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Lecture by Whittington on the History of Life on Earth
Typology: Lecture notes
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OVERVIEW: LOST WORLDS
Past organisms were very different from
those now alive
The fossil record shows macroevolutionary
changes over large time scales including
The emergence of terrestrial vertebrates The origin of photosynthesis Long-term impacts of mass extinctions
Fig. 25-
NORTH AMERICA Chicxulub Yucatán^ crater Peninsula
In each of the five mass
extinction events, more
than 50% of Earth’s species
became extinct
Fig 25-UN
MOLECULES OF LIFE
Nucleic acids Proteins Carbohydrates Lipids
http://images.google.com/imgres?imgurl=http://www.gifs.net/Animation11/Animals/Barn_Animals/Big_cow.gif&imgrefurl=http://www.animationlibrary.com/animation/29576/Big_cow/&h=214&w=300&sz=9&hl=en&start=6&tbnid=Qccnhz- Bdl0snM:&tbnh=83&tbnw=116&prev=/images%3Fq%3Deating%2Banimation%2Banimation%2Blibrary%26gbv%3D2%26svnum%3D10%26hl%3Den
ECOSYSTEM DYNAMICS
SYNTHESIS OF ORGANIC COMPOUNDS
Earth formed about 4.6 billion years ago,
along with the rest of the solar system
Earth’s early atmosphere likely contained
water vapor and chemicals released by
volcanic eruptions (nitrogen, nitrogen oxides,
carbon dioxide, methane, ammonia,
hydrogen, hydrogen sulfide)
http://www.toysperiod.com/blog/lego/gold-rushes-a-playful-history/
POSSIBLE SEQUENCE membrane-bound proto-cells living cells
self-replicating system enclosed in a selectively permeable, protective lipid sphere
DNA RNA (^) other proteinsenzymes and
formation of protein-RNA systems, evolution of DNA
formation of lipid spheres
spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions
replicating, catalytic RNA would have been more effective at using resources and would have increased in number through natural selection
might have formed an “RNA world”
Fig. 22-
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human Cat Whale Bat
MORPHOLOGICAL DIVERGENCE
Fig. 22-
Younger stratum with more recent fossils
Layers of deposited sediment
Older stratum with older fossils
THE CAMBRIAN EXPLOSION
The Cambrian explosion refers to the
sudden appearance of fossils resembling
modern phyla in the Cambrian period (535 to
525 million years ago)
The Cambrian explosion provides the first
evidence of predator-prey interactions
By about 2.7 billion years ago, O 2 began
accumulating in the atmosphere and rusting
iron-rich terrestrial rocks
The source of O 2 was likely bacteria similar
to modern cyanobacteria
This “oxygen revolution” from 2.7 to 2.
billion years ago
Posed a challenge for life Provided opportunity to gain energy from light Allowed organisms to exploit new ecosystems
PHOTOSYNTHESIS AND THE OXYGEN REVOLUTION
Similarities in inner membrane structures and functions
Division is similar in these organelles and some prokaryotes
These organelles transcribe and translate their own DNA
Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes
THE FIRST EUKARYOTES
Fig. 22-
Hawks and other birds
Ostriches
Crocodiles
Lizards and snakes
Amphibians
Mammals
Lungfishes
Tetrapod limbs
Amnion
Feathers
Homologous characteristic
Branch point (common ancestor)
Birds
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