Can we revive old species?
Molecular paleontology
There are many species that have gone extinct as a direct result of human activity. Some examples include the dodo, the great auk, the Tasmanian tiger, the Chinese river dolphin, and the passenger pigeon. An extinct species can be revived by using allelic replacement of a closely related species that is still living. By only having to replace a few genes within an organism, instead of having to build the extinct species' genome from scratch, it could be possible to bring back several species in this way, even Neanderthals.
Dolly (sheep)
Cloning may have uses in preserving endangered species and may become a viable tool for reviving extinct species. In January 2009, scientists from the Centre of Food Technology and Research of Aragon, in northern Spain announced the cloning of the Pyrenean ibex, a form of wild mountain goat, which was officially declared extinct in 2000. Although the newborn ibex died shortly after birth due to physical defects in its lungs, it is the first time an extinct animal has been cloned, and may open doors for saving endangered and newly extinct species by resurrecting them from frozen tissue.
Rejuvenation therapy in trees
Rejuvenation is the process of regaining the productivity of a fruit tree when it loses its economic life .This is a branch of science, and this technology can be practiced in almost all trees except trees like coconut, areacanut like palmea family.Paracitic plants like Loranthus,Ferns can be removed through the heading back process of old branches also it will help to reduce the height of the tree and there by harvesting become easy.This can be done by heading back the age old,disease affected branch  the cut should be given below the parasitic plant Association with tree.This should be done in a balanced conditions of logic and science. Heading back the cuted portion is treated with fungicide and this portion tis covered by using plastic sheet to prevent the entry of rain water or snow drops.According to the type of tree the new flushes will come.And this new flushes should be protected from fungal infection.The less yielding fruit trees can be changed to heigh yielding varieties through top working grafting method.In this process according to the size of the tree the fuel wood become an extra benefit.
Restoration of the Everglades
The species that is causing the most impediment to restoration is the Old World climbing fern ("Lygodium microphyllum"), introduced in 1965. The fern grows rapidly and thickly on the ground, making passage for land animals such as black bears and panthers problematic. The ferns also grow as vines into taller portions of trees, and fires climb the ferns in "fire ladders" to scorch portions of the trees that are not naturally resistant to fire.
Coral reef protection
The aim of coral restoration is to help coral adapt to stressors and changing environments. NOAA's Coral Reef Conservation Program and Damage Assessment, Remediation and Restoration Program approaches restoration by responding to and restoring physically damaged reefs, preventing the loss of habitat, implementing coral conservation projects, focusing on restoring endangered coral species and controlling invasive species. The Coral Restoration Foundation has restored over 100 genotypes of staghorn corals ("Acropora cervicornis") using coral nurseries, and also has research goals of determining ecological success, ideal restoration locations and how surrounding organisms affect restoration.
List of Plasmodium species
"P. vivax" strains can be separated into two distinct types depending on the organisation of the A and S rRNA genes. A gene conversion occurred in an Old World strain and this mutated strain give rise to a new calde of parasites in the New World. The Old World strains were subsequently re introduced - possibly via the slave trade - and these are related to the monkey parasite "P. simium". The specific name "Plasmodium collinsi" has been proposed for the New World strains but this has not yet been accepted.
Bird conservation
Captive breeding, or "ex-situ" conservation, has been used in a number of instances to save species from extinction. The principle is to create a viable population of a species in either zoos or breeding facilities, for later reintroduction back into the wild. As such a captive population can either serve as an insurance against the species going extinct in the wild or as a last-ditch effort in situations where conservation in the wild is impossible. Captive breeding has been used to save several species from extinction, the most famous example being the California condor, a species that declined to less than thirty birds. In order to save the California condor the decision was made to take every individual left in the wild into captivity. From these 22 individuals a breeding programme began that brought the numbers up to 273 by 2005. An even more impressive recovery was that of the Mauritius kestrel, which by 1974 had dropped to only four individuals, yet by 2006 the population was 800.
Passenger pigeon
Today, more than 1,532 passenger pigeon skins (along with 16 skeletons) are in existence, spread across many institutions all over the world. It has been suggested that the passenger pigeon should be revived when available technology allows it (a concept which has been termed "de-extinction"), using genetic material from such specimens. In 2003, the Pyrenean ibex ("Capra pyrenaica pyrenaica", a subspecies of the Spanish ibex) was the first extinct animal to be cloned back to life; the clone lived for only seven minutes before dying of lung defects. A hindrance to cloning the passenger pigeon is the fact that the DNA of museum specimens has been contaminated and fragmented, due to exposure to heat and oxygen. American geneticist George M. Church has proposed that the passenger pigeon genome can be reconstructed by piecing together DNA fragments from different specimens. The next step would be to splice these genes into the stem cells of rock pigeons (or band-tailed pigeons), which would then be transformed into egg and sperm cells, and placed into the eggs of rock pigeons, resulting in rock pigeons bearing passenger pigeon sperm and eggs. The offspring of these would have passenger pigeon traits, and would be further bred to favor unique features of the extinct species. Reviving the passenger pigeon may help conserve woodland biodiversity in the eastern US.
Ancestral reconstruction
Ancestral reconstruction (also known as Character Mapping or Character Optimization) is the extrapolation back in time from measured characteristics of individuals (or populations) to their common ancestors. It is an important application of phylogenetics, the reconstruction and study of the evolutionary relationships among individuals, populations or species to their ancestors. In the context of evolutionary biology, ancestral reconstruction can be used to recover different kinds of ancestral character states of organisms that lived millions of years ago. These states include the genetic sequence (ancestral sequence reconstruction), the amino acid sequence of a protein, the composition of a genome (e.g., gene order), a measurable characteristic of an organism (phenotype), and the geographic range of an ancestral population or species (ancestral range reconstruction). This is desirable because it allows us to examine parts of phylogenetic trees corresponding to the distant past, clarifying the evolutionary history of the species in the tree. Since modern genetic sequences are essentially a variation of ancient ones, access to ancient sequences may identify other variations and organisms which could have arisen from those sequences. In addition to genetic sequences, one might attempt to track the changing of one character trait to another, such as fins turning to legs.
Species reintroduction
Many factors can attribute to the success or failure of a reintroduction. Predators, food, pathogens, competitors, and weather can all affect a reintroduced population's ability to grow, survive, and reproduce.The number of animals reintroduced in an attempt should also vary with factors such as social behavior, expected rates of predation, and density in the wild. Animals raised in captivity may experience stress during captivity or translocation, which can weaken their immune systems.
The IUCN reintroduction guidelines emphasize the need for an assessment of the availability of suitable habitat as a key component of reintroduction planning. Poor assessment of the release site can increase the chances that the species will reject the site and perhaps move to a less suitable environment. This can decrease the species fitness and thus decrease chances for survival. They state that restoration of the original habitat and amelioration of causes of extinction must be explored and considered as essential conditions for these projects. Unfortunately, the monitoring period that should follow reintroductions often remains neglected.
Conservation genetics
The genetic diversity of a species is always open to change. No matter how many variants of a gene are present in a population today, only the variants that survive in the next generation can contribute to species diversity in the future. Once gene variants are lost, they cannot be recovered.Specific genetic techniques are used to assess the genomes of a species regarding specific conservation issues as well as general population structure. This analysis can be done in two ways, with current DNA of individuals or historic DNA.
Rewilding (conservation biology)
A controversial 2005 editorial in "Nature", signed by a number of conservation biologists, took up the argument, urging that elephants, lions, and cheetahs could be reintroduced in protected areas in the Great Plains. The Bolson tortoise, discovered in 1959 in Durango, Mexico, was the first species proposed for this restoration effort, and in 2006 the species was reintroduced to two ranches in New Mexico owned by media mogul Ted Turner. Other proposed species include various camelids, equids, and peccaries.
