Review Questions

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Review Questions

• Why cant the Hardy Weinberg idea exist in our
  world?
• What are the five factors that can lead to
  evolution?
• What is convergent evolution and divergent
  evolution?
• 4. What are the 3 types of Isolation?.

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1. Why cant the Hardy Weinberg idea exist in
our world?For the 5 conditions to be met is not
possible. People will move into and out of
populations, we will always choose our mating
partners and mutations will always occur.2.
What are the five factors that can lead to
evolution?1. Genetic Drift.2. Gene Flow 3.
Mutation4. Sexual Selection 5. Natural
Selection
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3. What is convergent evolution and
divergent evolution?Convergent evolution is
when two organisms evolve closer to each other
and divergent evolution is when two organisms
evolve going further away from each other.4.
What are the 3 types of isolation?BehavioralGeo
graphicTemporal
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Chapter 12 The History of Life
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The Fossil Record

• Words to Know Relative Dating, Radiometric
  Dating, Isotope, Half-Life
• Fossils Can form in Several Ways
• There are many processes that make fossils.
• 1. Permineralization occurs when minerals
  carried by water are deposited around a hard
  structure.
• 2. Natural Casts form when flowing water
  removes all of the original bone or tissue,
  leaving just an impression in sediment. This can
  be filled by minerals recreating the original
  shape of the organism.

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Fossils Can form in Several Ways

• 3. Trace Fossils record the activity of an
  organism. They include nests, burrows, imprint
  of leaves and footprints.
• 4. Amber-preserved Fossils organisms that
  become trapped in tree resin that hardens into
  amber after the tree gets buried underground.
• 5. Preserved Remains form when an entire
  organism becomes incased in material such as ice
  or volcanic ash or immersed in bogs.
• Most fossils form in sedimentary rock, which is
  made by many layers of sediment or small rock
  particles.
• The environments for fossil creation are
  wetlands, bogs river mouths, lakebeds, and
  floodplains.

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Dating

• Relative Dating estimates the time during which
  an organism lived by comparing the placement of
  fossils of the organism with the placement of
  fossils in other layers of rock.
• Relative dating allows scientists to infer the
  order in which groups of species existed, but
  does NOT give actual ages.

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Dating

• Radiometric Dating is a technique that uses the
  natural decay rate of unstable isotopes found in
  material in order to calculate the age of that
  material.
• Isotopes are atoms of an element that have the
  same number of protons, but a different number of
  neutrons.
• Ex Carbon 14 is a common tool used for dating
  fossils.
• The decay rate of many radioactive isotopes has
  been measure and is expressed as the isotopes
  half-life.
• A Half-Life is the amount of time it takes for
  half of the isotope in a sample to decay into a
  different element.
• Radiocarbon Dating
• A fossils age can be estimated by comparing the
  ratio of stable isotope, such as Carbon 12, to
  the difference between the amounts of Carbon 12
  and Carbon 14 there will be.

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Determining Earths Age

• Scientists have used radiometric dating to
  determine the age of Earth.
• Meteorites do not break down like rocks on Earth
  and are believed to have been on Earth from the
  beginning.
• Meteorites provide an unspoiled sample for
  radiometric dating.
• Scientists measure the Earths age at about 4.5
  Billion years.

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Geologic Time Scale

• Words to Know Index Fossil, Geologic Time
  Scale, era, Period, Epoch, mass extinction,
  adaptive radiation.

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Index Fossils

• Index fossils are fossils of organisms that
  existed only during specific spans of time over
  large geographic areas.
• Using index fossils for age estimates of rock
  layers is not a new idea (been around since the
  1700s).
• The best index fossils are common, easy to
  identify, found widely around the world, and only
  existed for a short period of time.
• Ex Fusulinids disappeared after a mass
  extinction and indicates that a rock layer must
  be between 248 million and 360 million years old.

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The Geologic Time Scale

• The Geologic Time Scale is a representation of
  the history of Earth.
• It organizes Earths history by major changes or
  events that have occurred, using evidence from
  the fossil and geologic records.
• The time scale is divided into units
• 1. Eras last tens to hundreds of millions of
  years and consist of two or more periods.
• 2. Periods the most commonly used units of
  time on the geologic time scale, lasting tens of
  millions of years. Each period is associated
  with a particular type of rock.
• 3. Epochs the smallest units and last several
  million years.

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Origin of Life

• Words Nebula, Ribozyme
• Earth was very Different Billions of Years ago
• Most scientists agree on two points when it comes
  to the origin of the Earth
• 1. Earth is billions of years old.
• 2. The conditions of the early planet and its
  atmosphere were very different from those of
  today.

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Earth was very Different Billions of Years ago.

