Topic 9: Origin of Life

Question 1

The three main biological polymers,
nucleic acids, proteins, and
polysaccharides, are built from:

Answer 1

five
nucleotide bases, 20 amino acids, and
a few sugars

Question 2

What an entity needs to be considered alive:

Answer 2

Organization, metabolism, stimuli, homeostasis, adaptation, reproduction

Question 3

Organization

Answer 3

structurally
composed of one or more cells
(basic units of life)

Question 4

Metabolism

Answer 4

a system of
management of energy and
materials via chemical reactions

Question 5

Stimuli

Answer 5

Response to stimuli: via changes in
growth, alteration of chemical
reactions, or movement

Question 6

Homeostasis

Answer 6

maintenance of
some internal chemical and/or
thermal consistency relative to
variation outside of the organism

Question 7

Adaptation

Answer 7

the ability to change
over time in response to the
environment

Question 8

Reproduction

Answer 8

ability to produce

new individual organisms

Question 9

Viruses

Answer 9

• have nucleic acids that can replicate, mutate, and respond to natural selection
• lack metabolism and homeostasis, and cannot reproduce without using the cellular machinery of a host cell

Question 10

Earth formed ___ years ago

Answer 10

4.6 billion

Question 11

First replicating life:

Answer 11

3.9 billion years ago

Question 12

The geologic record is divided into:

Answer 12

the Archaean, the Proterozoic, and

the Phanerozoic eons

Question 13

Three eras of phanerozoic

Answer 13

Paleozoic, Mesozoic, and Cenozoic

Question 14

Fossils

Answer 14

the preserved
remains/evidence of organisms that
lived in the past.

Question 15

Fossils are used for:

Answer 15

calibrate
phylogenies, record extinct species (e.g.
linkage between dinosaurs and modern
birds), and link evolutionary events (e.g.
mass extinctions) with geological and
environmental changes on Earth.

Question 16

Probability of an organism (or part of)

becoming fossilized increases if:

Answer 16

• Existed for a long time.
• Was abundant and widespread.
• Hard rather than soft-bodied.
• Aquatic rather than terrestrial.
• Inshore marine rather than offshore
  marine.
• Decomposing organisms were absent

Question 17

Types of fossils recorded

Answer 17

Cast, Replacement, trace, preserved

Question 18

Cast fossils

Answer 18

A cast forms when minerals fill
space in sediment where the
organism decayed after having
been buried

Question 19

Replacement fossil

Answer 19

fossils
have had their tissues replaced by
minerals

Question 20

Trace fossils

Answer 20

record evidence of

behavior (tracks, burrows, feces).

Question 21

Preserved fossils

Answer 21

retain the original
organic material (carbon films,
amber, tar or peat, frozen)

Question 22

Sedimentary strata reveal ____

ages of fossils

Answer 22

relative

Question 23

Radioactive dating

Answer 23

Radioactive decay of isotopes of
various elements provides a means
of determining the age of fossils or
rocks. Radioactive isotopes decay
from one form to
another at a known
constant rate.

Question 24

Half life of C14

Answer 24

5,730 years

Question 25

time when there was a supercontinent

Answer 25

1.1 billion, 600

million, and 250 million years ago.

Question 26

Plate tectonics theory

Answer 26

considers
that Earth’s crust is composed of
large plates that have been slowly
moving since about 3.4 billion
years ago

Question 27

Continental drift during pangea

Answer 27

• Deepening of ocean basins.
  − Reduction in shallow water habitats.
  − Colder and drier climate inland.

Question 28

Continental drift effect on biodiversity

Answer 28

• Changes to the environment and climate as
  continents move north or south.
  − Opportunities for diversification. (e.g. when land masses are isolated, each can develop unique
  species via allopatric speciation.)
  − Mass extinctions.

Question 29

The fossil record shows that most
species that have ever lived are
now ___

Answer 29

extinct

Question 30

In each of the 5 mass extinctions, ___ of species went extinct

Answer 30

50%

Question 31

Permian mass extinction

Answer 31

• the boundary between the Paleozoic and Mesozoic eras
• 252 million years ago
• greatest extinction
• caused by extensive volcanism in Siberia
• during formation of Pangea (more shallow shorelines and reduced temperature gradient)

Question 32

Cretaceous mass extinction

Answer 32

• separates Mesozoic from Cenozoic
• 65.5 million years
• 20% of families went extinct
• extinction of dinos
• Presence of iridium in sedimentary rocks suggests a massive meteorite impact about 65 mya

Question 33

It can take ____ years for biodiversity to recover after a mass-extinction

Answer 33

5 to 100 million

years

Question 34

Mass extinctions can lead to

Answer 34

adaptive radiation

Question 35

Adaptive radiation

Answer 35

the rapid
evolution of diversely adapted
species from an ancestral species

Question 36

When does adaptive radiation happen

Answer 36

Adaptive radiation occurs when a
change in the environment makes
new ecological niches available

