1. Samples of a microbial colony obtained from the natural environment are not pure culture. They are mixed cultures because the environment consists of an array of microorganisms and not one specific organism. A sample obtained from the natural environment such as water or soil may contain several species of microbes that need to be further isolated to obtain a pure culture.
2. Isolation streak plate technique involves the dilution of the sample several folds and then streaking a small amount using a sterile inoculation loop on an agar plate in a zig-zag manner. This is done to obtain a pure culture of bacteria from a mixed population by separating the microprocessor. When the sample is diluted into a small concentration and is streaked onto agar placed, widely spaced, discrete colonies of bacteria can be observed. These isolated colonies can be further cultured to obtain pure cultures by picking and re-streaking them on fresh agar plates.
3. A microbial colony is considered a pure culture because it consists of single species. A single species of bacteria cluster and form an isolated colony on an agar plate which can be further plated on fresh medium.
3-1 - If your agar plate shows discrete uncluttered colonies then you have obtained an isolated colony. The following picture might help you to understand.
3-2. If you subculture isolated microbes into a sterile nutrient broth without any contamination, it will still be considered pure culture because it is single isolated species in a sterile aseptic environment of the nutrient broth.
3.3. A pure culture can become a mixed culture due to contamination. This could be caused by airborne bacteria if your conditions are not aseptic. Contamination is possible if the work area is not clean and sterile or if the glassware is not sterile. The contamination can transform your pure culture into a mixed culture and is hence problematic. So, it is very important to maintain a sterile and aseptic environment, glassware, and instruments.
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Answer:
Her sample is not representative of college students as a whole
Explanation:
Lucy just distributed the survey in three of her classes and this is not encompassing enough hence cannot be used to draw a conclusion on the population. She could have gone across different sections of students in the college and make the selection such that every part is duely represented, after which she can conduct her survey.
Answer:
<h3>The Brown v Board of Education case addresses whether public institutions can legally be divided by race.
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Explanation:
- The Brown v School of Education was a landmark case regarding public school segregation on the basis of race.
- Thurgood Marshall was the chief attorney for the plaintiffs in Brown v. Board of Education. The plaintiff attorney ruled out that segregation policy violated the provisions of the Fourteenth Amendment of the Constitution.
- The case won an unanimous verdict against school segregation.
- After the case was won, the Supreme Court outlawed the practice of segregation in any public institutions.
Answer:
Key Takeaways
Explanation:
Market economies utilize private ownership of the means of production and voluntary exchanges/contracts. In a command economy, governments own the factors of production such as land, capital, and resources. In reality, all economies blend aspects of the two.
Answer:
They easily traveled over water
Explanation:
