Evolutionary Biology Midterm 2

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Stratigraphy

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A method that places fossils in relative sequence to each other. Sheets of similar rock, called "strata," layered upon one another, are built up in chronological order. The method yields no absolute age but does establish a sequence.

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Index Fossils

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By matching rock strata in one location to comparable rocks in another location, it is possible to build up an overlapping chronological sequence longer than that represented at any single site by itself. The actual correlation of rock strata between two distantly located sites is done by comparison of mineral content and structure. An INDEX FOSSIL is an organism, usually a hard-shelled invertebrate animal, that previous work has shown to occur within only one specific time horizon of rock. The presence of an index fossil in a rock layer confirms that the stratigraphic layer belongs to the same time horizon as strata elsewhere that contain the same fossil.

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Radiometric Dating

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A technique that takes advantage of the natural transformation over time of an unstable elemental isotope to a more stable form or product. Such radioactive decay of the isotope of an element into another isotope occurs at a constant rate, expressed as the characteristic HALF LIFE of an isotope. These isotopes, with half lives measured in millions of years, are suitable for dating very ancient events.

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Radiocarbon Dating

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For more recent events, radiocarbon decay is used, wherein the halflife is only 5730 years. It uses radiocarbon, rating the fossil, not the rock. Fossils over 60,000 years have 14C too small to measure.

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Tree Rings

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By matching overlapping patterns in trees of different ages, a continuous sequence of tree rings, collectively greater than any tree alone, can be extended back into the past.

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Hadean Eon

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The earliest eon, when most water existed in gaseous form and the Earth was still largely molten, leaving no rock record.

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Archean Eon

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The oldest dated rocks, at 3.8 bya, mark the beginning of the archean, and its conclusion is taken as 2.5 bya. Fossils include impressions of microorganisms and STROMATOLITES, layered mats of trapped bacteria. These are PROKARYOTIC MICROORGANISMS, simple cells that lack a nucleus. Through the archean, the Earth and moon received heavy meteorite bombardment. Around each impact the crust melted and was perhaps punctured, allowing enormous outpouring of lava that flooded the surrounding surface. We would still find the Earth cratered and scarred if not for geological remixing.

Origin of life in remote past; first fossil evidence at 3500 mya; diversification of prokaryotes; photosynthesis generates oxygen, replacing earlier oxygen-poor atmosphere; evolution of aerobic respiration

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Stromatolites

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Layered mats of trapped bacteria

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Prokaryotic microorganisms

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Simple cells that lack a nucleus

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Proterozoic Eon

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Eukaryotes appear as microfossils--microscopic impressions in rocks 2 billion years old. Unlike prokaryotes, EUKARYOTES have a nucleus, speciliazed cellular equipment, and the ability to reproduce sexually, rather than by just dividing. This was also a time when the world's one large continental landmass broke into small continents. By the late part of the proterozoic, the small continents were scattered around the equatorial belt. 700mya to 800mya the Earth descended into the most severe ice age ever and remained for 200my. Ice was 1km thick. Evidence is from equatorial rocks which were clearly formed from compacted deposits of dirt and debris left behind when the ice melted.
Cause: CO2 levels plummeted, heavy raid fell on land, washing CO2 from air, temperatures dropped, ice accumulated at poles which reflected sun's heat back away. Oceans froze. Many microorganisms perished but some found refuge. Volcanoes then spewed ash out and CO2 once again accumulated, caused a greenhouse effect, and the ice started melting. Then, 542 mya, life rebounded and multicellular organisms appeared.

Earliest eukatyotes (ca. 1900-1700 mya); origin of eukaryotic kingdoms; trace fosils of animals (ca. 1000 mya); multicellular animals from ca. 640 mya.

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Phanerozoic Eon

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Divided into 3 eras
1: Paleozoic (Old Animal Life)
2: Mesozoic (Middle Animal Life)
3: Cenozoic (Recent Animal Life)

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Paleozoic Era

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Invertebrates dominated, as they still do today. But among the vertebrates, fish were the most diverse, so the Paleozoic was the "age of the fishes." The term BIOLOGICAL RADIATION applies to an evolving group that spreads into different environments and exhibits diversity of structure. The first vertebrates to live on land, the tetrapods, appeared in the Paleozoic, and by late in this era an extensive radiation of their own was underway, giving rise to modern day amphibians.

