The is a layer of the embryo, which will become the circulatory system, bones, muscles, excretory system, and reproductive syste

Answer;

Mesoderm

The mesoderm is a layer of the embryo, which will become the circulatory system, bones, muscles, excretory system, and reproductive system.

Explanation;

-The germ layers develop early in embryonic life, through the process of gastrulation. An inner layer, called endoderm, and an outer layer, called ectoderm and a middle layer called mesoderm.

-The embryonic endoderm develops into the interior linings of two tubes in the body, the digestive and respiratory tube. the lining of the follicles of the thyroid gland and the epithelial component of the thymus.

-Ectoderm develops into parts of the skin, the brain and the nervous system. Mesoderm gives rise to bones, muscles, the heart and circulatory system, and internal sex organs.

Mesoderm.

Explanation:

The development of the embryo undergoes through the several cleavage or division. The gastrula contains all the three layers- ectoderm, endoderm and the mesoderm.

The mesoderm layer is present between the ectoderm and endoderm layer. The mesoderm layer forms the future bones, muscles and reproductive system of the embryo. The circulatory system and excretory system is also derived from the mesoderm.

Thus, the correct answer is mesoderm.

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.