Unit 5: Animals & Plants

Do Now:

Set up the timeline on the back of your notes, by marking one end “4,500 MYA” and

the other “Present”

In the “Do Now” section: How many billion is 4,500 million?

Our final unit will investigate the animals, plants, and other organisms which developed after the Cambrian Explosion about 543 million years ago:◦ Plants◦ Complex animals

But First… their history as told by the fossil record.

Our Final Unit

The Precambrian Eon begins with the formation of the solar system about 4,500 MYA (= 4.5 BYA).

The Pre-Cambrian is incomprehensibly long: it is 86% of Earth’s history. ◦ Rocks form: 4,000 MYA◦ Abiogenesis (life “evolves”): 3,800 MYA◦ Eukaryotes evolve (endosymbiosis): 2,700 MYA

The Precambrian Eon lasts until 543 MYA, with an event commonly called the Cambrian Explosion

Pre-Cambrian Earth

Prokaryotes are the only life on Earth for over a billion years.

By the end of the Precambrian Eon, some simple animals (sponges, flatworms, roundworms, cnidarians) had evolved.

A mass extinction occurs (Vendian) 543 MYA, officially ending the Precambrian Eon

Pre-Cambrian Life

The Cambrian Explosion (or Cambrian diversification; 540 MYA) was a brief period in history where many new types of organisms evolve:◦ Arthropods◦ Chordates◦ Hard-Shelled animals

No major animal phyla have evolved since the Cambrian Explosion… why?

Cambrian Explosion (4th box) 540 MYA

Cambrian Life

Cambrian refers to the first geological period within the larger Paleozoic Eon.

The “Cambrian” and “Paleozoic”

Land Plants and Fishes Evolve: 480 MYA

Reptiles Evolve: 350 MYA

These are boxes 5 and 6…

Later in the Paleozoic

“The mother of all extinctions.”

Somewhere between 70 and 95% of all organisms become extinct 250 MYA.

Worst mass extinction ever recorded on Earth. Competing hypotheses over cause.

End of the Paleozoic: the Permian Extinction

Dinosaur and Mammal Ancestors survive the “Great Dying”

Dinosaurs and Mammals Evolve: 220 MYA (Box 7)

Mesozoic Eon = “Age of the Dinosaurs” 248 – 65 MYA

TriassicJurassic

Cretaceous

Birds evolve 150 MYA (Box 8)

Birds – Branch of the Dino Family Tree

You are living in the Cenozoic Eon, the “Age of Mammals.”

Begins with the K-T extinction 65 million years ago (meteorite that wiped out the dinosaurs) Box 9

Box 10: Humans diverge from ape populations 6 MYA.

Cenozoic Eon: 64 MYA to Today

Looking Back

Can you imagine a reason why no major animal phylum has evolved in the last 500 million years?

THINK