Marine animals diversify; First appearance of most animal phyla and many classes within a short interval; Mass extinction at end of Ordovician period; Origin of jawed fishes; Earliest terrestrial vascular plants; Diversification of bony fishes; origin of ammonoids, amphibians, insects, ferns, seed plants; Mass extinction at end of Devonian period; Gondwanaland and small northern continents form; extensive forests of early vascular plants; early orders of winged insects; first reptiles; Continents aggregated into Pangaea; glaciations; “reptiles,” including mammal-like forms; major mass extinctions, especially of marine life, at end of Permian period.

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Biological Radiation

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n evolving group that spreads into different environments and exhibits diversity of structure

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Tetrapods

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First vertebrates to live on land (Paleozoic era). Gave rise to amphibians.

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Mesozoic Era

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2nd era of Phanerozoic eon. One later group derived from the early tetrapods, the reptiles, underwent an extraordinary radiation that took them to all environments. The mesozoic is thus often called the "Age of the Reptiles."

Continents begin to separate; marine diversity increases; “gymnosperms” become dominant; first dinosaurs, first mammals in Triassic period; Continents separating; first birds; archaic mammals; Most continents separated; continued radiation of dinosaursl mass extinction at end of Cretaceous period, including last ammonoids and dinosaurs.

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Cenozoic Era

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3rd Era of Phanerozoic eon. The cenozoic is often called the "Age of Mammals." The vast extinction of dinosaurs that mark the end of the Mesozoic opened evolutionary opportunities for mammals. As a result, mammals enjoyed a period of their own expansive radiation into the ensuing Cenozoic, taking up dominant positions in most terrestrial ecosystems.

Continents nearing modern positions; increasingly cool, dry climate; radiation of mammals, birds, snakes, angiosperms, pollinating insects, teleost fishes; Continents in modern positions; repeated glaciations and lowering of seal level; shifts of geographic distributions; extinctions of large mammals and birds; evolution of Homo Erectus to Homo Sapiens; rise of agriculture and civilizations.

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Ectotherms

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Animals that depend largely upon sunlight or radiation from the surrounding environment to heat their bodies are cold-blooded, or "ectotherms," like turtles, crocodiles, lizards, or snakes.

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Endotherms

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"Warm-blooded animals" that produce heat inside their bodies by metabolizing proteins, fats, and carbs.

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Dinosaur debate (warm blooded or cold blooded?)

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Large Mesozoic reptiles are found in temperate regions. When winter arrives, for a large and bulky animal there are no cracks into which they can retreat to avoid the cold. Thus, large animals must be endothermic to survive.
The ratio of predators to prey was consistent for dinosaurs to be endothermic.
The microarchitecture of dinosaur bone is similar to that of endothermic mammals, not to that of ectothermic reptiles.

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Organic chemistry

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based on carbon

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Inorganic chemistry

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based on all elements besides carbon

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Stanley Miller and Harold Urey

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1953 simulation of Earth's atmosphere. Heated mixture with sparks to emulate lightning. Organic molecules formed within the simulation. Follow-ups by others produced even more organic molecules, including compounds found in the basic structure of genes, DNA.

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Heterotrophs

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Organisms nourished by others, which did not directly manufacture ingredients needed for their own maintenance and duplication (reproduction), but instead subsisted on organic chemicals available in their environments

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Cell- Prokaryotic, Heterotroph

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Their cellular DNA was free within the cytoplasm- no nuclear membrane wrapped it, making it PROKARYOTIC. They were HETEROTROPHS, soaking up available organic molecules in the environment to feed their cellular appetites. SEXUAL REPRODUCTION, based on the fusion of male and female sex cells (GAMETES), is absent in prokaryotes. They reproduce ASEXUALLY by means of BINARY FISSION, whereby a single prokaryotic cell divides in two; these cells then divide again repeatedly, forming an expanding colony.

