Fossils & The History Of Life Flashcards
How biologists define “life”:
-cellular organization
-must be able to respond to external stimuli and assimilate energy to grow, develop, and reproduce by regulating and coordinating internal processes
-homeostasis
-contains a complex genetic code allowing for adaptation and evolution
The ability not maintain a constant state of internal conditions that differs from the outside environment.
Homeostasis
The preserved remains of an organism.
The impression, trace, or track of an organism.
Fossil
Modes of Fossil Formation (6 ways)
-permineralization
-replacement
-compression
-encasement
-impressions
-trace fossils
Mode of fossil formation.
Dissolved minerals in groundwater permeate soft tissues, then crystallize to form rock that is shaped like the organism.
-hard tissues like bones, teeth, or wood are left behind
-most common method of fossil formation
Permineralization
Mode of fossil formation.
Similar to permineralization, except hard tissues are dissolved and replaced by minerals.
Replacement
Mode of fossil formation.
Heat and pressure cause the release of hydrogen and oxygen from the remains of an organism, leaving behind only a thin layer of carbon residue.
-most commonly occurs through carbonization
-occurs more often with plants than animals
Compression
Mode of fossil formation.
The entire body of an organism can be preserved if frozen, dried, or trapped in tar or resin that hardens into amber.
-soft tissues still degrade and decompose
Encasement
Mode of fossil formation.
Casts and molds.
The rigid outer surface of an organism can form an imprint in sediment as it decomposes.
Impressions
Mode of fossil formation.
An organism moving over soft sediment leaves tracks or trails.
-these markings are preserved if the sediment hardens or is covered by another layer
Trace Fossils
The organic molecules left behind by an organism.
-most can be found in kerogen
Molecular Fossils
Solid, water-insoluble organic matter embedded in rock (along with coal and shale).
Kerogen
Traces of organic chemicals that indicate former life.
Chemical Fossils
Estimates the age of a feature based on the layers around it.
Relative Dating
Used quantitative, laboratory-based techniques to determine the age of an object or feature.
-typically focuses on radioactive elements or changes in the Earth’s magnetic field
Absolute Dating
Only compares the age of things (ex. before X but after Y).
With fossils, done by comparing layers in which fossils are found n(older layers are always underneath newer ones).
Relative Dating
Come from organisms that were known to live in a specific time period and in many places.
Index Fossils
Done through radioactive dating.
Absolute Dating
Radioactive isotopes of some elements exist in nature and they decay at a steady rate.
-each isotope has a known half life and by comparing the amount that has decayed to the amount that would have been there originally, the absolute age can be determined
Radioactive Dating
Relative dating methods:
The Law of Superposition
Cross-Cutting Relationships
Relative Dating Method.
States that lower strata are older than the layers deposited on top of them, and the oldest rocks are at the bottom.
The Law of Superposition
Relative Dating Method.
A geological principle stating that the geological feature that intrudes into another is younger than the feature it intrudes into.
-these features are usually created by fault movements and span multiple strata
Cross-Cutting Relationships
Laboratory techniques that quantitatively estimate the age of organic materials, fossils, minerals, or rocks are used.
Absolute Dating
Type of Absolute Dating.
Based on the decay of radioactive isotopes of elements.
Radioactive Dating
Type of Absolute Dating.
Measures the magnetic field of Earth.
Paleomagnetism
Absolute Dating
Unstable isotopes undergo ___________ _____ ejecting matter and energy from their nuclei to reach a stable state.
Radioactive Decay
The length of time it takes for half of the radioactive elements in a sample to decay.
Half Life
Used to discuss how an environment changes over time and how that influences the species in that environment.
Microevolution —> addresses short-term evolutionary changes within a species or a population over relatively few generations.
Ecological Time
Measures the history of Earth by marking times when important changes happened.
Considers the entire history of Earth.
-divided into eons, eras, periods, and epochs based on geologic events (such as changes in climate).
Macroevolution —> focuses on long-term changes in speciation and extinction over vast amounts of time.
Geologic Time
Largest units of geologic time (lasting millions of years).
