the history of life (ch. 25)

age of earth- 4.6 billion years

oldest fossils- 3.5 billion years

stromatolite- a map of prokaryotes, cyanobacteria existing on a thin surface. as the map grows, organic material gets trapped and ultimately a pancake layer is formed. consided to be the oldest life forms. made up of single cells

what do you need to form a cell?

• a bag of complex organic chemistry

enclosed in plasma membrane or cell membrane

abiotic synthesis of organic molecules

• amino aids, mitrogenous bases, RNA nucleotides

• miller- urey, NASA stardust, volcanoes

• miller-urey experiment: a system that replicted conditions of earth

  • water source connected to a tube with chemical compounds

  • condenser where water turned into vapor

  • nitrogenous bases were found and # of amino acids were greater than what was recorded

• nasa star dust mission

  • a satelite flew thru the wild-2 comet

  • sample taken were nitrogenous bases and amino acids

• small organic molcules to macromolecules

  • rna nucleotides, AA dripped in sand and clay yield polymers of these molecules

  • evidence of abiotic synthesis

packaging of molecules into membranes

• concentration of organic molecules

• a way to keep the chemistry localizd

• keeping lipids in water forms vesicles

• 

• vesicle formation can replicate themselves and continue to grow

• can exchange things through the membrane

• may have formed the first membranes, localized it and allowed complex organisms to grow

self replicating molecules

• ribozyme - small bit of rna that can self replicate or small pieces

  • can take genetic materials and make daughter cells

• both genetic material and a catalyst

• some are self replicating

• rna was the first genetic material as it can store and works as a catalyst

evidence of the first cells- plausible scenario

• abiotic synthesis of small organic molecules (AA, N bases)

• organic molecules join to make larger molecules macromolecules

• packaging of molecules into membranous droplets (protocells)

• self replication of molecules allowing for inheritance

• replication has potential for reproduction

fossils and the fossil record

• preserved remains or traces of a prehistoric organism

• tell a story of the history of life on earth

• can give record of how life was distributed

fossil formation

• often occurs in sedimentary rock

• immediate burial is needed

• allows for time to be mineralized

• burial slows down rapid decay

  • bias in the fossil record?

  • organisms with bones or shells are more likely to leave a record than those that dont

  • do have fossils of soft bodied organisms

  • fossils that were more abundant are more likely to be fossilized

  • animals and plants are more likely to be fossilized than terrestrial things

relative dating- based on position

• principles in geology

  • original horizontality- rocks were formed horiontality

  • principle of superposition- things that are lower in the sequence are older than the ones above

absolute dating

• radiometric methods

• half life is 2 million years. what is the rocks are is 1/8 of parent material is still present

stratego griffey of earth

• rocks in section c are good for radiometric dating

  

the geologic record

• cenozoic= recent life

• mesozoic= recent life

• paleozoic= ancient life

• zoic= sanimals present

• proterozoic and below = precambrian

• before the cambrian period, early earth, most of earths history

precambrian

• the first single celed organisms

  • 3.5+ BYA

  • procaryotes

• photosynthesis and the oxygen revolution

  • O2 produced by oxygenic photosynthesis produces banded iron formations and continental red beds

• the first eukaryotes

  • 1.8+ BYA

  • eukaryotic features?

  • endosymbiosis- model that described the evidence surrounding how prokaryote to eukaryotes

• the origin of multicellularity

  • q.2+BYA

  • evolved independently in several lineages likely by specialization of cells colonial protists

  • 

  • most of life is unicellular

• ediacaran fauna

  • end of precambrian- 600 mya

  • soft bodied benthic forms

  • attached to a substrate or the bottom of the ocean

• the cambrian explosion

  • the sudden appearance of fossils resembling modern animal phyla in the cambrian period

  • 

  • an explosion of diversity

• the colonization of land

  • fungi, plants, and animals began to colonize land about 500 mya

  • plants and fungi may have colonized land together

extinction events are part of earths history

• groups of life go extinct when their death rates exceed their birth rates over a period of time

mass extinctions

• result of disruptive global environmental changes

• 5/5 mass extinctions 50% or more of marine species became extinct

after a mass extinction event

• adaptive radiation