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DEVELOPMENT OF THE BIOSPHERE: How did today's biosphere originate and…
DEVELOPMENT OF THE BIOSPHERE
:
How did today's biosphere originate and develop?
ORIGIN OF LIFE
Urey-Miller experiment
A shallow water setting as a result of lightning strike
An ocean floor setting due to hydrothermal activity
Life in the solar system
"Outer space theory"
suggests that organic molecules arrived to earth via comets and meteorite collisions during early Earth and evolved in more complex molecules on Earth.
Panspermia
suggests that life did not originate on Earth but came from somewhere else
Early life was microscopic and soft bodied
ORIGIN OF PHOTOSYNTHESIS
first life
first single-celled organisms appear in archaen rock around 3.5 bya
presence of oxygen is found around 2.5 bya
photosynthethic cyanobacteria are found around 2.5bya
chemosynthesis around 3bya
The archaea
(chemosynthesisers)
single-celled, anaerobic bacteria organisms which live in extreme environments (hydrothermal vents)
Photolysis (2.5bya)
splitting of water molecules by light into Oxygen & Hydrogen
chemical step in photosynthesis
"Great Oxygenation Event" world goes oxic
oxygen react with iron in the ocean create BIFs
Extinctions
"rusting of earth"
Stromatolites
structures of cyanobacteria in warm, shallow seas
ORIGIN OF MULTICELLULAR
LIFE
Endosymbiotic Hypothesis
as cells reproduced, they stayed together in "colonies" becoming colonial
colonies became specialised to a function, beginning tissues, organs, true muticellularity
Ediacaran Metazoans (600-550mya)
pre-cambrian
soft-bodied therefor less fossils, Filter feeding, no shells,skeletons,teeth or jaws. (e.g. jellyfish,soft corals or worms)
Cambrian Explosion (545mya)
hard-bodied therefore more fossils, shells and exoskeletons, predation (e.g. trilobites, brachiopods)
survival advantages of hard bits (e.g. protection, larger, powerful movements)
CONQUEST OF THE
LAND
development of ozone layer protected lethal UV radiation
Plants
adaptations of plants: vascular system (xylem and phloem), waxy cuticle, stomates, lignin strengthens stems, seeds
larger vascular plants
archaeopteris tree
Earliest plants
algae, lichens, liverworts and mosses
Earliest vascular plants(425mya)
cooksonia
earliest seed (365mya)
Animals
adaptations: Waterproof external layers, internal gas exchange systems (lungs), internal fertilisation, eggs with waterproof shell , internal development of embryo, strong support systems (endo and exoskeletons)
Tetrapods
4 legged terrestrial vertebrates
animals tentatively ventured onto land early in Cambrian
Arthropods
arachnids and wingless insects
problems: Water conservation,gas exchange,reproduction and dispersal, no bouyancy
Tiktaalik (417-354mya)
first tetrapod (labyrinthodont amphibian)
transition from aquatic to terrestrial life
first reptiles
Dimetrodon (260mya)
reasons: light for photosynthesis, New food sources, safety from predators