with very little genetic variability, usually forming species aggregates . For example, the dandelion Taraxacum officinale and the blackberry Rubus fruticosus are aggregates with many microspecies—perhaps 400 in the case of the blackberry and over 200 in the dandelion, complicated by hybridisation , apomixis and polyploidy , making gene flow between populations difficult to determine, and their taxonomy debatable. Species complexes occur in insects such as Heliconius butterflies, vertebrates such as Hypsiboas treefrogs, and fungi such as
6026-490: Is governed by nutrition. Migration patterns and seasonal breeding take place in conjunction with food availability, and courtship displays are used to display an animal's health. Animals develop positive and negative associations with foods that affect their health, and they can instinctively avoid foods that have caused toxic injury or nutritional imbalances through a conditioned food aversion . Some animals, such as rats, do not seek out new types of foods unless they have
6157-726: Is hard or even impossible to test. Later biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, and the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: (1) agamospecies for asexual organisms (2) biospecies for reproductively isolated sexual organisms (3) ecospecies based on ecological niches (4) evolutionary species based on lineage (5) genetic species based on gene pool (6) morphospecies based on form or phenotype and (7) taxonomic species,
6288-535: Is little support for the prior theory as there is not much correlation between body size and the presence of sexual cannibalism. Not all species of spiders which partake in sexual cannibalism exhibit size dimorphism. The avoidance of sexual cannibalism is present in males of certain species to increase their rate of survival, whereby the male uses cautionary methods to lower the risk of his consumption. Male orb weaving spiders would often wait for females to moult or to finish eating before attempting to initiate mating, as
6419-560: Is low. Cannibalism is an ineffective method of disease spread as cannibalism in the animal kingdom is normally a one-on-one interaction, and the spread of disease requires group cannibalism; thereby it is rare for a disease to have evolved to rely solely on cannibalism to spread. Usually there are different means of transmission, such as with direct contact, maternal transmission, coprophagy , and necrophagy with different species. Infected individuals are more likely to be consumed than non-infected individuals, thus some research has suggested that
6550-554: Is managed by humans through animal feed . Fodder and forage are provided to livestock. Specialized pet food has been manufactured since 1860, and subsequent research and development have addressed the nutritional needs of pets. Dog food and cat food in particular are heavily studied and typically include all essential nutrients for these animals. Cats are sensitive to some common nutrients, such as taurine , and require additional nutrients derived from meat. Large-breed puppies are susceptible to overnutrition, as small-breed dog food
6681-570: Is more energy dense than they can absorb. Most plants obtain nutrients through inorganic substances absorbed from the soil or the atmosphere. Carbon, hydrogen, oxygen, nitrogen, and sulfur are essential nutrients that make up organic material in a plant and allow enzymic processes. These are absorbed ions in the soil, such as bicarbonate , nitrate , ammonium , and sulfate , or they are absorbed as gases, such as carbon dioxide, water, oxygen gas, and sulfur dioxide . Phosphorus, boron, and silicon are used for esterification . They are obtained through
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#17328486958866812-422: Is mostly focused on ensuring paternity of the future generations. It was found that cannibalistic females produced offspring with greater survival rates than non-cannibalistic females, as cannibals produced greater clutches and larger egg sizes. Hence, species such as the male dark fishing spider of the family Dolomedes self-sacrifice and spontaneously die during copulation to facilitate their own consumption by
6943-403: Is no easy way to tell whether related geographic or temporal forms belong to the same or different species. Species gaps can be verified only locally and at a point of time. One is forced to admit that Darwin's insight is correct: any local reality or integrity of species is greatly reduced over large geographic ranges and time periods. The botanist Brent Mishler argued that the species concept
7074-468: Is not valid, notably because gene flux decreases gradually rather than in discrete steps, which hampers objective delimitation of species. Indeed, complex and unstable patterns of gene flux have been observed in cichlid teleosts of the East African Great Lakes . Wilkins argued that "if we were being true to evolution and the consequent phylogenetic approach to taxa, we should replace it with
7205-457: Is often displayed in lions ; a male lion encroaching on the territory of a rival pride will often kill any existing cubs fathered by other males; this brings the lionesses into heat more quickly, enabling the invading lion to sire his own young. This is an example of cannibalistic behaviour in a genetic context. In many species of Lepidoptera , such as Cupido minimus and the Indianmeal moth ,
