Earth and space science.
complete the sentences to explain how photosynthetic organisms changed our lives on earth.
the in the atmosphere that all living beings depend on was generated by cyanobacteria during the archaean and proterozoic eras. the presence of this substance is what makes possible on earth.

1.
a. carbon dioxide
b. oxygen
c. water vapor
d. nitrogen

2.
a. the water cycle
b. visibility
c. photosynthesis
d. combustion

1. Oxygen

2. Combustion

Explanation:

Cyanobacteria are known as the first photosynthetic organism on Earth. They used H2O instead of H2S to fix carbon dioxide into energy-rich molecules such as glucose. The process, therefore, produced a tremendous amount of oxygen (99% of total oxygen), which was then released from oceans to Earth's atmosphere.

We know that oxygen is an oxidizer that helps in burning (combustion). When the oxygen started accumulating in the atmosphere, oxidation of many compounds started occurring, e.g. iron oxidation. Water was already available at that time. Photosynthesis also existed because cyanobacteria produced oxygen through photosynthesis. Thus the presence of oxygen didn't influence photosynthesis. In fact, the presence of oxygen, due to oxidation processes, leads to the formation of complex life processes that we see today. Previously, earth atmosphere was mostly reduced because of very limited availability of other oxidizers.

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!