where does our first normal flora come from
Gut flora In humans, a gut flora similar to an adult's is formed within one to two years of birth.[4] The gastrointestinal tract of a normal fetus is considered sterile, but microbial colonisation may occur in the fetus[41] and Lactobacillus and Bifidobacterium species were present in placental biopsies in one study.[42] During birth and rapidly thereafter, bacteria from the mother and the surrounding environment colonize the infant's gut.[4] As of 2013, it was unclear whether most of colonizing arise from the mother or not.[4] Infants born by caesarean section may also be exposed to their mothers' microflora, but the initial exposure is most likely to be from the surrounding environment such as the air, other infants, and the nursing staff, which serve as vectors for transfer.[41] During the first year of life, the composition of the gut flora is generally simple and it changes a great deal with time and is not the same across individuals.[4]
Multicellular organism Multicellularity has evolved independently at least 46 times in eukaryotes,[5][6] and also in some prokaryotes, like cyanobacteria, myxobacteria, actinomycetes, Magnetoglobus multicellularis or Methanosarcina. However, complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and land plants.[7] It evolved repeatedly for Chloroplastida (green algae and land plants), once or twice for animals, once for brown algae, three times in the fungi (chytrids, ascomycetes and basidiomycetes)[8] and perhaps several times for slime molds and red algae.[9] The first evidence of multicellularity is from cyanobacteria-like organisms that lived 3–3.5 billion years ago.[5] To reproduce, true multicellular organisms must solve the problem of regenerating a whole organism from germ cells (i.e. sperm and egg cells), an issue that is studied in evolutionary developmental biology. Animals have evolved a considerable diversity of cell types in a multicellular body (100–150 different cell types), compared with 10–20 in plants and fungi.[10]