Ch 12 History of Life on Earth Study Guide
Vocabulary Words
Radiometric dating: method used to compute how many half-lives have passed since a rock was formed
The Primordial Soup model: hypothesis that the early oceans were filled with many different organic
molecules formed by chemical reactions energized by the sun, volcanoes, and lightning
The Bubble model: hypothesis that the process that formed the chemicals needed for life took place
within an environment protected from ultraviolet radiation
Heredity: characteristic of living things that was initiated by the linking of amino acids and sugars within
microspheres and coacervates, and the evolution of RNA molecules
Prokaryotes: appeared about 2.5 million years ago and form two groups, one of which contains
organisms that cause disease
Eukaryotes: appeared about 1.5 billion years ago and have a complex system of internal membranes
Cambrian period: characterized by great evolutionary expansion and origination of most phyla that exist
today
Arthropods: first organisms to have wings whose success is probably connected to the ability to fly
Vertebrates: some examples are fishes, salamanders, dinosaurs, birds, and humans
Continental drift: over geologic time, this process contributed to the geographic distribution of some
species
Plants likely evolved from protists
The significance to the development of life on Earth from the first formation of RNA molecules was that
they were capable of storing information, they were self-replicating, and they could change from one
generation to the next
The third and most devastating of all mass extinctions occurred at the end of the Permian period of
Earth’s history
The mass extinction of the dinosaurs 65 million years ago allow for the rise of mammals and birds by
having many resources becoming available to the surviving mammals and birds, the climate became
more moist, and the reptiles advantage was not so great, and small, feathered reptiles survived and
gave rise to modern birds
Both mitochondria and chloroplasts descended from bacteria because they both have circular DNA
similar to that found in bacteria
The breakdown of unstable isotopes results in smaller and more stable isotopes
The formation of ozone in the upper atmosphere caused the Earth’s surface to be a safe place to live for
the first time
The earliest traces of life on Earth are fossils of bacteria
Birds and mammals have become the dominate vertebrates on land partly because of the shift toward a
moister climate
Reptiles evolved from amphibians
Primitive cyanobacteria were among the first bacteria to appear on Earth, produced the first oxygen in
Earth’s atmosphere, and are believed to be the ancestors of chloroplasts
The first vertebrates on land were amphibians
In a unique biological association known as mycorrhizae, fungi provide minerals to plants, and the plants
provide food to the fungi
Radiometric dating compares the proportions of specific radioisotopes with their more stable isotopes