Question

why only bacteria come first​

Answer 1

Hi buddy

Bacteria are unicellular organism from unicellular organism only all the organisms came so bacteria comes first

Answer 2

Answer:

Bacteria have been the very first organisms to live on Earth. They made their appearance 3 billion years ago in the waters of the first oceans. At first, there were only anaerobic heterotrophic bacteria (the primordial atmosphere was virtually oxygen-free). The first autotrophic bacteria, very similar to the current cyanobacteria, appeared approximately 2 billion years ago. Photosynthesis occurred in these organisms and this is how the atmosphere was enriched with precious oxygen. Cyanobacteria or blue algae made the primitive atmosphere breathable and allowed life to colonise the lands above sea level.

Man has just recently become aware of the existence of bacteria because they were too small to be observed or studied before the microscope was invented.

The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. Although bacterial fossils exist, such as stromatolites, their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species. However, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage.The most recent common ancestor of bacteria and archaea was probably a hyperthermophile that lived about 2.5 billion–3.2 billion years ago.

Bacteria were also involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea.This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya (sometimes in highly reduced form, e.g. in ancient "amitochondrial" protozoa). Later, some eukaryotes that already contained mitochondria also engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants.This is known as primary endosymbiosis.

In July 2018, scientists reported that the earliest life on land may have been bacteria living on land 3.22 billion years ago.