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Cell- Prokaryotic, Autotroph

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The first photosynthesizing, prokaryotic cells were AUTOTROPHS (self-nourishing), so their energy came from conversion of the sun's energy. The Earth was not born with atmospheric oxygen, it was created by the water-splitting process of photosynthesis.

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Cell- Prokaryote to Eukaryote

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Microfossils appear that are noticeably difference in appearance. They are larger, exhibiting evidence of internal membranes and thick walls. These Eukaryotic cells have DNA enclosed in a specialized membrane-- the NUCLEAR ENVELOPE-- and the cell contains organelles dedicated to particular functions and enclosed in membranes. One such organelle is the MITOCHONDRION, a small power factory within the cytoplasm where oxygen is consumed in organic fuels to obtain energy used by the cell. Plant cells, in addition, have a CENTRAL VACUOLE (storage depot collecting proteins, pigments, waste, etc...) and CHLOROPLASTS (organelles dedicated to photosynthesis).
While prokaryotic cells reproduced asexually by cell division through MITOSIS, eukaryotic cells can also reprodudce by MEIOSIS, the fusion of two specialized sex cells, which code DNA as a genetic mixture of both parent cells. This leads to genetic recombination, generating variation, and thus evolution.

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Mitochondrion

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A small power factory within the cytoplasm of eukaryotic cells where oxygen is consumed in organic fuels to obtain energy used by the cell

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Central Vacuole

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The storage depot in plant cells which collect proteins, pigments, waste, etc...

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Chloroplasts

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Organelles in eukaryotic cells dedicated to photosynthesis.

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Meiosis

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the fusion of two specialized sex cells, which code DNA as a genetic mixture of both parent cells

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Endosymbiosis

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Eukaryotic cells developed partnerships with prokaryotic organisms living within their cell borders.

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DNA

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Chains of nucleotides which code for genetics

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RNA

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The DNA is a template. To carry out its coded instructions it produces-- TRANSCRIBES-- a complimentary messenger moluecule of RNA (ribonucleic acid), which is involved in a helper role in protein synthesis.

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Bacteria (Eubacteria)

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The bacteria include the CYANOBACTERIA, sometimes called "blue-green algae." They are photosynthetic and their appearance about 3.5bya coincided with the onset of free oxygen buildup in the atmosphere, which changed the environment in which subsequent life evolved.

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Nitrogen fixation

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When chemoautotrophs (eubacteria that obtain their energy not from sunlight but from chemical bonds of inorganic molecules) convert nitrogen to ammonia, eventually producing nitrate, which is taken up by plants. This is critical because nitrogen is an important component of proteins and nucleic acids, yet only these eubacteria, and no other organisms, have the ability to take nitrogen and fix it in usable compounds. In so doing, the single-celled prokaryotes make nitrogen available to other organisms, mostly plants.

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Bacteria (Archaebacteria)

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Grew in young Earth, breaking down cellulose into methane

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Protists

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Most diverse form of eukaryotes. They include algae, like PHYTOPLANKTON, which are at the base of most marine and freshwater food webs, as well as responsible for much of the worlds O2 production.

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Vascular tissue

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tubular cells running throughout a plant that act as a plumbing system.

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Plant reproduction

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Unlike animals, plants have a life cycle that includes an alteration of generations, wherein multicellular diploid (2a) individuals and multicellular haploid (a) individuals successfully alternate with each other. The cycle alternates between SPOROPHYTE INDIVIDUALS and GAMETOPHYTE INDIVIDUALS.

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Bryophtes

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Some of the earliest land plants, mosses being the most common example.

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Seed Plants

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Vascular Plants that include the gymnosperms (e.g. conifers, or cone bearing plants) and angiosperms (flowering plants). The seed protects the young embryo, and pollen is handy transport for the sperm.

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Gymnosperms

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Conifers. The earliest of the seed plants to evolve, they are present in the Carboniferous along with the then more abundant seedless plants.

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Angiosperms

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Flowering plants. Also vascular seed plants, they debuted after gymnosperms during the mid Mesozoic.

