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    Timelines – Biodiversity

    Time PeriodEventDescription
    4.6 billion years agoFormation of EarthOur planet initially formed from dust and gas left over after the formation of the Sun.
    4 billion years agoAppearance of Life (Prokaryotes)The first forms of life were simple cells (prokaryotes), which lacked a nucleus or any other cell organelles. They primarily lived in the ocean.
    ~3.5 billion years agoPhotosynthesis BeginsSome of these early prokaryotic cells developed the ability to perform photosynthesis, which created oxygen as a byproduct.
    ~2.7 billion years agoOxygen AccumulationThe steady production of oxygen by photosynthesizing bacteria started to gradually change the Earth’s atmosphere.
    ~2 billion years agoEukaryotes EmergeMore complex cells (eukaryotes) emerged that contained organelles, including a nucleus.
    ~1.5 billion years agoMulticellular Life BeginsSome eukaryotes evolved into multicellular organisms.
    ~600 million years agoEdiacaran BiotaThe first large, complex multicellular organisms appeared.
    541 – 485.4 million years agoCambrian ExplosionThere was a rapid diversification and increase in the number and variety of animal species. Many of the major groups of animals that exist today first appeared during this time.
    ~360 million years agoPlants Colonize LandPlants developed adaptations that allowed them to survive and reproduce outside of water, leading to the colonization of land.
    350 – 300 million years agoInsects and Amphibians EmergeThe first insects and amphibians evolved, diversifying life on land further.
    ~252 million years agoPermian Mass ExtinctionThis was the Earth’s most catastrophic extinction event, with as much as 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct.
    230 – 66 million years agoAge of Dinosaurs (Mesozoic Era)Dinosaurs were the dominant terrestrial vertebrates. This era saw the diversification of birds, mammals, and flowering plants.
    ~66 million years agoK-T extinctionThe dinosaurs went extinct, possibly due to a large asteroid or comet impact. Mammals subsequently diversified.
    66 million years ago – presentAge of Mammals (Cenozoic Era)Mammals became the dominant land animals and human beings eventually appeared.