Lecture 6

Question 1

4 requirements for life

Answer 1

1. metabolism
2. response to stimuli
3. homeostasis
4. reproduction with potential for error

Question 2

are viruses alive?

Answer 2

no, lack metabolism and homeostasis, cannot reproduce without host cell

Question 3

fossil

Answer 3

a preserved remnant/ evidence of organisms that lived in the past

Question 4

strata

Answer 4

distinct layers in rock

Question 5

why is our understanding of the diversity and distribution of past life is biased and incomplete?

Answer 5

fossils more likely to form if hard, aquatic, inshore, and decomposing organisms absent after death

Question 6

3 types of fossils

Answer 6

1. trace fossils (evidence of behaviour)
2. cast (minerals fill space in sediment where organism decayed)
3. petrified (tissues replaced by minerals)

Question 7

ichnology

Answer 7

study of trace fossils

Question 8

sub-fossil

Answer 8

high % organic material (thin carbon film, amber, tar, peat, frozen)

Question 9

relative dating

Answer 9

done via sedimentary stratigraphy, can’t tell how long ago fossil was created but can tell which fossil came 1st, 2nd, etc

Question 10

index/indicator fossils

Answer 10

help to read incomplete or scrambled layers, existed for a brief time with wide geographic distribution

Question 11

geologic time scale

Answer 11

created based on the appearance and disappearance of major taxa, major events correlated with changes in eon, era, period or epoch

Question 12

radiometric dating

Answer 12

measurement of radioactive isotopes in fossils or rocks to determine absolute dates for geologic time scale

Question 13

Carbon 12

Answer 13

common, 6 neutrons

Question 14

Carbon 14

Answer 14

8 neutrons, decays to N-14

Question 15

half-life

Answer 15

when 50% of atoms in a given amount of radioactive substance have decayed

Question 16

carbon dating

Answer 16

when organism dies, C-12 stays but C-14 decays - increasing ratio of C-12:C-14 in fossils allows fossils to be dated

Question 17

half-life of carbon

Answer 17

5730 years, carbon dating only good for young fossils up to 75 000 years old

Question 18

half-life of uranium

Answer 18

4.5 billion years, better for older fossils

Question 19

continental drift

Answer 19

relative locations of land masses have changed over time, fossils provided first evidence

Question 20

Pangaea

Answer 20

first supercontinent

Question 21

Gondwana

Answer 21

Australia, Antarctica, and South America, same genus of fossil plant found

Question 22

2 mass extinctions

Answer 22

1. End-Permian

2. End-Cretacious

Question 23

End-Permian

Answer 23

245 MYA, 60% of families and 90% of marine species extinct, formation of Pangaea

Question 24

End-Cretacious

Answer 24

65 MYA, at Cretaceous-Paleogene boundary, 20% of families including non-avian dinosaurs and ammonites extinct, climate change or asteroid strike

Question 25

planet formed

Answer 25

4.6 BYA, bombarded by large chunks of rocks until 3.9 BYA

Question 26

oldest fossil evidence of life

Answer 26

3.5 BYA, hypothesized to have existed up to 3.9 BYA - single-celled prokaryotes

Question 27

prokaryotes

Answer 27

lack membrane-bound organelles, DNA not contained in nucleus, only type of fossil evidence for 1.5 BYA

Question 28

stromatolites

Answer 28

where many of the oldest prokaryotic fossils are found, many species of prokaryotes living together on substrate, sediments accumulate, grow up through sediment, creates banded rock

Question 29

cyanobacteria aka blue-green algae

Answer 29

oxygen began accumulating 2.7 BYA when photosynthetic cyanobacteria started using sun’s energy to split water into hydrogen & oxygen

Question 30

banded iron rock

Answer 30

first oxygen released through photosynthesis probably reacted with dissolved iron in oceans to create iron oxide, iron oxide precipitated out

Question 31

early 02

Answer 31

toxic to early life, attacks chemical bonds

Question 32

obligate anaerobes

Answer 32

descendants of species that could survive only in very little 02, present in rotting oxygen-free substrates and guts of animals

Question 33

spontaneous generation

Answer 33

until 1800’s, how we thought that microbes arose

Question 34

Louis Pasteur’s beef broth experiment

Answer 34

broth spoiled only if bacterial spores could drop from the air, disproved spontaneous generation

Question 35

how early cell-like structures may have arisen

Answer 35

free-floating amino acids created, and spontaneous formation of hollow lipid vesicles

Question 36

Montmorillonite

Answer 36

volcanic clay 4 BYA that vesicles form faster in

Question 37

Where did life originate?

Answer 37

original: shallow water bodies
now: hot, mineral-rich deep-sea vents

Question 38

panspermia hypothesis

Answer 38

first prokaryotes came from space, supported by nanobes in meteorite

Question 39

most important condition for life to arise

Answer 39

free non-toxic water