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Tetrapods

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First chordates (vertebrates) to employ limbs, including early amphibians. Arising later within the tetrapods were the reptiles, birds, and mammals. Tetrapod literally means "four-footed," but it also can include legless and finned forms like snakes and whales. Evolving from amphibians were the AMNIOTES, including reptiles, birds, and mammals. Their name is taken from an embryonic innovation. The eggs of amniotes are typically laid in water and hatched there.

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Cleidoic Egg

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Sometimes called the "amniotic egg" the cleidoic egg includes the embryo floated in a water jacked formed from a thin membrane, the amnion, and several other embryonic membranes.

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Biogeographic Realms

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Where each continent sports its defining complement of species

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Plate tectonics

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The energy that drives the shifting of the plates, caused largely from activity beginning deep within the Earth's molten mantle. Convection currents of molten material rise to the surface and split through the crust at suture zones, powering the plates apart. As the molten lava wells up and hardens, it adds new rock along the edges of the plates. Where they are pushed into other plates, great mountain ranges might be pushed up.

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Corridors

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Uninterrupted connections, easy routes of travel across continental areas.

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Founder effect

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The phenomenon in which rare traits are more common in new and isolated locations.

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Catastrophic/Mass Extinctions

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Include the loss of species from many groups, take large numbers of species, and occur abruptly over a relatively short period of geological time.

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Uniform/Background Extinctions

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Members of taxonomic groups are lost gradually over long time periods without abrupt loss of large numbers. Most species were lost this way.

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Co-Evolution

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Where two taxa are tightly coupled and interdependent in a co-evolutionary relationship. They are like a coupled set of evolutonary siamese twins. The loss of one places the other at risk (i.e. koalas and eucalyptus trees)

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Islands: Species-Area Relationships

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The larger an island, the more species of plants and animals the island supports. The smaller the arae, the fewer the species. The relationship is direct. If the island is near the mainland, the IMMIGRATION RATE is higher. Another factor is the EXTINCTION RATE, the rate at which species already on an island go extinct. As teh island begins to fill up with species, competition increases, resources become more scarce, and the rate of extinction therefore increases.

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Van Valen's Red Queen

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Van Valen, in the 1970s, discovred that most groups of species became extinct gradually, at a constant rate characteristic of their taxonomic group. He examined the fossil record of a group and followed it through evolutionary time. He plotted them on a graph and noticed it as gradual. A species must then evolve faster just to stay in the same place competitively. If a species falls behind, it becomes more vulnerable to extinction. Biotic challenges usually change too fast for species to catch up.

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Mass Extinctions

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One attempt to mark mass extinction events starts reasonable. Select at random, 10 samples of genera from a large data set of fossils, then plot the maximum and minimum numbers becoming extinct over available intervals of time. The result is a graph of peak extinctions over the Phanerozoic, almost 600my. Five common extinction peaks are noted- late in or at the end of the Ordovician, Devonian, Permian, Triassic, and Cretacous.

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Trophic Stability

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Trophic means food or nourishment. This hypothesis suggests that the stability of trophic resources affects species survival. The more stable the trophic resources, the more species; and conversely, the less stable, the fewer the species.
When plate tectonics bring continents together into one supercontinent, mass extinctions should occur (increased instability of trophic resources, loss of some perimeter area). When a supercontinent fragments into separate continents, mass extinctions should be absent (increased trophic stability, additional perimeter area).

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Ice Age

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An ice age is made up of cycles wherein there is a GLACIAL PHASE (climate cools, ice sheets form and spread) and and INTERGLACIAL PHASE (climate temporarily warms, ice sheets retreat)

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Igenous Rocks

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Rocks formed by volcanic activity. Thus, fossils are rare.

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Sedimentary Rocks

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formed from sediments, accumulating over long periods of time. Contain materials that solidify/precipitate from water, or breakdown of rocks from land, settle, and form rock (erosion of old rock). Most common to find fossils.

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Metamorphic Rocks

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rocks that changed in form due to pressure and heat. Rare and usually deformed.

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Geographic Bias

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Fossils from marine areas & lowland areas, but not much elsewhere

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Taxonomic Bias

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Bulk of fossils are of marine fossils/organisms (though 10% of all species are marine). Only the hard parts are fossilized, so only few of the vertebrates are represented in fossils. Soft parts are underrepresented, as well as flowers

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Temporal Bias

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Earth’s crust is constantly recycled, rosion of exposed earth (high elevations). Subduction: where one layer gets transferred to a lower area and will be too hard to find. We find more recent things than old things. Supports Darwin’s gradualism (gradual change over time).