Passenger pigeon
The general idea of re-creating extinct species has been criticized, since the large funds needed could be spent on conserving currently threatened species and habitats, and because conservation efforts might be viewed as less urgent. In the case of the passenger pigeon, since it was very social, it is unlikely that enough birds could be created for revival to be successful, and it is unclear whether there is enough appropriate habitat left for its reintroduction. Furthermore, the parent pigeons that would raise the cloned passenger pigeons would belong to a different species, with a different way of rearing young.
De-extinction
Mammoth expert Adrian Lister questions the ethics of such recreation attempts. In addition to the technical problems, he notes that there is not much habitat left that would be suitable for woolly mammoths. Because the species was gregarious, creating a few specimens would not be ideal. He also notes that the time and resources required would be enormous, and that the scientific benefits would be unclear; these resources should instead be used to preserve extant elephant species which are endangered. However, it was reported in March 2014 that blood recovered from a frozen mammoth carcass in 2013 now provides a "High chance" of cloning the woolly mammoth, despite previous hindrances. Another way to revive the woolly mammoth would be to migrate genes from the mammoth genome into the genes of its closest living relative, the Asian elephant, to create hybridized animals with the notable adaptations that it had for living in a much colder environment than modern day elephants. This is currently being done by Harvard geneticist George Church, and they have already successfully made changes in the elephant genome with the genes that gave the woolly mammoth its cold-resistant blood, longer hair, and extra layer of fat. A revived woolly mammoth or mammoth-elephant hybrid may find suitable habitat in the tundra and taiga forest ecozones, and may also find refuge in Pleistocene Park, a Pleistocene rewilding experiment by Russian scientist Sergey Zimov to recreate the mammoth steppe, the former habitat of the woolly mammoth. While mammoths are not required for the recreation of the steppe, they would be highly effective in doing so by quickly clearing brush and forest and allowing grasses to colonize the area, a capability that modern arctic megafauna do not have.
Paul S. Martin
Martin also championed the concept of “rewilding”, or “resurrection ecology” in which extinct N. American Pleistocene fauna could be restored by establishing breeding populations of surviving animals from other continents (llamas, camels, lions and cheetahs) and introducing populations of animals analogous to extinct species, i.e., elephants for mammoths. However, he is especially focused on returning elphants to North America, as shown in The World Without Us. Alan Weisman, The World Without Us, p. 348, Picador, 2007
Biological immortality
Planarian flatworms have both sexually and asexually reproducing types. Studies on genus Schmidtea mediterranea suggest these planarians appear to regenerate (i.e. heal) indefinitely, and asexual individuals have an "apparently limitless [telomere] regenerative capacity fueled by a population of highly proliferative adult stem cells". "Both asexual and sexual animals display age-related decline in telomere length; however, asexual animals are able to maintain telomere lengths somatically (i.e. during reproduction by fission or when regeneration is induced by amputation), whereas sexual animals restore telomeres by extension during sexual reproduction or during embryogenesis like other sexual species. Homeostatic telomerase activity observed in both asexual and sexual animals is not sufficient to maintain telomere length, whereas the increased activity in regenerating asexuals is sufficient to renew telomere length... "
Ancestral reconstruction
Ancestral protein and DNA reconstruction allows for the recreation of protein and DNA evolution in the laboratory so that it can be studied directly. With respect to proteins, this allows for the investigation of the evolution of present-day molecular structure and function. Additionally, ancestral protein reconstruction can lead to the discoveries of new biochemical functions that have been lost in modern proteins. It also allows insights into the biology and ecology of extinct organisms. Although the majority of ancestral reconstructions have dealt with proteins, it has also been used to test evolutionary mechanisms at the level of bacterial genomes and primate gene sequences.
Multicellular organism
This kind of severely co-dependent symbiosis can be seen frequently, such as in the relationship between clown fish and Riterri sea anemones. In these cases, it is extremely doubtful whether either species would survive very long if the other became extinct. However, the problem with this theory is that it is still not known how each organism's DNA could be incorporated into one single genome to constitute them as a single species. Although such symbiosis is theorized to have occurred (e.g., mitochondria and chloroplasts in animal and plant cells—endosymbiosis), it has happened only extremely rarely and, even then, the genomes of the endosymbionts have retained an element of distinction, separately replicating their DNA during mitosis of the host species. For instance, the two or three symbiotic organisms forming the composite lichen, although dependent on each other for survival, have to separately reproduce and then re-form to create one individual organism once more.
Restoration ecology
Restoration is used as a tool for reducing the spread of invasive plant species in a number of ways. The first method views restoration primarily as a means to reduce the presence of invasive species and limit their spread. As this approach emphasizes control of invaders, the restoration techniques can differ from typical restoration projects. The goal of such projects is not necessarily to restore an entire ecosystem or habitat. These projects frequently use lower diversity mixes of aggressive native species seeded at high density. They are not always actively managed following seeding. The target areas for this type of restoration are those which are heavily dominated by invasive species. The goals are to first remove the species and then in so doing, reduce the number of invasive seeds being spread to surrounding areas. An example of this is through use of biological control agents (such as herbivorous insects) which suppress invasive weed species while restoration practitioners concurrently seed in native plant species that take advantage of the freed resources. These approaches have been shown to be effective in reducing weeds, although it is not always a sustainable solution long term without additional weed control, such as mowing, or re-seeding.
De-extinction
Cloning is the method discussed as an option for bringing back extinct species, by extracting the nucleus from a preserved cell from the extinct species and swapping it into an egg of the nearest living relative. This egg can then be inserted into a relative host. It is important to note that this method can only be used when a preserved cell is available. This means that it is most feasible for recently extinct species.
Although de-extinction efforts have not yet succeeded in producing viable offspring of a previously extinct species, the same process has been applied successfully to endangered species. The banteng is an endangered species that was successfully cloned, and the first to survive for more than a week (the first was a gaur that died two days after being born). Scientists at Advanced Cell Technology in Worcester, Massachusetts, United States extracted DNA from banteng cells kept in the San Diego Zoo's "Frozen Zoo" facility, and transferred it into eggs from domestic cattle, a process called somatic cell nuclear transfer. Thirty hybrid embryos were created and sent to Trans Ova Genetics, which implanted the fertilized eggs in domestic cattle. Two were carried to term and delivered by Caesarian section. The first hybrid was born on April 1, 2003, and the second two days later. The second was euthanized, but the first survived and, as of September 2006, remained in good health at the San Diego Zoo.
Moa
The creature has frequently been mentioned as a potential candidate for revival by cloning. Its iconic status, coupled with the facts that it only became extinct a few hundred years ago and that substantial quantities of moa remains exist, mean that it is often listed alongside such creatures as the dodo as leading candidates for resurrection. Preliminary work involving the extraction of DNA has been undertaken by Japanese geneticist Ankoh Yasuyuki Shirota.
Silviculture
Regeneration is basic to the continuation of forested, as well as to the afforestation of treeless land. Regeneration can take place through self-sown seed ("natural regeneration"), by artificially sown seed, or by planted seedlings. In whichever case, the performance of regeneration depends on its growth potential and the degree to which its environment allows the potential to be expressed. Seed, of course, is needed for all regeneration modes, both for natural or artificial sowing and for raising planting stock in a nursery.
Species reintroduction
"In situ" sourcing for restorations involves moving individuals from an existing wild population to a new site where the species was formerly extirpated. Ideally, populations should be sourced "in situ" when possible due to the numerous risks associated with reintroducing organisms from captive populations to the wild. To ensure that reintroduced populations have the best chance of surviving and reproducing, individuals should be sourced from populations that genetically and ecologically resemble the recipient population. Generally, sourcing from populations with similar environmental conditions to the reintroduction site will maximize the chance that reintroduced individuals are well adapted to the habitat of the reintroduction site .
