Extinction - Ani...

Extinction

Ani Mardiastuti

Extinction

• The end of an organism or group of taxa

• Moment of extinction the death of the last individual of that species

• Determining moment of extinction is difficult Lazarus taxa: where a species presumed extinct abruptly "re-appears" (typically in the fossil record after a period of apparent absence

Extinction

• Present extinction: very rapid

• High effort to avoid extinction of species

• Lesson learned from the past

Extinctions over the past 600 million years

• Age for the Earth and the rest of the solar system is about 4.54 billion years

• Life began nearly 3.5 billion years ago

• Extinction is a natural phenomenon

• It is estimated that 99.9% of all species that have ever lived are now extinct.

Five Largest Mass Extinction

Five Largest Mass Extinction • Late Ordovician (about 438 million years ago)

• Extinct: 100 families, more than half of the bryozoan and brachiopod species

• Late Devonian (360 mya) • Extinct: 30% of animal families

• Permian - Triassic (245 mya) • Extinct: Trilobites, 50% of all animal families, 95% of all marine

species, and many trees die out • Late Triassic (208 mya)

• Extinct: most early dinosaur families, most synapsids (except mammals); 35% of all animal families die out

• Cretaceous-Tertiary (K-T) (65 mya) • Extinct: about half of all life forms, including the dinosaurs,

may families of fishes, clams, snails, sponges, sea urchins, etc.

Dinosaurs

• Beginning in the Triassic Period and into the late Cretaceous

• Dinosaurs existence: 165 million years Age of the Reptiles

• Why the dinosaurs ‘suddenly’ extinct?

EXTINCTION OF DINOSAURS: some theories

1. UNABLE TO ADAPT TO CHANGES o warmer at the end of the Cretaceous than it is now

2. ASTEROID THEORY (by Luis and Walter Alvarez, 1980) o Great extinctions have occurred at 26 million year intervals o Based on unusually high concentrations of the rare metal,

Iridium, near rock levels close to the level of last dinosaur remains.

3. SUPERNOVA THEORY (exploding star)

4. NEMESIS THEORY

o Death Star, or Nemesis, orbits around the earth, 26 million years cycles

5. PLANET K THEORY (Proposes a tenth planet)

Nemesis Theory

Milky Way: Bima Sakti

Extinction is happening now!

The Sixth (Modern) Extinction • Caused by human

• Rate of extinction:

– Past extinction: between 10 and 100 species per year

– Modern extinction: between 17,000 and 100,000 species per year

• Major causes of modern extinction:

– Habitat loss and fragmentation

– Biological invasion

– Pollution

– Over-harvesting

– Human-induced climate change