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UMass Amherst BIOLOGY 280 - Chapter 3B (2)

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Eukaryotic multicelluar lifeKey ConceptsThe dawn of animalsSearch for early animals can be controversialEdiacaran faunaEvolution of Ediacaran faunaSlide 7Chordates emerged during early CambrianKey ConceptsTransition from ocean to land a major event in evolutionFirst terrestrial plant and fungal lifeFirst terrestrial animal lifeFirst terrestrial vertebratesFamiliar forms of life did not emerge until recentlyEvolution of mammalsDiversification of mammalsOldest human fossils are ~200,000 years oldEvolution of other major lineagesKey Concepts1/12/13Eukaryotic multicelluar life •Earliest fossils of algae date to 1.6 bya–Red algae: 1.2 bya–Green algae: 750 mya Red algae fossil; 1.2 bya1/12/13Key Concepts•Transition to multicellular life began at least 2.1 billion years ago•Transition occurred multiple times independently1/12/13The dawn of animals•Early animal life resemble sponges–Oldest fossils 650 myo–Biomarkers also demonstrate existence of sponges during this time1/12/13Search for early animals can be controversialAnimal embryos or animal relatives?1/12/13Ediacaran fauna•Diverse and unique animals dominated the oceans from 575 – 535 mya–Many hard to place taxonomically1/12/13Evolution of Ediacaran fauna1/12/13Currently existing lineages recognizable during the early Cambrian Early Cambrian: 542 – 511 mya1/12/13Chordates emerged during early Cambrian1/12/13Key Concepts•Only a fraction of Ediacaran fauna share traits with existing lineages–Almost all extinct within 40 million years•Most existing lineages are found in the fossil record during the Cambrian period–Includes our own lineage, the chordates1/12/13Transition from ocean to land a major event in evolution•Prokaryotes colonized terrestrial environments first–Fossils date to 2.6 bya•Terrestrial animals, plants, and fungi, appeared much later1/12/13First terrestrial plant and fungal life•Oldest terrestrial plant fossils are 475 myo–Early plants resembled mosses and liverworts•Large forest ecosystems within 100 million years•Fungi appear ~ 400 myo–Associated with plants1/12/13First terrestrial animal life•Invertebrate trackways date to 480 mya–Probably relatives of insects and spiders–Not clear whether they lived on land permanently•Oldest fossil of fully terrestrial animal dates to 428 mya1/12/13First terrestrial vertebrates•Oldest trackways date to 390 mya•Oldest fossils of tetrapods date to 370 mya1/12/13Familiar forms of life did not emerge until recently•350 million years ago many currently existing lineages had yet to evolve–Teleost fish–Mammals–Birds–Flowering plants1/12/13Evolution of mammals•Mammals evolved from synapsids–Dominant vertebrates around 280 myo–First mammals emerged 150 mya1/12/13Diversification of mammals•Mammals diversified after dinosaurs went extinct (~65 mya)•Whales, bats, and primates all emerged around 50 mya1/12/13Oldest human fossils are ~200,000 years old1/12/13Evolution of other major lineages•Birds: ~150 mya–Descendants of dinosaurs•Flowering plants: ~132 mya–Grasses did not diversify until ~20 mya•Insects: emerged ~400 mya but most current lineages appear much later1/12/13Key Concepts•Many of the most diverse existing plant and animal lineages evolved relatively


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