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
First Land Inhabitants
After fungi, plants were the first multicellular organisms to inhabit dry land. Their ancestors were likely green algae that adapted to life out of the water
Evolution in Oceans
Approximately 80-85% of life’s evolutionary history took place entirely in the oceans before life moved onto land
Human History Summer Day Analogy
Using a summer day analogy, if Earth’s history were compressed into 24 hours, human history would occupy only the last few seconds, illustrating the brief time humans have existed relative to the Earth’s age
Earth’s Formation
Earth is estimated to have formed about 4.6 billion years ago. The planet’s early environment laid the groundwork for the eventual emergence of life
First Multicellular Life
Multicellular life began to emerge around 550 million years ago. Fungi were among the first multicellular organisms to adapt to life on land, followed by plants and animals
Evolution of Vertebrates
Vetebrates, organisms with a backbone, first appeared around 500 million years ago, starting with jawless fish. Amphibians evolved around 380 million years ago, followed by reptiles at 330 million years ago
Dinosaurs and Mammals
They both appeared approximately 230 million years ago. After the mass extinction of the dinosaurs 65 million years ago, mammals diversified into a wide variety of species
Mass Extinction Events
Significant events in Earth’s history when a large number of species became extinct in a relatively short period of time. One of the most notable events was the extinction of dinosaurs about 64 million years ago, which allowed mammals to diversify
Vertebrate Evolution Timeline
Vertebrates evolved in stages, starting with jawless fish (~500 million years ago), amphibians (~380 million years ago), and reptiles (~330 million years ago). This gradual evolution highlights the transition from aquatic to terrestrial life
