Deep Time Discovered Flashcards
Macroevolutionary Events
Large-scale evolutionary changes that occur over long periods of time, such as the origin of life (~3.8 billion years ago), the Cambrian Explosion (~541 million years ago), and the emergence of Homo Sapiens (~300,000 years ago)
Acasta Shale
A rock formation in Canada, located in the Northwest Territories, containing some of the oldest known rocks on Earth, estimated to be around 4 billion years old, significant for studying early Earth geology
Darwin’s View of Earth’s Age
Darwin believed that the Earth was much older than the 6,000 years proposed by some of his contemporaries, as he required vast amounts of time for gradual evolution
Lord Kelvin’s Age Estimate
Lord Kelvin estimated Earth’s age to be much younger (~20-40 million years), due to his reliance on heat loss calculations, but his error came from not knowing about radioactive decay as a heat source
Half-Life
The time it takes for half of the atoms in a radioactive element to decay. Potassium-40 has a long half-life of 1.25 to 1.3 billion years, which is useful for dating geological formations over long periods
Potassium-40 (K-40) Dating
A method of radiometric dating based on the decay of potassium-40 into argon-40. With a half-life of about 1.25 to 1.3 billion years, this method is useful for dating volcanic rocks and determining the age of fossils found in nearby sedimentary layers
Argon-40
A gas produced by the radioactive decay of potassium-40. When volcanic lava cools into rock, argon-40 escapes, leaving only potassium-40. By measuring the ratio of K-40 to Ar-40 in rocks, scientists estimate the time since the rock solidified
Margin of Error in Acasta Rocks
The estimated age of the Acasta rocks has a margin of error of +/- 50 million years, which equates to 0.3%
Meteorites
Solid extraterrestrial objects that survive passage through the Earth’s atmosphere and impact the surface. They ate important for understanding the early solar system and dating Earth’s formation
Carbon-14 Dating
A method used to date organic materials up to 50,000 years old, making it useful for studying human history because of its relatively short half-life (5,730 years)
First Prokaryotic Cells
Prokaryotic cells, the simples form of life, first appeared around 3.5 billion years ago. These single-celled organisms are thought to have been the earliest life forms on Earth
First Eukaryotic Cells
Cells, which are more complex and contain membrane-bound organelles like a nucleus, evolved around 1.5 billion years ago, likely from prokaryotic ancestors
Precambrian Rock Layers
These ancient layers, lacking obvious signs of life, troubled Darwin because they didn’t show the gradual buildup of complexity he expected. Later discoveries of microscopic life forms and soft-bodied organisms helped resolve this concern
Precambrian Period
Spanning from the formation of the Earth (~4.6 billion years ago) to the start of the Cambrian period (~541 million years ago), the Precambrian includes about 88% of Earth’s hisotry and saw the emergence of early life forms, including prokaryotes and eukaryotes
Fungi on Land
Fungi were among the first multicellular organisms to adapt to life on land around 550 million years ago, paving the way for the evolution of other land-dwelling organisms