There are many human activities that could contribute significantly to the creation of dead zones, and here are some of them:
1. the use of chemical fertilizers
2. urban land use
3. coastal littering, as well as runoff from sewage
4. use of harmful phosphates in detergents
Dead zones are places in waters on Earth where there is so little oxygen left due to pollution that marine life cannot survive there.
The three primary germ layers (called the ectoderm, mesoderm, and endoderm) are the primary layers of cells in the embryo from which all tissues and organs develop. Human pluripotent stem cells are also known as human embryonic stem cells.
<span>The geologic time scale is divided into periods, which are then divided into epochs, which are further divided into ages. For example, the time of the dinosaurs lasted 3 periods (Triassic, Jurassic, Cretaceous), each period had 3 epochs (late, early, middle), and each age fit into one of those. Many epochs have more than 1 age associated with them.
As for the basis for differentiating the eras, I'm not so sure. The only one I can say for sure is the end of the Cretaceous, which is when the dinosaurs suddenly became extinct due to a meteor impact. I think the divisions are based on significant, global-scale events that changed the world.
Sorry its so long but that the answer i think >:) ur welcome
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Answer: During the Cambrian Explosion of Animal Life
