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What does the pneumonic Can Oscar See Down My Pants Pocket stand for?
Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, Permian
Fossil
Any remains, trace, or imprint, of a plant or animal that is preserved in the Earth’s crust since past geologic or prehistoric time
Dogma
Something held as an established opinion
Species
Group of organisms that can interbreed and produce fertile offspring having similar structure, habitats, and functions
Niche
The position of an organism or population in the environment as determined by its mode of life
Trace fossil
Animal tracks and/or burrows preserved in rocks
Trigger mechanism associated with extinction
A disturbance that brings one or more kill mechanisms into play
Kill mechanism associated with extinction
Physiologically disruptive process that causes death
Adaptive radiation
the process of diversification or multi-branching of a lineage of organisms. Each variant develops a significant structural and/or environmental breakthrough.
DIfference between punctuated equilibrium and natural selection
large extinctions have occurred both locally and globally many times in Earth’s history. The extinctions are followed by a period of adaptive radiation as vacant niches are filled. Once the niches are filled by the most well adapted species, a period of species stability occurs, which lasts until the next large extinction
Convergent evolution
Species that live in similar environments and evolved similar features but are only very distantly related
Configuration of continents
Cretaceous: many conclude Earth lacked significant ice during the Cretaceous. The lack of ice was due to the circum-equatorial Tethys ocean, which was effectively a giant furnace. Circum-equatorial oceanic circulation persisted through the end of the Eocene (33.9 Ma)
Cenozoic: circum-polar (Antarctic) oceanic and atmospheric circulation began in the Paleogene (53 Ma), and Earth was relatively cold by the start of the Oligocene (33.9 Ma). More recently, the last 2.5 million years have been particularly cold, and it is probably related to the closing of the Isthmus of Panama
Combined effect of N-S oriented continents and circum-polar circulation: Isolation of Antarctica facilitates ice sheet growth on the south pole, and the ice sheet acts like a gigantic fridge. It sends cold water north as form of density currents within Earth’s oceans.
Milankovitch radiation cycles
Milankovitch was a Serbia astronomer who correctly proposed that glaciation during the Pleistocene (last 1.5 million years of Earth’s history) was strongly related to solar insolation
Argued that amount of radiation reaching Earth’s northern hemisphere has a major impact on global temp, especially glaciation because most landmasses on Earth are in N. hemisphere
Amount of glaciation dependent on 3 things:
Eccentricity of Earth’s equinoxes (400,000 and 100,000 year cycles)
Tilt of Earth’s axis (41,000 year cycles)
Precession of the equinoxes (23,00 year cycles)
Greenhouse gasses (emphasis on CO2)
Earth is relatively warm because of greenhouse gasses in atmosphere
Sun mostly radiates visible light, which passes through greenhouse gasses and heats Earth’s surface
Consequence of heating caused by visible light: Earth’s surface emits infra-red radiation, heating the atmosphere and being absorbed by gasses → gasses emit infra-red radiation which increases temp even more
Six conditions that facilitate existence of liquid water on the surface of a planet
Volcanoes and plate tectonics
Comet that hit Earth may have contributed H2O as ice
Distance from sun that allows water to be liquid – not vapor or ice
Planet has sufficient mass so that atmosphere is not lost to space
Magnetosphere – prevents atmospheric gasses from being stripped from Earth by solar wind
Sufficient size so it does not cool too quickly (like Mars)
Oceans: act as a sink for CO2 as CO2 dissolves in oceans and remove it from the atmosphere where it acts as a greenhouse gas
Stanley Miller’s experiments and the results
Miller passed energy (electric sparks) through a mixture of hydrogen, ammonia, and methane to try and simulate likely conditions in the Early earth
Chemical products fell into a protected flask. Products included cyanide and formaldehyde, aka amino acids which are the vital components of all living cells
Best results came when Miller added volcanic gas to his mixture; discovered after his death
Most likely places for the first complex organic molecules and where life came into existence
Surface or shoreline habitats in lakes, lagoons, oceans
Unlikely to have formed in the open sea
Complex organic molecules vulnerable to damage from sodium and chlorine in seawater
Likely to have formed in lakes or seashore lagoons supplied with river water
Most likely tectonic settle of where the first complex organic molecules formed and the most likely place where life (as filamentous and tubular structures) first appeared
Clay mineral grains at sea floor spreading centers
Age range of rocks that contain the oldest known fossil evidence for life
3.77 to 4.28 Ga (billion years)
Notable characteristics of Kingdom Monera + time period during which stromatolites were the most advanced organisms on Earth
Kingdom Monera: single celled organisms that have no nucleus; aka prokaryotes. Include bacteria and blue-green algae. Only prokaryotes in the kingdoms.
