Chapter 1 Multiple Choice Questions

. What is photosynthesis?

The biological process whereby light is emitted after the catabolism of energy rich compounds

A process whereby geothermal energy is used to produce electricity

The abiotic process whereby light is used to synthesise complex compounds on the water-rock interface

The biological process whereby light is used to power the formation of complex organic molecules from inorganic precursors

. What are the main products of the light reactions of photosynthesis?

ATP, NADPH, and O₂ as a by-product

Carbohydrates and amino acids

DNA and protein

ATP and H₂O

. What is a phylogenetic tree?

A methodology to read genome and protein sequences

A way to represent the evolutionary relationships of organisms, genomes, genes, or proteins

It describes the evolutionary relationships of photosynthetic life

None of the above

. When did life originate on Earth?

After the first Great Oxygenation Event, 2.4 billion years ago

There is evidence that life originated 3.0 billion years ago

It is unclear, but there are biosignatures over 3.8 billion years old

Life did not originate on Earth, but it arrived to Earth via panspermia over 4.0 billion years ago

. What is the LUCA?

This represents the first well defined cell after the origin of life

This represents the last common ancestor of all Eukaryotes

The last universal common ancestor. The point at which Archaea, Eukaryotes, and Bacteria started to diverge

The last universal common ancestor. The point at which Archaea and Bacteria started to diverge

. How did Eukaryotes originate?

From an intimate symbiosis between an alphaproteobacterium and an archaeon, the latter likely belonging to the Asgard Archaea group

It is thought that the nucleus of Eukaryotes originated from a methanogenic archaeon while the mitochondria originated from an alphaproteobacterium

From the engulfment of a cyanobacterium by an ancestral archaeon

From an intimate symbiosis between an alphaproteobacterium and a cyanobacterium

. If you travelled 3.0 billion years into the past, would you have been able to breathe normally?

Yes, because the atmosphere has remained unchanged over the entire history of the planet

Yes, but with difficulty, there should have been just enough oxygen to support a living animal

No, because the atmosphere only formed after the first Great Oxygenation Event, 2.4 billion years ago

No. Although it is plausible that oxygenic photosynthesis had already evolved at this stage, the levels of oxygen were over five orders of magnitude below the present level

. What happened during the first Great Oxygenation Event?

There was a heavy bombardment of asteroids that resulted in the oxidation of the atmosphere

Cyanobacteria appeared for the first time in the geological record

Oxygen concentrations rose globally and permanently by several orders of magnitude

All of the above

. How did photosynthetic Eukaryotes originate?

Some Archaea were ancestrally photosynthetic, and this trait was retained in some lineages of Eukaryotes after the acquisition of the mitochondria

A group of Eukaryotes known as Archaeplastida evolved photosynthetic plastids from the invaginations of the cytoplasmic membrane

A group of Eukaryotes obtained photosynthesis from the endosymbiosis of a betaproteobacterium

None of the above

. What is the Neoproterozoic Oxygenation Event

This refers to a second major rise in the concentration of oxygen in the atmosphere, about 800 million years ago

It is when the ozone layer formed for the first time

This coincides with the origin of the first photosynthetic eukaryotes

This coincides with a major extinction of life triggered by the oxidation of the atmosphere after widespread vulcanism in the supercontinent Rodinia

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