Extinction

Extinction is when a species ends, meaning the last one has died. This can happen if a group can’t make more of itself or change to fit its world. Because many animals and plants live over big areas, scientists often only learn they are gone by looking at old bones or records. Sometimes, a species thought to be lost is found again. Scientists call this a Lazarus taxon.

Many species have disappeared over Earth’s history. Today, there are many kinds of living things, with even more that we don’t see. Famous extinct animals include non-avian dinosaurs, saber-toothed cats, and mammoths. Species vanish when they can’t live with changes or compete with others. Most disappear soon after they appear, but a few survive for a very long time.

Mass extinctions, when many species vanish together, are rare, but single extinctions happen often and are part of evolution. Scientists have noticed that people are causing many species to disappear. Losing homes, like forests cut for farms, is a big reason. Many plants and animals are in danger of being lost.

Definition

A species is considered extinct when the very last member of that species dies. This means there are no individuals left that can reproduce and create new offspring. Sometimes, a species can become functionally extinct before the last member dies. This happens when only a few individuals remain and they cannot reproduce due to reasons like poor health, age, or being spread out over a large area.

In ecology, the term "extinction" can also refer to a local extinction, where a species disappears from a specific area but still exists elsewhere. For example, wolves were reintroduced to certain areas after they had disappeared from them. Scientists work hard to protect species that are in danger of disappearing completely, often by keeping them in zoos and using special breeding programs to help them survive.

Causes

Species have been disappearing since life began. Over 99.9% of all species that ever lived are no longer around. On average, a species exists for between 1 and 10 million years, but this can change. Many things can cause a species to vanish. Sometimes it happens fast, like when pollution makes a habitat too dangerous to live in. Other times, it’s slow, like when a species can’t get enough food because others are better at finding it.

Humans have helped cause many recent disappearances. Things like overharvesting, pollution, and destroying habitats have made many species vanish. As more people live and need more resources, it becomes harder for other species to survive. Scientists work to protect species that are in danger and stop more from disappearing.

Mass extinctions

Earth has had at least five big times when many plants and animals disappeared quickly. One famous example is the Permian–Triassic extinction event about 250 million years ago. This was likely caused by huge volcanic eruptions that filled the air with particles. Another well-known event happened 66 million years ago. This ended the time of the dinosaurs and many other species.

Today, many scientists think we might be starting another big extinction because of human activities. They say that if we do not make big changes, many plants and animals could disappear in the next few decades. This is happening faster than natural extinctions and is driven by things like pollution, habitat loss, and overconsumption.

History of scientific understanding

For much of history, people thought the world was perfect, so the idea that a species could disappear seemed impossible. This belief was strong in the 1700s with a concept called the great chain of being, where all life was linked in a perfect order. Even Thomas Jefferson did not believe that the woolly mammoth could go extinct.

However, discoveries of fossils that looked different from any living animals made scientists wonder what happened. Some, like Robert Hooke and Sir Thomas Molyneux, thought these animals might still exist somewhere unknown. It wasn’t until Georges Cuvier in 1796 that the idea of extinction became widely accepted. Cuvier studied fossils, like mammoth skulls, and argued that these animals truly were gone. He suggested that huge floods and other disasters caused many species to die out suddenly.

Later, scientists like Charles Lyell and Charles Darwin thought extinction happened slowly over time. Today, we know that both sudden disasters and gradual changes can cause species to disappear.

Human attitudes and interests

Extinction is an important topic in zoology and biology. Many groups, such as the Worldwide Fund for Nature, work to protect animals from disappearing. Governments also try to save animals by making laws to stop habitat loss, over-hunting, and pollution.

Scientists like Bruce Walsh say we should save animals for three reasons: genetic resources, to keep ecosystems stable, and because it is the right thing to do. Sometimes, businesses hurt wildlife, but some also help with conservation.

Some diseases have been removed completely, like the smallpox virus and rinderpest virus. Scientists have also talked about removing certain mosquitoes that spread diseases. Biologist Olivia Judson believes this could save many lives each year.

There are also ideas about bringing back extinct animals through cloning. Scientists have tried to clone animals like the mammoth and the dodo. While these attempts have been difficult, it shows how science is exploring ways to bring back lost species.