History of Life on Earth PDF

History of Life Composed of cells Order and complexity Respond to their environment Reproduce and develop Obtain and use energy Maintain internal balance (homeostasis) Adapt over generations (evolution) DNA is the Genetic Material of All Living Things Deoxyribonucleic acid (DNA) is a molecule that c...

History of Life Composed of cells Order and complexity Respond to their environment Reproduce and develop Obtain and use energy Maintain internal balance (homeostasis) Adapt over generations (evolution) DNA is the Genetic Material of All Living Things Deoxyribonucleic acid (DNA) is a molecule that contains a molecular sequence that encodes an organism’s genetic information. Continuity of life depends on faithful copying of DNA into progeny cells and offspring Different types of organisms store their DNA in different ways Cell Theory: Cells are the basic unit of life All living things are composed of at least one cell and all cells come from preexisting cells. Single Cellular Organisms: made up of only one cell Multicellular Organisms: made up of many cells Single cellular organisms can cooperate in communities Life is organized into three domains 1. Bacteria 2. Archaea 3. Eukarya (Plants, Animals, Fungi, and Protists) Which Domains of Life are sister group LUCA: The Last Universal Common Ancestor The most recent organisms that all living things alive today directly descended from. Likely had Prokaryotic feature: Autotrophic Anaerobic 2 The Great Age of the Earth Earth estimated to be 4.568 billion years old based on measurements of Rubidium-87 isotope decay Zircon crystal from early earth dated to 4.4 billion years old (BYA) History of Life on Earth EONS ERAS PERIODS EPOCHS Eons of Earth’s History Hadean (4.6 - 4 BYA) Archean (4 -2.5 BYA) Proterozoic (2.5 BYA – 540 MYA) Phanerozoic (540 MYA – Present) Eras of the Phanerozoic Eon Paleozoic (540 – 360 MYA) Mesozoic (360 – 65 MYA) Cenozoic (65 MYA – Present) Origins of Life on Earth Life formed ~3.5 billion years ago in the Archean Eon The first life on earth was prokaryotic Life arose spontaneously as a single celled organism Ocean’s edge, hydrothermal deep-sea vents, or possibly elsewhere Dawn of Photosynthesis Cyanobacteria arose 3.4 BYA - First known photosynthetic organisms 3 BYA: Oxygen Revolution - Created atmospheric oxygen in mass quantities, killed many anaerobic bacterial species First Eukaryotes Single celled Eukaryotes first arose about 2.5 billion years ago, likely through Life 2 Billion Years Ago All three domains of life now exist: Bacteria Archaea Eukarya Almost all life is single celled Many branches of life not yet formed No plants, animals, or fungi Early Multicellular Eukaryotes Evolved independently in different lineages Extant organisms provide clues about origin of multicellularity First multicellular fossil is 2.1 BYA The Cambrian Explosion Began 541 MYA Dramatic Animals diversification Marks beginning of Phanerozoic Eon The First Plants Plants evolved on land ~500 million years ago Animals move out of the oceans First animals fully adapted to land about 350-400 million years ago The Age of the Dinosaurs Mesozoic 240-65 MYA First birds, expansion of insects, first flowering plants in this era as well Emergence of Mammals First mammals evolved during the age of the dinosaurs, about 200 MYA Diversification of mammals Mammals diversified after dinosaurs went extinct (~65 mya) Whales, bats, and primates all emerged around 50 mya Human Evolution Homo sapiens first appeared 300,000 years ago in Africa Human Evolution: Out of Africa Homo sapiens began to migrate out of Africa 100,000 years ago and reached the America’s somewhere between 15,000 and 20,000 years ago This migration can be observed in the fossil record and in the DNA sequences of living people today Fossils and Recent Human Relatives Denisovans are a species closely related to humans Fossil record includes mainly small finger bone fragments and a few teeth Full genome was sequenced Denisovans, Neanderthals, and Humans Three species lived at the same time Genetic evidence from modern humans indicate that these three species could produce hybrid offspring Mass Extinctions have Occurred Several Times 5 Mass Extinctions have occurred in the history of life Each killed 75-95% of all living things on earth The vast majority of all living things that have every existed are now extinct Adaptive Radiation Follows Extinction Events Adaptive radiation occurs when a single species rapidly diverges and speciates to fill many niches