An organism that uses CO2: as its carbon source is a:
Autotroph
Heterotroph
Parasite
The Correct Answer is A
A. Autotroph: Autotrophs are organisms that use carbon dioxide (CO₂) as their primary carbon source, converting it into organic molecules through processes like photosynthesis or chemosynthesis. They are capable of synthesizing all the carbon compounds they need for growth, making them independent of other organisms for carbon.
B. Heterotroph: Heterotrophs obtain carbon by consuming organic compounds produced by other organisms. They cannot fix CO₂ directly and rely on autotrophs or other heterotrophs for their carbon supply, which is why they are considered consumers rather than primary producers.
C. Parasite: Parasites are organisms that live on or within a host organism, deriving nutrients at the host’s expense. While many parasites are heterotrophic, being parasitic describes their lifestyle rather than their carbon source.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Lead: Lead is a heavy metal that has historical use in paints and plumbing but has limited antimicrobial properties. While toxic to humans and microbes at high concentrations, it is not commonly used as an effective antimicrobial agent in commercial products today due to safety concerns and poor efficacy compared with modern agents.
B. Carbohydrate: Carbohydrates serve primarily as nutrients and energy sources for organisms. They do not possess intrinsic antimicrobial properties and therefore are ineffective in killing microorganisms in commercial products.
C. Bacteriostatic: Bacteriostatic chemicals inhibit the growth and reproduction of microorganisms but do not directly kill them. These agents rely on the host immune system to eliminate the inhibited microbes. While useful, bacteriostatic agents are generally less immediately effective than bactericidal compounds when rapid microbial killing is desired.
D. Bactericidal: Bactericidal chemicals actively kill microorganisms by disrupting essential cellular structures or metabolic processes, such as the cell wall, cell membrane, or protein synthesis. Commercial products containing bactericidal agents, such as bleach, alcohol, and phenolic compounds, are more effective at eliminating microbial populations quickly and reducing the risk of infection.
Correct Answer is B
Explanation
A microorganism that is not motile and has stopped metabolizing is not necessarily dead. Some microorganisms can enter a dormant or quiescent state under adverse conditions, such as nutrient deprivation, extreme temperatures, or exposure to antimicrobial agents. In this state, metabolic activity and motility may temporarily cease, but the organism remains viable and capable of resuming growth and reproduction when favorable conditions return. True microbial death is defined as the irreversible loss of the ability to reproduce under optimal conditions, regardless of temporary changes in metabolism or motility. Therefore, absence of movement or metabolic activity alone does not confirm death.
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