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Our Evolving Planet. Life Evolves – It Changes. Everything on Earth that has ever lived is connected through, and is the result of, evolution . It’s a process that’s been happening since the first tiny life forms appeared some four billion years ago.

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life evolves it changes
Life Evolves – It Changes
  • Everything on Earth that has ever lived is connected through, and is the result of, evolution.
  • It’s a process that’s been happening since the first tiny life forms appeared some four billion years ago.
  • Our story begins with our understanding of time.
geologic time
Geologic Time
  • The Earth is around 4.5 billion years old.
  • To help organize and understand this immense expanse of time, scientists divide Earth’s history into smaller chunks, such as eras and periods.
  • Together, these make up the geologic time scale.
    • Think of the geologic time scale as the table of contents in the history of Earth.
    • The eras and periods are chapters in the story of evolution.
    • Each chapter has its own tale to tell—when life began, when mammals first appeared, when humans entered the scene, etc.

Precambrian Time

  • - Began 4.5 Billion Years Ago -
    • Made up of:
      • Hadean Era
      • Archaean Era
      • Proterozoic Era
  • In Earth’s first four billion years—the time known as the Precambrian — life first evolved, flourished, and changed the planet forever.
  • The atmosphere contained mostly carbon dioxide, nitrogen, and water vapor.
    • Most oxygen molecules were bound to other molecules, not free in the atmosphere.
    • You could not have breathed.
  • High levels of carbon dioxide trapped the sun’s heat, creating surface temperatures of up to 120 degrees Fahrenheit.
  • Meteorites bombarded the planet.
  • Volcanoes poured lava and released gases from deep inside the Earth.
    • As the lava cooled, it hardened to form the first continents.
    • Volcanic steam condensed into heavy rains, which accumulated into shallow oceans.
origin of life theories
Organic compounds may have formed on Earth, perhaps in underwater thermal vents.Origin of Life Theories

Organic compounds may have been carried to Earth aboard meteorites from outer space.

Scientists who study ancient meteorites have discovered that some contain organic compounds, life’s building blocks.

Such meteorites may well have brought the raw material of life to Earth.

1. Beneath the ocean floor, chemical-rich water is heated by molten rock. This water spews up through openings in Earth’s crust.

2. When the hot water meets cold seawater, dissolved minerals precipitate (they separate out as solids) and accumulate, forming the vent’s chimney.

4. This charge may have caused chemicals to react and combine inside honeycomb-like chambers in the chimney’s walls, forming organic compounds.

3. The hot and cold waters have different chemical make-ups, creating an electric charge inside the chimney’s walls.

first life
First Life
  • By 3.5 billion years ago, tiny single-celled organisms called prokaryotes were living in Earth’s oceans.
  • We find fossil evidence of these organisms in some of the oldest rocks on Earth’s surface.
    • These ancient rocks, found in Australia and Greenland, range from 3.8 billion to 3.5 billion years old.
  • Photosynthetic bacteria changed the earth dramatically.
    • Used the sun’s energy to make food and water as well as oxygen that was released into the atmosphere and the oceans.
  • Around 2.5 billion years ago, some cells began engulfing other cells.
  • These cells were able to function together, forming a new type of cell: a eukaryote.
    • These different parts perform different tasks within the cell.
  • Reproduction
    • For billions of years by binary fission
    • Later by sexual reproduction
      • exchanging DNA
      • Natural Selection

Paleozoic EraCambrian and Ordovician Periods - Began 543 Billion Years Ago -

  • Immense, shallow oceans covered much of the planet.
  • After three billion years of evolution, Earth witnessed an explosion of life. (AKA: Cambrian Explosion)

--Arthropods --Sponges --Mollusks

  • Most animal groups living today evolved in the Cambrian seas.
    • Among the new animal groups, many had developed skeletons (plates, shells, and bones), backbones, and other new features that would change the shape of life forever.
  • The first mass extinction came at the end of the Ordovician Period.
    • Global cooling was probably the cause.
      • A large landmass moved over theSouth Pole, causing glaciers to form and global temperatures to cool.
      • Many species of trilobites, brachiopods, echinoderms, graptolites, and corals became extinct.
        • due to cooler conditions and suffered from habitat loss as water turned to ice, lowering sea levels worldwide.