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Cenancestor (LUCA)

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The cenancestor is the “last universal common ancstor,” which gave rise to all modern living things. It is the hypothetical latest living organism from which all organisms now living on Earth descend. Thus it is the most recent common ancestor of all current life on Earth. It is estimated to have lived some 3.5 to 3.8 billion years ago (sometime between the Basin Groups and Paleoarchean eras)[

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Outline the events of the Precambrian explosion most important in the history of life

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Anaerobic prokaryotes: bacteria, cyanobacteria (blue green algae), Archaea (close relatives of Eukaryotes) ~3.5bya
Origin of Eukaryotes (Margulis’ endosymbiotic theory) ~2.2 bya: Arose from prokaryotes engulfed other prokaryotes to make eurkaryotes. Ate other cells = fagocytes. Went through adaptive radiation.
Multicellularity (sponges, jellyfish) ~600mya: had cell specialization (different cells in organisms do different jobs than others.

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Summarize the events of the Cambrian explosion most important in the history of life.

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The theory of the Cambrian Explosion holds that, beginning some 545 million years ago, an explosion of diversity led to the appearance over a relatively short period of 5 million to 10 million years of a huge number of complex, multi-celled organisms. Moreover, this burst of animal forms led to most of the major animal groups we know today, that is, every extant Phylum. It is also postulated that many forms that would rightfully deserve the rank of Phylum bothCambrian Fossils appeared in the Cambrian only to rapidly disappear. Natural selection is generally believed to have favored larger size, and consequently the need for hard skeletons to provide structural support - hence, the Cambrian gave rise to the first shelled animals and animals with exoskeletons (e.g., the trilobites). The early Cambrian and the size of many animals also "exploded".
-Brachiopods, crustaceans and other anthropods (e.g. trilobites), onychophorans (velvet worms), sipunculid worms (peanut worms), segmented worms, chordates.
-Mass extinction at end of Cambrian.

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Outline the events of the Mesozoic era most important in the history of life.

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The Mesozoic era is one of three geologic eras of the Phanerozoic eon. Lying between the Paleozoic and the Cenozoic, Mesozoic means 'middle animals'. It is often called the 'Age of the Reptiles', after the dominant fauna of the era.

The Mesozoic was a time of tectonic, climatic and evolutionary activity. The continents gradually shifted from a state of connectedness into their present configuration; the drifting provided for speciation and other important evolutionary developments. The climate was exceptionally warm throughout the period, also playing an important role in the evolution and diversification of new animal species. By the end of the era, the basis of modern life was in place.

Following the Paleozoic, the Mesozoic extended roughly 180 million years: from 251 million years ago (Mya) to when the Cenozoic era began 65 Mya. This time frame is separated into three geologic periods. From oldest to youngest:

* Triassic (251.0 Mya to 199.6 Mya)
* Jurassic (199.6 Mya to 145.5 Mya)
* Cretaceous (145.5 Mya to 65.5 Mya)

The lower (Triassic) boundary is set by the Permian-Triassic extinction event, during which approximately 90% to 96% of marine species and 70% of terrestrial vertebrates became extinct. It is also known as the "Great Dying" because it is considered the largest mass extinction in history. The upper (Cretaceous) boundary is set at the Cretaceous-Tertiary (KT) extinction event, which may have been caused by the impactor that created Chicxulub Crater on the Yucatán Peninsula. Approximately 50% of all genera became extinct, including all of the non-avian dinosaurs.

The era featured the dramatic rifting of the supercontinent Pangaea. Pangaea gradually split into a northern continent, Laurasia, and a southern continent, Gondwana. This created the passive continental margin that characterizes most of the Atlantic coastline (such as along the U.S. East Coast) today.

By the end of the era, the continents had rifted into nearly their present form. Laurasia became North America and Eurasia, while Gondwana split into South America, Africa, Australia, Antarctica and the Indian subcontinent, which collided with the Asian plate during the Cenozoic, the impact giving rise to the Himalayas.

