If eras are marked by major changes in life forms, what distinguishes one period from the next

Answer;

-Periodic large-scale mass extinctions

If eras are marked by major changes in life forms, periodic large-scale mass extinctions distinguishes one period from the next.

Explanation;

The geological time scale is that the history of the planet counteracted into spans of your time marked by varied events. There are alternative markers, just like the forms of species and the way they evolved, that distinguish just one occasion from another on the geological time scale.

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explanation:

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!