If radiometric dating identifies the rock in layer C as 425 million years old, what can you infer about the age of the fossils in layer C? In layers B and D? Explain.


Silurian & Devonian Periods - Began 443 Million Years Ago -

  • When the Silurian Period began, continents that once were separate had come together along the equator.
  • Life landed ashore during the Silurian & Devonian periods.
    • Plantscolonized the continents, creating habitats for the ancestors of today’s animals.
      • The first land plants evolved from water plants.
        • green algae
      • Early plants had to live near water.
        • Nonvascular
          • Movement by osmosis
      • Stems let plants move away from the water’s edge.
        • Vascular
          • Movement through tissues(xylem & phloem)
      • Pollen and seeds broke plants’ last ties to wet environments.

In the seas, massive reefs— larger than at any other time in history—covered the ocean floor, and fishes.

    • The development of jaws allowed fishes and other emerging vertebrates to catch larger prey.
    • The development of tetrapods paved the way for animals that could walk on land. (limbs and digits)
  • Arthropods that evolved to live on land during this time are ancestors of today’s insects and spiders.
  • Mass extinction #2 continents had moved over the South Pole.
    • Climate too cold for many species.
    • 70% of life in ocean died out.
carboniferous begins 354 billion years ago divided into mississippi and pennsylvanian
Carboniferous- Begins 354 billion years ago –Divided into Mississippi and Pennsylvanian
  • Landmasses moved towards the equator and continents began shifting from east to west.
    • A resulting milder climate helped great forests flourish.
  • Swampy tropical forests covered the continents.
    • Over time and under pressure, the remains of these forests would become the great coal fields mined for fuel we use today.
  • Fossils tell us arthropodsand tetrapods thrived here (some were giants). --insects --millipedes --arachnids

Permian - Began 290 Million Years Ago -

  • Earth’s continents had assembled into one giant landmass called Pangaea.
  • Three basic environments:


  • Ever-increasing diversity of plant and animal life.
  • Tetrapods that waded ashore in previous periods diversified into to two new groups.
    • Reptiles
      • Amniotic Egg
    • Synapsids
      • Ancestor of Mammals
    • Third mass extinction at the end.
      • Global warming (volcanic activity)
      • Nearly wiped out all life on earth
        • 90% of Marine Animals died out
        • 80% of Land Animals died out
mesozoic began 248 billion years ago divided into triassic jurassic cretaceous
Mesozoic- Began 248 Billion Years AgoDivided intoTriassicJurassicCretaceous
  • This era saw the evolution of the largest animals to have ever walked the earth.
    • Called the Age of Dinosaurs
    • They would give rise to birds.
    • Crocodiles, snakes, and turtles making their first appearance.
  • The emergence of mammals, from which humans eventually evolved.
  • The emergence of birds, which are the living dinosaurs of today.
  • The emergence of flowering plants, which created rich and varied habitats where new forms of life could evolve and diversify.
    • Angiosperm
4th Mass Extinction

Early Mesozoic

Volcanic Activity lead to global warming.

50% of Marine Life went extinct

5th Mass Extinction

Late Mesozoic

Possible Meteorite

50% of all Life went extinct

cenozoic era tertiary period began 65 million years ago
Cenozoic Era:TertiaryPeriod- Began 65 Million Years Ago -
  • Age of Mammals
    • hoofed mammals, rodents, and carnivores evolved
    • First warm tropical forests, then cooler, drier grasslands provided rich habitats where mammal species could thrive and diversify.
    • Three types of mammals:
      • Monotremes - hatch from eggs.
      • Marsupials - are born before they are fully developed and continue development outside the womb, often in a pouch.
      • Placentals - develop completely in their mother’s wombs before they are born.
        • also grouped by differences in their features
          • Claws/Hooves
          • Teeth Differences (eating)
          • Grasping Hands & Feet
the age of early human
The Age of Early Human
  • Primates
    • Grasping Hands & Feet
    • Forward Facing Eyes (depth perception)
    • Large Brain (in relation to rest of body)
  • Humans belong to the primate group called hominids.
    • First appeared eight million years ago.
    • Evolved from an ape ancestor.
      • did not all evolve in a single direct progression from apes
    • Evolved through the same unpredictable process as every other living thing

