Evolution

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Evolution
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The History of Life
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Early history of Earth

• Earth is thought to have formed about 4.6 billion
  years ago.
• It began as a hot ball of rock.
• Meteorites bombarded its surface.
• Volcanoes shook the planet shot out gases that
  formed an atmosphere.

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Early history of Earth

• About 3.9 billion years ago, the Earth cooled
  enough for water vapor to condense.
• Violent rainstorms occurred the oceans formed.
• About 3.5 billion years ago, the first living
  organisms appeared.

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Early history of Earth
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Fossils

• Oldest rocks are about 3.9 billions years old.
• Fossils
• Any evidence of an organism that lived long ago.

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Paleontologists

• Scientists who study ancient life

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Relative dating technique

• Based on the premise that the deeper an organism
  is buried in sediment, the older it is.

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Relative dating technique
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Radiometric dating technique

• Involves using radioactive isotopes that give off
  radiation and form a different element.
• Scientists determine the ages of rocks/fossils by
  comparing the amount of the original radioactive
  element to the amount of the new element formed
  from decay.

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Radiometric dating technique
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Radiometric dating technique

• Example K-40 (potassium-40) decays to form
  Are-40 (Argon-40) in 1.3 billion years.

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Geologic time scale

• A type of calendar that allows scientists to
  communicate about events that have occurred since
  Earth was formed.
• Based on the different types of living organisms
  that have appeared during Earths history.

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Geologic time scale

• The scale is divided into 4 eras
• Precambrian
• Paleozoic
• Mesozoic
• Cenozoic
• These 4 eras are then subdivided into periods.

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Precambrian era

• Contains the oldest evidence of life (around 3.5
  billion years old).
• Prokaryotes simple eukaryotic organisms (algae,
  sponges jellyfish).

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Precambrian era
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Paleozoic era

• Invertebrates (worms primitive arthropods)
• Fishes (earliest vertebrates)
• Plants
• Amphibians
• Reptiles

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Paleozoic era
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Mesozoic era

• Dinosaurs
• Mammals
• Flowering plants

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Cenozoic era

• Mammals flourished.
• Primates evolved.

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Spontaneous generation

• The idea that life was produced from nonliving
  matter.

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Francisco Reid

• In 1668, he disproved the theory of spontaneous
  generation of larger organisms.
• People still believed that microorganisms arose
  spontaneously from a vital force in the air (air
  theory).

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Louis Pasteur

• In the mid-1800s, he disproved the air theory
  and established the concept of biogenesis.

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Biogenesis

• The idea that living organisms come only from
  other living organisms.

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Alexander Oaring

• In the 1930s, he hypothesized that life began in
  the early oceans.
• He suggested that energy from the sun and
  lightning triggered chemical reactions with the
  primitive atmosphere. The products rained down
  into the oceans to form primordial soup.

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Oparins molecules
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Evolution of cells

• First forms of life were anaerobic, heterotrophic
  prokaryotes, which probably evolved from some
  type of protocell.
• Competition for nutrients by heterotrophic
  prokaryotes led to the evolution of the first
  autotrophs (similar to archaebacteria).

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Evolution of cells

• Photosynthesizing prokaryotes evolved next, which
  increased the oxygen concentration in Earths
  atmosphere.
• Aerobic respiration evolved with the increase of
  oxygen.

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The Theory of Evolution
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Charles Darwin

• English scientist who is considered the founder
  of modern evolutionary theory.
• In 1831, he sailed on the HMS Beagle to South
  America the South Pacific.
• On the Galapagos Islands, Darwin studied
  compared the anatomy of many organisms.

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Charles Darwin

• Darwin used his theory of natural selection to
  explain how organisms evolve.

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Natural selection

• A mechanism for change in populations that occurs
  when organisms with favorable variations for a
  particular environment survive, reproduce and
  pass these variations on to the next generation.

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Natural selection

• Those with less favorable variations are less
  likely to survive and pass on traits to the next
  generation.
• Each new generation is largely made up of
  offspring from parents with the most favorable
  variations.

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Natural selection

• Natural selection is also known as the survival
  of the fittest.

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Evidence for evolution

• The following provide evidence for evolution
• Fossils
• Anatomical studies
• Embryological development
• Biochemistry

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Fossil evidence

• Scientists use fossil records to understand the
  general pathway of evolution.

A model of evolution from small-toed to
one-toed horses.
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Anatomical studies

• A homologous structure is a modified structure
  that is seen among different groups of
  descendents.

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Anatomical studies

• An analogous structure is any body part that is
  similar in function but different in structure.
• Example Insect and bird wings have the same
  function but are not similar in structure (bird
  wings are made up of a set of bones while insect
  wings are mainly made of chitin).

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Anatomical studies

• A vestigial structure is any body structure that
  is reduced in function in a living organism but
  may have been used in an ancestor.

Pelvic bones of a baleen whale.
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Embryological development

• In the earliest stage of embryological
  development in a fish, reptile, bird and mammal,
  a tail and gill slits can be seen in all species.
• As development continues, the embryos become more
  more distinct, in the stages before birth,
  they attain their distinctive forms.

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Biochemistry

• Scientists use DNA, RNA and proteins to determine
  levels of relationships among species within
  major taxonomic groups.

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The Evolution of Species
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Types of selection

• Natural selection acts upon the variation in
  populations.
• There are 3 types of selection
• Stabilizing selection
• Directional selection
• Disruptive selection

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Stabilizing selection

• The type of natural selection that favors average
  individuals in a population.
• Large spiders are at a disadvantage b/c they can
  be seen captured more easily.
• Small spiders might not be able to catch enough
  prey to survive reproduce.
• Average-size spiders are just right.

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Directional selection

• When one of the extreme forms of a trait is
  favored by natural selection.
• Woodpeckers feed by pecking holes in trees to get
  insects that live under the bark.
• One year, the trees are invaded by a species of
  insect that lives deep within the trees.
• Woodpeckers with long beaks have the selective
  advantage over those with short or average-size
  beaks.

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Disruptive selection

• Individuals with either of 2 extreme forms of a
  trait are at a selective advantage.
• Limpets are shell-covered marine organisms that
  live attached to rocks.
• On light-colored rocks, white-shelled limpets are
  able to blend in with the rock.
• On dark-colored rocks, dark-colored limpets are
  able to blend in with the rock.
• Tan-colored limpets, the intermediate forms, are
  easily spotted on either color rock.

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Speciation

• It is the process by which a new species is
  formed.
• This can only occur when either interbreeding or
  the production of fertile offspring is somehow
  prevented.
• Isolation can cause speciation.

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Types of isolation

• Geographic isolation occurs if a physical barrier
  separates a population into groups.
• Reproductive isolation occurs when formerly
  interbreeding organisms are prevented from
  producing fertile offspring.

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Speciation rates

• Gradualism is the idea that species originate
  through a gradual buildup of new adaptations.
• It is supported by fossil evidence, such as those
  for the slow steady buildup of adaptations of
  camels horses.

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Speciation rates

• Punctuated equilibrium states that speciation
  occurs quickly in rapid bursts, with long periods
  of stability in between.

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Patterns of evolution

• Divergent evolution is the pattern of evolution
  in which species that once were all similar to
  the ancestral species become more and more
  distinct.
• Human feet are different from monkey feet because
  humans began to walk upright on the ground rather
  than swinging through the trees.

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Patterns of evolution
Monkey feet
Human feet
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Patterns of evolution

• Convergent evolution is the pattern of evolution
  in which distantly related organisms evolve
  similar traits.