A scientist collects a protist from a rotting log. He grows the protist in a petri dish that contains Escherichia coli bacteria; the protist engulfs the bacteria. For a while the protist multiplies as single cells. When the E. coli are all consumed, the
protists aggregate to form a clump that rises up to become a stalked structure with a globular head. What kind of protist does the scientist have?
A) a plasmodial slime mold
B) a cellular slime mold
C) a free-living amoeba
D) a water mold
Answer: B
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Which of the following can be used as vectors for cloning DNA fragments?
A. bacteriophages B. plasmids C. cosmids D. All of the choices are correct.
The first law of thermodynamics states that energy can be transformed from one state to another, but it cannot be created or destroyed. Taking this into consideration, what can be said about the energy transferred between levels in a trophic pyramid?
A. Some of the energy in a trophic level is converted to heat and is unavailable to the next level. B. All the energy is transferred between trophic levels because components that have no energy, that is, light, are used to create the energy in the chemical bonds of carbohydrates. C. All the energy necessary for a trophic level is transferred. Because there is less biomass at each trophic level, less energy needs to be transferred. D. Some of the energy is held in one trophic level, and only the energy needed to support the smaller biomass at a higher level is transferred. E. Organisms at higher trophic levels only consume the energy they need from lower trophic levels, leaving a "bank" of energy to support the higher level when food is scarce.
BAC stands for bacterial artificial chromosome
Indicate whether the statement is true or false
In the endosymbiosis theory, what benefit did the host cell receive from the symbiont?
a. protection b. immune response c. energy d. cytoskeletal elements