Question

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ees unit 3: study guide
objective 1: geologic time and fossils

1. how is geologic time organized?
2. what is the oldest and longest era? what life existed then?
3. what is the most recent era? what life is dominant?
4. in which eras were there extinctions and what were the accepted causes of those extinctions?
5. when(in geologic time) did pangaea form and start breaking up?
6. explain how pangaea broke up.
7. how do fossils help explain climates that may have once existed on continents?
8. list the four types of fossils and give examples of each.
9. what are the conditions that favor fossil formation?
10. what does the principle of fossil succession state and how does it help to establish geologic history?
11. what are the three characteristics of an index fossil?

Explanation:

1. Geologic time is organized into eons, eras, periods, epochs, and ages based on major geological and biological events.
2. The Hadean is the oldest and the Precambrian is the longest era. Early simple life - forms like bacteria and archaea existed then.
3. The Cenozoic is the most recent era. Mammals are the dominant life - form.
4. Extinctions occurred in eras like the Permian (massive volcanic activity and climate change) and the Cretaceous (asteroid impact).
5. Pangaea formed around 335 million years ago and started breaking up around 175 million years ago.
6. Pangaea broke up due to tectonic plate movements driven by convection currents in the mantle.
7. Fossils can indicate past climates as certain organisms thrive in specific climates. For example, coal deposits suggest a warm, wet climate.
8. The four types of fossils are body fossils (e.g., dinosaur bones), mold fossils (e.g., impression of a shell in rock), cast fossils (e.g., a rock filling a mold), and trace fossils (e.g., dinosaur footprints).
9. Conditions favoring fossil formation include rapid burial, low oxygen environments, and hard body parts.
10. The principle of fossil succession states that fossils occur in a definite, recognizable order. It helps in dating rocks and establishing geologic history.
11. Index fossils are widespread, abundant, and existed for a short geologic time.

Answer:

1. Organized into eons, eras, periods, epochs, ages.
2. Oldest - Hadean, Longest - Precambrian; Bacteria, archaea.
3. Cenozoic; Mammals.
4. Permian (volcanic activity, climate change), Cretaceous (asteroid impact).
5. Formed ~335 million years ago, started breaking up ~175 million years ago.
6. Due to tectonic plate movements.
7. Indicate past climates as organisms have climate preferences.
8. Body (dinosaur bones), Mold (shell impression), Cast (rock - filled mold), Trace (dinosaur footprints).
9. Rapid burial, low oxygen, hard body parts.
10. Fossils occur in a definite order; helps in dating rocks and history.
11. Widespread, abundant, short - lived geologically.