Origins of Life

Question 1

Earliest actual cells

Answer 1

prokaryotic heterotrophic anaerobes

Question 2

prokaryotic heterotrophic anaerobes

Answer 2

obtained energy by consuming organic material contained in the organic soup; performed fermentation bc there was no free O2

Question 3

What happened to the first cells once the supply of organic food depleted?

Answer 3

natural selection occured; Autotrophic cells were selected for (formed by mutation) since they no longer depended on organic food

Question 4

How did the first autotrophic cells function?

Answer 4

Used energy from the sun and inorganic materials (H 2 S) as hydrogen/electron source to produce organic materials, releasing
sulfur

Question 5

What evolved after the autotrophs?

Answer 5

Cyanobacteria

Question 6

Cyanobacteria

Answer 6

first to use water as a source for hydrogen and electrons

Question 7

What process did cyanobacteria perform?

Answer 7

photosynthesis

Question 8

what did cyanobacteria release as a waste product?

Answer 8

O2

Question 9

What evolved after O2 became a thing? Why?

Answer 9

Aerobes evolved- used oxygen to extract more energy from food–>more efficient than anaerobes

Question 10

What happened when aerobes evolved?

Answer 10

Carbon started cycling throughout the biosphere, from the physical environment (CO 2 ) to autotrophs to heterotrophic aerobes and back out

Question 11

What would happen when sunlight would break the double bonds of oxygen?

Answer 11

O3 was formed

Question 12

O3

Answer 12

ozone. protected surface of earth and allowed organisms to move to land

Question 13

What happened once ozone formed?

Answer 13

Eukaryotes formed from prokaryotes

Question 14

Endosymbiotic theory

Answer 14

eukaryotic cells formed a symbiotic relationship between prokaryotic cells, in which the prokaryotic cells were ingested by other prokaryotic cells
eventually they became permanent part of their hosts (chloroplasts + mitochondria)

Question 15

Chloroplasts

Answer 15

evolved from photosynthetic bacteria living inside heterotrophic cells

Question 16

Mitochondria

Answer 16

evolved from aerobic bacteria living inside anaerobic cells

Question 17

evidence of endosymbiotic theory

Answer 17

Mitochondria and chloroplasts possess their own DNA in circular form; have their own ribosomes that resemble prokaryotic ribosomes; can reproduce independently; thylakoid membranes resemble photosynthetic membrane of cyanobacteria

Question 18

Chemical Evolution

Answer 18

scientists believed that life developed from nonliving matter

Question 19

Step by step chemical evolution

Answer 19

spontaneously formed small organic molecules –> Large organic macromolecules (proteins, nucleic acids) –>Complicated structures that could replicate–>cell-like structures–>first structures

Question 20

Early earth atmosphere

Answer 20

atmosphere def had CO2, water vapor, carbon monoxide, hydrogen, and nitrogen. might’ve had ammonia (NH 3 ), hydrogen sulfide (H 2 S), and methane (CH 4 ), but that would’ve been quickly broken down by UV rays. all these condensed into seas as the earth cooled

Question 21

requirements early earth

Answer 21

Little or no free oxygen; High energy (thunderstorms, volcanoes, strong UV rays) Chemical building blocks (water, gases) and time (4.6 billion years old; life appeared 3.8 billion years ago)

Question 22

why couldn’t early earth have free O2?

Answer 22

O2 is very reactive – would’ve interfered with formation of organic molecules

Question 23

Formation of organic molecules hypotheses

Answer 23

Prebiotic soup hypothesis or Iron-sulfur world hypothesis-

Question 24

Iron-sulfur world hypothesis-

Answer 24

organic precursors formed at hydrothermal vents

Question 25

Prebiotic soup hypothesis-

Answer 25

organic molecules formed near Earth’s surface

Question 26

A.I. Oparin

Answer 26

Prebiotic soup hypothesis. over time, the organic molecules accumulated in shallow seas to form a “sea of organic soup”. There, monomers would join to form polymers

Question 27

Stanley Miller-

Answer 27

designed a closed apparatus that simulated conditions existing in early Earth and exposed it to electrical charges (simulated lightning). Found that after a week, organic molecules were formed

Question 28

suggestion first cells

Answer 28

Polymers that have formed may have spontaneously created proteins

Question 29

proof of polymers–>proteins

Answer 29

protenoids

Question 30

protenoids

Answer 30

abiotically produced polypeptides

Question 31

Protobionts

Answer 31

groups of abiotic organic polymers. formed after the polymers spontaneously created proteins. Can resemble living cells–grow, maintain homeostasis, carry out reactions.

Question 32

Microspheres

Answer 32

are a type of protobiont formed by adding water to abiotically formed polypeptides. Their cell membranes contain an electrochemical gradient and are
selectively permeable

Question 33

RNA world

Answer 33

model that suggests self replicating RNA formed first, that functions as an enzyme and substrate for
its own replication

Question 34

Ribozymes

Answer 34

RNA molecules that can catalyze their own reactions w/o using enzymes

Question 35

How did RNA function without DNA?

Answer 35

RNA molecules can weakly bind to amino acids causing protein synthesis (on its own)

Question 36

How could DNA have come about?

Answer 36

Perhaps double stranded copies of itself, forming DNA, which is more stable than
RNA. Once DNA was formed, it had the selective advantage and became the
information storage molecule

Question 37

hydrothermal vents

Answer 37

deep cracks in the ocean’s floor which consist of hot water, carbon monoxide, and minerals