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.
A decrease in the population of bears
Answer:
At least 17 PCR cycles or 16 PCR cycles
Explanation:
As we know -
In one chain of heating and cooling of polymerase chain reaction (PCR), the strands of DNA gets doubled.
The general mathematical representation of this is

where "n" is the number of PCR cycles.
It is given that DNA strands to be produced is 16 times the original quantity of DNA.
So the PCR cycle must be carried out at least 17 times in order to have DNA strand not less than 16 times the original quantity of DNA
Answer:
The correct answer is - tend to lose water by osmosis since their internal salt concentration is lower than that of seawater.
Explanation:
In freshwater fishes, the body of fishes has a higher salt concentration inside their body than the surrounding water, water enters through the osmosis process. Without any active regulation of this process, fishes would swell and get bigger and bigger. They have specialized cells called chloride cells in gills to take ions from water as they do not have kidneys.
In contrast, the marine fishes have a lower salt concentration in their body than surrounding water of sea or ocean and they lose water continuously and to compensate for this they need to drink water regularly.