5.13 Extinction

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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.

Types of Extinction

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

Multiple Choice

How might volcanic eruptions lead to the climate becoming warmer?

• A volcanic eruption results in high concentrations of ash in the atmosphere, blocking out the sun‘s rays.

• A volcanic eruption results in high concentrations of greenhouse gases in the atmosphere, trapping heat near Earth‘s surface.

• A volcanic eruption emits carbon dioxide, which causes an increase in the ocean‘s pH.

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

Multiple Choice

What is the number one anthropogenic (human) cause of extinction?

• habitat detruction

• poaching

• volcanic eruptions

• asteroids

Poll

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

• 1😳

• 2😬

• 3🙂

• 4😎

• 5🤩

compare past mass extinction events in Earth‘s history

Multiple Choice

According to "When will the next mass extinction occur?", which of the following statements best describes the current mass extinction event?

• It is happening at the same rate as past mass extinctions, due to natural causes alone.

• It is occurring at a much faster rate than normal, largely driven by human activities.

• It is expected to begin in the distant future, as Earth's climate returns to Ice Age conditions.

Poll

compare past mass extinction events in Earth‘s history

• 1😳

• 2😬

• 3🙂

• 4😎

• 5🤩

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

Multiple Select

Why is habitat conservation an important method for mitigating extinction?

• Habitat conservation helps prevent extinction since habitat destruction is the number one cause of extinction.

• Habitat conservation helps prevent extinction by decreasing the rate of predation of vulnerable and endangered species.

• Habitat conservation helps prevent extinction because it ensures organisms have a place to live that meets their needs.

• Habitat conservation helps prevent extinction because invasive species are more closely monitored in habitat conservations.

Multiple Choice

What is one way humans can mitigate accelerated extinction rates?

• By increasing urbanization and expanding agricultural land.

• By reducing habitat destruction and implementing conservation efforts.

• By promoting the use of pesticides and herbicides in farming.

Poll

explain conservation efforts intended to prevent and mitigate extinction

• 1😳

• 2😬

• 3🙂

• 4😎

• 5🤩

​Summary

​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.