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Distinguish between the two groups of prokaryotes
Describe the evolution of eukaryotes Recognize an evolutionary advance first
seen in protists Summarize how mass extinctions have
affected the evolution of life on Earth
Fossil: the preserved mineralized remains (bone, tooth, shell) or imprint of an organism that lived long ago ◦ Oldest fossil from prokaryotes, 2.5 billion years
old
Before cyanobacteria oxygen was scarce As cyanobacteria photosynthesized,
released oxygen gas into oceans After hundreds of millions of years the
oxygen began to escape into the air Today oxygen makes up 21% of Earth’s
atmosphere
Eubacteria Ex. E.Coli Prokaryotes that
contain a chemical called peptidoglycan in their cell walls
Often cause disease and decay
Archaebacteria Ex. Sulfolobus Prokaryotes that lack
peptidoglycan in their cell walls and have unique lipids in their cell membranes
Are found living in extreme environments
Endosymbiosis: mitochondria are the descendants of symbiotic, aerobic (oxygen-requiring) eubacteria and chloroplasts are the descendents of symbiotic, photosynthetic eubacteria
Steps of endosymbiosis:◦ Bacteria entered large cells either as parasites or
undigested prey◦ Instead of being digested, bacteria began to live
inside host cell where performed cellular respiration (mitochondria) or photosynthesis (chloroplast)
Ideas to support endosymbiosis:◦ Size and structure
Mitochondria and chloroplasts about the same size as bacteria
Both have two membranes (outer membrane thought to be derived from endoplasmic reticulum of host cell)
Ideas to support endosymbiosis:◦ Genetic material
Both have circular DNA similar to chromosomes in bacteria
Both contain genes that are different from those found in nucleus of host cell
Ideas to support endosymbiosis◦ Ribosomes
Moitochondria and chloroplast ribosomes have a size and structure similar to the size and structure of bacterial ribosomes
Ideas to support endosymbiosis:◦ Reproduction
Like bacteria both reproduce by simple fission Replication takes place independently of cell cycle of
host cell
Eubacteria and Archaebacteria◦ Single celled protists
Protists◦ Eukaryotic ◦ Large varied group that includes both
multicellular and unicellular organisms Fungi, Plants, Animals
◦ Eukaryotic, multicellular
Unicelluar body plan◦ Very sucessful◦ Half the biomass ◦ Single cell must carry out all of the activities of an
organism
Multicellular◦ Distinct types of cells in one body can have
specialized functions ◦ Almost all organisms large enough to be seen by
the naked eye are multicellular
Most animal phyla probably originated during a relatively short time ◦ 10 to 100 million years ago,
during the late Precambrian and early Cambrian periods
◦ Cambrian explosion Trilobites: marine
arthropods that became extinct about 250 million years ago
Sudden change occurred at end of Ordovician period
About 440 million years ago a large percentage of organisms on Earth suddenly became extinct
Extinction: death of all members of a species ◦ First of five major mass extinctions that have
occurred on earth Mass extinction: is an episode during
which large numbers of species become extinct
Permian period mass extinction: 245 million years ago ◦ About 96% of all species of animals living at the
time became extinct ◦ Worldwide geological and weather changers are
likely factors