Leonard Betts
According to biology professor and science advisor to the "X-Files" Anne Simon, the manner in which Betts can regrow limbs is somewhat similar to the way in which amphibians and newts can regenerate tails and other limbs. She notes that many amphibian cells can "turn back the clock [and] revert back to an [embryonic] time when any fate was possible". In humans, only two types of cells—blood cells and liver cells—are able to regenerate, however, the process is different via the stem cell. Simon also postulates that Betts was able to regenerate because he had a specific relationship between his immune system and his cellular growth. She notes that what Scully and Burks mistook for tumors were actually blastema, or masses of cells capable of growth and regeneration into organs or body parts. Simon also suggests that, for Betts to truly be composed entirely of cancer cells, he would have to lack functioning p53, the tumor suppressor protein. This condition, however, is always fatal.
Ernst Mayr
Although Charles Darwin and others posited that multiple species could evolve from a single common ancestor, the mechanism by which this occurred was not understood, creating the "species problem". Ernst Mayr approached the problem with a new definition for species. In his book "Systematics and the Origin of Species" (1942) he wrote that a species is not just a group of morphologically similar individuals, but a group that can breed only among themselves, excluding all others. When populations within a species become isolated by geography, feeding strategy, mate choice, or other means, they may start to differ from other populations through genetic drift and natural selection, and over time may evolve into new species. The most significant and rapid genetic reorganization occurs in extremely small populations that have been isolated (as on islands).
Species
Louis-Marie Bobay and Howard Ochman suggest, based on analysis of the genomes of many types of bacteria, that they can often be grouped "into communities that regularly swap genes", in much the same way that plants and animals can be grouped into reproductively isolated breeding populations. Bacteria may thus form species, analogous to Mayr's biological species concept, consisting of asexually reproducing populations that exchange genes by homologous recombination.
Extinct in the wild
Reintroduction is the deliberate release of species into the wild, from captivity or relocated from other areas where the species survives. This may be an option for certain species that are endangered or extinct in the wild. However, it may be difficult to reintroduce EW species into the wild, even if their natural habitats were restored, because survival techniques, which are often passed from parents to offspring during parenting, may be lost. While conservation efforts may preserve some of the genetics of a species, the species may never fully recover due to the loss of the natural memetics of the species.
Island restoration
The ecological restoration of islands, or island restoration, is the application of the principles of ecological restoration to islands and island groups. Islands, due to their isolation, are home to many of the world's endemic species, as well as important breeding grounds for seabirds and some marine mammals. Their ecosystems are also very vulnerable to human disturbance and particularly to introduced species, due to their small size. Island groups such as New Zealand and Hawaii have undergone substantial extinctions and losses of habitat. Since the 1950s several organisations and government agencies around the world have worked to restore islands to their original states; New Zealand has used them to hold natural populations of species that would otherwise be unable to survive in the wild. The principal components of island restoration are the removal of introduced species and the reintroduction of native species.
Leopold Report
Restoring the primitive scene is not done easily nor can it be done completely. Some species are extinct. Given time, an eastern hardwood forest can be regrown to maturity but the chestnut will be missing and so will the roar of pigeon wings. The colorful drapanid finches are not to be heard again in the lowland forests of Hawaii, nor will the jack-hammer of the ivory-bill ring in southern swamps. The wolf and grizzly bear cannot readily be reintroduced into ranching communities, and the factor of human use of the parks is subject only to regulation, not elimination. Exotic plants, animals, and diseases are here to stay. All these limitations we fully realize. Yet, if the goal cannot be fully achieved it can be approached. A reasonable illusion of primitive America could be recreated, using the utmost in skill, judgment, and ecologic sensitivity. This in our opinion should be the objective of every national park and monument.
Pseudoextinction
Another concept of species on the tree of life is the composite species concept. It sees one species as occupying all internodes of the tree that have the same combination of (morphological, ecological, etc.) characters. Here, a species starts with the acquisition of a character and ends when another change is fixed in its lineage. This process - of one lineage turning into what is afterwards seen as another species because of the fixation of a novel character - is often called anagenesis. But we have a similar situation here where a species is considered to end by definition but is not really extinct (it survived, after all, in the form of one descendent species with a different character combination), and so we could also consider it to be pseudoextinction. On the other hand, under the composite species concept a species continues through a lineage split if only one of the two resulting lineages acquires a new character, an event that is sometimes called speciation through "budding". The one that has a new character is now a new species but the other lineage, the one that looks identical to the common ancestor, is considered to be the common ancestor. An example would be a widespread breeding group remaining unchanged while "budding off" a small isolated population that accumulates changes until it cannot interbreed with the others any more.
Taxidermy
Re-creation mounts are accurate life-size representations of either extant or extinct species that are created using materials not found on the animal being rendered. They utilize the fur, feathers, and skin of another species of animal. According to the National Taxidermy Association:" "Re-creations, for the purpose of this [competition] category, are defined as renderings which include no natural parts of the animal portrayed. A re-creation may include original carvings and sculptures. A re-creation may use natural parts, provided the parts are not from the species being portrayed. For instance, a re-creation eagle could be constructed using turkey feathers, or a cow hide could be used to simulate African game"." A famous example of a re-creation mount is a giant panda created by taxidermist Ken Walker that he constructed out of dyed and bleached black bear fur.
DNA damage theory of aging
Studies comparing DNA repair capacity in different mammalian species have shown that repair capacity correlates with lifespan. The initial study of this type, by Hart and Setlow, showed that the ability of skin fibroblasts of seven mammalian species to perform DNA repair after exposure to a DNA damaging agent correlated with lifespan of the species. The species studied were shrew, mouse, rat, hamster, cow, elephant and human. This initial study stimulated many additional studies involving a wide variety of mammalian species, and the correlation between repair capacity and lifespan generally held up. In one of the more recent studies, Burkle et al. studied the level of a particular enzyme, Poly ADP ribose polymerase, which is involved in repair of single-strand breaks in DNA. They found that the lifespan of 13 mammalian species correlated with the activity of this enzyme.
Genetic erosion
It can be possible to save an endangered species from extinction by preserving only "parts" of specimens, such as tissues, sperm, eggs, etc. – even after the death of a critically endangered animal, or collected from one found freshly dead, in captivity or from the wild. A new specimen can then be "resurrected" with the help of cloning, so as to give it another chance to breed its genes into the living population of the respective threatened species. Resurrection of dead critically endangered wildlife specimens with the help of cloning is still being perfected, and is still too expensive to be practical, but with time and further advancements in science and methodology it may well become a routine procedure not to far into the future.
Relict (biology)
A notable example is the thylacine of Tasmania, a relict marsupial carnivore that survived into modern times on an island whereas the rest of its species on mainland Australia had long ago gone extinct. When a relict is representative of taxa found in the fossil record, and yet is still living, such an organism is sometimes referred to as a living fossil. However, a relict need not be currently living. An evolutionary relict is any organism that was characteristic of the flora or fauna of one age and that persisted into a later age, with the later age being characterized by newly evolved flora or fauna significantly different from those that came before.
Silviculture
An even-aged regeneration method that can employ either natural or artificial regeneration. It involves the complete removal of the forest stand at one time. Clearcutting can be biologically appropriate with species that typically regenerate from stand replacing fires or other major disturbances, such as Lodgepole Pine ("Pinus contorta"). Alternatively, clearcutting can change the dominating species on a stand with the introduction of non-native and invasive species as was shown at the Blodgett Experimental Forest near Georgetown California. Additionally, clearcutting can prolong slash decomposition, expose soil to erosion, impact visual appeal of a landscape and remove essential wildlife habitat. It is particularly useful in regeneration of tree species such as Douglas-fir ("Pseudotsuga menziesii") which is shade intolerant.. In addition, the general public's distaste for even-aged silviculture, particularly clearcutting, is likely to result in a greater role for uneven-aged management on public lands as well. Across Europe, and in parts of North America, even-aged, production-orientated and intensively managed plantations are beginning to be regarded in the same way as old industrial complexes: something to abolish or convert to something else.
