A dichotomous key helps you identify unknown specimens based on their traits because there are only two options available per trait. Selecting one from the two options (usually contrasting characteristics) from each step leads to smaller and smaller groups until the option is reduced to single and unique trait of an organism.
Considering you need to identify an organism. So, on the top of they key is animal with options: (a) with red blood cells and (b) no red blood cells. The option you will select is no red blood cells and under option b, you’re given two choices again: (a) hard bodies and (b) soft bodies. You’ll select soft bodies, then two options again are given: (a) with shell and (b) without shell. The option you’ll select would be without shell, and so on.
Answer:
In acid-fast staining, carbon fuchsin is used as a primary stain which dissolves the mycolic acid present in the cell wall of <em>Mycobacterium smegmatis </em>and penetrates through it which results in staining <em>Mycobacterium</em> red.
Staphylococcus aureus cell wall does not contain mycolic acid so carbon fuchsin does not penetrate its cell wall, therefore, it becomes colorless after destaining with acid alcohol.
After destaining step methylene blue is added to stain non-acid-fast bacteria blue. So if I mistakenly forgot to use methylene blue during the procedure <em>Mycobacterium smegmatis</em> will appear red due to carbon fuchsin present in their cell wall and S<em>taphylococcus aureus</em> will appear colorless because it is destained.
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Answer:
The correct answer is - option B. They are small because they lack a nucleus.
Explanation:
Red blood cells or erythrocytes are specialized cell that produce in bone marrow and have specific role such as carrying oxygen from lungs to deliver it to the various organs and carry out carbon dioxide.
In mammals these cells lack cell organelles such as nucleus and mitochondria, a major factor that determined its smaller size. The size of RBC are move through narrow vessels throughout a organism because of its specific size and shape that provide it space for hemoglobin and allow to be flexible and bend to move through narrow vessels.
Thus, the correct answer is : option B. They are small because they lack a nucleus.
