Lecture 5

Question 1

What was the Cambrian Explosion?

Answer 1

a dramatic increase in animal and plant diversity at the beginning of the Cambrian era

Question 2

Biologist are convinced that without them, the first life could not have formed on Earth. What was that?

Answer 2

catalysts

Question 3

Which one is the most important difference between prokaryotes and eukaryotes?

Answer 3

prokaryotes have no nucleus in which the genetic material is contained

Question 4

What is “LUCA”?

Answer 4

The organism from which all current life on Earth originates

Question 5

Which one of the following is not considered an important step in the origin of life on Earth?

Answer 5

the protective ozone layer that shields us from harmful ultraviolet radiation

Question 6

Biologists think that the processes that led to the origin of life resemble most closely:

Answer 6

Prebiotic chemistry naturally formed the molecular building blocks and catalytic reactions then led to more complex and replicating molecules

Question 7

The origin of life on Earth most likely occurred:

Answer 7

Between 4.0 and 3.5 billion years ago

Question 8

Some of the first living organisms probably resembled:

Answer 8

cells without nuclei that used RNA as their genetic material

Question 9

Why do we talk about clay minerals in connection with the origin of life on Earth?

Answer 9

Because their layered structure has been shown to facilitate the formation of long-chained organic molecules

Question 10

Early life arose in an oxygen-free environment, but if any of these microbes had somehow come in contact with oxygen, the most likely effect would have been:

Answer 10

To kill them

Question 11

The oxygen in Earth’s oceans and atmosphere was originally released by

Answer 11

cyanobacteria

Question 12

Which one of the following is not considered a possible cause of the Cambrian explosion?

Answer 12

the impact of a 10-km sized asteroid

Question 13

Importance of ribozymes?

Answer 13

Most important for the origin of life

Question 14

Importance of catalytic reactions?

Answer 14

Transitions from no-life to life

Question 15

RNA-world process

Answer 15

1. Naturally forming organic molecules are the building blocks of life
2. Clay minerals catalyze production of RNA and membranes that form pre-cells
3. Molecular natural selection favors efficient, self-replicating RNA molecules
4. True living cells with RNA genome, give us rise to “DNA world”

Question 16

RNA-world

Answer 16

a hypothetical stage in the evolutionary history of life on Earth, in which self-replicating RNA molecules proliferated before the evolution of DNA and proteins

Question 17

Prokaryotes are

Answer 17

the most successful organisms on Earth. Only life for over 2 Gyr

Question 18

Major cell structure difference between prokaryotes and eukaryotes

Answer 18

Eukaryotes have a nucleus while prokaryotes do not

Question 19

Evidence for when life first emerged

Answer 19

The earliest life forms we know of were microscopic organisms (microbes) that left signals of their presence in rocks about 3.7 billion years old. The signals consisted of a type of carbon molecule that is produced by living things.

Question 20

Where did life first begin

Answer 20

Hydrothermal deep-sea vents

Question 21

Importance of pre-biotic chemistry?

Answer 21

first replicating macro-molecules (maybe
ribozymes => RNA) helped by catalysts

Question 22

Importance of Cambrian explosion

Answer 22

1. Increased oxygen levels
2. Earth was recovering from a Snowball event
3. Evolution of eyes
4. 550 myrs