Climate

The Triassic was generally dry, a trend that began in the late Carboniferous, and highly seasonal, especially in the interior of Pangaea. Low sea levels may have also exacerbated temperature extremes. With its high specific heat capacity, water acts as a temperature-stabilizing heat reservoir, and land areas near large bodies of water—especially the oceans—experience less variation in temperature. Because much of the land that constituted Pangaea was distant from the oceans, temperatures fluctuated greatly, and the interior of Pangaea probably included expansive areas of desert. Abundant evidence of red beds and evaporites such as salt support these conclusions.

Sea levels began to rise during the Jurassic, which was probably caused by an increase in seafloor spreading. The formation of new crust beneath the surface displaced ocean waters by as much as 200 m more than today, which flooded coastal areas. Furthermore, Pangaea began to rift into smaller divisions, bringing more land area in contact with the ocean by forming the Tethys Sea. Temperatures continued to increase and began to stabilize. Humidity also increased with the proximity of water, and deserts retreated.

The climate of the Cretaceous is less certain and more widely disputed. Higher levels of carbon dioxide in the atmosphere are thought to have caused the world temperature gradient from north to south to become almost flat: temperatures were about the same across the planet. Average temperatures were also higher than today by about 10°C. In fact, by the middle Cretaceous, equatorial ocean waters (perhaps as warm as 20 °C in the deep ocean) may have been too warm for sea life, and land areas near the equator may have been deserts despite their proximity to water. The circulation of oxygen to the deep ocean may also have been disrupted. For this reason, large volumes of organic matter accumulated because they were unable to decompose and were eventually deposited as "black shale".

Not all of the data support these hypotheses, however. Even with the overall warmth, temperature fluctuations should have been sufficient for the presence of polar ice caps and glaciers, but there is no evidence of either. Quantitative models have also been unable to recreate the flatness of the Cretaceous temperature gradient.[citation needed]

Oxygen levels in the Mesozoic atmosphere were probably lower (12 to 15 %) than today's level (20 to 21 %). Some researchers have postulated levels of 12 % because that was assumed to be the lowest concentration at which natural combustion could occur. However, a 2008 study concludes that at least 15 % is necessary.[2]

Life

The extinction of nearly all animal species at the end of the Permian period allowed for the radiation of many new lifeforms. In particular, the extinction of the large herbivorous and carnivorous dinocephalia left those ecological niches empty. Some were filled by the surviving cynodonts and dicynodonts, the latter of which subsequently became extinct. Animal life during the Mesozoic was dominated, however, by large archosaurian reptiles that appeared a few million years after the Permian extinction: dinosaurs, pterosaurs, and aquatic reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs.

The climatic changes of the late Jurassic and Cretaceous provided for further adaptive radiation. The Jurassic was the height of archosaur diversity, and the first birds and placental mammals also appeared. Angiosperms radiated sometime in the early Cretaceous, first in the tropics, but the even temperature gradient allowed them to spread toward the poles throughout the period. By the end of the Cretaceous, angiosperms dominated tree floras in many areas, although some evidence suggests that biomass was still dominated by cycad and ferns until after the KT extinction.

Some have argued that insects diversified with angiosperms because insect anatomy, especially the mouth parts, seems particularly well-suited for flowering plants. However, all major insect mouth parts preceded angiosperms and insect diversification actually slowed when they arrived, so their anatomy originally must have been suited for some other purpose.

As the temperatures in the seas increased, the larger animals of the early Mesozoic gradually began to disappear while smaller animals of all kinds, including lizards, snakes, and perhaps the ancestor mammals to primates, evolved. The KT extinction exacerbated this trend. The large archosaurs became extinct, while birds and mammals thrived, as they do today.

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Summarize the evolution of amniotes in the Mesozoic era

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The amniotes are a monophyletic group (clade), with all modern reptiles, birds, and mammals sharing a common ancestor.
An evolutionary radiation of amniotes during the early Mesozoic era gave rise to three main groups, called synapsids, anapsids, and diapsids.
• These names are based on key differences in skull anatomy.

