1. Pleistocene Park is one example
Pleistocene Park is one example. Situated in a corner of north-eastern Siberia, the dream is to restore the mammoth steppe - an ecosystem of grassland tendered by large herbivores such as reindeer, bison and the extinct woolly mammoth.
The reindeer and bison have already been reintroduced - the woolly mammoth poses a bigger problem.
Discovering frozen woolly mammoth tissue, offers the tantalising prospect of using extracted DNA to clone a new one. Such ideas have long been the preserve of science fiction, but can it realistically be accomplished?
Prof Adrian Lister, a palaeontologist at the Natural History Museum, in London, doesn't think so, "because the remains of these animals have been buried for thousands of years. The DNA has become fragmented and shattered. You've got an alphabet soup of bits and pieces of DNA left in that frozen tissue."
Without the complete DNA, cloning a mammoth seems unlikely. However, fragments of DNA might still be useful. One plan involves piecing together the mammoth genome, using broken strands, collected from many different samples.
By comparing this genome with the mammoth's closest living relative, the Asian elephant, researchers hope to find the genetic variation that made a mammoth a mammoth.
They will then use Asian elephant DNA to plug any holes in the code, much like the technique used in the Jurassic Park film where (distantly related) frog DNA plugged the holes in the dinosaur DNA. The method used to clone Dolly the sheep - might then create a living mammoth.
Some scientists are now seriously considering the possibility of bringing back extinct animals. But can it be done, and if so, what would be the use?
The film Jurassic Park - based on a novel by Michael Crichton - is a rather cautionary take on the merits, or otherwise, of using technology to revive extinct species.
The movie, directed by Steven Spielberg, was released 20 years ago and tells the story of an eccentric billionaire who hatches the idea of a theme park populated by cloned dinosaurs.
Needless to say, it all goes horribly wrong, leaving the protagonists to fight for their lives against voracious velociraptors and a fearsome Tyrannosaurus Rex.
The basic science that originally inspired the story has matured to the point where some scientists are now seriously considering the possibility of resurrecting some extinct animals, and the habitats they occupied.

2. For this, an elephant egg cell containing the reconstructed mammoth nucleus is implanted into an Asian elephant for gestation. This could lead to a baby mammoth being born. But as Prof Lister point out, there are "an awful lot of ifs and buts" in this plan.
Questions about technological feasibility aside, many ecologists argue that we shouldn't focus attention on de-extinction when so many living species face extinction themselves.
However, there are people who see the usefulness of de-extinction technology for current conservation. Oliver Ryder, director of genetics at the San Diego Zoo Institute for Conservation Research, currently heads Frozen Zoo, a "biobank" that contains frozen tissue including preserved sex cells, embryos and cell cultures from more than 1,000 species.
Prof Ryder hopes Frozen Zoo can help the critically endangered northern white rhinoceros, which has been hunted to near extinction. Only four reproductively capable individuals exist in captivity and these are all related to one other.
However, the Frozen Zoo has cells from 12 other, unrelated individuals. These could potentially be used in breeding programmes, providing conservationists with one last chance to save these creatures.
Unlike the fictional Jurassic Park, scientists need technology to catch up with these ideas before the first reincarnated animals, or even northern white rhinos, are created.
While no-one is seriously considering bringing back dinosaurs - the essence of Jurassic Park - bringing back animals that have gone extinct (albeit locally) might just influence ecosystems of the future.
Questions:
1.) Describe the process by which they plan to try to clone a mammoth.
2.) Why would it be difficult to use the mammoth DNA?
3.) Describe the process by which they plan to try to clone a mammoth.
4.) How could cloning technology one day help non-extinct animals?
5.) The mammoth was a creature that became extinct around 5000 years ago.
Is it right that we should try to bring them back?
Explain your answer, try to write a balanced argument.