exam 3 (practice questions) Flashcards by Ayesha Rashid

Which of the following statements supports the argument that viruses are nonliving?

they do not carry out metabolic processes

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Which of the following processes can viruses carry out?

they can use the host cell to copy themselves and make viral proteins

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what is the main structural difference between viruses with envelopes and viruses without envelopes?

Viruses with envelopes have a phospholipid membrane outside their capsid, whereas viruses without envelopes do not have a phospholipid membrane.

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The host range of a virus is determined by ________

the proteins on its surface and that of the host

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Which of the following events or characteristics accounts for someone who has had regular herpesvirus-mediated cold sores or genital sore flare-ups?

copies of the herpesvirus genome permanently maintained in host nuclei

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Which of the following characteristics is typical of the lytic cycle of a bacteriophage?

A large number of phages are released at a time.

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Which of the following statements accurately describes the lysogenic cycle of lambda (λ) phage?

The phage genome is integrated in the host chromosome where it is replicated along with the host genome.

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Which of the following characteristics correctly describes retroviruses?

They have a single-stranded RNA that acts as a template for DNA synthesis.

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What is the function of reverse transcriptase in retroviruses?

It uses viral RNA as a template for DNA synthesis.

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The virus genome and viral proteins are assembled into virus particles during which of the following parts of the reproductive cycle?

the lytic cycle only

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Which of the following viruses would most likely have reverse transcriptase inside them?

an RNA-based lysogenic virus

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Which of the following human diseases is caused by a virus that requires reverse
transcriptase to transcribe its genome inside the host cell?

AIDS

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why do RNA viruses appear to have higher rates of mutation?

replication of their genomes does not involve proofreading

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Effective antiviral drugs are usually associated with which of the following properties?

interference with viral replication

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Which of the following statements best reflects what we know about how the flu virus moves between species?

An animal such as a pig is infected with more than one virus, genetic recombination occurs,
the new virus mutates, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans.

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Why do scientists consider HIV to be an emerging virus?

HIV suddenly became apparent and widespread in the 1980s.

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A population of viruses with similar characteristics is called a ________

class

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Emerging viruses arise by

mutation of existing viruses
the spread of existing viruses to new host species
the spread of existing viruses more widely within their host species

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RNA viruses require their own supply of certain enzymes because

host cells lack enzymes that can replicate the viral genome.

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Eukaryotes that are not closely related and that do not share many anatomical similarities can
still be placed together on the same phylogenetic tree by comparing their ________.

homologous genes that are highly conserved

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Which statement represents the best explanation for the observation that the nuclear DNA of
wolves and domestic dogs has a very high degree of sequence homology? Dogs and wolves

share a very recent common ancestor

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The most important feature that permits a gene to act as a molecular clock is ________

a reliable average rate of mutation

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Molecular clocks are more reliable when ________

a significant proportion of mutations are not acted upon by natural selection

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Which of the following would, if it had acted upon a gene, prevent this gene from acting as a
reliable molecular clock?

natural selection

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Which eukaryotic kingdom includes members that are the result of endosymbioses that included an ancient aerobic bacterium and an ancient cyanobacterium?

plantae

What kind of evidence has recently made it necessary to assign the prokaryotes to either of two different domains, rather than assigning all prokaryotes to the same kingdom?

rRNA genes

In a comparison of birds and mammals, the condition of having four limbs is

a shared ancestral character

A bacterium's ability to survive in a human who is taking penicillin pulls may be due to the presence of ________

a gram-negative cell wall

Adherence to the intestinal lining by this bacterium is due to its possession of _______

fimbriae

In which feature should one be able to locate a complete chromosome of this bacterium?

nucleiod

Which of the following observations about flagella is accurate and is consistent with the scientific conclusion that the flagella from eukaryotes and bacteria evolved independently?

The protein structure and the mechanism of movement in eukaryotes flagella are different from those of bacteria flagella.

In a bacterium that possesses antibiotic resistance and the potential to persist through very adverse conditions, such as freezing, drying, or high temperatures, DNA should be located within, or be part of, which structures?

plasmids, nucleoid, and endospore

If the experimental population of E. coli lacks an F factor or F plasmid, and if bacteriophages are excluded from the bacterial cultures, then beneficial mutations might be transmitted horizontally to other E. coli cells via _______

transformation

heterotrophs and autotrophs differ in their

sources of carbon

While examining a rock surface, you have discovered an interesting new organism. Which of the following criteria will allow you to classify the organism as belonging to Bacteria but not Archaea or Eukarya?

