Ch. 23 Cnidarian Diversity: Polyps QUESTIONS
The digestive track of the cnidarians consists only of a and a
(the coelenteron or )

The digestive tract of cnidarians consists of only of an orifice and a gastrovacular cavity (the coelenteron or blind gut)

Explanation:

Cnidarians are a group of simple organisms whose habitat is predominantly aquatic, such as sponges and jellyfish. They are diblastic organisms -as they are formed from two embryonic leaves, the ectoderm and gastroderm- and radial symmetry, with an incipient nervous system.

One of the main characteristics of Cnidarians is that they have a single orifice that communicates the exterior with the single cavity that forms the coelenteron, or gastrovascular cavity, which together form their digestive and excretory tracts. While in the cavity occur the processes of absorption of nutrients, distribution of them throughout the body and disposal of waste (vascular function), the single orifice acts as a mouth and anus.

satellites are frequently used to make observations of the orbit on earth

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.