History of life on Earth

Question 1

How long ago?

• Earth, solar system formed
• first single-celled prokaryotes
• first single-celled eukaryotes
• first multi-celled eukaryotes
• colonization of land
• Homo sapiens species

Answer 1

4.6 bya
3.5 bya
2.1 bya
1.2 bya
500 mya
200,000 years ago

Question 2

How long ago?

• Cambrian explosion
• colonization of land
• Permian mass extinction
• Cretaceous mass extinction

Answer 2

540 mya
500 mya
250 mya
66 mya

Question 3

3 most recent eras (Phanerozoic eon) and boundaries

Answer 3

(Present)
Cenozoic
(Cretaceous extinction, 66 mya)
Mesozoic
(Permian extinction, 250 mya)
Paleozoic
(Cambrian explosion, 540 mya)

Question 4

Eons

Answer 4

(Present)
Phanerozoic
(Cambrian explosion 540 mya)
Proterozoic
(Oxygen increases 2.3 bya)
Archaean
(Solar system, Earth formed 4.6 bya)

Question 5

heterochrony

Answer 5

an evolutionary change in the rate or timing of developmental events; ex: paedomorphosis, increased growth rate of finger bones leads to wings in bats

Question 6

paedomorphosis

Answer 6

when an adult retains features of a juvenile; example of heterochrony w.r.t. timing of reproductive development

Question 7

homeotic genes

Answer 7

genes that control the placement or spatial organization of body parts; ex: Hox genes

Question 8

Hox genes

Answer 8

homeotic genes that provide positional information in an animal embryo

Question 9

adaptive radiation

Answer 9

a process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges and opens environmental niches

Question 10

Cambrian explosion

Answer 10

many present-day animal phyla appear suddenly in the fossils formed in the Cambrian period (540 mya)

Question 11

Burgess Shale

Answer 11

located in the Canadian Rockies of British Columbia, is one of the world’s most celebrated fossil fields. It is famous for the exceptional preservation of the soft parts of its fossils. At 500 mya (Middle Cambrian) old, it is one of the earliest fossil beds containing soft-part imprints.

Question 12

stromatolites

Answer 12

layered rocks that form when certain prokaryotes bind thin films of sediment together; fossilized stromatolite are the earliest direct evidence of life (3.5 bya)

Question 13

endosymbiont theory

Answer 13

mitochondria and plastids were formerly small prokaryotes that began living within larger eukaryotic cells

Question 14

Permian extinction

Answer 14

250 mya, a mass extinction, more marine predators afterwards

Question 15

Cretaceous extinction

Answer 15

66 mya, a mass extinction, most dinos die :’(