Meiosis occurs in a series of different phases and creates genetically unique reproductive cells. The steps of meiosis are shown. Which process helps make meiotic cells genetically different and occurs during prophase I, but not during prophase II?

Crossing-over

Explanation:

Meiosis is a kind of cell division that occurs only in sexually-reproducing organisms. It is the process by which they produce gametes. Meiosis is that division in which the number of chromosomes in the resulting cells are reduced by half. Due to this reason, meiosis occurs in a two step division process viz: Meiosis I and II.

Meiosis produces genetically different reproductive cells. This is as a result of a phenomenon unique to only meiosis called CROSSING-OVER. Crossing-over is a process whereby non-sister chromatids of homologous chromosomes exchange a segment of their genetic material. It occurs only in Prophase 1 of meiosis where the TETRAD structure is formed. This exchange of genetic material causes a recombination of DNA in the resulting cell (gamete).

Crossing-over only occurs between non-sister chromatids of homologous chromosomes, hence, it can only occur in Prophase 1. Prophase II involves sister chromatids.

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.