7336-586: Is similar to Mayr's Biological Species Concept, but stresses genetic rather than reproductive isolation. In the 21st century, a genetic species could be established by comparing DNA sequences. Earlier, other methods were available, such as comparing karyotypes (sets of chromosomes ) and allozymes ( enzyme variants). An evolutionarily significant unit (ESU) or "wildlife species" is a population of organisms considered distinct for purposes of conservation. In palaeontology , with only comparative anatomy (morphology) and histology from fossils as evidence,
7467-620: Is sometimes an important source of genetic variation. Viruses can transfer genes between species. Bacteria can exchange plasmids with bacteria of other species, including some apparently distantly related ones in different phylogenetic domains , making analysis of their relationships difficult, and weakening the concept of a bacterial species. Nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life . It provides organisms with nutrients , which can be metabolized to create energy and chemical structures. Failure to obtain
7598-539: Is suspected of having practiced intrauterine cannibalism, also, due to the sharp teeth of the recently born (or possibly aborted) juveniles, and the presence of fecal matter in the juveniles' intestines. Animals have evolved protection to prevent and deter potential predators such as those from their own kind. Many amphibian eggs are gelatinous and toxic to decrease edibility. Often, adults would lay their eggs in crevices, holes, or empty nesting sites to hide their eggs from potential conspecific predators which tend to ingest
7729-605: Is the simplest form of carbohydrate. Carbohydrates are broken down to produce glucose and short-chain fatty acids , and they are the most abundant nutrients for herbivorous land animals. Carbohydrates contain 4 calories per gram. Lipids provide animals with fats and oils. They are not soluble in water, and they can store energy for an extended period of time. They can be obtained from many different plant and animal sources. Most dietary lipids are triglycerides , composed of glycerol and fatty acids. Phospholipids and sterols are found in smaller amounts. An animal's body will reduce
7860-594: Is threatened by hybridisation, but this can be selected against once a pair of populations have incompatible alleles of the same gene, as described in the Bateson–Dobzhansky–Muller model . A different mechanism, phyletic speciation, involves one lineage gradually changing over time into a new and distinct form (a chronospecies ), without increasing the number of resultant species. Horizontal gene transfer between organisms of different species, either through hybridisation , antigenic shift , or reassortment ,
7991-626: The Great Depression and the Second World War. Due to its importance in human health, the study of nutrition has heavily emphasized human nutrition and agriculture, while ecology is a secondary concern. Nutrients are substances that provide energy and physical components to the organism, allowing it to survive, grow, and reproduce. Nutrients can be basic elements or complex macromolecules . Approximately 30 elements are found in organic matter , with nitrogen , carbon , and phosphorus being
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#17328486958868122-523: The ICZN for animals and the ICN for plants, do not make rules for defining the boundaries of the species. Research can change the boundaries, also known as circumscription, based on new evidence. Species may then need to be distinguished by the boundary definitions used, and in such cases the names may be qualified with sensu stricto ("in the narrow sense") to denote usage in the exact meaning given by an author such as
8253-440: The carbon cycle , sulfur cycle , nitrogen cycle , water cycle , phosphorus cycle , and oxygen cycle , among others that continually recycle along with other mineral nutrients into productive ecological nutrition. Biogeochemical cycles that are performed by living organisms and natural processes are water , carbon , nitrogen , phosphorus , and sulfur cycles . Nutrient cycles allow these essential elements to return to
8384-400: The diet of an organism is the sum of the foods it eats. A healthy diet improves the physical and mental health of an organism. This requires ingestion and absorption of vitamins , minerals , essential amino acids from protein and essential fatty acids from fat-containing food. Carbohydrates , protein and fat play major roles in ensuring the quality of life , health and longevity of
8515-399: The fly agaric . Natural hybridisation presents a challenge to the concept of a reproductively isolated species, as fertile hybrids permit gene flow between two populations. For example, the carrion crow Corvus corone and the hooded crow Corvus cornix appear and are classified as separate species, yet they can hybridise where their geographical ranges overlap. A ring species is
8646-498: The jaguar ( Panthera onca ) of Latin America or the leopard ( Panthera pardus ) of Africa and Asia. In contrast, the scientific names of species are chosen to be unique and universal (except for some inter-code homonyms ); they are in two parts used together : the genus as in Puma , and the specific epithet as in concolor . A species is given a taxonomic name when a type specimen
8777-402: The soil and the atmosphere. Fungi absorb nutrients around them by breaking them down and absorbing them through the mycelium . Scientific analysis of food and nutrients began during the chemical revolution in the late 18th century. Chemists in the 18th and 19th centuries experimented with different elements and food sources to develop theories of nutrition. Modern nutrition science began in