Oldest known stromatolites about 3.7 Ga
Were most advanced from 3.7 Ga to 1.8 or 1.6 Ga (when eukaryotes appeared)
Differences between Prokaryotic cells and Eukaryotic cells
Eukaryotic cells are more complex than prokaryotic cells. Eukaryotes are hypothesized to have evolved from prokaryotes and have a symbiotic relationship as a result.
Prokaryote: single celled organisms that have no nucleus
Eukaryote: nucleus and organelles
Most prokaryotes are anaerobic, most eukaryotes need oxygen for respiration and are aerobic
Gift that stromatolites gave to Earth and development of banded iron formations (BIFs)
Uranium and pyrite ores in 2.3 Ga sandstone indicate O2 concentration in the atmosphere was about 1-2% compared to modern day. As stromatolites thrived, they released O2 into the atmosphere, allowing the concentration of O2 to reach a necessary level to support complex life.
Protist evolutionary highlights and the time period during which they were the most advanced on Earth
Difference between K. protista (eukaryote) and K. monera (prokaryote) is the presence of a nucleus
Presence of organelles is significant. Organelles include mitochondria and plastids
Protists have significantly more sophisticated locomotion structures than monera
Protists were first predators
Protists were first organism to reproduce secually
Evolutionary step that included acquiring a nucleus was big. The next step was the appearance of metazoans (multi-celled organisms)
Timeline:
3.7 Ga: Prokaryotes → 2.1 Ga (or 1.8 to 1.6): Eukaryotes → 1.1 Ga: appearance of Eukaryotes capable of sexual reproduction → 640 Ma: Metazoans → 540 Ma: metazoans with skeletons
Fundamental difference between sponges and cnidarians, in terms of nervous system (or lack of nervous system).
Sponges are the simplest multi-celled organism, between protists and cnidarians for the sake of evolutionary continuity
how cnidarians are different from coelomates
Cnidarians have a nervous net and defense mechanisms, but only 2 body layers. Coelomates have 3 body layers with no body cavity (or coelum)
Ediacara Fauna
Fossils of Ediacara Fauna are the first evidence for abundant, multicellular life
Consists of jelly fish and anemone-like organisms preserved in fine-grained sediments
Interpreted by some as cnidarians or proto mollusks but most believe they are soft-bodied organisms as a lineage that has no living representatives
What evolutionary development accounts for the apparent “Cambrian explosion”?
Natural selection: caused by environmental stresses associated with snowball earth effect. Snowball earth “trimmed the evolutionary tree”
Snowball/hothouse period cleared out many niches and allowed for eukaryotes to dominate Earth
Defense: appearance of predators may have made skeletons an important feature to successfully compete for resources as they offer protection from predators
Locomotion: skeletons provide anchor points and leverage for muscles and tendons. Better moving organisms are likely to be more successful at compete for resources
Increase of calcium concentration in oceans starting in the early Proterozoic and culminating in the Early Cambrian facilitated development of calcium carbonate and calcium phosphate skeletons in organisms
Cal Steven’s Hypothesis: presence of eukaryotic cells led to rapid evolution, so it was just ‘a matter of time’ before life ‘exploded’
Significance of Burgess Shale biota
Burgess Shale organisms are soft bodied organisms that are significantly different from any existing organisms. This suite of fossils is important because it is a more complete illustration of Paleozoic life than the record of animals with skeletons, which represents around 10% of the organisms that existed during the Cambrian time
two hypothesis that attempt to explain the significance of Burgess Shale Biota
Most burgess shale biota were beasts belonging to present day phyla but are now extinct and have view or no descendants that persisted for significant time
Implication is that all phyla and their associated body plans developed in the early Cambrian and their modern day organisms represent diversifications of the limited number of body plans that existed since early Cambrian time
Most Burgess Shale biota were beasts belonging to phyla which are now extinct that had few or no descendants that persisted for significant time
Implication is that in early through mid Cambrian time there were substantially more phyla and body plans than exist today, but organisms having these “experimental” body plans have no descendants because they did not survive the extinctions that occurred in the Cambrian
