Fossils And Geological History Flashcards
What is earths time scale?
The geological time scale is a record of the life forms and geological events in earths history.
What does the geological time scale provide?
Provides a system of chronologic measurement relating stratigraphy to time that is used by geologist, palaeontologist, and other earth scientists.
Used to describe the timing and relationship between events that have occurred during the history of earth
How did scientists develop the geological time scale?
By studying rock layers and fossils worldwide
Radioactive dating helped determine the absolute divisions in the time scale
How do geologists refer to this time scale?
Referring to time: early, middle, and late
Referring to rocks: lower, mid, and upper
What is the division of the geologic time scale?
Earths history is subdivided into time units based on the fossil record and extinctions
Name the divisions from largest to smallest
Eon (largest unit of geologic time)
Era (smaller division of an eon)
Period (smaller division of an era)
Epoch (smaller division of a period)
What are the four eons?
Pre-Archean or Hadean (4.6-3.8 Billion years)
Archean (3.8-2.5 Billion years)
Proterozoic (2.5 billion - 560 million years)
Phanerozoic (570 million years - present)
What does geologic time begin with?
Precambrian
What happened in the pre-archean or hadean eon?
~4.6 BYA: formation of earth and moon
~4 BYA: likely origin of life
What happened in ghetto Archean eon?
The eon of first life
~3.8 BYA: oldest known rocks
~3.5 BYA: oldest known fossils (singles celled organisms resembling bacteria)
3.2 BYA: first known plants (algae)
What happened in the Proterozoic eon?
The eon of first multi-celled life
1.2 BYA: first known animal (jellyfish)
What happened in the Phanerozoic eon?
The eon of complex life
What are the four eras?
Precambrian (88% of earths history)
Paleozoic (ancient life. 544 MYA. Lasted 300 million years)
Mesozoic (middle life. 240 MYA. Lasted 180 million years)
Cenozoic (recent life. 65 MYA. Continues through present day)
What geologic time are we living in?
The Holocene Epoch of the Quaternary Period of the Cenozoic Era
What era is the Paleozoic Era?
Ancient life (542 MYA - 250 MYA)
What are the 6 periods of the paleozoic era?
- Cambrian period
- Ordovician period
- Silurian period
- Devonian period
- Carboniferous period (Mississippian period and Pennsylvanian period)
- Permian period
What happened in the Cambrian period?
Age of the trilobites
What happened in the Ordovician period?
The only life on Earth was found in the seas. However, by the end of the Ordovician Period, life moved to land. Plants began to colonize out of the water paving the way in later periods for animals to follow
What happened in the Silurian period?
Various invertebrates move on to land
What happened in the Devonian period?
Saw vertebrates join the other animals on land. The first ones to leave the water were similar to amphibians and they eventually evolved into reptiles
What happened in the Carboniferous period?
Much of the coal we use today was made during the later stages of this time period
What happened in the Permian period?
The largest mass extinction ever on Earth happened. This mass extinction, known as the Permian Extinction, completely wiped out about 95% of all life in the oceans on Earth.
What are trilobites?
• lived in earth’s ancient seas
• extinct before the dinosaurs came into existence
• Cambrian period is known as the “age of the trilobites”
What are brachiopods?
• existed in the early canbrian period
• marine animals that resemble clams
What are early fish?
• existed in the Cambrian period
• did not have jaws
• some species of sharks were in existence at this time
What shark was considered a living fossil?
The frilled shark that was found in Japan in January 2007
What are some early land plants?
Cone bearing plants
Mosses
Ferns
What era was the Mesozoic era?
• middle life
• sometimes called “age of the dinosaurs”
• began 250 MYA
What were the three periods in the Mesozoic era?
- The Triassic period
- The Jurassic period
- The Cretaceous period
What happened during the Triassic period?
• first small dinosaurs appeared in this period
• on land, the amphibians and small reptiles like turtles were dominant during the early Triassic period
What happened during the Jurassic period?
• larger and more abundant dinosaurs appeared in this period
• land animals during the Jurassic period had more diversity
• the end of the Jurassic period, birds evolved from dinosaurs
What happened during the Cretaceous period?
• flowering plants appeared during the end of this era
• on land, the first small mammals started to appear during the Cretaceous period (small, warm-blooded animals. Hair covering their bodies)
What was the main plant life of the Mesozoic era?
Gymnosperms - plants that produce seeds, but not flowers
How did the Mesozoic era end?
Ended with a mass extinction event about 65 MYA
many groups of animals, including dinosaurs disappeared suddenly at this time
Many scientists believe that this event was caused by a comet or asteroid colliding with the earth
What era is the Cenozoic era?
Recent life
Began about 65 MYA and continues today
What was the climate like in the Cenozoic era?
warm and mild
What were the two periods in the Cenozoic era?
- Tertiary period ( paleogene and neogene)
- Quaternary period
What animals existed and evolved in the Cenozoic era?
• marine animals such as whales and dolphins existed
• mammals began to increase and evolve adaptations that allowed them to live in many different environments (land, air, sea)
• as the climate changed, the animals had to adapt to the rise and fall of the oceans caused by melting glaciers
What helped cool down the climate in the Cenozoic era?
Growth of mountains
What provided food for mammals in the Cenozoic era?
Grasses increased
When did ice ages occur?
They occurred late in the Cenozoic era (quaternary period)
What is Cenozoic era sometimes called?
Age of the mammals
What are some examples of marine animal life in the Cenozoic era?
Algae, mollusks, fish and mammals
What are some land animal examples in the Cenozoic era?
Bats, cats, dogs, cattle, and humans
Humans are thought to have appeared around 3.5 MYA (during the most recent period - quaternary)
What was the most common plant life in the Cenozoic era?
Flowering plants