8908-427: The wood frog , tadpoles showed that those that exhibited cannibalistic tendencies had faster growth rates and higher fitness levels than non-cannibals. An increase of size and growth would give them the added benefit of protection from potential predators such as other cannibals and give them an advantage when competing for resources. The nutritional benefits of cannibalism may allow for the more efficient conversion of
9039-406: The "cynical species concept", and arguing that far from being cynical, it usefully leads to an empirical taxonomy for any given group, based on taxonomists' experience. Other biologists have gone further and argued that we should abandon species entirely, and refer to the "Least Inclusive Taxonomic Units" (LITUs), a view that would be coherent with current evolutionary theory. The species concept
9170-404: The 1910s as individual micronutrients began to be identified. The first vitamin to be chemically identified was thiamine in 1926, and vitamin C was identified as a protection against scurvy in 1932. The role of vitamins in nutrition was studied in the following decades. The first recommended dietary allowances for humans were developed to address fears of disease caused by food deficiencies during
9301-419: The 20th century allowed mass production and food fortification to better meet the nutritional needs of humans. Human behavior is closely related to human nutrition, making it a subject of social science in addition to biology. Nutrition in humans is balanced with eating for pleasure, and optimal diet may vary depending on the demographics and health concerns of each person. Humans are omnivores that eat
9432-622: The Origin of Species explained how species could arise by natural selection . That understanding was greatly extended in the 20th century through genetics and population ecology . Genetic variability arises from mutations and recombination , while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures . Genes can sometimes be exchanged between species by horizontal gene transfer ; new species can arise rapidly through hybridisation and polyploidy ; and species may become extinct for
9563-405: The abbreviation "sp." in the singular or "spp." (standing for species pluralis , Latin for "multiple species") in the plural in place of the specific name or epithet (e.g. Canis sp.). This commonly occurs when authors are confident that some individuals belong to a particular genus but are not sure to which exact species they belong, as is common in paleontology . Authors may also use "spp." as
9694-476: The amount of energy required to raise 1 kilogram of water by 1 degree Celsius. Carbohydrates are molecules that store significant amounts of energy. Animals digest and metabolize carbohydrates to obtain this energy. Carbohydrates are typically synthesized by plants during metabolism, and animals have to obtain most carbohydrates from nature, as they have only a limited ability to generate them. They include sugars , oligosaccharides , and polysaccharides . Glucose
9825-585: The amount of fatty acids it produces as dietary fat intake increases, while it increases the amount of fatty acids it produces as carbohydrate intake increases. Fats contain 9 calories per gram. Protein consumed by animals is broken down to amino acids, which would be later used to synthesize new proteins. Protein is used to form cellular structures, fluids, and enzymes (biological catalysts ). Enzymes are essential to most metabolic processes, as well as DNA replication , repair , and transcription . Protein contains 4 calories per gram. Much of animal behavior
9956-418: The amount of food availability so that there is a decreased chance that the individuals will turn to cannibalism as an additional food source. Species A species ( pl. : species) is a population of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring , typically by sexual reproduction . It is the basic unit of classification and
10087-570: The amount of hybridisation is insufficient to completely mix their respective gene pools . A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology , genes can move freely even between distantly related bacteria, possibly extending to the whole bacterial domain. As a rule of thumb, microbiologists have assumed that members of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA–DNA hybridisation to decide if they belong to
10218-847: The amount of protein in a food. Humans can also obtain energy from ethanol , which is both a food and a drug, but it provides relatively few essential nutrients and is associated with nutritional deficiencies and other health risks. In humans, poor nutrition can cause deficiency-related diseases, such as blindness , anemia , scurvy , preterm birth , stillbirth and cretinism , or nutrient-excess conditions, such as obesity and metabolic syndrome . Other conditions possibly affected by nutrition disorders include cardiovascular diseases , diabetes , and osteoporosis . Undernutrition can lead to wasting in acute cases, and stunting of marasmus in chronic cases of malnutrition. In domesticated animals , such as pets , livestock , and working animals , as well as other animals in captivity , nutrition
