The Cambrian The Cambrian ExplosionExplosion

By Andy GormanBy Andy Gorman

Cambrian?Cambrian? In the Cambrian period, the super continent In the Cambrian period, the super continent

of Pangaea was breaking up into smaller partsof Pangaea was breaking up into smaller parts Many climate changes took place at this time. Many climate changes took place at this time. Oxygen was increasingOxygen was increasing Carbon Dioxide was decreasing (this caused Carbon Dioxide was decreasing (this caused

the planet to cool down)the planet to cool down) There was a huge glacial movement and a There was a huge glacial movement and a

very harsh ice age. very harsh ice age. And after the ice age was finished And after the ice age was finished

temperatures rose to levels higher than they temperatures rose to levels higher than they are todayare today. .

What is the Cambrian What is the Cambrian Explosion!?!?!?!?!!!!!!!!!!!!!!Explosion!?!?!?!?!!!!!!!!!!!!!!

!11111111one!11111111one At first look, the Cambrian explosion At first look, the Cambrian explosion

would sound totally sweet. Just think, would sound totally sweet. Just think, explosions!explosions!

But in fact, it is only semi-sweet But in fact, it is only semi-sweet (not really)(not really)

What actually happened, was a lot of What actually happened, was a lot of complex organisms appeared between 543 complex organisms appeared between 543 and 530 million years ago. and 530 million years ago.

Organisms like brachiopods, arthropods Organisms like brachiopods, arthropods and echinoderms appeared in large and echinoderms appeared in large variationsvariations

Why So Much Life?Why So Much Life?

Many Theories have been created to Many Theories have been created to explain this sudden increase in life, explain this sudden increase in life, but many contradict each other. but many contradict each other.

One theory was that the changing One theory was that the changing climate could have caused some of climate could have caused some of the life created in the period. the life created in the period.

Evolution?Evolution?

This Cambrian Explosion drew attention This Cambrian Explosion drew attention to the evolutionary theory. to the evolutionary theory.

Charles Darwin even brought it up in his Charles Darwin even brought it up in his book, book, Origin of Species.Origin of Species.

It is at this period, many organisms It is at this period, many organisms attained or improved preservational attained or improved preservational characteristics, or in lay man’s terms, characteristics, or in lay man’s terms, hard parts. hard parts.

GIVE GIVE ANDYANDY

ANANAA

View points View points

Everybody agrees that there was a Everybody agrees that there was a big biological event that happened at big biological event that happened at that time. that time.

Where there is controversy is Where there is controversy is whether this event was a true whether this event was a true radiation of metazoan forms from a radiation of metazoan forms from a single Precambrian ancestor or an single Precambrian ancestor or an explosion of fossils rather than phyla explosion of fossils rather than phyla

One Ancestor One Ancestor

There is a sudden increase in fossils There is a sudden increase in fossils at the timeat the time

Trace fossils also increase in Trace fossils also increase in behavior and in abundance.behavior and in abundance.

Soft-bodied Precambrian faunas can Soft-bodied Precambrian faunas can be preserved, so why are there no be preserved, so why are there no assemblages of 'true' metazoan soft-assemblages of 'true' metazoan soft-bodied faunas from the Precambrianbodied faunas from the Precambrian

Just abundance of Just abundance of Fossils?Fossils?

Soft bodied organisms fossilize over only Soft bodied organisms fossilize over only exceptional circumstances. exceptional circumstances.

cladistic analysis shows that the cladistic analysis shows that the divergence times of most Cambrian divergence times of most Cambrian organisms must have occurred in the organisms must have occurred in the Precambrian Precambrian

Precambrian organisms could have been Precambrian organisms could have been very small and therefore fossilization very small and therefore fossilization would have been impossible would have been impossible