During the early Mesozoic radiation of amniotes, the diapsids split into two evolutionary branches, the lepidosaurs (including lizards, snakes, and tuataras) and the archosaurs (including crocodiles and alligators, dinosaurs, and birds).

* The closest living relatives of birds are the crocodiles and alligators, but they are even more closely related to the extinct dinosaurs.
* In fact, neither dinosaurs nor reptiles represent monophyletic taxa unless we also include birds.

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Outline the events of the Cenozoic era most important in the history of life

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The Cenozoic Era:
Age of Mammals

The last and most recent of the geologic periods is the Cenozoic Era. Its name means “new life” coming from the Greek root kainos, meaning “new,” and zoic, “life.” While this new life came to refer to mammals-thus coined The Age of Mammals- this new life could have just as easily been the angiosperm or flowering plants, the insects, the newest fish (teleostei) or modern birds. All of these groups, including the mammals, continued to evolve during this present Era.

mammals evolved from their somewhat insignificant stature during the Mesozoic to include giant species that have gone extinct in modern times. While none of the mammals ever reached the size of the dinosaurs, there were some species that dwarfed their modern-day relatives. Everyone knows about mammoths, but during the Cenozoic Era some birds stood 7-feet tall. There were beavers 7 feet long! These creatures were typical of the growth achieved by the “new life” in the early Cenozoic. Cenozoic Flowering Plants

Flowering Plants
Flowering plants or angiosperms were widespread in the Cenozoic Era. This was beneficial to insects, many of which evolved symbiotic relationships with flowering plants.

The Quaternary and Tertiary
The Cenozoic includes the period that began roughly 65 million years ago to the present. Historically, the Era has been divided into two periods: the Tertiary and the Quaternary. These terms came from the 19th century when rock formation in Europe was classified as primary (being the oldest), secondary and tertiary, with quaternary being coined slightly later. As more sophisticated geologic understanding evolved, primary and secondary were dropped from use. Only Tertiary and Quaternary remained as the divisions of the era.

Changes In The Naming System
But these divisions don’t seem appropriate in the light of current understanding about the geologic changes that occurred during the Cenozoic. New terms are being used that relate more closely and accurately to the stratigraphy of the planet: Paleogene for the early part of the Cenozoic including the early two-thirds of the Tertiary Period, and Neogene for the last part of the Tertiary and the Quaternary. Suffice it to say, regardless of what it is called, the geology that occurred remains the same!

But let us not forget that the Cenozoic Era is a geologic classification and get back to the geology that distinguishes this period.

The Continents Move
During this time, the continents continued the separation that had begun at the end of the Mesozoic Era during the Cretaceous Period. The Atlantic Rift was widening and forcing more continental separation, in particular Greenland from Europe. Other ocean spreading rifts caused the separation of Australia from Antarctica and Africa from India. The supercontinents of Gondwanaland and Laurasia that had been the result of tectonic movement during the Mesozoic, were now transforming into the continents of modern day.

Volcanic Activity Builds Mountains
The rifts that occurred around the globe resulted in volcanic activity that formed mountain ranges. The Cascade Range that extends along the coast of North America from British Columbia to California is one example of this rifting/volcanic activity. Volcanic activity in Europe, Asia and Africa resulted in the formation of the Himalayan and Alpine mountain systems.

The Cenozoic Era: Time Marches On
And so the Cenozoic era continues. It is the era we live in, though we could hardly say this is the era of humans. We have been present as a species only about 1.5 million years of the 65 million of the current era. That represents about 7 seconds on the clock of eras!

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Describe the dramatic climatic events of the Pleistocene epoch

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About a third of the way into the Pleistocene the first Ice Age hit. There were a series of advances and retreats of the ice as the climate fluctuated between cold (glacial) and warm (interglacial) periods. The sea level rose during the melting of the glaciers, then dropped again during the next long cold spell (ice formation). The lowered sea levels formed land bridges that enabled the migration of animals and humans across continents.

