Breeding Wild Animals Today's domestic species were once wild, but have been changed to suit human needs through the process known as domestication. Few species have been domesticated, even though attempts have been made to domesticate a wide range of species. The London Zoological Garden, the French Jardin Zoologique d'Acclimatation, and several acclimatization societies attempted to domesticate additional species in the late eighteenth century, but none were successful. The acclimatization facilities of these societies eventually closed or evolved into zoos that maintained, exhibited, and bred wild animals without changing them into tame or domestic animals. Zoos and aquariums have always been concerned with wildlife conservation, although their effectiveness has been dependent on the era's zoological and animal husbandry knowledge, as well as the society's perceived importance of conservation. As the importance of conservation increased and the sciences related to wildlife conservation improved, zoo and aquarium conservation efforts improved. These conservation efforts included propagation programs that bred endangered species and species extinct in the wild. These propagation programs involve species studbooks, studying small populations of animals, introducing animals back into the wild, and other modern techniques. Breeding wild animals over many generations, however, runs the risk of domesticating these animals. Of course, no such intentional domestication program has been successful. The greater risk is that the animals will become tame, will be unable to survive in the wild, and will lose their wildness. Because the breeding of wild animals is based on the animal's needs rather than human needs, propagation efforts with wild species are quite different from efforts made with domesticated animals. Nevertheless, the methods are similar. Both wild animal breeding and domestic animal breeding require detailed studbooks in order to keep track of an animal's lineage, and the pairing of appropriate individuals is closely controlled. Many sciences provide knowledge important to the propagation programs, such as veterinary medicine, nutrition, reproductive biology, genetics, and biotechnology. Frozen tissues, artificial insemination, bioengineering, and recombinant deoxyribonucleic acid (DNA) technology play an increasingly important role in modern breeding programs. Breeding wild animals is often more difficult than breeding domestic animals, since unusual breeding behavior is part of the reason some species are endangered. Improved knowledge about the species' social behavior and population biology needs are of assistance in the successful breeding of these difficult wild species, as is biotechnology. Frozen zoos have been established to maintain reproductive and other tissues for artificial insemination. Sometimes this artificial insemination involves the use of related surrogate species; for instance, using domestic cattle to give birth to endangered gaur. Back breeding is being attempted in order to revive extinct species; for example, breeding zebra so as to re-create the extinct quagga. As an increasing number of species become endangered and as their natural habitat continues to disappear, it is increasingly important to maintain these species through appropriate breeding programs.
Paleontology When organisms die, their soft parts usually decompose into their constituent elements, leaving no trace. The harder parts, such as wood, exoskeletons, bones, teeth, and shells, may survivemanyyears, but eventually even they decompose. Sometimes, however, organisms are buried in an avalanche, are covered by volcanic ash, or sink into mud. If the burial inhibits decomposing microorganisms and prevents the rapid replacement of the buried tissue with inorganic material, a fossil is likely to form. There are a number of different ways in which fossils form. Most fossils form through a process of mineralization. In this type of fossilization, buried material is slowly replaced by minerals such as calcium carbonate (CaCO3), silicate (SiO2), pyrite (FeS2), sulfate (Ca [SO4]2- H2O), and iron-phosphate (Fe3[PO4]2 - H2O). These mineralized remains can be separated from the surrounding sediment and may superficially appear to be the actual remains. Sometimes fossils can form when the remains completely decompose. Organisms encased in a highly compacted sediment or covered by volcanic ash that quickly hardens, imprint into the covering a replica of their surfaces. When the organisms degrade, the space fills with minerals that harden. This is how surface replicas of organisms form. Mineralization and replication are responsible for most fossils. In some cases, organisms crawling through or stepping in sediment leave imprints of their passing, called trace fossils. Imprinted sediment explains some fossils. Microorganisms, plants, and animals often get caught in tree sap (resin) that ages over millions of years, first into copal and then into amber. Amber and the organisms encased in it are often referred to as fossils. Ethanol or isopropyl alcohol dropped on copal makes its surface sticky but has no effect on amber. Copal is usually less than 2 million years old, whereas the oldest ambers are about 150 million years old. The hard parts (skin, cellulose walls, wood, and exoskeletons) of organisms are generally preserved in copal and amber, although some tissues are replaced by minerals such as pyrite (FeS2). The pyrite turns portions or all of the fossil black. Completely blackened fossils retain little of the original organism. The fossils in copal and amber have given paleontologists a picture of life during different ancient (Jurassic and Cretaceous) and recent (Tertiary and Quaternary) periods.