10349-477: The amount of time and energy spent foraging. It was created to analyze the foraging habits of animals, but it can also be extended to other organisms. Some organisms are specialists that are adapted to forage for a single food source, while others are generalists that can consume a variety of food sources. Nutrient deficiencies, known as malnutrition , occur when an organism does not have the nutrients that it needs. This may be caused by suddenly losing nutrients or
10480-467: The available gene pool . Kin recognition has been observed in tadpoles of the spadefoot toad, whereby cannibalistic tadpoles of the same clutch tended to avoid consuming and harming siblings, while eating other non-siblings. The act of cannibalism may also facilitate trophic disease transmission within a population, though cannibalistically spread pathogens and parasites generally employ alternative modes of infection. Cannibalism can potentially reduce
10611-474: The biological species concept, "the several versions" of the phylogenetic species concept, and the idea that species are of the same kind as higher taxa are not suitable for biodiversity studies (with the intention of estimating the number of species accurately). They further suggested that the concept works for both asexual and sexually-reproducing species. A version of the concept is Kevin de Queiroz 's "General Lineage Concept of Species". An ecological species
10742-505: The biological species concept, a cladistic species does not rely on reproductive isolation – its criteria are independent of processes that are integral in other concepts. Therefore, it applies to asexual lineages. However, it does not always provide clear cut and intuitively satisfying boundaries between taxa, and may require multiple sources of evidence, such as more than one polymorphic locus, to give plausible results. An evolutionary species, suggested by George Gaylord Simpson in 1951,
10873-428: The boundaries between closely related species become unclear with hybridisation , in a species complex of hundreds of similar microspecies , and in a ring species . Also, among organisms that reproduce only asexually , the concept of a reproductive species breaks down, and each clone is potentially a microspecies. Although none of these are entirely satisfactory definitions, and while the concept of species may not be
11004-559: The cannibalistic individual and its kin as resources such as extra shelter, territory and food are freed, thereby increasing the fitness of the cannibal by lowering crowding effects. However, this is only the case if the cannibal recognizes its own kin as this will not hinder any future chances of perpetuating its genes in future generations. The elimination of competition can also increase mating opportunities, allowing further spread of an individual's genes. Animals which have diets consisting of predominantly conspecific prey expose themselves to
11135-504: The capacity to impact the developmental growth of the cannibal's offspring. Hence, predators normally partake in a cannibalistic diet in conditions where alternative food sources are absent or not as readily available. Failure to recognize kin prey is also a disadvantage, provided cannibals target and consume younger individuals. For example, a male stickleback fish may often mistake their own "eggs" for their competitor's eggs, and hence would inadvertently eliminate some of its own genes from
11266-745: The carbon of other organisms, while autotrophs are organisms that produce their own nutrients from the carbon of inorganic substances like carbon dioxide . Mixotrophs are organisms that can be heterotrophs and autotrophs, including some plankton and carnivorous plants . Phototrophs obtain energy from light, while chemotrophs obtain energy by consuming chemical energy from matter. Organotrophs consume other organisms to obtain electrons, while lithotrophs obtain electrons from inorganic substances, such as water , hydrogen sulfide , dihydrogen , iron(II) , sulfur , or ammonium . Prototrophs can create essential nutrients from other compounds, while auxotrophs must consume preexisting nutrients. In nutrition,
11397-416: The carrying capacity for that resource in the area may be reached, thus forcing individuals to look for other resources such as conspecific prey. Sexual cannibalism is present largely in spiders and other invertebrates , including gastropods . This refers to the killing and consumption of conspecific sexual partners during courtship, and during or after copulation. Normally, it is the female which consumes
11528-433: The concept of a chronospecies can be applied. During anagenesis (evolution, not necessarily involving branching), some palaeontologists seek to identify a sequence of species, each one derived from the phyletically extinct one before through continuous, slow and more or less uniform change. In such a time sequence, some palaeontologists assess how much change is required for a morphologically distinct form to be considered
11659-418: The conspecific male organism, though there have been some reported cases of the male consuming the adult female, however, this has only been recorded under laboratory conditions. Sexual cannibalism has been recorded in the female redback spider , black widow spider , praying mantis , and scorpion , among others. In most species of spiders, the consumption of the male individual occurs before copulation and
