Archaeplastids, which include red and green algae and land plants, are thought to have descended from a heterotrophic protist that engulfed a(n)
answer
cyanobacterium
Structural and molecular biological evidence supports the idea that endosymbiotic cyanobacteria gave rise to the chloroplasts found in red and green algae and land plants.
question
Which of the following statements supports the hypothesis of an endosymbiotic origin of mitochondria?
answer
Each mitochondrion has its own DNA molecule.
The fact that mitochondria have their own DNA provides strong support for the hypothesis of an endosymbiotic origin of mitochondria.
question
Carl Woese and collaborators identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?
answer
genetic characteristics such as ribosomal RNA sequences
question
Why has the kingdom Protista been abandoned?
answer
The kingdom Protista is polyphyletic.
Some protists are more closely related to plants, animals, or fungi than they are to other protists.
Recognizing that the kingdom Protista as originally defined was polyphyletic and that some protists are more closely related to other eukaryotes than to each other, scientists have abandoned the kingdom Protista and reorganized the entire domain Eukarya.
question
Which statement about the genomes of prokaryotes is correct?
answer
Prokaryotic genomes are composed of circular DNA.
question
In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population. Which term best describes what has occurred among the experimental populations of cells over this eight-year period?
answer
microevolution
question
Prokaryotic ribosomes differ from those present in eukaryotic cytosol. Because of this, which of the following is correct?
answer
Some antibiotics can block protein synthesis in bacteria without effects in the eukaryotic host.
question
If archaeans are more closely related to eukaryotes than to bacteria, then which of the following is a reasonable prediction?
answer
Archaean ribosomes should be larger than typical prokaryotic ribosomes.
question
In this eight-year experiment, 12 populations of E. coli, each begun from a single cell, were grown in low-glucose conditions for 20,000 generations. Each culture was introduced to fresh growth medium every 24 hours. Occasionally, samples were removed from the populations, and their fitness in low-glucose conditions was tested against that of members sampled from the ancestral (common ancestor) E. coli population.
If new genetic variation in the experimental populations arose solely by spontaneous mutations, then the most effective process for subsequently increasing the prevalence of the beneficial mutations in the population over the course of generations is
answer
binary fission.
question
Which of the features below are found in all protist lineages?
answer
Mitochondria
Scientists used to think that some groups of protists lacked mitochondria, but they have since discovered that many of these protists have at least modified mitochondria. Read about the diplomonads and parabasalids.
question
Earth probably formed _____ years ago, and the first life evolved as early as _____ years ago.
answer
4.5 billion years ago ... 3.9 billion years ago
Because fossils of bacterial communities have been discovered that are 3.5 billion years old, it is reasonable to assume life originated around 3.9 billion years ago.
question
Chloramphenicol is an antibiotic that targets prokaryotic (70S) ribosomes, but not eukaryotic (80S) ribosomes. Which of these questions stems from this observation, plus an understanding of eukaryotic origins?
answer
If chloramphenicol inhibits prokaryotic ribosomes, should it not also inhibit mitochondrial ribosomes?
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Which group was not described in Woese's tree of life analysis?
answer
Prokarya was not one of the groups described in Woese's tree of life analysis.
question
What characteristics were used to classify organisms before Woese's tree of life analysis?
answer
Presence of a membrane-bound nucleus
Before the tree of life analysis, organisms were classified as prokaryotes if they lacked a membrane-bound nucleus or eukaryotes if they possessed a membrane-bound nucleus.
question
Which of the following statements about phylogenetic trees is true?
answer
A paraphyletic group consists of a common ancestor and some of its descendants.
This statement is true; the common characteristics of a paraphyletic group may have arisen from lateral gene transfer to some, but not all, lineages.
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True or false? Data showing that the Bacteria were the first lineage to diverge from the common ancestor of all living organisms suggest that the Archaea and Eukarya are more closely related to each other than they are to the Bacteria.
answer
true
question
Which molecule did Carl Woese study to produce his tree of life?
answer
Ribosomal RNA
Ribosomal RNA was the molecule used to produce Woese's phylogeny because it evolves slowly and is critical to the function of the ribosome, which serves the same function in all three domains in the tree of life.
question
What is lateral gene transfer?
answer
Physical transfer of a gene from a species in one lineage to a species in another lineage.
Lateral gene transfer is the physical transfer of a gene between distantly related lineages.
question
An ecological relationship between organisms of different species that are in direct contact can best be described as _____.
answer
symbiotic
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