MBIO 3401
MBIO 3401 Exam 3 Study Questions and
Answers 2025
What are the fundamental conditions require to sustain life? -Correct Answer
✔1.essential elements
2.continual source of energy (sun)
3.temperature range permitting liquid water
What is another name for "evidence of early life?" -Correct Answer ✔biosignature
what are three biosignatures -Correct Answer ✔1. isotope ratios
2. stromatolites
3. microfossils
What are the models for the first cells? -Correct Answer ✔1. prebiotic soup
2. early oxidation-reduction reactions
3. RNA world
What is a stromatolite? -Correct Answer ✔layers deposits (cyanobacteria) formed by the
growth of blue-green algae
What is prebiotic soup? -Correct Answer ✔blend of gases forming a broth when
exposed to light or head then forming the building blocks of life
How did organisms diverge from each other? -Correct Answer ✔1. random mutations
2. natural selection
3. reductive (degenerative) evolution
What is a molecular clock? -Correct Answer ✔method used by researchers that uses
mutation rates in DNA to estimate the length of time that two species have been
evolving independently
what is the most widely used molecular clock? -Correct Answer ✔The gene encoding
the small subunit rRNA (SSU rRNA)
what does DNA sequence alignment compare? -Correct Answer ✔the similarity and
identity of amino acids and DNA
what are the three domains of life? -Correct Answer ✔Bacteria, Archaea, Eukarya
What is the criteria for a working definition of a species -Correct Answer ✔1. SSU rRNA
greater/equal to 95%
2. avg. nucleotide identity of ortholog genes greater/equal to 95%
MBIO 3401
, MBIO 3401
3. shared ecotype between organisms greater/equal to 95%
What is vertical gene transfer? -Correct Answer ✔transmission of genes from parent to
offspring
What is horizontal gene transfer? -Correct Answer ✔acquisition of genes from another
organism in the same generation
What is symbiosis? -Correct Answer ✔the intimate association of two species
What is mutualism? -Correct Answer ✔both organisms benefit
What is parasitism? -Correct Answer ✔One organism benefits and the other is harmed
When does endosymbiosis occur? -Correct Answer ✔when one partner grows within
the body of another
Streptomyces -Correct Answer ✔-linear chromosome with telomeres
-major antibiotic producer
-looks like mold but is bacteria
what is an example of actinomycetes? -Correct Answer ✔streptomycin
Mycobacterium -Correct Answer ✔-thick cell walls containing mycolic acids
(mycomembrane)
-appears gram-negative because of tightly packed mycolic acid cell wall
what are some examples of mycobacterium -Correct Answer ✔M. Tuberculosis, M.
Leprae
What are the gram positive bacteria? -Correct Answer ✔Actinomycetes and
Nonmycelial actinobacteria
Proteobacteria -Correct Answer ✔-triple layered cell envelope
-DIVERSE METABOLISM
what is photoheterotropy? -Correct Answer ✔able to switch metabolic pathways
Alphaproteobacteria -Correct Answer ✔-Oligotroph- capable of living in low-nutrient
environments such as deep oceanic sediments, glacial ice, or deep undersurface soil
what are the endosymbionts of alphaproteobacteria -Correct Answer ✔-nitrogen fixers
-rhizobium
-sinorhizobium
MBIO 3401
MBIO 3401 Exam 3 Study Questions and
Answers 2025
What are the fundamental conditions require to sustain life? -Correct Answer
✔1.essential elements
2.continual source of energy (sun)
3.temperature range permitting liquid water
What is another name for "evidence of early life?" -Correct Answer ✔biosignature
what are three biosignatures -Correct Answer ✔1. isotope ratios
2. stromatolites
3. microfossils
What are the models for the first cells? -Correct Answer ✔1. prebiotic soup
2. early oxidation-reduction reactions
3. RNA world
What is a stromatolite? -Correct Answer ✔layers deposits (cyanobacteria) formed by the
growth of blue-green algae
What is prebiotic soup? -Correct Answer ✔blend of gases forming a broth when
exposed to light or head then forming the building blocks of life
How did organisms diverge from each other? -Correct Answer ✔1. random mutations
2. natural selection
3. reductive (degenerative) evolution
What is a molecular clock? -Correct Answer ✔method used by researchers that uses
mutation rates in DNA to estimate the length of time that two species have been
evolving independently
what is the most widely used molecular clock? -Correct Answer ✔The gene encoding
the small subunit rRNA (SSU rRNA)
what does DNA sequence alignment compare? -Correct Answer ✔the similarity and
identity of amino acids and DNA
what are the three domains of life? -Correct Answer ✔Bacteria, Archaea, Eukarya
What is the criteria for a working definition of a species -Correct Answer ✔1. SSU rRNA
greater/equal to 95%
2. avg. nucleotide identity of ortholog genes greater/equal to 95%
MBIO 3401
, MBIO 3401
3. shared ecotype between organisms greater/equal to 95%
What is vertical gene transfer? -Correct Answer ✔transmission of genes from parent to
offspring
What is horizontal gene transfer? -Correct Answer ✔acquisition of genes from another
organism in the same generation
What is symbiosis? -Correct Answer ✔the intimate association of two species
What is mutualism? -Correct Answer ✔both organisms benefit
What is parasitism? -Correct Answer ✔One organism benefits and the other is harmed
When does endosymbiosis occur? -Correct Answer ✔when one partner grows within
the body of another
Streptomyces -Correct Answer ✔-linear chromosome with telomeres
-major antibiotic producer
-looks like mold but is bacteria
what is an example of actinomycetes? -Correct Answer ✔streptomycin
Mycobacterium -Correct Answer ✔-thick cell walls containing mycolic acids
(mycomembrane)
-appears gram-negative because of tightly packed mycolic acid cell wall
what are some examples of mycobacterium -Correct Answer ✔M. Tuberculosis, M.
Leprae
What are the gram positive bacteria? -Correct Answer ✔Actinomycetes and
Nonmycelial actinobacteria
Proteobacteria -Correct Answer ✔-triple layered cell envelope
-DIVERSE METABOLISM
what is photoheterotropy? -Correct Answer ✔able to switch metabolic pathways
Alphaproteobacteria -Correct Answer ✔-Oligotroph- capable of living in low-nutrient
environments such as deep oceanic sediments, glacial ice, or deep undersurface soil
what are the endosymbionts of alphaproteobacteria -Correct Answer ✔-nitrogen fixers
-rhizobium
-sinorhizobium
MBIO 3401