• Today, the most widely accepted hypothesis of
  Earths origins suggests that the solar system
  was formed by a condensing Nebula, a cloud of gas
  and dust in space.
• This idea is supported by research and suggests
  that the Earth is 4.6 Billion years old.
• Early Earth was violent and very hot for the
  first 700 million years.
• Hydrogen, carbon monoxide and nitrogen gas were
  in the atmosphere.
• What was not present was OXYGEN.
• As the planet cooled, water vapor condensed and
  fell as rain that collected as pools.
• Once water was present, organic compounds could
  form.

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Organic Molecule Hypothesis

• There are two general hypotheses about how
  life-supporting molecules appeared on early
  Earth.
• Miller-Urey Experiment
• In 1953, Miller and Urey designed an experiment
  to test a hypothesis first proposed in the
  1920s.
• Miller and Urey built a system to model early
  Earth.
• They demonstrated that organic compounds could be
  made by passing an electrical current through a
  closed system of early gases.
• These gases were Methane, ammonia, hydrogen and
  water vapor.

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Meteorite Hypothesis

• Analysis of a meteorite that fell in Australia in
  1969 revealed that amino acids are present on
  meteors.
• This evidence suggests that amino acids could
  have been present when Earth formed, or that
  these organic molecules may have arrived on Earth
  through meteorite or asteroid impacts.

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Early Cell Structure Hypotheses

• Iron-Sulfide Hypothesis
• Martin and Russell noted that hot iron sulfide
  rising from below the ocean floor combines with
  the cooler ocean water to form chimney-like
  structures made of many compartments.
• They proposed that 4 billion years ago,
  biological molecules combined in the compartments
  of these chimneys.

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Early Cell Structure Hypotheses

• Lipid Membrane Hypothesis
• Several scientists have proposed that the
  evolution of lipid membranes was a crucial step
  for the origin of life.
• Lipid molecules spontaneously form
  membrane-enclosed spheres, call liposomes.
• In 1992, Harold Morowitz tested the idea that at
  some point liposomes were formed with a double,
  or bilayer, lipid membrane.
• These liposomes could then form around a variety
  of organic molecules, such as amino acids, fatty
  acids, sugars and nucleotides.
• The liposomes would act as membranes and would
  later give rise to the first true cells.

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RNA as Early Genetic Material

• A hypothesis that has become much supported
  recently states that RNA, rather than DNA, was
  the genetic material that stored information in
  living things on early Earth.
• In the 1980s it was discovered that RNA can
  catalyze reactions.
• Ribozymes are RNA molecules that can catalyze
  specific chemical reactions.
• RNA can copy itself, chop itself into pieces, and
  from these pieces make even more RNA.

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Early Single-Celled Organisms

• Words to Know Cyanobacteria, Endosymbiosis
• MICROBES
• Single-celled organisms changed Earths surface
  by depositing minerals.
• They changed the atmosphere by giving off oxygen
  as a by-product of photosynthesis.

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Microbes

• Before photosynthesis evolved, the first
  prokaryotes would have been anaerobic, living
  without oxygen.
• Scientists have found evidence that
  photosynthetic life evolved more than 3.5 billion
  years ago.
• These fossils are of Cyanobacteria, which are
  bacteria that could carry out photosynthesis and
  release oxygen.
• Some cyanobacteria live in colonies.
• Higher oxygen levels in the atmosphere and ocean
  allowed the evolution of aerobic prokaryotes,
  which need oxygen to live.

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Eukaryotic Cells

• The fossil record shows that eukaryotic organisms
  evolved 1.5 billion years ago.
• Eukaryotes have a nucleus and other membrane
  bound organelles.
• One hypothesis of eukaryotic evolution is. the
  theory of endosymbiosis
• Endosymbiosis is a relationship in which one
  organism lives within the body of another, and
  both benefit from that relationship.
• The Theory of Endosymbiosis suggests that early
  mitochondria and chloroplasts were once simple
  prokaryotic cells that were taken up by larger
  prokaryotes around 1.5 billion years ago.
• Instead of being digested, some of the smaller
  prokaryotes may have survived inside of the
  larger ones.
• If the cell took in a prokaryote that acted like
  a mitochondria, the larger cell got the energy
  from ATP.
• If the cell took in a prokaryote that acted like
  a chloroplast, the larger cell got nutrients
  through photosynthesis.
• In exchange, the mitochondria and chloroplasts
  found a stable environment and nutrients.
• Support for this theory is based on the fact that
  both chloroplasts and mitochondria have their own
  DNA and are the same size as prokaryotes.

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Eukaryotic Cells
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Evolution of Sexual Reproduction

• The first prokaryotes and eukaryotes could only
  reproduce asexually.
• Sexual reproduction may have resulted in an
  increase in the rate of evolution by natural
  selection.
• Sexual reproduction creates more genetic
  variation.
• Sexual reproduction may have been the first step
  in the evolution of multicellular life.

