chapter 11
Among the oldest fossils yet discovered on Earth are microfossils from 600 meters below the Agnes gold mine of South Africa, which are __________ years old.
3.2 billion
Why is the higher fidelity of DNA proofreading and repair (compared to RNA) evolutionarily important?
A lower mutation rate allows for longer genes and more storage of information in the genome.
Which gas was most likely the LEAST abundant in early Earth's atmosphere?
O2
Which two scientists elaborated on Darwin's idea of the "warm little pond" and formulated the "prebiotic soup hypothesis" as the first hypothesis for the abiotic origin of life on Earth?
Oparin and Haldane
Eugene Koonin and his colleagues used the distributions of genes in the minimal gene sets of Haemophilus influenza and Mycoplasma genitalium to predict the distribution of a minimal gene set for Bacillus subtilis (Koonin 2003). What did they conclude from their comparison?
The predicted distribution of genes in B. subtilis was a close fit to the minimal gene sets observed.
In light of recent achievements in the field of genomics, would it be reasonable to expect that the use of comparative genomics might shed light on the extinct genomes of early life?
Comparative genomics and studies of bacteria with very small genomes shed light on a common ancestor, and researchers can estimate the minimal characteristics that a cell would need to operate as a living organism.
The origin of cell structures might be hypothesized to have involved a hypercycle, based on mutualism at the molecular level. Which of the following is correct regarding the hypercycle model?
Natural selection will favor a hypercycle that is enclosed in a membrane.
The first genetic material on Earth was most likely __________.
RNA
In order to understand the origin of life on Earth, evolutionary biologists collaborate with__________.
chemists, geologists, atmospheric scientists all of the answer options are correct
Which of the following molecules involved in membrane structure was likely favored by natural selection in the evolution of early cells?
fatty acids
All of the following are true regarding Sol Spiegelman's experiment on the origins of life, except that __________.
there was no selection for any of the variations in length
What do we know about horizontal gene transfer (HGT) in the evolution of early life?
HGT was probably a powerful force during early cell evolution, leading to complex cellular organisms.
Which of the following statements about LUCA is NOT correct? -it refers to a single, ancestral organism. -It represents a base to the tree of life. -The acronym stands for "last universal common ancestor." -It represents a phylogenetic event horizon.
-it refers to a single, ancestral organism.
Itay Budin and Jack Szostak sought to understand how cell membranes composed of single-chain lipid molecules could possibly evolve to the more complex phospholipids seen in modern cell membranes (Budin and Szostak 2009). Which statement best summarizes their results?
Adding a small fraction of phospholipid molecules resulted in vesicles with higher phospholipid content; these cells tended to grow in size conferring a selective advantage. EXPLANATION: Adding just a few phospholipid molecules slowed down the rate of movement of fatty acid molecules out of the membrane. This resulted in vesicles with the higher phospholipid content tending to grow in size, rather than shrink. Cells with a greater ability to synthesize phospholipids outcompeted other cells, leading to the evolution of membranes dominated by phospholipids. Read the subsection titled
Why did the role of horizontal gene transfer ultimately become diminished over evolutionary time?
As cells became more complicated, they also became more integrated, less modular and less likely to take up new genes by horizontal gene transfer.
The human parasite Mycoplasma genitalium, with one of the smallest genomes of any organism that can be grown in a laboratory, as well as Chlamydia trachomatis, an obligate intracellular parasite, are examples of the types of organisms that functional genomics researchers have focused on. What is the main purpose of the study of such genomes?
By studying such genomes, researchers try to discover the basic and essential cellular functions of early life.
Which of the following statements regarding the benefit of making the switch from an RNA- to a DNA-based genetic system during the evolution of life is correct?
DNA is a more stable molecule because deoxyribose is less reactive than is ribose.
In 1977, Sidney Fox tried a different approach to testing the prebiotic synthesis of biological molecules. He mixed a number of different amino acids together at a high temperature (120°C) in an environment lacking water. When he subsequently placed the mixture into water to investigate what the amino acids would form, what happened next?
He found some peptide-like structures, but the bonds between the amino acids were weak and unstable.
Which of the following statements about the Lincoln and Joyce experiment on self-replicating ribozymes is most likely correct?
The self-replicating ribozymes that had more efficient catalytic activities would soon began to dominate their populations. FEEDBACK: After establishing that the template RNAs in this system could self-replicate, Lincoln and Joyce conducted an experiment in which several variant template molecules were supplied with variant substrate molecules (Lincoln and Joyce 2009). This variation was heritable, and different templates replicated at different rates. They also found evidence for selection, because the self-replicating ribozymes that had more efficient catalytic activities soon began to dominate their populations of self-replicating ribozymes.
Stanley Miller and Harold Urey developed and conducted experimental tests for a "prebiotic soup" model of the origin of life, which had been proposed a few decades earlier by Aleksandr Oparin and J.B.S. Haldane. What did Miller and Urey show could be synthesized abiotically?
amino acids
