well as a number of organizations that have species preservation as their main goal. There are some species that have been driven to extinction or near-extinction by poaching or overhunting of a species. There are ethical reasons why people oppose extinction. There is also an advantage to the world to have a greater degree of biodiversity. Ecotourism suffers if species become extinct, which is why nature preserves have become important. One of the big problems with human-related extinction is that humans often favor day to day issues over species conservation. Agricultural needs have led to slash and burn agricultural practices. There are rare events when man successfully plans the extinction of a species. The main purpose of this is to eradicate infectious diseases. Smallpox has been driven to extinction. The rinderpest virus, which affects cattle, has been rendered extinct. The organism that causes yaws and the organism that causes polio are currently being eradicated. Some have advocated for the extinction of certain mosquito species that carry many diseases. The phenomenon of de-extinction involves using genetics and technology to revive an extinct species through cloning. This has been proposed for mammoths and for the Pyrenean ibex. This has already been tested for the Pyrenean ibex, which was cloned so that embryos could be transferred into female mountain goats. While some aspects of the process have been successful, no clone to date has survived past a few minutes of life due to birth defects.
BACKGROUND EXTINCTION Background extinction is referred to as normal extinction. This is measured as the background extinction rate throughout history prior to the contributions of humans and in between major extinction events. Extinctions are a normal part of evolution and occur at differing rates throughout geologic time. Background extinction rates can be evaluated by determining the number of species that become extinct over time. It can also be measured in million species years. If one species goes extinct every year out of a million species, this is what is referred to as million species years or MSY. Finally, the background rate can be measured as the species survival rates over time. This lists the number of years it takes for a species to go extinct. There are estimates given for the average lifespan of a species in millions of years. Mammals tend to have the shortest species lifetime, while invertebrates can live the longest, with species living around 10 million years before dying out. It is difficult to make these types of estimates
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