History of Life on Earth

• what is the highest level of classification?

  domain
• what are the three domains?

  bacteria, eukaryotes and archaea
• what are prokaryotes?

  Single-celled organisms without a nucleus, mitochondria or membrane-bound organelles
• what are the six kingdoms of life?

  archaebacteria, eubacteria, protists, fungi, plantae and Animalia
• how old is the earth?

  4.5 billion years old
• what did a reducing atmosphere allow for?

  the formation of carbon rich compounds
• when did life on earth begin?

  3.8 billion years ago
• what are the earliest fossils of?

  prokaryotes
• what are the two main evolutionary branches of prokaryotes?

  Bacteria and Archaea
• where are archaea found?

  hostile anaerobic environments
• what are cyanobacteria?

  photosynthetic algae which are oxygen generating
• what did cyanobacteria do to allow for the generation of life on earth?

  raise atmospheric oxygen levels, enabling the ozone layer to form, protecting the earth from strong UV radiation
• what is it likely that eukaryotes evolved from?

  ancestral prokaryotes combining
• why was the evolution of sex important?

  it enabled genetic recombination which led to variation which speeds up the evolutionary process
• when was there a huge explosion in eukaryotic diversity?

  at the end of the ice age 750 million years ago
• why is there often an increase in biodiversity after mass extinctions?

  there is less competition
• what is thought to have caused the mass extinction which ended the dinosaurs?

  K-T asteroid impact
• what is the earliest known mass extinction?

  the ordovician extinction
• what is thought to be the cause of the ordovician extinction?

  climate change and a major ice age
• what is the largest mass extinction on record?

  the permian triassic extinction
• when was the permian triassic extinction?

  250 million years ago
• what caused the permian triassic extinction?

  warming climates and its associated changes to the oceans