11790-550: The consumption of the male by the female individual before, during or after copulation. Other forms of cannibalism include size-structured cannibalism and intrauterine cannibalism. Behavioral, physiological and morphological adaptations have evolved to decrease the rate of cannibalism in individual species. In environments where food availability is constrained, individuals can receive extra nutrition and energy if they use members of their own species, also known as conspecifics , as an additional food source. This would, in turn, increase
11921-423: The decrease of potential competition. Although it may benefit the individual, it has been shown that the presence of cannibalism decreases the expected survival rate of the whole population and increases the risk of consuming a relative. Other negative effects may include the increased risk of pathogen transmission as the encounter rate of hosts increases. Cannibalism, however, does not—as once believed—occur only as
12052-476: The eggs for an additional nutritional benefit or to get rid of genetic competition. In amphibians, the development of non-aquatic egg deposition has helped increase the survival rates of their young by the evolution of viviparity or direct development. In bees, worker policing occurs to prohibit worker reproduction, whereby workers cannibalize other worker laid eggs. Queen laid eggs have a different scent than worker laid eggs, allowing workers to differentiate between
12183-492: The environment after being absorbed or consumed. Without proper nutrient cycling, there would be risk of change in oxygen levels, climate, and ecosystem function. Foraging is the process of seeking out nutrients in the environment. It may also be defined to include the subsequent use of the resources. Some organisms, such as animals and bacteria, can navigate to find nutrients, while others, such as plants and fungi, extend outward to find nutrients. Foraging may be random, in which
12314-412: The environment. This is because the encounter rate between predator and prey increases, making cannibalism more convenient and beneficial than foraging within the environment. Over time, the dynamics within the population change as those with cannibalistic tendencies may receive additional nutritional benefits and increase the size ratio of predator to prey. The presence of smaller prey, or prey which are at
12445-435: The evidence to support hypotheses about evolutionarily divergent lineages that have maintained their hereditary integrity through time and space. Molecular markers may be used to determine diagnostic genetic differences in the nuclear or mitochondrial DNA of various species. For example, in a study done on fungi , studying the nucleotide characters using cladistic species produced the most accurate results in recognising
12576-406: The female, thereby increasing the chance of survivorship of future offspring. Sexual dimorphism has been theorised to have arisen from sexual selection as smaller males were captured more easily than larger males; however, it is also possible that sexual cannibalism only occurs due to the difference in size between male and females. Data comparing female and male spider body length shows that there
12707-434: The females are less likely to attack. Males which are vulnerable to post-copulation consumption may gather mating thread to generate a mechanical tension which they could use to spring away after insemination, while other spiders such as the crab spider may tangle the female's legs in webs to reduce the risk of the female capturing him. Male choice is common in mantids whereby males were observed to choose fatter females due to
12838-534: The fetus eats sibling embryos, while in oophagy it feeds on eggs. Adelphophagy occurs in some marine gastropods ( calyptraeids , muricids , vermetids , and buccinids ) and in some marine annelids ( Boccardia proboscidia in Spionidae ). Intrauterine cannibalism is known to occur in lamnoid sharks such as the sand tiger shark , and in the fire salamander , as well as in some teleost fishes. The Carboniferous period chimaera , Delphyodontos dacriformes ,
12969-400: The first larvae to hatch will consume the other eggs or smaller larvae on the host plant, decreasing competition. Intrauterine cannibalism is a behaviour in some carnivorous species, in which multiple embryos are created at impregnation, but only one or two are born. The larger or stronger ones consume their less-developed siblings as a source of nutrients. In adelphophagy or embryophagy,
13100-743: The inability to absorb proper nutrients. Not only is malnutrition the result of a lack of necessary nutrients, but it can also be a result of other illnesses and health conditions. When this occurs, an organism will adapt by reducing energy consumption and expenditure to prolong the use of stored nutrients. It will use stored energy reserves until they are depleted, and it will then break down its own body mass for additional energy. A balanced diet includes appropriate amounts of all essential and non-essential nutrients. These can vary by age, weight, sex, physical activity levels, and more. A lack of just one essential nutrient can cause bodily harm, just as an overabundance can cause toxicity. The Daily Reference Values keep
