Because Precambrian rocks are in short supply, hence fossil evidence is harder to find.they only discovers sections of some Precambrian rocks there were no bones or shells to be permineralized.
According to Darwin, evolution occurs because of natural selection.
Septum <span>the left and right sides of the heart are separated by a structure called the interventricular septum. The right side of the heart is oxygen poor, and the left side is oxygen rich. </span>
Answer:
The correct answer is option 3, that is, blastomeres.
Explanation:
A kind of cell formed by cleavage of the zygote post-fertilization is called a blastomere, it is an important constituent of blastula formation. The formation of blastomere starts instantaneously post-fertilization and is carried through the initial week of the development of embryo. The division of zygote after fertilization is regarded as the first mitotic outcome of the fertilized oocyte. These mitotic divisions take place spontaneously and lead to a grouping of cells known as blastomeres.