Species reintroduction
Species reintroduction is the deliberate release of a species into the wild, from captivity or other areas where the organism is capable of survival. The goal of species reintroduction is to establish a healthy, genetically diverse, self-sustaining population to an area where it has been extirpated, or to augment an existing population. Species that may be eligible for reintroduction are typically threatened or endangered in the wild. However, reintroduction of a species can also be for pest control. For example, wolves being reintroduced to a wild area to curb an overpopulation of elk or deer. Because reintroduction may involve returning native species to localities where they had been extirpated, some prefer the term "reestablishment".
Mistletoe
Once a mistletoe plant is established on its host, it usually is possible to save a valuable branch by pruning and judicious removal of the wood invaded by the haustorium, if the infection is caught early enough. Some species of mistletoe can regenerate if the pruning leaves any of the haustorium alive in the wood.
Sea anemone
Sea anemones have great powers of regeneration and can reproduce asexually, by budding, fragmentation, or by longitudinal or transverse binary fission. Some species such as certain "Anthopleura" divide longitudinally, pulling themselves apart, resulting in groups of individuals with identical colouring and markings. Transverse fission is less common, but occurs in "Anthopleura stellula" and "Gonactinia prolifera", with a rudimentary band of tentacles appearing halfway up the column before it splits horizontally. Some species can also reproduce by pedal laceration. In this process, a ring of material may break off from the pedal disc at the base of the column which then fragments, the pieces regenerating into new clonal individuals. Alternatively, fragments detach separately as the animal creeps across a surface. In "Metridium dianthus", fragmentation rates were higher in individuals living among live mussels than among dead shells, and all the new individuals had tentacles within three weeks.
Forest restoration
Tree planting is not always essential to restore forest ecosystems. A lot can be achieved by studying how forests regenerate naturally, identifying the factors that limit regeneration and devising methods to overcome them. These can include weeding and adding fertilizer around natural tree seedlings, preventing fire, removing cattle and so on. This is "accelerated" or "assisted" natural regeneration. It is simple and cost-effective, but it can only operate on trees that are already present, mostly light-loving pioneer species. Such tree species are not usually those that comprise climax forests, but they can foster recolonization of the site by shade-tolerant climax forest tree species, via natural seed dispersal from remnant forest. Because this is a slow process, biodiversity recovery can usually be accelerated by planting some climax forest tree species, especially large-seeded, poorly dispersed species. It is not feasible to plant all the tree species that may have formerly grown in the original primary forest and it is usually unnecessary to do so, if the framework species method can be used.
Introduced species
Species that humans intentionally transport to new regions can subsequently become successfully established in two ways. In the first case, organisms are purposely released for establishment in the wild. It is sometimes difficult to predict whether a species will become established upon release, and if not initially successful, humans have made repeated introductions to improve the probability that the species will survive and eventually reproduce in the wild. In these cases it is clear that the introduction is directly facilitated by human desires.
Endangered species recovery plan
The United States congress said in 1973 that endangered species "are of aesthetic, ecological, educational, historical, recreational, and scientific value to the Nation and its people." They therefore set laws to protect endangered species. Section 4(f) of the United States Endangered Species Act from 1973 directs the Secretary of the Interior and the Secretary of Commerce to develop and implement recovery plans to promote the conservation of endangered and threatened species. The Fish and Wildlife Service and the National Oceanic and Atmospheric Administration (NOAA) National Marine Fisheries Service are responsible for administering the act. The recovery plan is a document which specifies what research and management actions are necessary to support recovery, but does not itself commit manpower or funds. Recovery plans are used in setting funding priorities and provide direction to local, regional, and state planning efforts. Recovery is when the threats to species survival are neutralized and the species will be able to survive in the wild.
Ageing
The rate of ageing varies substantially across different species, and this, to a large extent, is genetically based. For example, numerous perennial plants ranging from strawberries and potatoes to willow trees typically produce clones of themselves by vegetative reproduction and are thus potentially immortal, while annual plants such as wheat and watermelons die each year and reproduce by sexual reproduction. In 2008 it was discovered that inactivation of only two genes in the annual plant "Arabidopsis thaliana" leads to its conversion into a potentially immortal perennial plant. The oldest animals known so far are 15,000-year-old Antarctic sponges, which can reproduce both sexually and clonally.
Neontology
A taxon can be classified as extinct if it is broadly agreed or certified that no members of the group are still alive. Conversely, an extinct taxon can be reclassified as extant if there are new discoveries of extant species ("Lazarus species"), or if previously-known extant species are reclassified as members of the taxon.
Ancient woodland
Planted ancient woodland (PAWS) is an ancient woodland site where the native species have been partially or wholly replaced with a non locally native species (usually but not always conifers). These woodlands typically have a plantation structure, with even aged crops of one or two species planted for commercial purposes. Many of these ancient woodlands were converted to conifer plantations following war-time fellings. PAWS sites, whilst not being of such high ecological value as ASNW, typically contain remnants of semi-natural species where shading has been less intense, and restoration of more semi-natural structures through gradual thinning is often possible. Since the recognition of the ecological and historical values of ancient woodland, PAWS restoration has been a priority amongst many woodland owners and governmental and non-governmental agencies, and has been supported by various grant schemes. Some restored PAWS sites are now practically indistinguishable from ASNW. There is no formal method for reclassifying restored PAWS as ASNW, although some woodland managers now use the acronym RPAWS for a restored site.
Species which are particularly characteristic of ancient woodland sites are called ancient woodland indicator species, such as bluebells, Ramsons, wood anemone, yellow archangel and primrose for example, representing a type of ecological indicator. The term tends to be applied more usefully to desiccation-sensitive plant species, and particularly lichens and bryophytes, than to animals, as they are slower to colonise planted woodlands, and are thus viewed as more reliable indicators of ancient woodland sites. Sequences of pollen analysis are also indicators of forest continuity.
Invasive species
Although most people focus on the negative effects of invasive and non-native species, they can actually be harmless or even beneficial in some cases. Ecosystems thrive because of biodiversity and some need non-native species in order to succeed. There are four major ways that non-natives can be very beneficial for an ecosystem. The first is that they can provide a suitable habitat or food source for other organisms. In areas where a native has become extinct or reached a point that it cannot be restored, non-native species can fill their role. A good example of this is the Tamarisk, a non-native woody plant, and the Southwestern Willow Flycatcher, an endangered bird. 75% of Southwestern Willow Flycatcher were found to nest in these plants and their success was the same as the flycatchers that had nested in native plants. The removal of Tamarisk would be detrimental to Southwestern Willow Flycatcher as their native nesting sites are unable to be restored.
World Association of Zoos and Aquariums
The IUCN list also contains other species which were extinct in the wild in the past but which have survived in human care, and several of them have been reintroduced by zoos and wildlife parks to their original habitat (Californian condor CR, red wolf CR, black-footed ferret EN, Przewalski's horse EN, mhorr gazelle CR, Arabian oryx VU, European bison VU, American bison NT).
However the IUCN does not list two species of Seychelles giant tortoises which were rediscovered recently surviving in human care.
Partners in Flight
Helping Species at Risk - Species must be conserved before they become imperiled. Allowing species to become threatened or endangered results in long-term and costly recovery efforts whose success is far from guaranteed. Endangered species must not only be protected from extinction but must be recovered to once again play their roles in ensuring the future of healthy ecosystems.
