test 4

• how many years old did lord kelvin estimate the earth to be?

  no more than 100 million years old
• what are radioisotopes?

  unstable form of elements that decay to more stable forms at a constant rate over time
• the application of isotope studies to geology brought the current estimate of the earths age to approximately?

  4.6 billion years
• what is geologic time?

  the time span since earth was formed
• about how many species have been described and how many more await discovery?

  1.7 million species
• present day species are thought to represent less than what percentage of all species that have ever lived and why?

  1% due to many life forms becoming extinct
• what is macroevolution?

  large scale changes in organisms, generally occurring over millions of years
• what are fossils?

  preserved remains or impressions of individual organisms that lived in the past and often found in sedimentary rock
• what is carbon dating?

  it reveals the age of recent fossils
• to little carbon-14 remains to date fossils formed more than?

  70,000 years ago
• elements such as uranium-235, which has a half-life of how many years that can be used to date much older materials?

  700 million years
• which mammal has a relatively complete fossil record?

  whales
• how old is the oldest known rock on earth?

  3 billlion years old, contains carbon deposits that hint at life
• cell like structures have been found in stromatolites that formed how many years ago?

  3.5 billion
• what where the first life forms?

  prokaryotes
• when where eukaryotes first seen in the fossil record?

  about 2.1 billion years ago
• roughly how many years ago has a group of bacteria evolved a type of photosynthesis that releases oxygen as a by-product?

  2.8 billion years ago
• when did eukaryotes, with their larger cells and greater energy needs evolve?

  when oxygen reached 2-3 percent of present day levels
• when did multicellular life evolve?

  when oxygen levels reached present day levels
• when did the first multicellular organisms (soft bodied animals) evolve?

  in the shallow seas during Precambrian period 650 mya
• what is the cambrian explosion?

  a dramatic increase in the diversity of animal life lasting 5-10 million years
• what where the first organisms to colonize land?

  green algae
• what covered the earth by the end of the devonian period (360 mya)?

  plants
• what where the first definite fossils of terrestrial animals?

  spiders and milipedes
• what are key innovations land plants evolved to deal with the challenges of terrestrial life?

  Cuticle, vascular systems, structural support, leaves and roots, seeds, tree growth, reproduction structures
• the slow movement of the continents over times relative to one another is called?

  plate tectonics
• what is earths mantle?

  a hot layer of semisolid rock
• what do fossil records show?

  5 mass extinctions
• what are thought to be the cause of mass extinctions?

  climate change, volcano eruptions, asteriod impacts
• what are the effects of mass extinctions?

  entire groups of organisms perishing and extinction of dominant groups of organisms that where of minor importance
• how can we define evolution more specifically?

  a change in allele frequencies of a gene pool
• what is s a gene pool?

  a pool of all genetic information carried by all the individuals in a population
• what are four mechanisms that can change the composition of a populations gene pool?

  Mutation, gene flow, genetic drift, natural selection.
• what is the ultimate source of all genetic variation and result of changes in DNA sequence ?

  mutation
• what are gene mutation accidents?

  mistakes in DNA replication, collisions of DNA, damage from heat
• what is natural selection?

  how the environment and the need to survive shapes which traits get passed on
• what is taxonomy?

  classifying the diversity of life on earth
• what is an evolutionary tree?

  it illustrates the evolutionary history of groups of organisms
• what is the goal phylogenetics?

  to construct evolutionary trees that illustrates the patterns of species evolution
• what is linnaean hierarchy?

  system of biological classification devised by swedish naturalist named carolus linnaeus