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:
Crowd psychology is the broad study of how individual behavior is impacted when large crowds group together. This field of social science has progressed from the early examination of negative social groupings to the study of crowds in more socially proactive or emergency-type of environments.
The Great Wall of China........................
Answer: The US Army
Explanation: established on June 14, 1775 the US Army is the oldest branch of military. The army was essential to the US gaining independence because of the bravery of its soldiers and during the revolutionary war. Today more than two centuries later its members continue to define and protect the country and its people.
The correct answer to the assertion and reason is D. A is wrong but R is correct
<h3>What is an Assertion?</h3>
This refers to the statement that is meant to be proven by the use of a valid supporting detail.
Hence, we can see the given assertion that modern farming methods decrease the yield of production, there is a need to show a valid reason and this is not done, hence, we can conclude that option D is correct because A is wrong but R is correct.
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