Unit of selection
It remains controversial among biologists whether selection can operate at and above the level of species. Proponents of species selection include R. A. Fisher (1929); Sewall Wright (1956); Richard Lewontin (1970); Niles Eldredge & Stephen Jay Gould (1972); Steven M. Stanley (1975). Gould proposed that there exist macroevolutionary processes which shape evolution, not driven by the microevolutionary mechanisms of the Modern Synthesis. If one views species as entities that replicate (speciate) and die (go extinct), then species could be subject to selection and thus could change their occurrence over geological time, much as heritable selected-for traits change theirs over generations.
For evolution to be driven by species selection, differential success must be the result of selection upon species-intrinsic properties, rather than for properties of genes, cells, individuals, or populations within species. Such properties include, for example, population structure, their propensity to speciate, extinction rates, and geological persistence. While the fossil record shows differential persistence of species, examples of species-intrinsic properties subject to natural selection have been much harder to document.
Save China's Tigers
Ideally, a former zoo tiger which has been rewilded and reintroduced into a natural habitat will not only be able to survive in the wild, but pass necessary skills on to any offspring, thus contributing to the survival of the species. Save China's Tigers has also proved that not only zoo tigers can learn to hunt, they can also learn to hunt by themselves through the "adaptive process". The roles of humans are limited to that monitoring and providing a suitable environment.
Multicellular organism
Until recently, phylogenetic reconstruction has been through anatomical (particularly embryological) similarities. This is inexact, as living multicellular organisms such as animals and plants are more than 500 million years removed from their single-cell ancestors. Such a passage of time allows both divergent and convergent evolution time to mimic similarities and accumulate differences between groups of modern and extinct ancestral species. Modern phylogenetics uses sophisticated techniques such as alloenzymes, satellite DNA and other molecular markers to describe traits that are shared between distantly related lineages.
Extinction
Through evolution, species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche—and species become extinct when they are no longer able to survive in changing conditions or against superior competition. The relationship between animals and their ecological niches has been firmly established. A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive with virtually no morphological change for hundreds of millions of years.
Conservation in India
Some endangered species in the country were reintroduced via ex situ conservation. Ex-situ conservation is rearing or cultivating, including reintroducing, a plant or animal outside their natural habitat. The reintroduction of the Indian rhinoceros at the Dudhwa National Park was a form of ex-situ conservation; it was extinct in that area. Similarly the Gangetic gharial was reintroduced in Uttar Pradesh, Madhya Pradesh and Rajasthan.Ecological issues are an integral and important part of environmental issues challenging India. Poor air quality, water pollution and garbage pollution – all affect the food and environment quality necessary for ecosystems.
Riparian-zone restoration
Restoration often focuses on reestablishing plant communities, probably because plants form the foundation for other organisms within the community. Restoration of faunal communities often follows the “Field of Dreams” hypothesis: “if you build it, they will come”. Many animal species have been found to naturally recolonize areas where habitat has been restored. For example, abundances of several bird species showed marked increases after riparian vegetation had been reestablished in a riparian corridor in Iowa.
Some riparian restoration efforts may be aimed at conserving particular animal species of concern, such as the Valley elderberry longhorn beetle in central California, which is dependent on a riparian tree species (blue elderberry, "Sambucus mexicana") as its sole host plant. When restoration efforts target key species, consideration for individual species’ needs (e.g., minimum width or extent of riparian vegetation) are important for ensuring restoration success.
Restoration ecology
In addition, conservation biology often concentrates on vertebrate animals because of their salience and popularity, whereas restoration ecology concentrates on plants. Restoration ecology focuses on plants because restoration projects typically begin by establishing plant communities. Ecological restoration, despite being focused on plants, may also have "poster species" for individual ecosystems and restoration projects. For example, the Monarch butterfly is a poster species for conserving and restoring milkweed plant habitat, because Monarch butterflies require milkweed plants to reproduce. Finally, restoration ecology has a stronger focus on soils, soil structure, fungi, and microorganisms because soils provide the foundation of functional terrestrial ecosystems.
De-extinction
Selective breeding is the process by which living relatives of the extinct species are identified and specifically mated to reproduce the traits of the extinct species. This method can recreate the traits of an extinct species, but the genome will differ from the original species.
Ageing
Human beings and members of other species, especially animals, necessarily experience ageing and mortality. Fungi, too, can age. In contrast, many species can be considered immortal: for example, bacteria fission to produce daughter cells, strawberry plants grow runners to produce clones of themselves, and animals in the genus "Hydra" have a regenerative ability by which they avoid dying of old age.
List of resurrected species
This is a list of resurrected species. So far, there is no scientifically verified method of DNA resurrection of a previously dead species.
Rewilding (conservation biology)
Pleistocene rewilding was proposed by the Brazilian ecologist Mauro Galetti in 2004. He suggested the introduction of elephants (and other proxies of extinct megafauna) from circuses and zoos to private lands in the Brazilian cerrado. In 2005, stating that much of the original megafauna of North America—including mammoths, ground sloths, and sabre-toothed cats—became extinct after the arrival of humans, Paul S. Martin proposed restoring the ecological balance by replacing them with species which have similar ecological roles, such as Asian or African elephants.
Mammal
Among mammals, species maximum lifespan varies significantly (for example the shrew has a lifespan of two years, whereas the oldest bowhead whale is recorded to be 211 years). Although the underlying basis for these lifespan differences is still uncertain, numerous studies indicate that the ability to repair DNA damages is an important determinant of mammalian lifespan. In a 1974 study by Hart and Setlow, it was found that DNA excision repair capability increased systematically with species lifespan among seven mammalian species. Species lifespan was observed to be robustly correlated with the capacity to recognize DNA double-strand breaks as well as the level of the DNA repair protein Ku80. In a study of the cells from sixteen mammalian species, genes employed in DNA repair were found to be up-regulated in the longer-lived species. The cellular level of the DNA repair enzyme poly ADP ribose polymerase was found to correlate with species lifespan in a study of 13 mammalian species. Three additional studies of a variety of mammalian species also reported a correlation between species lifespan and DNA repair capability.
Unicellular organism
Bacteria are one of the world’s oldest forms of life, and are found virtually everywhere in nature. Many common bacteria have plasmids, which are short, circular, self-replicating DNA molecules that are separate from the bacterial chromosome. Plasmids can carry genes responsible for novel abilities, of current critical importance being antibiotic resistance. Bacteria predominantly reproduce asexually through a process called binary fission. However, about 80 different species can undergo a sexual process referred to as natural genetic transformation. Transformation is a bacterial process for transferring DNA from one cell to another, and is apparently an adaptation for repairing DNA damage in the recipient cell. In addition, plasmids can be exchanged through the use of a pilus in a process known as conjugation.
Introduction to evolution
Given the right circumstances, and enough time, evolution leads to the emergence of new species. Scientists have struggled to find a precise and all-inclusive definition of "species". Ernst Mayr defined a species as a population or group of populations whose members have the potential to interbreed naturally with one another to produce viable, fertile offspring. (The members of a species cannot produce viable, fertile offspring with members of "other" species). Mayr's definition has gained wide acceptance among biologists, but does not apply to organisms such as bacteria, which reproduce asexually.
How to Clone a Mammoth
Several chapters deal with the genetic material itself and how to obtain it, along with the difficulties of recovering viable DNA samples from mummified or fossilized remains. Due to the actions of nucleases after cell death, most DNA of extinct species is fragmented into small pieces that have to be reconstructed at least partially if it is to be cloned. This fragmentation means that recovery of a full extinct genome is largely impossible. Thus, only partial genes can be utilized and the most viable method is to use a close evolutionary relative of the extinct species and insert the genes that differ into an embryo of the living species. For mammoth de-extinction, any trait consideration would involve the Asian elephant, the closest still-living relative. Using genes from extrapolated mammoth DNA, the Asian elephant could be made to survive across a wider range, including cold environments, protecting it against possible extinction. This gene transfer to benefit living species is one of the primary sources of research done with de-extinction technology in addition to the desire to revive lost species.
Ancestral sequence reconstruction
Ancestral sequence reconstruction (ASR) – also known as ancestral gene/sequence reconstruction/resurrection – is a technique used in the study of molecular evolution. The method consists of the synthesis of an ancestral gene and expression of the corresponding ancestral protein. The idea of protein 'resurrection' was suggested in 1963 by Pauling and Zuckerkandl. Some early efforts were made in the eighties-nineties, led by the laboratory of Steven A. Benner, showing the potential of this technique – one that only started to be fulfilled in the post-genomic era. Thanks to the improvement of algorithms and of better sequencing and synthesis techniques, the method was developed further in the early 2000s to allow the resurrection of a greater variety of and much more ancient genes. Over the last decade, ancestral protein resurrection has developed as a strategy to reveal the mechanisms and dynamics of protein evolution.
Bush regeneration
Weed species can be important habitat for native fauna (e.g. blackberry is important habitat for wrens and the southern brown bandicoot) and this should be taken into consideration with bush regeneration, for example by not clearing invasive species until adequate habitat alternatives have been established nearby with native vegetation.
Speciation
New species have been created by animal husbandry, but the dates and methods of the initiation of such species are not clear. Often, the domestic counterpart of the wild ancestor can still interbreed and produce fertile offspring as in the case of domestic cattle, that can be considered the same species as several varieties of wild ox, gaur, yak, etc., or domestic sheep that can interbreed with the mouflon.
Species
In biology, a species (, is the basic unit of classification and a taxonomic rank, as well as a unit of biodiversity, but it has proven difficult to find a satisfactory definition. Scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If as Carl Linnaeus thought, species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, and to grade into one another. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, when looked at more closely it is problematic. For example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clone is potentially a microspecies. Problems also arise when dealing with fossils, since reproduction cannot be examined; the concept of the chronospecies is therefore used in palaeontology. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche.
Endangered species
Another problem with the listing species is its effect of inciting the use of the "shoot, shovel, and shut-up" method of clearing endangered species from an area of land. Some landowners currently may perceive a diminution in value for their land after finding an endangered animal on it. They have allegedly opted to silently kill and bury the animals or destroy habitat, thus removing the problem from their land, but at the same time further reducing the population of an endangered species. The effectiveness of the Endangered Species Act – which coined the term "endangered species" – has been questioned by business advocacy groups and their publications but is nevertheless widely recognized by wildlife scientists who work with the species as an effective recovery tool. Nineteen species have been delisted and recovered and 93% of listed species in the northeastern United States have a recovering or stable population.
Aurochs
Scientists of the Polish Foundation for Recreating the Aurochs (PFOT) in Poland hope to use DNA from bones in museums to recreate the aurochs. They plan to return this animal to the forests of Poland. The project has gained the support of the Polish Ministry of the Environment. They plan research on ancient preserved DNA. Other research projects have extracted "ancient" DNA over the past 20 years and their results have been published in such periodicals as "Nature" and "PNAS". Polish scientists Ryszard Słomski and Jacek A. Modliński believe that modern genetics and biotechnology make it possible to recreate an animal almost identical to the aurochs. They say this research will lead to examining the causes of the extinction of the aurochs, and help prevent a similar occurrence with domesticated cattle.
Captive breeding
There is reason to demand for the release of animals from captivity programs for four main reasons: a lack of sufficient space due to overly successful breeding programs, closure of facilities due to financial reasons, pressure from animal rights advocacy groups, and to aid the conservation of endangered species. Additionally, there are many ethical complications to reintroducing animals born in captivity back into the wild. For example, when scientists were reintroducing a rare species of toad back into the Mallorcan wild in 1993, a potentially deadly fungus that could kill frogs and toads was unintentionally introduced. It is also important to maintain the organism’s original habitat, or replicate that specific habitat for species survival.
Iberian ribbed newt
"Pleurodeles waltl" is a model system for the study of adult regeneration. Similar to other salamanders, "P. waltl" animals can regenerate lost limbs, injured heart tissue, lesioned brain cells in addition to other body parts such as eye lens and the spinal cord. The 20 Gb genome of "P. waltl" has been sequenced to facilitate research into the genetic basis of this extraordinary regenerative ability.
Old-growth forest
Old-growth forests are often biologically diverse, and home to many rare species, threatened species, and endangered species of plants and animals, such as the northern spotted owl, marbled murrelet and fisher, making them ecologically significant. Levels of biodiversity may be higher or lower in old-growth forests compared to that in second-growth forests, depending on specific circumstances, environmental variables, and geographic variables. Logging in old-growth forests is a contentious issue in many parts of the world. Excessive logging reduces biodiversity, affecting not only the old-growth forest itself, but also indigenous species that rely upon old-growth forest habitat.
Quagga
Introduction of these quagga-like zebras could be part of a comprehensive restoration programme, including such ongoing efforts as eradication of non-native trees. Quaggas, wildebeest, and ostriches, which occurred together during historical times in a mutually beneficial association, could be kept together in areas where the indigenous vegetation has to be maintained by grazing. In early 2006, the third- and fourth-generation animals produced by the project were considered looking much like the depictions and preserved specimens of the quagga. This type of selective breeding is called breeding back. The practice is controversial, since the resulting zebras will resemble the quaggas only in external appearance, but will be genetically different. The technology to use recovered DNA for cloning does not yet exist.
Extinction
Some, such as Harvard geneticist George M. Church, believe that ongoing technological advances will let us "bring back to life" an extinct species by cloning, using DNA from the remains of that species. Proposed targets for cloning include the mammoth, the thylacine, and the Pyrenean ibex. For this to succeed, enough individuals would have to be cloned, from the DNA of different individuals (in the case of sexually reproducing organisms) to create a viable population. Though bioethical and philosophical objections have been raised, the cloning of extinct creatures seems theoretically possible.
Echinoderm
Many echinoderms have remarkable powers of regeneration. Many species routinely autotomize and regenerate arms and viscera. Sea cucumbers often discharge parts of their internal organs if they perceive themselves to be threatened. The discharged organs and tissues are regenerated over the course of several months. Sea urchins are constantly replacing spines lost through damage. Sea stars and sea lilies readily lose and regenerate their arms. In most cases, a single severed arm cannot grow into a new starfish in the absence of at least part of the disc. However, in a few species a single arm can survive and develop into a complete individual and in some species, the arms are intentionally detached for the purpose of asexual reproduction. During periods when they have lost their digestive tracts, sea cucumbers live off stored nutrients and absorb dissolved organic matter directly from the water.
Island restoration
In many cases the removal of introduced species is sufficient to allow a return to a pre-disturbance state, but generally active management, often in the form of replanting native flora and reintroduction of extirpated fauna is needed to achieve restoration goals. Planting of native species helps to replenish species that were either grazed or out competed. Species of animal can be translocated either from existing populations, or from captive bred populations. These reintroductions need to be carefully managed, particularly in the case of endangered species, where the potential benefits need to be weighed against the possibility of failure. Not all translocations succeed, and it may be necessary to help the reintroduced animals along with supplementary feeding or other kinds of management.
Push of the past
If a BDM is forward-modelled, i.e. if the fate of an original single species is modelled through time, then a wide range of possible outcomes can occur, as the process is stochastic. With significant extinction rates, any particular clade is likely to be short-lived. However, we know that relatively long-lived clades such as the plants or animals by definition did "not" go extinct. As a result, their patterns of diversification will be a sub-set of all the possible outcomes for diversifications with their particular values of formula_1 and formula_2 - all patterns with early extinction will be excluded. Imposing the condition of survival on a clade implies that rates of early diversification will be higher than expected. It can be shown that for a long-lived clade, the expected initial early rate of diversification is approximately formula_11, as opposed to the long-term rate of formula_6. However, the wide confidence intervals on this value mean that values of initial diversification of up to formula_13 fall within the 95% range. Long-lived clades should thus show a characteristic early burst of diversification that quickly declines to the long-term rate, an effect called the "push of the past".