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Radiation of Multicellular Life.

• Words to Know Paleozoic, Cambrian Explosion,
  Mesozoic, and Cenozoic.
• Life Moved onto Land
• One hypothesis suggests that it was an advantage
  for early one-celled organisms to increase in
  size by becoming multicellular.
• Cells that cooperated could compete more
  effectively for limited resources.
• Multicellular organisms first appeared during the
  Paleozoic Era, which began 544 million years ago.

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Life Moved onto Land

• Members of every major animal group evolved
  within only a few million years.
• The era ended 248 million years ago with a mass
  extinction.
• More than 90 of marine animal species and 70 of
  land animal species of that time became extinct.
• The earliest part of the Paleozoic Era, the
  Cambrian Period is often called the Cambrian
  explosion.
• A huge diversity of animal species evolved.
• The middle of the Paleozoic Era was a time of
  great diversity as life moved onto land.
• The number and variety of plant groups greatly
  increased.
• Four-legged vertebrates, such as amphibians,
  became common.

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Reptiles Radiated During the Mesozoic Era

• The Mesozoic Era began 248 million years ago and
  ended 65 million years ago.
• Called the Age of Reptiles because the dinosaurs
  roamed Earth during this era.
• The Mesozoic era also feature birds and flowering
  plants.
• The oldest direct ancestor of mammals first
  appeared.
• The Mesozoic era is divided into three periods
  Triassic, Jurassic and Cretaceous.
• Life took off slowly in the early Triassic.
• The Jurassic was marked by the dinosaurs.
• The peak in dinosaur diversity though is the
  Cretaceous.
• This era ended with the most famous mass
  extinction when it is believed a meteorite struck
  the Earth and blocked the sun.

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Mammals Radiated during the Cenozoic Era.

• The Cenozoic Era began 65
• million years ago and continues today.
• It is divided into two periods Tertiary and
  Quaternary.
• During the Tertiary Period, placental mammals and
  monotremes evolved and diversified.
• During the Tertiary period, birds, ray-finned
  fishes, and flowering plants also underwent
  dramatic radiations.
• The earliest ancestors of the modern humans
  evolved near the end of the Tertiary.
• However, homo sapiens anatomically modern humans,
  did not appear until about 100,000 years ago.

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Primate Evolution

• Words to Know Primate, Prosimian, Anthropoid,
  Hominid, Bipedal

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Humans Share a Common Ancestor

• The common ancestor of all primates probably
  arose before the mass extinction that closed the
  Cretaceous period 65 million years ago.
• Primates make up a category of mammals with
  flexible hands and feet, forward-looking eyes,
  and enlarged brains relative to their body size.
• Primates also have arms that can rotate in a
  circle around their shoulder joint, and many
  primates have opposable thumbs.

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Primate Evolution

• The relationship of primate evolution forms a
  multi-branched tree.
• Prosimians are the oldest living primate group,
  and most are small and active at night.
• Ex lemurs, lorises, and tarsiers.
• Anthropoids, the humanlike primates, are further
  subdivided into the New World monkeys, and
  hominoids.
• Many species have prehensile, or grasping, tails,
  that allows them to hang.
• They have larger brains and can manipulate
  objects.
• Hominids walk upright, have long lower limbs,
  thumbs that oppose, four other fingers and
  relatively large brains.
• This group includes ALL the human lineage, both
  modern and extinct.
• Walking Upright
• Fossil discoveries have revealed that one trait
  had a huge impact on development walking on 2
  legs.
• Bipedal is an adjective that describes two-legged
  or upright walking.
• What is another common animal that is bipedal?

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There are Many Fossils of Extinct Hominids

• Most hominid species are classified into two
  group the genus Australopithecus and the genus
  Homo
• The earliest member of the genus Homo was Homo
  habilis. (handy man).
• He lived 2.4-1.5 million years ago in what are
  now Kenya nd Tanzania.
• Made stone tools and more closely resembled the
  modern human brain in shape.
• H. neanderthalensis lived from 200,000 30,000
  years ago, in Europe.
• Some evidence suggests that he existed with Homo
  sapiens (modern day humans).

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Modern Humans Arose about 100,000 Years Ago.

• Fossil evidence reveals that the first Homo
  sapiens (modern humans) appeared in Ethiopia.
• The Role of Culture
• Human evolution is influenced by culture.
• Objects such as tools demonstrate a steady trend
  of increasing sophistication and usefulness.
• Evolution of the Human Brain
• The human brain and skull size have both
  increased.
• These traits evolved much faster in human than in
  other hominids.