Telling Hominids


Apes Apart

1. Skull

The opening for an ape’s spinal column is towards the back of the skull, so the spine extends backwards and down.The opening for a hominid’s spinal column is at the bottom of the skull, so the spine extends directly down underneath the skull.

6. Toes

An ape’s big toe is splayed off to the side. This thumb-like toe is great for grasping, but not for weight bearing.A human’s big toe is lined up parallel with the other toes, bearing the weight of the body during the “push-off” to the next step.

3. Pelvis

An ape’s pelvis is tall and narrow.A human’s shorter and wider pelvis makes for more stable walking on two legs.

4. Femur

An ape’s femur (upper leg bone) extends straight down.A hominid’s femur is angled inward, positioning the knees and feet directly under the body’s center of gravity during walking.

5. Foot arches

An ape’s foot is flat.A human’s foot is arched, absorbing shock when the foot falls.

2. Teeth

An ape’s canine teeth are relatively large.A hominid’s canine teeth are smaller by comparison.

  • One of the earliest hominids
    • Smaller than the average modern human
    • Smaller brains
    • Protruding jaws
    • Large molars
      • grinding down tough plant material
    • Walked upright
      • some probably spent time in trees
  • The female hominid, a young adult named “Lucy”, lived in eastern Africa 3.2 million years ago.
homo ergaster
Homo ergaster
  • Earliest species of the genus Homo
  • First appeared in Africa
    • around 2 million years ago
  • The first true humans
    • Characteristics:
      • Larger brains
      • Flatter faces with projecting, flat, noses
      • Smaller teeth
        • Could now eat meat
      • Larger with shorter arms and longer legs
      • A life spent completely on the ground, not in the trees
key trends in hominid evolution
Key Trends in Hominid Evolution
  • Leaving the trees and walking on land
  • Bigger brains relative to body size
    • more sophisticated thinking processes
  • Remnants of primate body parts that we no longer use
  • Wisdom teeth
    • Needed for chewing to break down plants
  • Third eyelid
    • Small pink fold in the inner corner of the eye
    • Helped keep eyes clean.
      • Reptiles have this membrane too, so we have a common ancestor
  • Ear wiggling muscles
    • Early primates could move their ears independently
      • cats and dogs
  • Palmaris muscle
    • long, narrow muscle that runs from wrist to elbow
      • important for climbing and hanging
      • about 11% of us are missing this
  • Goosebumps
    • Muscle fibers that make your hair stand on end
      • When cold or scarred
      • Early primates used for insulation or to intimate
  • Fifth toe
    • For grasping or clinging to branches.
    • Big toe used for balance
climate shapes evolution
Climate Shapes Evolution

Homo sapiens VS Neanderthals

  • Homo sapiens
    • Originated in Africa 195,000 years ago
    • Slender body great for warm environment
  • Neanderthals
    • first evolved in Europe, at least 400,000 years ago.
    • Stockier body to help retain heat
  • Neanderthals were our neighbors, not our ancestors.
quartenary began 1 8 million years ago
Quartenary- Began 1.8 Million Years Ago -
  • Commonly known as the Ice Age
  • Changing climate and the formation of new land bridges.
    • Dramatically affected the evolution of mammals
      • Led to diversity
      • Mammals became massive
  • Continents moved to their current locations
  • Glaciers at the poles
6 th mass extinction
6th Mass Extinction





  • For the first time in Earth’s history, a single species is the primary cause of a mass extinction.
  • http://www.fieldmuseum.org/evolvingplanet/exhibition.asp
  • http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_13