Prehistoric Creatures Unit Study - Lesson 2: Overview

We populated our evolution timeline noting mass extinction events, the types of creatures living during each time period and major evolutionary changes.

It is important to have an overall understanding of how life evolved into its current diverse forms before we can truly understand any one part of evolution. In studying this evolution lesson, we read the book DK Eyewitness Books: Prehistoric Life slowly over a period of several weeks. The book begins with an evolution timeline, followed by a section describing the characteristics of the creatures which were living during each time period.

Timeline periods listed below were on the timeline from the previous lesson. During this lesson, mass extinction events and types of creatures were added to the timeline.

 A. 4.5 billion-570 million - Pre-Cambrian
    - one celled organisms
     * MASS EXTINCTION EVENT (99% of species died, Earth's surface completely frozen)    

I. 570-245 million - Paleozoic Era

 A. 570-500 million - Cambrian
    - shells evolved
    - shallow seas
    - molluscs, sponges, trilobites
    - all animals were aquatic
    * MASS EXTINCTION EVENT
 B. 500-440 million - Ordovician
    - jawless fish
    - early land based plants
    - 1st vertibrates
     * MASS EXTINCTION EVENT (60% of marine species died, Earth cooled)
 C. 440-410 million - Silurian
    - jaws evolved
    - spore based plants
 D. 410-360 million - Devonian
    - lots of oxygen
    - limbs evolved (1st tetrapods)
    - 1st land animals (amphibians)
    - wingless insects and spiders
 E. 360-290 million - Carboniferous
    - plants evolved
    - mostly spore based plants
    - amniotic eggs evolved
    - 80% Oxygen
    - lots of giant insects
   i. 360-320 million - Mississippin
   ii. 320-290 million - Pennsylvanian
 F. 290-245 million - Permian
    - primitive reptiles
     * MASS EXTINCTION EVENT (95% of species died, Severe volcanic eruptions)    

II. 245-65 million - Mesozic Era (Dinosaurs)

 A. 245-210 million - Triassic Period
    - ferns in south, conifers in north
    - hot and humid
   - 1st flowering plants
    - marine reptiles (plesiosaurs, ichthyosaurs)
    - flying dinosaurs (pterosaurs)
    - 1st dinosaurs (size of small turkeys)
    - primitive mammals
    * MASS EXTINCTION EVENT
 B. 210-140 million - Jurassic Period
    - plant and meat eating dinosaurs
    - pterosaurs were abundant
    - marine animals (ichthyosaurs, plesiosaurs, crocodiles, bivalves)
    - brachiopods, allosaurs

 C. 140-65 million - Cretaceous Period
    - ray fish widespread
    - 1st sharks
    - 1st flowers and grasses
    - dinosaurs (T-Rex, triceratops, velociraptor, spinosaurs)
    - birds evolved
    - 1st ants, butterflies, grasshoppers
    * MASS EXTINCTION EVENT (Asteroid Impact)

III. 65 million-present - Cenozoic Era

 A. 65-23 million - Paleogene Period
   i. 65-54 million - Paleocene Epoch
    - turtles, crocodiles, lizards, fish
    - nocturnal mammals
   ii. 54-37 million - Eocene Epoch
    - running animals (horse)
    - grasses evolved and prairies formed
    - beech elm, chestnut, magnolia, redwood, larch, cedar trees
    - small mammals
   iii. 34-23 million - Oligocene Epoch
    - elephants and rhinos
    - cooler climate (woodlands)
    - 1st apes
 B. 23-2.5 million - Neogene Period
   i. 23-5 million - Miocene Epoch
    - increased grasslands
    - cooler, dryer climate
    - cattle and deer evolved
    - wolves, horse, deer, birds - similar to today
   ii. 5-1.8 million - Pliocene Epoch
    - modern climate - deciduous and coniferous forests, tundra, grasslands and deserts
    - 1st humans
    - seals and sea lions thrived (mammals)
    - Mediterranean Sea formed
 C. 2.5 million-present - Quaternary Period
   i. 2.5 million-11,700 - Pleistocene
    - Great Lakes formed
    - glaciers formed and retreated 
    - some mammals became extinct (mastodons, saber-toothed cats, grounds sloths, cave bears)
    - Neanderthals became extinct
    - migratory birds evolved
    - smaller, swifter mammals developed
   ii. 11,700-present - Holocene


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