13231-1112: The individual were to consume contaminated beef. The spread of parasites such as nematodes may also be facilitated by cannibalism as eggs from these parasites are transferred more easily from one host to another. Other forms of diseases include sarcocystis and iridovirus in reptiles and amphibians; granulosus virus, chagas disease , and microsporidia in insects; stained prawn disease, white pot syndrome, helminthes and tapeworms in crustaceans and fish. Cannibalism may become apparent when direct competition for limited resources forces individuals to use other conspecific individuals as an additional resource to maintain their metabolic rates. Hunger drives individuals to increase their foraging rates, which in turn decreases their attack threshold and tolerance to other conspecific individuals. As resources dwindle, individuals are forced to change their behaviour which may lead to animal migration , confrontation, or cannibalism. Cannibalism rates increase with increasing population density as it becomes more advantageous to prey on conspecific organisms than to forage in
13362-856: The majority of people from nutrient deficiencies. DRVs are not recommendations but a combination of nutrient references to educate professionals and policymakers on what the maximum and minimum nutrient intakes are for the average person. Food labels also use DRVs as a reference to create safe nutritional guidelines for the average healthy person. Animals are heterotrophs that consume other organisms to obtain nutrients. Herbivores are animals that eat plants, carnivores are animals that eat other animals, and omnivores are animals that eat both plants and other animals. Many herbivores rely on bacterial fermentation to create digestible nutrients from indigestible plant cellulose, while obligate carnivores must eat animal meats to obtain certain vitamins or nutrients their bodies cannot otherwise synthesize. Animals generally have
13493-400: The male fails to transfer his sperm into the female. This may be due to mistaken identity such as in the case of the orb weaving spider which holds little tolerance to any spider which is present in its web and may mistake the vibrations for those of a prey item. Other reasons for male consumption before mating may include female choice and the nutritional advantages of cannibalism. The size of
13624-417: The male spider may play a part in determining its reproductive success as smaller males are less likely to be consumed during pre-copulation; however, larger males may be able to prevent the smaller ones from gaining access to the female. There exists a conflict of interest between males and females, as females may be more inclined to turn to cannibalism as a source of nutritional intake while the male's interest
13755-824: The most important. Macronutrients are the primary substances required by an organism, and micronutrients are substances required by an organism in trace amounts. Organic micronutrients are classified as vitamins , and inorganic micronutrients are classified as minerals . Nutrients are absorbed by the cells and used in metabolic biochemical reactions. These include fueling reactions that create precursor metabolites and energy, biosynthetic reactions that convert precursor metabolites into building block molecules, polymerizations that combine these molecules into macromolecule polymers , and assembly reactions that use these polymers to construct cellular structures. Organisms can be classified by how they obtain carbon and energy. Heterotrophs are organisms that obtain nutrients by consuming
13886-536: The numbers. Possible explanations as to why this is so include increasing oxygen availability to the remaining eggs, the negative effects of accumulating embryo waste, and predation. In some species of eusocial wasps, such as Polistes chinensis , the reproducing female will kill and feed younger larvae to her older brood. This occurs under food stressed conditions in order to ensure that the first generation of workers emerges without delay. Further evidence also suggests that occasionally filial cannibalism might occur as
14017-478: The numerous fungi species of all the concepts studied. Versions of the phylogenetic species concept that emphasise monophyly or diagnosability may lead to splitting of existing species, for example in Bovidae , by recognising old subspecies as species, despite the fact that there are no reproductive barriers, and populations may intergrade morphologically. Others have called this approach taxonomic inflation , diluting
14148-433: The organism seeks nutrients without method, or it may be systematic, in which the organism can go directly to a food source. Organisms are able to detect nutrients through taste or other forms of nutrient sensing , allowing them to regulate nutrient intake. Optimal foraging theory is a model that explains foraging behavior as a cost–benefit analysis in which an animal must maximize the gain of nutrients while minimizing
14279-425: The organism. Some cultures and religions have restrictions on what is acceptable for their diet. A nutrient cycle is a biogeochemical cycle involving the movement of inorganic matter through a combination of soil, organisms, air or water, where they are exchanged in organic matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cyclic. Mineral cycles include
14410-585: The paper is accepted for publication. The type material is usually held in a permanent repository, often the research collection of a major museum or university, that allows independent verification and the means to compare specimens. Describers of new species are asked to choose names that, in the words of the International Code of Zoological Nomenclature , are "appropriate, compact, euphonious, memorable, and do not cause offence". Books and articles sometimes intentionally do not identify species fully, using
