Mass Extinctions

Widespread and rapid decreases in biodiversity that reshape ecosystems and pave the way for new species

CAPS Grade 10 Life Sciences

What is a Mass Extinction?

A mass extinction is defined as:

A widespread and rapid decrease in biodiversity

Typically occurring when over 50% of all living species die out within a relatively short geological time frame.

Mass extinctions remove large numbers of species, but they also change which groups survive, spread, and later diversify.

Quick Check

1. What percentage of species typically die out during a mass extinction?

Over 10% Over 25% Over 50% Over 90%

The "Big Five" Events

Among the various mass extinctions throughout Earth's history, five stand out as particularly significant. Understanding the two most impactful events is essential.

Mass Extinction Timeline

Permian

250 mya

K-Pg

66 mya

Click on an event marker to learn more

The Permian Extinction

"The Great Dying"

250 mya

95% of marine species

70% of terrestrial vertebrates

This event is recognized as the deadliest mass extinction in Earth's history, drastically altering the course of evolution.

Key Fact: Nearly all life on Earth was wiped out, making way for the age of dinosaurs in the following Triassic period.

Cretaceous-Paleogene (K-Pg)

The End of Dinosaurs

66 mya

75% of all species

Famously known for the extinction of the dinosaurs. This event allowed mammals to rise to prominence as the dominant land animals.

Key Fact: The impact created the Chicxulub crater in Mexico and led to the rise of mammals and eventually humans.

2. Which mass extinction is known as "The Great Dying"?

Cretaceous-Paleogene Permian Extinction Triassic Extinction Ordovician Extinction

Causes of Mass Extinctions

The CAPS curriculum identifies two primary categories of causes: intrinsic (Earth-bound) factors and extrinsic (space-bound) factors.

Intrinsic (Earth-bound)

Volcanic Activity: Massive eruptions (like Siberian Traps) release CO2, causing global warming or "volcanic winters"
Continental Drift: Movement of landmasses alters ocean currents and climates
Sea Level Changes: Fluctuations reduce available habitats for marine life

Example: The Siberian Traps eruptions are linked to the Permian Extinction.

Extrinsic (Space-bound)

Asteroid/Meteorite Impacts: Catastrophic collisions create dust clouds blocking sunlight
Disruption of photosynthesis: Leads to collapse of food chains
Global cooling/warming: Sudden climate shifts from impact events

Example: Chicxulub impact caused the K-Pg extinction that killed the dinosaurs.

Match the Extinction to its Cause

Select an extinction event, then choose its primary cause.

Permian Extinction

K-Pg Extinction

Volcanic Activity (Siberian Traps)

Asteroid Impact (Chicxulub)

The "Sixth Extinction"

Current scientific discourse suggests we are experiencing a Sixth Mass Extinction, primarily driven by human activities (anthropogenic factors).

Anthropogenic Extinction

Human-driven factors causing rapid biodiversity loss today

Habitat Destruction

Deforestation, urbanization, and agriculture are destroying natural habitats.

Pollution & Climate Change

Industrial pollution and greenhouse gases are altering ecosystems globally.

Over-exploitation

Unsustainable hunting, fishing, and harvesting are depleting populations.

Current extinction rates are 100 to 1,000 times higher than natural background rates, primarily due to human activities.

3. What is the main cause of the current "Sixth Extinction"?

Asteroid impact Volcanic activity Human activities Continental drift

The Pattern of Life After Extinction

Adaptive Radiation

Following a mass extinction, the extinction of dominant species creates vacant ecological niches that surviving species rapidly evolve to fill.

Bats

Flying mammals

Whales

Marine mammals

Primates

Tree-dwelling

Elephants

Large herbivores

Classic Example: After the dinosaurs went extinct 66 mya, mammals underwent rapid diversification, evolving from small shrew-like creatures into the wide variety of species we see today.

4. What is the term for rapid evolution and diversification after a mass extinction?

Natural selection Adaptive radiation Genetic drift Mutation

Mass Extinctions: Final Quiz

Question 1: What percentage of marine species died in the Permian Extinction?

A) 95%

B) 50%

C) 75%

D) 30%

Question 2: What caused the K-Pg extinction?

A) Massive volcanic eruptions

B) Asteroid impact

C) Climate change

D) Sea level changes

Question 3: Which event allowed mammals to become the dominant land animals?

A) Permian Extinction

B) K-Pg Extinction

C) Triassic Extinction

D) Devonian Extinction

Exam Tip

Remember the two key extinctions: Permian (250 mya) - "The Great Dying" - 95% marine species extinct, caused by volcanic activity (Siberian Traps). K-Pg (66 mya) - End of dinosaurs - caused by asteroid impact (Chicxulub crater). Also know that after extinctions, adaptive radiation occurs - mammals diversified after dinosaurs went extinct.

Key Terms

Mass Extinction Biodiversity The Big Five Permian Extinction The Great Dying K-Pg Extinction Chicxulub Crater Siberian Traps Intrinsic Factors Extrinsic Factors Anthropogenic Sixth Extinction Habitat Destruction Adaptive Radiation Ecological Niche

Key Idea to Remember

Mass Extinction: Widespread loss of more than 50% of species in short geological time
Permian Extinction (250 mya): "The Great Dying" - 95% marine species, 70% terrestrial vertebrates extinct; caused by volcanic activity (Siberian Traps)
K-Pg Extinction (66 mya): End of dinosaurs; caused by asteroid impact (Chicxulub crater); allowed mammals to rise
Intrinsic Causes: Volcanic activity, continental drift, sea level changes
Extrinsic Causes: Asteroid and meteorite impacts
Sixth Extinction: Currently occurring due to human activities (habitat destruction, pollution, over-exploitation)
Adaptive Radiation: Rapid evolution and diversification after extinctions (e.g., mammals after dinosaurs)

Congratulations!

You have completed the Grade 10 Life Sciences CAPS curriculum outline on mass extinctions!