To understand the development of organisms on earth, we must look into the geological strata and rocks. These hold a window into the history of the world and life on it. By observing the fossil record of different organisms we can see how they gradually evolved into existence. I will now list from oldest to newest, the order in which organisms appear in each layer of strata. These are fossil records from 3.8billion years ago to the current day.

Lets start off at the Eoarchean era where the oldest Simple single-celled life are observed (bacteria and archaea) and the oldest probable microfossils are observed.

From the Paleoarchean Era where the first known oxygen-producing bacteria and Oldest definitive microfossils are observed along with the first formations of cratons which are caused by biofilms of microorganisms.

From the Mesoarchean Era where the first First stromatolites (colonial cyanobacteria) and the Oldest macrofossils are observed. From the Statherian Period the first complex single-celled life: protists with nuclei are Observed.

from the Tonian Period traces of fossils of simple multi-celled eukaryotes and the first radiation of dinoflagellate-like acritarchs are observed.

From the Ediacaran Period we find Good fossils of the first multicelled animals, Ediacaran biota Simple trace fossils of possible worm-like Trichophycus, First sponges and trilobitomorphs appear, Enigmatic forms include many soft-jellied creatures shaped like bags, disks, or quilts (like Dickinsonia).

The next ones are all through the large part of the Cambrian Explosion Period from early to furongian: Numerous fossils; most modern animal phyla appear. First chordates appear, along with a number of extinct, problematic phyla. Reef-building Archaeocyatha abundant; then vanish. Trilobites, priapulid worms, sponges, inarticulate brachiopods (unhinged lampshells) and many other animals. Anomalocarids, Prokaryotes, protists, fungi and algae. From the Ordovician Period we observe that Invertebrates diversified into many new types (e.g., long straight-shelled cephalopods). Early corals, articulate brachiopods (Orthida, Strophomenida, etc.), bivalves, nautiloids, trilobites, ostracods, bryozoa, many types of echinoderms (crinoids, cystoids, starfish, etc.), branched graptolites, and other taxa all common. Conodonts (early planktonic vertebrates) appear. First green plants and fungi on land.

From the Silurian Period the first Vascular plants are found (the rhyniophytes and their relatives), first millipedes and arthropleurids. First jawed fishes, as well as many armoured jawless fish,. large Sea-scorpions, Tabulate and rugose corals, brachiopods (Pentamerida, Rhynchonellida) crinoids, Trilobites. mollusks, Graptolites.

From the Devonian Period we observe that the first clubmosses, horsetails and ferns appear, as do the first seed-bearing plants (progymnosperms), , crinoids, Goniatite ammonoids, squid-like coleoids, jawed fishes (placoderms, lobe-finned and ray-finned fish, and early sharks) First amphibians though still aquatic. from the Carboniferous Mississippian Period we observe Large primitive trees, first land vertebrates, and amphibious sea-scorpions live amid coal-forming coastal swamps. Lobe-finned rhizodonts, sharks, echinoderms (especially crinoids and blastoids) Corals, bryozoa, goniatites and brachiopods (Productida, Spiriferida, etc.) trilobites and nautiloids, although those two decline, Testate forams.

From the Carboniferous Pennsylvania Period we observe Winged insects (esp. Protodonata and Palaeodictyoptera) . Amphibians, first reptiles, Goniatites, brachiopods, bryozoa, bivalves, and corals.

From the Permian Period we observe mosses, Beetles, flies productid and spiriferid brachiopods, bivalves forams, and ammonoids forams, and ammonoids, From the Triassic period we observe Archosaurs, Ichthyosaurs, nothosaurs, pterosaurs, Cynodonts, first mammals and crocodilia appear. Dicroidium flora, temnospondyl amphibians. Ceratitic ammonoids extremely common. Modern corals and teleost fish, many modern insect clades.

From the Jurassic Period we observe, Gymnosperms (especially conifers, Bennettitales and cycads) and ferns common. Many types of dinosaurs, such as sauropods, carnosaurs, and stegosaurs, the first birds and lizards. Ichthyosaurs and plesiosaurs. Bivalves, Ammonites and belemnites abundant. Sea urchins are very common, along with crinoids, starfish, sponges, and terebratulid and rhynchonellid brachiopods.

From the Cretaceous Period we observe Flowering plants, modern insects, More modern teleost fish, . Ammonites, belemnites, rudist bivalves, echinoids and sponges, Tyrannosaurs, Titanosaurs, duck bills, and horned dinosaurs Eusuchias, mosasaurs and modern sharks, Primitive birds which were gradually replacing pterosaurs. Monotremes, marsupials and placental mammals appear.

From the Paleogene Period we observe Rapid evolution and diversification of fauna, especially mammals and dispersal of modern types of flowering plants, Archaic mammals (e.g. Creodonts, Condylarths, Uintatheres, etc), Primitive whales, First grasses. From the Neogene Period we observe Modern mammal and bird families, Horses and mastodons, Grasses, First apes appear.

From the Quaternary Period (our period) we observe the rise of human civilization and we are discovering new life everyday to add to the diversity of evolution. Amazing isn't it?

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