Morphological distinction is one of the steps necessary for speciation to occur. What are the other two?

Genetic Separation / Geographic isolation

Explanation:

Morphological distinction (or phenotypic differentiation) can be defined as the diversification of a set of observable physical characteristics in a population, capable of differentiating certain species.

The genetic separation occurs when the division of a group of genes into two or more pools of genes separated over time and depending on several other situational factors.

Geographic isolation occurs due to the physical separation of subpopulations of a given species. The barriers that isolate these subpopulations can be, for example, a river that cuts through a plain, a valley that divides plateaus or a portion of the sea that separates islands and continents.

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.