L8 - History of Life on Earth

Question 1

When did Earth form from an accretionary disk?

Answer 1

4.5 Ga ago - From planetesimals

Question 2

What evidence is there for Earth’s formation?

Answer 2

Asteroids in western Algeria and Campo del Cielo, Argentina - 4.5 Ga old.
There are three main types of asteroid; chondrites, achondrites and irons.

Question 3

What are the oldest minerals on Earth?

Answer 3

4.4 Ga - Zircons, Australua

Question 4

What are the oldest rocks on Earth?

Answer 4

4. 0 Ga - 12% - Acasta Gniess - Canada

- Metamorphic rock, usually forms due to orogeny

Question 5

What is the earliest evidence for life?

Answer 5

3. 6 Ga - 21% - Odd isotope ratios - Pilbara, Australia
   - Carbon & Sulphur ratios
   - Controversial
4. 4 Ga - 25% - Blob-like structures that could be cells - Pilbara, Australia
   
   • Associated with pyrite - biotic anaerobic conditions
5. 3 Ga - 28% - Stromatolites, Australia
   
   • Cyanobacteria
   • Uncontroversial

Question 6

When is the first evidence for eukaryotic cells?

Answer 6

2. 1 Ga - 54% - Fossils with nuclei and organelles
   
   • Likely origin of sexual reproduction
   • Likely spurred by Great Oxygenation Event

Question 7

When is the first evidence for multicullular life emerge?

Answer 7

1. 4 Ga - 69% - Fossils
2. 2 Ga - 74% - Bangiomorpha. Canada
   
   • Algae-like

Question 8

When do the first ‘hard’ organisms appear in the fossil record.

Answer 8

565 mya - 88% - Small shelled fauna

- Associated with another rise in oxygen levels
- 'Soft' organisms increase in complexity - Ediacaran fauna

Question 9

When was the Cambrian Explosion

Answer 9

530 mya - 88% - Cambrian Explosion

- Period of radiation
- Fossil record 'suddenly' enriched
- Origin of arthropods, corals, molluscs and chordates

Question 10

List the post-Cambrian geologic periods

Answer 10

Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene, Neogene, Quaternary.

Sentence - “Quit nagging poking Canadians, just tolerate pokes” Can Dakota sustain outrageous craze?

Question 11

When did terrestrial life emerge?

Answer 11

435 mya - 91% - Silurian

- Small invertebrates and plants on in close proximity land

Question 12

When did vascular plants/trees and amphibians first emerge?

Answer 12

385 mya - 91.5% - Devonian

- Earth is colonised by the first forests.

Question 13

When did winged insects and reptiles emerge?

Answer 13

325 mya - 93% - Carboniferous

Question 14

When did synapsids and diapsids develop?

Answer 14

306-302 mya - 93.5% - Carboniferous

- Synapsids -> Mammals
- Diapsids -> Modern reptiles & Birds

Question 15

When did Pangaea first assemble?

Answer 15

280 mya - 93.5% - Permian

- Not first supercontinent

Question 16

When did the archosaurs first emerge from diapsids?

Answer 16

255 mya - 95% - Permian

- Crocodiles, birds, dinosaurs, pterosaurs

Question 17

When did the Permian Mass Extinction event occur

Answer 17

252 mya - 95% - Permian/Triassic boundary

- 96% species went extinct
- Impacted insects
- Most mass extinction event yet

Question 18

When did mammals first emerge and Pangaea break up?

Answer 18

195 mya - 96% - Jurassic

Question 19

When did marsupials first emerge?

Answer 19

125 mya - 97% - Cretaceous

- Marsupials distributed predominantly in former Gondwana

Question 20

When did the KT extinction event occur?

Answer 20

65 mya - 98% - Creaceous/Paleogene boundary

Question 21

When is the earliest monkey fossil from?

Answer 21

47 mya - 99% - Paleogene

• Darwinius ‘Ida’
• Either ancestor of monkeys or lemurs

Question 22

When did apes diverge?

Answer 22

25 mya - 99% - Paleogene

Question 23

When did humans diverge?

Answer 23

7 mya - 99.9% - Neogene

Question 24

Highlights of L8?

Answer 24

• No geological record for first 12% of Earths history
• Life formed between 21-28% Earths history
• Multicellular life formed not until 69%, animals not until 88%
• Terrestrial life only after 91%
• Dinosaurs extinct at 98%
• Humans at 99.9%