Your lab manual says that the nutrient agar control plate in this experiment, is "a comparison for growth quality." Explain why the results on the nutrient agar plate are necessary to justify your conclusions about the mannitol salt agar plate\.\*

Nutrient agar lets us know about the presence/absence of any kind of bacteria.

Mannitol salt agar let us know about the presence/absence of osmotolerant bacteria.

The difference between them lets us know which bacteria are osmotolerant and which ones are not.

Explanation:

The mannitol salt agar is useful to identify organisms with specific traits. It is a selective medium that only allows the growth of osmotolerant cells. It is used to identify bacteria such as Staphylococcus aureus.

The comparison between nutrient agar and mannitol salt agar is significant because it gives more information about the bacteria type. If no cell grows in these two mediums means that there are no bacteria at all. But if cells can grow in the nutrient agar and not in the mannitol salt agar, it means the growing bacteria are not tolerant to salty mediums. They are not osmotolerant.    

A comparison between the presence/absence of bacteria growing in each medium lets us know which species are osmotolerant and which ones are not.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.