14541-674: The person who named the species, while the antonym sensu lato ("in the broad sense") denotes a wider usage, for instance including other subspecies. Other abbreviations such as "auct." ("author"), and qualifiers such as "non" ("not") may be used to further clarify the sense in which the specified authors delineated or described the species. Species are subject to change, whether by evolving into new species, exchanging genes with other species, merging with other species or by becoming extinct. The evolutionary process by which biological populations of sexually-reproducing organisms evolve to become distinct or reproductively isolated as species
14672-478: The possible adaptive value of filial cannibalism. One of these is the energy-based hypothesis, which suggests that fish eat their offspring when they are low on energy as an investment in future reproductive success. This has been supported by experimental evidence, showing that male three-spined sticklebacks , male tessellated darters , and male sphinx blenny fish all consume or absorb their own eggs to maintain their physical conditions. In other words, when males of
14803-410: The prevalence of parasites in the population by decreasing the number of susceptible hosts and indirectly killing the parasite in the host. It has been shown in some studies that the risk of encountering an infected victim increases when there is a higher cannibalism rate, though this risk drops as the number of available hosts decreases. However, this is only the case if the risk of disease transmission
14934-429: The reduced risk of attack and were more hesitant to approach starved females. Size-structured cannibalism is cannibalism in which older, larger, more mature individuals consume smaller, younger conspecifics . In size-structured populations, (where populations are made of individuals of various sizes, ages, and maturities), cannibalism can be responsible for 8% ( Belding's ground squirrel ) to 95% ( dragonfly larvae ) of
15065-871: The required amount of nutrients causes malnutrition . Nutritional science is the study of nutrition, though it typically emphasizes human nutrition . The type of organism determines what nutrients it needs and how it obtains them. Organisms obtain nutrients by consuming organic matter , consuming inorganic matter, absorbing light, or some combination of these. Some can produce nutrients internally by consuming basic elements, while some must consume other organisms to obtain pre-existing nutrients. All forms of life require carbon , energy , and water as well as various other molecules . Animals require complex nutrients such as carbohydrates , lipids , and proteins , obtaining them by consuming other organisms. Humans have developed agriculture and cooking to replace foraging and advance human nutrition. Plants acquire nutrients through
15196-487: The result of misclassification leading to questions on whether there really are any ring species. The commonly used names for kinds of organisms are often ambiguous: "cat" could mean the domestic cat, Felis catus , or the cat family, Felidae . Another problem with common names is that they often vary from place to place, so that puma, cougar, catamount, panther, painter and mountain lion all mean Puma concolor in various parts of America, while "panther" may also mean
15327-573: The ring. Ring species thus present a difficulty for any species concept that relies on reproductive isolation. However, ring species are at best rare. Proposed examples include the herring gull – lesser black-backed gull complex around the North pole, the Ensatina eschscholtzii group of 19 populations of salamanders in America, and the greenish warbler in Asia, but many so-called ring species have turned out to be
15458-897: The root-like mycelium, which grows through the organism's source of nutrients and can extend indefinitely. The fungus excretes extracellular enzymes to break down surrounding matter and then absorbs the nutrients through the cell wall. Fungi can be parasitic, saprophytic, or symbiotic. Parasitic fungi attach and feed on living hosts, such as animals, plants, or other fungi. Saprophytic fungi feed on dead and decomposing organisms. Symbiotic fungi grow around other organisms and exchange nutrients with them. Protists include all eukaryotes that are not animals, plants, or fungi, resulting in great diversity between them. Algae are photosynthetic protists that can produce energy from light. Several types of protists use mycelium similar to those of fungi. Protozoa are heterotrophic protists, and different protozoa seek nutrients in different ways. Flagellate protozoa use
15589-433: The safety, quality, flavor, and nutritional content of food. Humans obtain most carbohydrates as starch from cereals, though sugar has grown in importance. Lipids can be found in animal fat , butterfat , vegetable oil, and leaf vegetables , and they are also used to increase flavor in foods. Protein can be found in virtually all foods, as it makes up cellular material, though certain methods of food processing may reduce
15720-508: The same species. This concept was narrowed in 2006 to a similarity of 98.7%. The average nucleotide identity (ANI) method quantifies genetic distance between entire genomes , using regions of about 10,000 base pairs . With enough data from genomes of one genus, algorithms can be used to categorize species, as for Pseudomonas avellanae in 2013, and for all sequenced bacteria and archaea since 2020. Observed ANI values among sequences appear to have an "ANI gap" at 85–95%, suggesting that