Eon
4 Enron’s throughout the history of Earth:
Hadean Eon
Archean Eon
Proterozoic Eon
Phanerozoic Eon
Eon
-no life on Earth
-Earth still forming (didn’t have a solid crust) —> Earth’s oceans didn’t exist yet because the water was vaporized into steam
Hadean Eon (4.6 - 4 billion years ago)
Eon
-formation of earliest rocks
-Earth’s crust cooled enough to form continents and oceans, still a large amount of volcanic activity
-atmosphere lacked oxygen
-earliest evidence of life
-earliest fossils
-evidence of bacterial life on land
-prokaryotes present (microorganisms started releasing oxygen molecules into the air as a byproduct of photosynthesis making the evolution of aerobic life possible)
Archean Eon (4 - 2.5 billion years ago)
Eon
-start marked by evolution of photosynthetic Cyanobacteria and the resulting introduction of oxygen into the atmosphere
-atmospheric oxygen levels significantly increased and resulted in the extinction of enormous numbers of anaerobic microorganisms
-evolution of eukaryotes leading to the acquisition of mitochondria and chloroplasts
-true multicellular organisms arose
Proterozoic Eon (2.5 billion years ago - 541 million years ago)
Eon
-initiated by the Cambrian Explosion
-appearance of trilobites and coral
-land plants, fish, insects, and tetrapods arose
-continents shifted leading to modern-day climate and life forms
Phanerozoic Eon (541 million years ago - today)
Marked the started of the Phanerozoic Eon.
An event of evolutionary radiation occurring over 20 million years ago that resulted in the evolution of most animal phyla.
Cambrian Explosion
A radiation event that occurred and the start of the Phanerozoic Eon and created most of the animal phyla that exist today.
Cambrian Explosion
United of geologic time spanning ~100 million years to a few hundred million years.
Eons are divided into ____.
Era
Phanerozoic Eon divided into 3 distinct eras:
Paleozoic Era
Mesozoic Era
Cenozoic Era
Era within the Phanerozoic Eon.
-aquatic invertebrates, mollusks, arthropods, fish, amphibians, and reptile diversified
-transition from aquatic to terrestrial environments aided by the evolution of land plants
-massive conifer forests covered the plant (allowing the evolution of gigantic insects in an oxygen-rich environment)
-ended with the catastrophic Permian extinction (volcanic activity in Siberia wiped out ~90% of all species)
Paleozoic Era (541 - 251 million years ago)
Era within the Phanerozoic Eon.
-“Age of the Reptiles”
-further increase in biodiversity
-dinosaurs, small mammals, birds, and flowering plants arose
-Pangea was slowly beginning to split apart
-temperatures variable and higher (than today)
-ended with a mass extinction
-climate was hot and humid, forest could be found at the poles, sea levels were much higher
Mesozoic Era
Era within the Phanerozoic Eon.
-mammals diversified
-continents moved to current positions
-climate began to dry and cool, Himalayan mountains formed —> because the exposed rock reacted with the carbon dioxide int he air, reducing the amount of greenhouse gases present in the atmosphere
Cenozoic Era (66 million years ago - today)
Each era can be further subdivided —> span 10s of millions of years.
Period
Periods can be further subdivided —> typically last 5-20 million years.
Epoch
-characterized by human-mediated changes to the earth
-would have begun post-WWII during the Atomic Age (demarcated by an increase in carbon dioxide and a dusting of abnormal radioisotopes across the planet)
-humans have excavated huge amounts of rock, disrupted the nitrogen cycle, spread countless invasive organisms, displaced a staggering number of species
The Anthropocene (Epoch)
2 concepts to explain speciation:
Phyletic Gradualism
Punctuated Equilibrium
Speciation
States that speciation occurs at a constant rate —> slow and gradually over time.
-there would be no clear differentiation between an ancestor and its descendants unless 2 different species evolve from 1
Phyletic Gradualism
Speciation
Recognizes that several descendant species quickly arise from a single ancestor at roughly the same point in geologic time
-which could happen through the sudden break-up os populations, destruction of different niches, or mass extinctions
Punctuated Equilibrium
The maximum capacity of an organism to reproduce under ideal environmental conditions.
-survival is a matter of optimizing fitness
Biotic Potential
The evolution of 2+ independent species that are in demented in ways that affect each other’s evolution.
-evolutionary change in 1 species can be directly linked to a change in another
-predators and prey, plants and herbivores, hosts and parasites, flowering plants and pollinators
2+ independent species evolve in ways that influence each other’s evolution.
Coevolution
Atmosphere in which oxidation can’t take place.
Reducing Atmosphere
Theory that states that the precursor molecules for life or life itself may not have originated on Earth at all, but instead from meteors carrying organic molecules bombarding the early Earth.
“Panspermia”
Life originated from no living materials.
Abiogenesis
Based on the dual function of RNA in sporting genetic information and catalyzing enzymatic reactions. —> **Essentially*, an RNA molecule would be capable of creating a duplicate of itself.
-over time, RNA molecules would have begun interacting with amino acids in the primordial soup to create polypeptides, eventually creating a ribosome capable of translating strands of RNA into proteins
RNA World
Where 1 cell lives inside another cell and both cells benefit from the relationship.
Endosymbiosis