Developmental biology
Regeneration indicates the ability to regrow a missing part. This is very prevalent amongst plants, which show continuous growth, and also among colonial animals such as hydroids and ascidians. But most interest by developmental biologists has been shown in the regeneration of parts in free living animals. In particular four models have been the subject of much investigation. Two of these have the ability to regenerate whole bodies: "Hydra", which can regenerate any part of the polyp from a small fragment, and planarian worms, which can usually regenerate both heads and tails. Both of these examples have continuous cell turnover fed by stem cells and, at least in planaria, at least some of the stem cells have been shown to be pluripotent. The other two models show only distal regeneration of appendages. These are the insect appendages, usually the legs of hemimetabolous insects such as the cricket, and the limbs of urodele amphibians. Considerable information is now available about amphibian limb regeneration and it is known that each cell type regenerates itself, except for connective tissues where there is considerable interconversion between cartilage, dermis and tendons. In terms of the pattern of structures, this is controlled by a re-activation of signals active in the embryo.
There is still debate about the old question of whether regeneration is a "pristine" or an "adaptive" property. If the former is the case, with improved knowledge, we might expect to be able to improve regenerative ability in humans. If the latter, then each instance of regeneration is presumed to have arisen by natural selection in circumstances particular to the species, so no general rules would be expected.
Plagiobothrys hirtus
Reintroduced populations of "P. hirtus" established by the Oregon Department of Agriculture have been thriving for sixteen years. To date, reintroductions projects have been successful in augmenting existing and creating new populations of the species, with plants persisting since the initial 1998 reintroductions. During this time, information has also been gathered concerning the life history and establishment ecology of the species. Under careful monitoring and management, this species now has an excellent chance to be self-sustaining in the future, assuming additional populations can be established on administratively protected lands.
Old-growth forest
Tree species succession may change tree species' composition once the old-growth stage has been achieved. For example, an old boreal forest may contain some large aspen trees, which may die and be replaced by smaller balsam fir or black spruce. Consequently, the forest will switch back to understory reinitiation stage. If old-growth stage is seen as an end point of stand development, it can be easily evaluated using structural or static attributes. However, in some forest ecosystems, this can lead to decisions regarding the preservation of unique stands or attributes that will disappear over the next few decades because of natural succession processes. Consequently, using stand dynamics to define old-growth forest is more useful in cases where the species that constitute old-growth forest can have long lifespan or in ecosystem where succession is very slow.
Island ecology
Active restoration on islands can be done for both animal species (translocations, induced breeding) and plant species (reforestation). Creating goals for restoration can be challenging because it is often impossible to restore the ecosystem to its “historic” or “normal” state, if that state can even be clearly defined. Restoration is never complete, as ecological communities are always in a state of change.
Endangered species
This technique has worked for many species for some time, with probably the oldest known such instances of captive mating being attributed to menageries of European and Asian rulers, an example being the Père David's deer. However, captive breeding techniques are usually difficult to implement for such highly mobile species as some migratory birds (e.g. cranes) and fishes (e.g. hilsa). Additionally, if the captive breeding population is too small, then inbreeding may occur due to a reduced gene pool and reduce immunity.
Enzyme promiscuity
The most recent and most clear cut example of enzyme evolution is the rise of bioremediating enzymes in the past 60 years. Due to the very low number of amino acid changes, these provide an excellent model to investigate enzyme evolution in nature. However, using extant enzymes to determine how the family of enzymes evolved has the drawback that the newly evolved enzyme is compared to paralogues without knowing the true identity of the ancestor before the two genes divereged. This issue can be resolved thanks to ancestral reconstruction.
First proposed in 1963 by Linus Pauling and Emile Zuckerkandl, ancestral reconstruction is the inference and synthesis of a gene from the ancestral form of a group of genes, which has had a recent revival thanks to improved inference techniques and low-cost artificial gene synthesis, resulting in several ancestral enzymes—dubbed "stemzymes" by some—to be studied.
Pleistocene rewilding
Pleistocene rewilding aims at the promotion of extant fauna and the reintroduction of extinct genera in the southwestern and central United States. Native fauna are the first genera proposed for reintroduction. The Bolson tortoise was widespread during the Pleistocene era, and continued to be common during the Holocene epoch until recent times. Its reintroduction from northern Mexico would be a necessary step to recreate the soil humidity present in the Pleistocene, which would support grassland and extant shrub-land and provide the habitat required for the herbivores set for reintroduction. Other large tortoise species might later be introduced to fill the roll of various species of Hesperotestudo. However, to be successful, ecologists must first support fauna already present in the region.
List of introduced species
A complete list of introduced species for even quite small areas of the world would be dauntingly long. Humans have introduced more different species to new environments than any single document can hope to record. This list is generally for established species with truly wild populations— not kept domestically—that have been seen numerous times, and have breeding populations. While most introduced species can cause a negative impact to new environments they reach, some can have a positive impact, just for conservation purpose.
Species reintroduction
Humans have been reintroducing species for food and pest control for thousands of years. However, the practice of reintroducing for conservation is much younger, starting in the 20th century.
Rewilding (conservation biology)
Both grassroots groups and major international conservation organizations have incorporated rewilding into projects to protect and restore large-scale core wilderness areas, corridors (or connectivity) between them, and apex predators, carnivores, or keystone species (species which interact strongly with the environment, such as elephant and beaver). Projects include the Yellowstone to Yukon Conservation Initiative in North America (also known as Y2Y) and the European Green Belt, built along the former Iron Curtain; transboundary projects, including those in southern Africa funded by the Peace Parks Foundation; community-conservation projects, such as the wildlife conservancies of Namibia and Kenya; and projects organized around ecological restoration, including Gondwana Link, regrowing native bush in a hotspot of endemism in southwest Australia, and the Area de Conservacion Guanacaste, restoring dry tropical forest and rainforest in Costa Rica. European Wildlife, established in 2008, advocates the establishment of a "European Centre of Biodiversity" at the German–Austrian–Czech borders.
Molecular paleontology
It is now possible to revive extinct species using molecular paleontology techniques. This was first accomplished via cloning in 2003 with the Pyrenean ibex, a type of wild goat that became extinct in 2000. Nuclei from the Pyrenean ibex's cells were injected into goat eggs emptied of their own DNA, and implanted into surrogate goat mothers. The offspring lived only seven minutes after birth, due to defects in its lungs. Other cloned animals have been observed to have similar lung defects.
Extinction
As long as species have been evolving, species have been going extinct. It is estimated that over 99.9% of all species that ever lived are extinct. The average lifespan of a species is 1–10 million years, although this varies widely between taxa.
There are a variety of causes that can contribute directly or indirectly to the extinction of a species or group of species. "Just as each species is unique", write Beverly and Stephen C. Stearns, "so is each extinction ... the causes for each are varied—some subtle and complex, others obvious and simple". Most simply, any species that cannot survive and reproduce in its environment and cannot move to a new environment where it can do so, dies out and becomes extinct. Extinction of a species may come suddenly when an otherwise healthy species is wiped out completely, as when toxic pollution renders its entire habitat unliveable; or may occur gradually over thousands or millions of years, such as when a species gradually loses out in competition for food to better adapted competitors. Extinction may occur a long time after the events that set it in motion, a phenomenon known as extinction debt.
