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ORIGIN AND SPREADING OF LIFE
ORIGIN AND SPREADING OF LIFE
All livning beings on Earth form so called BIOSPHERE (see chapter 4. Earth's Spheres). Biosphere has got strong influence to the surface of the planet all through the Earth's history. this is a reason enough to know basic facts about the EVOLUTION of life through time.
Sun and Solar system have been formed almost 5 billion years ago, Earth about 4.6 billion years ago, and Moon some hundred million years later.
Life appeared on Earth 4.4-3.5 billion years ago, possibly at the interface between water and the atmosphere or near Volcanic vents in the deep sea. The earliest known fossils are marine photosynthetic EUBACTERIA. Indirect evidence suggests that primitive life consisted of water, enzymes, a semipermeable external membrane and some form of genes that were freely shuffled between cells.
Firts EUKARYOTES (cells with nuclei) evolved about half of Earth's history later - about 2 billion years ago.
BACTERIA followed 1 billion years ago, FUNGI 800 million years ago.
VERTEBRATES (animals with spine) and LAND PLANTS evolved about 450 million years ago, DINOSAURS 300 million, BIRDS 180 million, and first MAMMALS 160 million years ago.
EVOLUTION THROUGH TIME
EVOLUTION THROUGH TIME
Figure 8.1: Timeline Evolution of life (picture: Wikimedia Commons)
Evidence about ever changing plant and animal life species is perserved in the, often "petrified" remains - FOSSILS. One of our EarthCaches deals with plant fossils (EC09-Castle Hill Secrets), the other one with fossilized footprints of long extinct dinosaur forbears (EC15-Dinosaur footprints).
You can find out more at the Open University web site's Interactive Tree of Life
Slika 8.2: Poenostavljeno "Drevo življenja"(klikni sliko za povečavo ali na povezavi poglejte interaktivno verzijo);
vir: The Open University, www.open.edu/ Figure 8.2: Simplified "Tree of life"(Click picture to enlarge, or click link to see interactive version);original poster from: The Open University, www.open.edu;
vir: The Open University, www.open.edu/ Figure 8.2: Simplified "Tree of life"(Click picture to enlarge, or click link to see interactive version);original poster from: The Open University, www.open.edu;
ZAČETEK IN RAZCVET ŽIVLJENJA
ZAČETEK IN RAZCVET ŽIVLJENJA
Vsa živa bitja na Zemlji tvorijo takoimenovano BIOSFERO (glej poglavje 4. Zemljine sfere). Ker biosfera skozi celo zemeljsko zgodovino močno vpliva na površino planeta, je za poznavanje geologije skoraj nujno poznati tudi razvoj življenja skozi čas na Zemlji, ozrioma EVOLUCIJO.
Sonce in Sončni sistem sta nastala pred skoraj 5 milijardami let, Zemlja približno 4,6 milijarde let nazaj, Luna kakih sto milijonov let kasneje.
Začetki življenja na Zemlji segajo v obdobje od 4,4 do 3,5 milijarde let v preteklost. Verjetno je nastalo v prepletu (stiku) vode in ozračja ali pri globokomorskih vulkanskih odduhih. Najstarejši znani fosili so morske fotosintetične EVBAKTERIJE. Posredni dokazi kažejo, da so primitivne življenjske oblike združevale vodo, encime, polprepustne zunanje ovojnice in nekakšne oblike genov, ki so prosto prehajali med celicami.
Prvi EVKARIOTI (celice s celičnimi jedri) so se razvili približno pol Zemeljske zgodovine kasneje - pred približno dvema milijardama let.
Sledile so BAKTERIJE, pred 1 milijardo leti, GLIVE pred 800 milijoni let.
VRETENČARJI (živali s hrbtenico) in KOPENSKE RASTLINE so se razvile približno pred 450 milijoni, DINOZAVRI pred 300 milijoni, PTICE pred 180 milijoni in SESALCI pred 160 milijoni let.
RAZVOJ ŽIVLJENJA SKOZI ČAS
RAZVOJ ŽIVLJENJA SKOZI ČAS
Slika 8.1: Časovni trak evolucije na Zemlji (slika: Wikimedia Commons, slovenski prevod napisov: Vane)
O spreminjanju in razvoju rastlinskih in živalskih vrst danes pričajo tudi številni, pogosto okamneli, ostanki - FOSILI. Z rastlinskimi fosili se ukvarja naš geološki zaklad EC09 - Skrivnosti Grajskega hriba, z odtisi davno preminulih prednikov dinozavrov pa EC15 - Dinozavnove stopinje.
Več lahko izveste na spletni strani Open University s pomočjo interaktivnega "Drevesa življenja" Interactive Tree of Life
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