15851-529: The same species. When two species names are discovered to apply to the same species, the older species name is given priority and usually retained, and the newer name considered as a junior synonym, a process called synonymy . Dividing a taxon into multiple, often new, taxa is called splitting . Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognising differences or commonalities between organisms. The circumscription of taxa, considered
15982-474: The soil as phosphates , boric acid , and silicic acid , respectively. Other nutrients used by plants are potassium, sodium, calcium, magnesium, manganese, chlorine, iron, copper, zinc, and molybdenum. Plants uptake essential elements from the soil through their roots and from the air (consisting of mainly nitrogen and oxygen) through their leaves . Nutrient uptake in the soil is achieved by cation exchange , wherein root hairs pump hydrogen ions (H ) into
16113-528: The soil in which they grow. This is made possible by the fact that largely inert atmospheric nitrogen is changed in a nitrogen fixation process to biologically usable forms in the soil by bacteria. As these nutrients do not provide the plant with energy, they must obtain energy by other means. Green plants absorb energy from sunlight with chloroplasts and convert it to usable energy through photosynthesis . Fungi are chemoheterotrophs that consume external matter for energy. Most fungi absorb matter through
16244-467: The soil through proton pumps . These hydrogen ions displace cations attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata open to take in carbon dioxide and expel oxygen . Although nitrogen is plentiful in the Earth's atmosphere, very few plants can use this directly. Most plants, therefore, require nitrogen compounds to be present in
16375-502: The species concept and making taxonomy unstable. Yet others defend this approach, considering "taxonomic inflation" pejorative and labelling the opposing view as "taxonomic conservatism"; claiming it is politically expedient to split species and recognise smaller populations at the species level, because this means they can more easily be included as endangered in the IUCN red list and can attract conservation legislation and funding. Unlike
16506-485: The spread of disease may be a limiting factor to the prevalence of cannibalism in the population. Some examples of diseases transmitted by cannibalism in mammals include the human disease Kuru which is a prion disease that degenerates the brain. This disease was prevalent in Papua New Guinea where tribes practiced endocannibalism in cannibalistic funeral rituals and consume the brains infected by these prions. It
16637-424: The survival rate of the cannibal and thus provide an evolutionary advantage in environments where food is scarce. For example, female Fletcher's frogs lay their eggs in ephemeral pools that lack food resources. Therefore, in order to survive, tadpoles within the same clutch are forced to consume each other and exploit their conspecifics as the only available source of nutrition. A study conducted on another amphibian,
16768-721: The total mortality, making it a significant and important factor for population and community dynamics. Size-structured cannibalism has commonly been observed in the wild for a variety of taxa . Vertebrate examples include chimpanzees , where groups of adult males have been observed to attack and consume infants. Filial cannibalism is a specific type of size-structured cannibalism in which adults eat their own offspring. Although most often thought of as parents eating live young, filial cannibalism includes parental consumption of stillborn infants and miscarried fetuses as well as infertile and still-incubating eggs. Vertebrate examples include pigs , where cannibalistic piglet savaging occurs at
16899-738: The two, allowing them to nurture and protect queen laid eggs rather than cannibalising them. Parental presence at nesting sites is also a common method of protection against infanticide committed by conspecific individuals, whereby the parent exhibits defensive displays to ward off potential predators. Parental investment in newborns are generally higher during their early stages of development whereby behaviours such as aggression, territorial behaviour, and pregnancy blocking become more apparent. Morphological plasticity helps an individual account for different predation stresses, thereby increasing individual survival rates. Japanese brown frog tadpoles have been shown to exhibit morphological plasticity when they are in
17030-537: The wild. It is difficult to define a species in a way that applies to all organisms. The debate about species concepts is called the species problem. The problem was recognised even in 1859, when Darwin wrote in On the Origin of Species : I was much struck how entirely vague and arbitrary is the distinction between species and varieties. He went on to write: No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of
17161-403: Was once suspected to practice this form of cannibalism but this turned out to be wrong, although Deinonychus may have done so. Skeletal remains from subadults with missing parts are suspected of having been eaten by other Deinonychus , mainly full-grown adults. Infanticide is the killing of a non-adult animal by an adult of the same species. Infanticide is often accompanied by cannibalism. It
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