The Precambrian time refers to the time 4.5 billion to 542 millions year ago. This period is characterized by having reduced atmosphere and included reduced compounds. Scientists believed that atmosphere at that time was devoid of free oxygen and CO2 was present in excess. Before the complex life evolved on the Earth, the Precambrian Earth's ocean contained dissolved carbon dioxide.
Answer:
This question lacks options, options are:
a) indirect
b) mosaic
c) determinative
d) regulative
e) direct.
The correct answer is d.
Explanation:
The egg (ovum) like the embryo during the first embryonic divisions, do not possess any sign of polarity. This development mechanism can be called regulative development(in contrast to the mosaic model) since the fate of the cells that originate is not fixed and can be modified during development. In regulative embryos, part of the embryo can be removed and the remaining cells can compensate for the loss and give a complete individual as the final product.The strongest evidence that continues to support this regulatory model is based on the plasticity or potential that mammalian cells possess before implantation. It is known that the blastomeres produced by the first divisions can be replaced with each other or even can be eliminated without apparently altering the embryonic development and therefore they are equivalent (without polarity).
the key element in the ecological concept of species is that individuals within a species can successfully interbreed and conceive healthy offspring
Answer:Sleep helps keep your heart healthy
A regular sleep pattern can help to lower the levels of stress and inflammation to your cardiovascular system, which in turn can reduce your chances of a heart condition.
Explanation:
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