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Discuss the importance of the historical processes of extinction, dispersal, and vicariance to the distribution of taxa

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Extinction: historically limited distribution of species. Equidae: horses, now extinct in neartic (N. America), but zebras still in Africa.
Dispersal (movement of individuals away from an area): Dispersal-and-colonization hypothesis explains how pop. of species dispersed to new areas, colonized & became residents permanently. Dispersal is the cause of expansion of species. Flies in Hawaii, many species are now endemic to one island, all from common founder pop.
Vicariance:
Allopatric speciation: caused by geographic separation/isolation of 2 or more populations.
Split species into 2 or more species geographically (rise of a mountain range or a drying event to split species). Separation of species caused by geologic or climate change.
Morphological species concept: relies on what critter looks like and compares it to other species. Most parsimonious explanation for distribution of taxa. Phylogeny reflects the sequence of geographic separations and subsequent variations (complicated by dispersal).

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Indicate the importance of ecological factors to the distribution of taxa

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Island biogeography: how far from mainland, how large island is. 2 hypotheses used to explain # of species found on island. (1) Nonequilibrium hypothesis (fewer species found on island than nearby mainland because they haven’t had time to get there: islands arose later than mainland). (2) Equilibrium hypothesis (suggests fewer species because of tradeoff between new invasional colonizations and extinctions). Smaller islands have a greater rate of extinction because of small area and less space for species, which means more competition.

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Briefly summarize the roles of interspecific competition and niche partitioning, and convergent evolution, in the distribution of species

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Interspecific competition, in ecology, is a form of competition in which individuals of different species vie for the same resource in an ecosystem (e.g. food or living space). The other form of competition is intraspecific competition, which involves organisms of the same species.

An example of interspecific competition, if a tree in a dense forest grows taller than surrounding trees, it is able to absorb more of the incoming sunlight. However, less sunlight is then available for nearby trees that are shaded by the taller tree. An example among animals could be the case of cheetahs and lions; since both species feed on the same prey, they are negatively impacted by the presence of the other because they will have less food. Also, lions sometimes steal prey items killed by cheetahs.

Niche Partitioning: 2 or more species cant occupy the same niche (food, habitat, time of day). They separate to avoid the difficulty coexisting. Gause’s hypothesis = principle of competitive exclusion.

Convergent Evolution: Similar ecological needs show common patterns (same kind of selection pressures as well) e.x. Lizards are not from similar ancestors but from similar patterns and needs.

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Species Richness

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A measure of the number of species in relation to the total number of individuals in a particular community.

Species richness is simply the number of species present in a sample, community, or taxonomic group. Species richness is one component of the concept of species diversity, which also incorporates evenness, that is, the relative abundance of species. Species diversity is one component of the broader concept of biodiversity. About 1.75 million living species and 300,000 fossil species have been described by scientists. Estimates of the total species richness of the Earth range from 3 – 10 million, with some estimates as high as 50 million.

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Discuss 3 factors (ecological specialization, population dynamics, and geographic distribution) that affect turnover rates of taxa

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Ecological specialization: Species highly adapted to specific habitat types have higher turnover rates.
Population dynamics: Populations with fewer individuals have a higher susceptibility for extinction.
Geographic distribution: The wider the geographic range of a taxon the greater organization and the lower the turnover rate.

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contrast the probability of extinction for higher taxa containing many and higher taxa containing few species

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Species must adapt and change faster in order to keep from going extinct. If you cannot compete with others you also might go extinct. Species staying the same will suffer.

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discuss 4 major factors (release from interspecific competition, evological divergence, coevolution, provinciality) that promote the origination and diversification of organisms (i.e., increase in biodiversity).

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Release from interspecific competition. Competitive displacement: a taxon or clade goes extinct because of competition (cannot compete with another taxon). Incumbent replacement: a taxon or clade goes extinct because of space/vacancy left by extinction of another species, the species can expand.
Ecological Divergence: When species comes up with innovation, altering ecology of taxon. Results in speciation and divergence from other members of the taxa (like insects, arthropods = jointed appendages allowed them to move more freely and explore new habitats so they could get more food)
Coevolution: Joint occurance of 2 different organisms, dependent upon each other for survival, 1 or both will diverge. E.x. Yucca trees & yucca moths, trees dependent on the moths for survival.
Provinciality: Being separated by land (when the continents separated, animals/flora went along.