Dr. Marissa Betts

It was certainly one of the most important biospheric but also geospheric revolutions in the history of the Earth.

And that is the Cambrian explosion.

It's when we see the relatively rapid appearance in the fossil record of lots of different kinds of complex animal body plans.

We see evolutionary innovations like the development of eyes, for example.

Organisms can start to swim in the water column and they can burrow down into the sediment.

We have actually got very little direct evidence for how these organisms were reproducing.

I guess you would say the ancestral state of all of these groups in terms of reproductive style would probably be broadcast spawning, where eggs and sperm are released into the water column.

I said direct evidence.

Right.

We do have some examples of...

Fossils where we have eggs preserved, for example, that seems to be by and large the most direct evidence that we get in the Cambrian fossil records for reproduction.

Animals that have been preserved, very remarkable fossils, with eggs associated with them, often inside their carapaces where they've been brooding them properly.

These are the broadcast borders and things that just sort of pump eggs and sperm together.

out into the world and just let them hope for the best.

No.

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