De-extinction
It has also been noted that a resurrected species, while being genetically the same as previously living specimens, will not have the same behaviour as its predecessors. The first animal to be brought back will be raised by parents of a different species (the fetus's host), not the one that died out and thus have differing mothering techniques and other behaviors. Another concern is that de-extinction plans have not discussed bringing back parasites or mutualists which co-existed with extinct species, which may have strong effects on the survival and success of resurrected species.
Bird conservation
Reintroductions of captive bred populations can occur to replenish wild populations of an endangered species, to create new populations or to restore a species after it has become extinct in the wild. Reintroductions helped bring the wild populations of Hawaiian geese (nene) from 30 birds to over 500. The Mauritius kestrel was successfully reintroduced into the wild after its captive breeding programme. Reintroductions can be very difficult and often fail if insufficient preparations are made, as species born in captivity may lack the skills and knowledge needed for life in the wild after living in captivity. Reintroductions can also fail if the causes of a birds decline have not been adequately addressed. Attempts to reintroduce the Bali starling into the wild failed due to continued poaching of reintroduced birds.
Anagenesis
When enough mutations have occurred and become stable in a population so that it is significantly differentiated from an ancestral population, a new species name may be assigned. A series of such species is collectively known as an evolutionary lineage. The various species along an evolutionary lineage are chronospecies. If the ancestral population of a chronospecies does not go extinct, then this is cladogenesis, and the ancestral population represents a paraphyletic species or paraspecies, being an evolutionary grade. This situation is quite common in species with widespread populations.
Ecological island
Increasingly over the last hundred years, New Zealand's Department of Conservation together with many volunteers have developed and perfected world-first methods of clearing some of these islands of all introduced pests, and island restoration, creating safe havens for the reintroduction of at-risk species, thereby saving them from extinction. These islands are also used to expand the range of rare species so that an ecological disaster on one island would not result in the total extinction of a species. As many species rebound in numbers in the absence of predators the islands act as species reservoirs enabling the periodic removal of some to create breeding colonies on other cleared islands, or on the mainland itself.
Breeding back
It must be kept in mind that a breeding-back breed may be very similar to the extinct wild type in phenotype, ecological niche, and to some extent genetics, but the initial gene pool of that wild type is lost forever with its extinction. It is not truly possible for a breeding-back attempt to actually recreate an extinct wild type that is the breeding target, as an extinct wild type cannot be resurrected via selective breeding alone. Furthermore, even the outward authenticity of a bred-back type depends on the quality of the stock used as the foundation of the project. As a result, some breeds, like Heck cattle, are at best a vague look-alike of the extinct wildtype aurochs, according to the literature.
Microbial genetics
Many types of virus are capable of genetic recombination. When two or more individual viruses of the same type infect a cell, their genomes may recombine with each other to produce recombinant virus progeny. Both DNA and RNA viruses can undergo recombination. 
When two or more viruses, each containing lethal genomic damage infect the same host cell, the virus genomes often can pair with each other and undergo homologous recombinational repair to produce viable progeny. This process is known as multiplicity reactivation. Enzymes employed in multiplicity reactivation are functionally homologous to enzymes employed in bacterial and eukaryotic recombinational repair. Multiplicity reactivation has been found to occur with pathogenic viruses including influenza virus, HIV-1, adenovirus simian virus 40, vaccinia virus, reovirus, poliovirus and herpes simplex virus as well as numerous bacteriophages.
Island restoration
Many island species evolved on small islands, or even restricted habitats on small islands. Small populations are vulnerable to even modest hunting, and restricted habitats are vulnerable to loss or modification of said habitat. More importantly, island species are often ecologically naive, that is they have not evolved alongside a predator, or have lost appropriate behavioural responses to predators. This often resulted in flightlessness, or unusual levels of tameness. This made many species susceptible to hunting (it is thought, for example, that moas were hunted to extinction in a few short generations) and to predation by introduced species. Some, such as the dodo, are thought to have become extinct because of the pressure of both humans and introduced animals. One estimate of birds in the Pacific islands puts the extinctions at 2000 species. Between 40 and 50% of the bird species of New Zealand have become extinct since 200 AD.
The field of island restoration is usually credited with having been started in New Zealand in the 1960s, but other smaller projects, such as the restoration of Nonsuch Island in Bermuda (which began in 1962) have been going on for almost as long. Nevertheless, the program undertaken by the Department of Conservation (DOC) is one of the largest in the world. It began on Cuvier Island, where ecologists removed stock, goats, feral cats and finally, in 1993, Pacific rats. The success of the project resulted in similar projects around New Zealand. The advantages to the DOC were considerable; in addition to protecting species endemic to smaller islands, like the magenta petrel, islands near the mainland, once restored, could act as habitat for species of birds that were unable to survive on the mainland. Species like the takahe, where the remaining wild population was at considerable risk from feral cats and dogs, could be moved to these islands to safeguard the species.
Species translocation
The second of the three types of translocation is re-introduction. Re-introduction is the deliberate or accidental translocation of a species into the wild in areas where it was indigenous at some point, but no longer at the present. Re-introduction is used as a wildlife management tool for the restoration of an original habitat when it has become altered or species have become extinct due to over-collecting, over-harvesting, human persecution, or habitat deterioration. An example of a successful translocation was the one performed with the plant Narcissus cavanillesii to prevent its flooding due to the construction of a dam.
Woolly mammoth
The existence of frozen soft tissue remains and DNA of woolly mammoths has led to the idea that the species could be recreated by scientific means. Several methods have been proposed to achieve this. Cloning would involve removal of the DNA-containing nucleus of the egg cell of a female elephant, and replacement with a nucleus from woolly mammoth tissue, a process called somatic cell nuclear transfer. For example, Akira Iritani, at the Kyoto University in Japan, reportedly planned to do this. The cell would then be stimulated into dividing, and implanted in a female elephant. The resulting calf would have the genes of the woolly mammoth. However, nobody has yet found a viable mammoth cell, and most scientists doubt that any living cell could have survived freezing in the tundra. Because of their conditions of preservation, the DNA of frozen mammoths has deteriorated significantly.
Storage effect
For species to coexist in a community, all species must be able to recover from low density. Not surprisingly, being a coexistence mechanism, the storage effect helps species when they become rare. It does so by making the abundant species’ effect on itself greater than its effect on the rare species. The difference between species’ response to environmental conditions means that a rare species’ optimal environment is not the same as its competitors. Under these conditions, the rare species will experience low levels of interspecific competition. Because the rare species itself is rare, it will experience little impact from intraspecific competition as well, even at its highest possible levels of intraspecific competition. Free from the impact of competition, the rare species is able to make gains in these good years or patches. Moreover, thanks to the buffered population growth, the rare species is able to survive the bad years or patches by "storing" the gains from the good years/patches. As a result, the population of any rare species is able to grow due to the storage effect.
Earthworm
Earthworms have the ability to regenerate lost segments, but this ability varies between species and depends on the extent of the damage. Stephenson (1930) devoted a chapter of his monograph to this topic, while G.E. Gates spent 20 years studying regeneration in a variety of species, but “because little interest was shown”, Gates (1972) only published a few of his findings that, nevertheless, show it is theoretically possible to grow two whole worms from a bisected specimen in certain species.
Gates’s reports included:
De-extinction
Opponents of de-extinction have claimed that efforts and resources used to resurrect extinct species could have been better used trying to conserve endangered species that might themselves become extinct. Featuring in the journal "Life Sciences, Society and Policy", a 2014 article claimed that the cost of reviving just a single species could amount to millions of dollars. At the same time, more than 20,000 extant species are currently threatened with extinction.
Tide pool
Some species of starfish can regenerate lost arms. Most species must retain an intact central part of the body to be able to regenerate, but a few can regrow from a single ray. The regeneration of these stars is possible because the vital organs are in the arms.