Question 37

Adaptive radiations may follow

Answer 37

mass extinctions, the evolution of novel characteristics, colonization of new regions

Question 38

Mass extinctions

Answer 38

By eliminating so many species, mass
extinctions can pave the way for
adaptive radiations

Question 39

Evolution of novel characteristics

Answer 39

The adaptive radiation of
photosynthetic prokaryotes, land
plants, insects, and tetrapods was
enabled by novel adaptations

Question 40

Colonization of new regions

Answer 40

Adaptive radiations can occur when
organisms colonize new
environments with little competition

Question 41

Earth’s first billion years

Answer 41

• The surface began to cool; unstable crust floated on the molten magma.
• Steaming gasses from cooling rock formed an atmosphere lacking oxygen.
• Atmospheric temperatures dropped:
  gasses condensed and rained down.
• Basins filled with water, forming transient
  oceans.
• Between 3.8 and 4.1 bya bombardment of Earth by asteroids and comets would have vaporized water, preventing seas from forming and sterilizing the planet’s surface
• Earth’s early atmosphere likely contained water vapour and chemicals from volcanic eruptions (nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia,
  hydrogen, hydrogen sulphide)

Question 42

hypothesized

sequence of stages for evolution of simple cells

Answer 42

1. Abiotic synthesis of small organic
molecules.
2. Joining of small organic molecules
into organic polymers (organic
macromolecules).
3. Packaging of molecules into
protocells.
4. Origin of self-replicating molecules.

Question 43

Abiotic synthesis of small organic molecules

Answer 43

inorganic to organic

- possibly due to terrestrial origins or extraterrestrial oragins

Question 44

Terrestrial origins of organic molecules on earth

Answer 44

organic molecule synthesis driven by energy sources, e.g. UV light, electrical discharges. Earth’s early atmosphere was initially hypothesized to be a reducing environment.

Question 45

Miller & Urey demonstrated:

Answer 45

the abiotic synthesis of organic molecules in a reducing atmosphere

Question 46

Instead of forming in the
atmosphere, abiotic synthesis may
have occurred:

Answer 46

near volcanoes or
deep-sea hydrothermal vents where
strongly reducing conditions are
found

Question 47

Abiotic synthesis of organic polymers

Answer 47

Wetting and drying cycles of water on hot surfaces, such sand, clay, or rock, may have concentrated small organic molecules, triggering the spontaneous formation of organic polymers

Question 48

Polyphosphates cause polymerization

of amino acids into

Answer 48

peptides

Question 49

Packaging of molecules into protocells

Answer 49

- Free-floating amino acids, proteins,
and nucleic acids would not have
been able to behave like cells
- there needed to be replication and metabolism
- In water, lipids and other organic
molecules can spontaneously form
hollow vesicles with a lipid bilayer
A sphere would have been able to
keep (or export) its products

Question 50

− Protocells

Answer 50

fluid-filled
vesicles with a membrane-like
structure

Question 51

w lipid vesicles form faster in the presence of

Answer 51

volcanic clay

Question 52

Lipid vesicles exhibit

Answer 52

simple reproduction and metabolism, and can maintain an internal chemical environment. Vesicles can increase in size and divide on their own.

Question 53

earliest genetic material was

Answer 53

RNA

Question 54

RNA

Answer 54

- RNA is single-stranded, fragile, and
self-replicating.
− RNA can store genetic information.
− Self-replicating RNA molecules have
been experimentally demonstrated.
− RNA could have provided a template
for the later evolution of DNA, a more
stable genetic material

Question 55

Some RNA molecules (ribosomes) can catalyze ______

Answer 55

chemical reactions

Question 56

The oldest fossil evidence of life is

of

Answer 56

prokaryotes (~3.5-3.7 bya)

Question 57

Prokaryotes

Answer 57

− Single-celled (unicellular).
− DNA is not contained in a nucleus.
− Lack membrane-bound organelles

Question 58

Two domains of prokaryotes

Answer 58

bacteria and archaea

Question 59

The oldest known fossils are

Answer 59

stromatolites

Question 60

Stromatolites

Answer 60

rocks formed by the accumulation of sedimentary layers on prokaryote mats (date back to 3.5-
3.7 bya)

Question 61

Oxygen revolution

Answer 61

− Oxygen began accumulating in the
atmosphere ~2.7 bya.
− Oceanic photosynthetic prokaryotes
(cyanobacteria) used the sun’s energy
to fix CO2, producing O2 as a byproduct.
− Initially, O2 produced by cyanobacteria
reacted with iron dissolved in oceans,
precipitating to form banded iron
formations

Question 62

Earth’s early prokaryotes evolved in O

2-free conditions and used

Answer 62

anaerobic metabolism