Cell walls are made primarily of peptidoglycan

Which of the following describe all existing bacteria?

tiny, ubiquitous, metabolically diverse

You have found a new prokaryote. What line of evidence would support your hypothesis that the organism is a cyanobacterium?

It is able to form colonies and produce oxygen

Which of the following traits do archaeans and bacteria share?

lack of a nuclear envelope and presence of circular chromosome

Genetic variation in bacterial populations cannot result from

meiosis

Photoautotrophs use

light as an energy source and CO2 as a carbon source

The chloroplasts of land plants are thought to have been derived according to which evolutionary sequence?

cyanobacteria → green algae → land plants

A particular species of protist has obtained a chloroplast via secondary endosymbiosis. You know this because the chloroplasts ________

have three or four membranes

all protists are ________

eukaryotic

Trypanosome infections evade attacks by host immune systems through which of the following mechanisms?

production of new cell-surface proteins with a different molecular structure by each new generation

Many parasitic members of the excavates lack plastids and have highly reduced mitochondria. Which of the following statements explains these observations?

These parasites live in dark, low-oxygen conditions and therefore loss of genes for plastids and mitochondria did not result in lower fitness.

Prokaryotic and eukaryotic flagella _______

have different structures

When a mosquito infected with Plasmodium first bites a human, the Plasmodium _______

cells infect the human liver cells

Which two genera have members that can evade the human immune system by frequently changing their surface proteins?

Plasmodium and Trypanosoma

Dinoflagellates ________.

possess two flagella

Which of the following is characteristic of ciliates?

They are often multinucleate.

A porous test (shell) of calcium carbonate, through which pseudopodia protrude, is characteristic of ________

foraminiferans

A gelatinous seaweed that grows in shallow, cold water and undergoes heteromorphic alternation of generations is most probably what type of alga?

brown

A biologist discovers an alga that is marine, multicellular, and lives at a depth reached only by blue light. This alga is most likely a type of _______

red algae

Green algae differ from land plants in that many green algae ______

are unicellular

what similarities do green algae and plants in the same phylogenetic group share

chloroplast structure and pigment composition

Previously recognized similarities that seemed to connect slime molds and fungi are now considered to be _______

examples of convergent evolution

are diatoms producers

yes

Plastids that are surrounded by more than two membranes are evidence of

secondary endosymbiosis

Biologists think that endosymbiosis gave rise to mitochondria before plastids partly because

all eukaryotes have mitochondria (or their remnants), whereas many eukaryotes do not have plastids

In a life cycle with alternation of generations, multicellular haploid forms alternate with

multicellular diploid forms

When a mycelium infiltrates an unexploited source of dead organic matter, what are most likely to appear within the food source soon thereafter?

fungal enzymes

The adaptive advantage associated with the filamentous nature of fungal mycelia is primarily related to ________

an extensive surface area well suited for invasive growth and absorptive nutrition

At which stage of a basidiomycete's life cycle would reproduction be halted if an enzyme that prevented the fusion of hyphae was introduced?

plasmogamy

Deuteromycetes _______

are the group of fungi that have, at present, no known sexual stage

Plasmogamy can directly result in which of the following?

heterokaryotic cells or dikaryotic cells

In most fungi, karyogamy does not immediately follow plasmogamy, which consequently _______

results in heterokaryotic or dikaryotic cells

The multicellular condition of animals and fungi seems to have arisen _______

by convergent evolution

Which feature seen in chytrids supports the hypothesis that they diverged earliest in fungal evolution?

flagellated spores

Arrange the following in order from largest to smallest: ascocarp, ascus, ascospore, ascomycete

ascomycete, ascocarp, ascus, ascospore

The closest relatives of fungi are thought to be the

animals

The most important adaptive advantage associated with the filamentous nature of fungal mycelia is

an extensive surface area well suited for invasive growth and absorptive nutrition

Which of the following tests could you use to determine whether the developing organism is a protostome or a deuterostome? See whether the embryo _______

exhibits spiral cleavage or radial cleavage

In examining an unknown animal species during its embryonic development, how can you be sure what you are looking at is a protostome and not a deuterostome?

You see a mouth, but not an anus.

Among protostomes, which morphological trait has shown the most variation?

type of body cavity (coelom versus pseudocoelom versus no coelom)

Soon after the coelom begins to form, a researcher injects a dye into the coelom of a deuterostome embryo. Initially, the dye should be able to flow directly into the _______

archenteron

The most ancient branch point in animal phylogeny is the characteristic of having _______

true tissues or no tissues

One of the characteristics unique to animals is

gastrulation