Influences on Earth’s History and Life-forms Standard Explain how Earth’s history has been influenced by catastrophes that have affected the conditions on Earth and the diversity of its life-forms.

Changes in Life Forms What are changes in life forms (additions and extinctions) often accompanied by? What are these environmental changes influenced by? changes in environmental conditions on Earth the impact of an asteroid or comet, climatic changes, & volcanic activity

Catastrophe: Impact of an Asteroid or Comet How does Earth’s atmosphere protect it from many meteors that enter it? When did many groups of animals, including the dinosaurs, disappear suddenly? they burn up before striking Earth’s surface at the end of the Mesozoic Era, when reptiles, early birds & mammals thrived

*Effects of the Asteroid/Comet* What do scientists hypothesize killed the dinosaurs? How did the impact affect organisms during that time? a large asteroid or comet that impacted with Earth caused dust & smoke to rise into the atmosphere & cause climatic changes, as well as the dying of many forms of plants, & animals that depended on those plants for food

Catastrophe: Climatic Changes What have Earth’s environments always been like? What were earliest life forms influenced by? many different climates, that are ever-changing conditions on Earth the climates produced by the forming atmosphere and oceans on Earth

*During the Paleozoic* Where did life develop & flourish? What happened throughout the era? in the tropical climates on land in warm, shallow seas different land environments formed sea levels changed new life forms developed

*During the Mesozoic* What caused many climate changes to occur? Plants & animals that survived through this time had what structures & systems that allowed for greater adaptations? plate tectonics & moving of landmasses seed covering for plants protective body covering or constant internal temperature for animals

*During the Cenozoic* What happened to climate conditions? What caused the climate to become much cooler? What did mountain range formation cause? continued to change major ice ages as ice sheets & glaciers covered much of Earth climate differences due to elevation & location near those ranges

*Catastrophe: Volcanic Activity: Precambrian Time* During Precambrian time, what made conditions for life forms hard? Who rarely survived these conditions? volcanic activity, including lava flows, ash clouds in the atmosphere, & heat simple life forms

*Volcanic Activity: Paleozoic & Mesozoic Eras* What caused volcanoes to form & become common during the Paleozoic Era? The Mesozoic Era? continents collided & mountains built up due to plate tectonics the rapid movement of plates in the collisions & subductions around plate boundaries, which are still the location of much of Earth’s volcanic activity

*Explosive Volcanoes* What can explosive volcanoes do? send ash & dust high into the atmosphere, where it’s carried great distances around the Earth blocking sun for a long time disrupt many of Earth’s processes, & ultimately the life forms that depend on those processes