Likely cause of 3 major trilobite extinctions that took place in the Upper Cambrian and evidence supporting them
Causes (trigger mechanism): short-lived cooling of oceans
Kill mechanism(s): loss of habitat as epicontinental seas vanished, warm, shallow seas became rare
Evidence:
Extinctions are preceded by periods when thick accumulations of limestone were deposited
‘Generalists’, ancestral organisms that gave rise to the adaptive radiations were offshore, cold water species
Characteristics that make Grapholites and other organisms good index fossils
They were “floaters”, so very widely distributed, therefore a good index fossil
Evolved and changed rapidly, recognizable species appeared every million years or so
Very abundant
Likely cause of the major extinction that took place at the end of the Ordovician, and evidence supporting this hypothesis
Caused by climate changes
Rock record and isotope records show a major but short lived (500,000 year) glacial period began in the late Ordovician
Probably related to movement of a large landmass over the south pole, which favors colder climate and glaciation
The burial of organic carbon, which locked up carbon and drove down CO2 content of the atmosphere
why, in terms of paleoenvironmental factors, organic reef communities thrived in the Silurian and Devonian
Sea level was relatively high so significant parts of most continents were below sea level
Reef communities thrived because the relatively high sea level led to the development of epicontinental seas, which were relatively shallow and warm, excellent reef environments
what feature is common to all chordates
a notochord: a stiff rod of dense tissue
Calcium phosphate skeleton (CaPO4)
why the calcium phosphate (CaSO4) skeleton of chordates is a big evolutionary advantage over the CaCO3 skeletons of their animals.
Calcium phosphatase skeletons make anaerobic glycolysis possible
Anaerobic glycolysis is cellular breakdown of sugar to make energy in the absence of oxygen → byproduct is lactic acid, which dissolves CaCO3 and is a problem when you have a CaCO3 skeleton
The physiological differences between Placoderms and Ostracoderms
Ostracoderms are jawless fishes
Placoderms are jawed fishes
which of the following lineage of fishes gave rise to all jawed fishes: ostracoderms, placoderms, cartilaginous fishes actinopterygians/ray-finned fishes, sarcopterygians/lobe-finned fishes.
Placoderms gave rise to all modern jawed fishes according to a 419 Ma (Silurian) fossil discovered in 2013
Why Actinopterygians (Ray finned fishes) were successful fishes
They had thin, lightweight bones and fins built for fast strokes and fast swimming. This meant they were good swimmers and became the dominant fishes
why fish that via mutations developed leg-like fins were successful
Lived in shallow, epicontinental seas subject to period desiccation. It was an advantage for these organisms to efficiently flop from pond to pond
Transitional organisms lived in swampy areas choked with vegetation so strong, limb-like fins helped them move through these environments
why amphibians outcompeted Rhipidistians
Amphibians could bask in the sun to warm up and speed digestion, leading to more rapid growth and maturity reached later in life, which favors more successful reproduction
Ability to use oxygen in air which is more concentrated and easier to absorb than oxygen in water
the cause of the extinction at the end of the Devonian, including the Kellwasser events
Glaciation at end of Devonian caused by cooling event
Large landmass at S. pole
Flourishing of first large forests in Devonian and photosynthetic drawdown of CO2
Burial of carbon as trees died further reduced availability for carbon for making CO2
Accelerated chemical weathering caused by CO2 respired from plant roots and microclimate effect of forests, which causes increased rainfall and cycling of water through forest soils
Kellwasser events were a trigger mechanism that is typically recorded as two 1.5-2.0 m thick beds of organic, rich, black shale
Kellwasser-related extinction: 40% of all marine genera died out, 70% of all marine invertebrate species died out
Deposited at time of high sea level, interpreted as deep water deposits that preceded a drop in sea level, indicating glaciation
Cooling may have causes turn over of water in oceans
Extinction is correlated to cold periods: warm-water invertebrates suffered the most while most cold-water species were unaffected
Marine placoderms as well as tabulate corals, rugose corals were devastated and rare throughout the Paleozoic and replaced by sponges, which favor cold water
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