5.13 Extinction

Objectives

• interpret the various natural and anthropogenic factors that can lead to species extinction

• compare past mass extinction events in Earth‘s history

• explain conservation efforts intended to prevent and mitigate extinction

Extinction

If the population of a species gets too low, the species becomes at risk of extinction.
There are two different categories of extinction:

• extinct in the wild = species can only be found in captivity.

• extinct = species can no longer can found in the wild, and all individuals in captivity have also died
  

​Most species do not quickly change from having a healthy population size to becoming extinct. There are typically warning signs of extinction as a healthy population size decreases over time.

Regional extinction is when a species no longer exists in a specific region of the world. They may live elsewhere in the world so there is a possibility of reintroducing the species to the region in which they went extinct.

Example: gray wolves

Global Extinction is when a species no longer exists anywhere in the world. Since the population no longer exists anywhere in the world, there is no hope for the rehabilitation of the species.

Example: dinosaurs

interpret the various natural and anthropogenic factors that can lead to species extinction

Natural Causes of Extinction

Extinctions are not a new phenomenon. Organisms have been going extinct for hundreds of thousands of years due to natural causes such as:

• asteroids

• volcanic ash

• climate change

• genetic factors

Anthropogenic (Human) Causes of Extinction

The Holocene extinction, the extinction event currently occurring on Earth, began in the late 1800s. The Holocene extinction is different from the previous five extinctions because it is caused entirely by human activity.

Some anthropogenic (human) causes of extinction include:

• habitat destruction

• fragmentation

• invasive species

• poaching

• pollution

compare past mass extinction events in Earth‘s history

explain conservation efforts intended to prevent and mitigate extinction

Extinction Mitigation

Since extinction rates have accelerated, humans have taken action to slow down extinction rates and to restore population sizes of endangered or vulnerable species. There are a few ways in which mitigation can be done, including:

• habitat conservation

• breeding

• enacting protective laws

​Today, you learned:

• about anthropogenic and natural causes of extinction;

• the similarities and the differences between Earth‘s mass extinction events; and

• about mitigation efforts to help prevent and reverse the extinction of species.

In an upcoming lesson, you learn about how scientists are attempting to bring species back from extinction.