ESCI 2020 - Discovering Dinosaurs Midterm 1 Important Terms

The Scientific Method

The commonsense but rigorous process by which one seeks to gain new knowledge or explain natural phenomena on the basis of observation, statement of a problem, formation of a hypothesis, experimentation or prediction to test the hypothesis, and, eventually, formation of a theory

Hypothesis

An educated guess, based on observation, that can be supported or refuted through

experimentation or more observation

Model

A hypothesis that has at least limited validity

Law

A description of a natural phenomenon or principle that invariably holds true under specific conditions and will occur under certain circumstances

Theory

A scientifically accepted general principle supported by a substantial body of evidence offered to provide an explanation of observed facts and as a basis for future discussion or investigation

The Theory of Evolution

Process by which organisms change over time as a result of changes in heritable physical or behavioral traits; The change is caused by genetic mutation; This change is driven by natural selection; This incremental change becomes significant over geologic time

The age of the Earth

Originally thought to be 20 to 100 million years, based on incorrect assumptions regarding the rate at which Earth lost heat, and the rate which salt has accumulated in the oceans; current estimate is 4.55 billon years based on radiometric age dating

Principle of Uniformitarianism

Coined by James Hutton, Charles Lyell - The present is the key to the past

Stratigraphy

Description, correlation and classification of strata in sedimentary and layered rocks.

Relative Age Dating

An ordering of events occurring RELATIVE to one another. Stratigraphy is used in this process.

Original Horizontality

Most sediments are deposited in horizontal layers

Superposition

Older rocks are below, younger rocks above

Cross-Cutting Relationship

If geological feature A cuts across geological feature B, then B is older than A.

Unconformities

Can represent lack of sedimentary deposition, or more commonly a period of erosion. Can represent significant gaps in time, an example is angular unconformity

Principles of Stratigraphy

Original Horizontality, Superposition, Cross-Cutting Relationships, Unconformities

Faunal (Bilogical) Succession

Organisms change or evolve through time, and appear in a definite, invariable sequence in the geologic record. Therefore, their preserved remains can by used to identify the relative age of rock units

Fossils

The remains or traces of a plant or animal that has been preserved in the Earth's crust

Index Fossils

Geographically widespread, geologically short existence, morphologically distinct.

Fossil Assemblages

Even if fossils have long stratigraphic ranges, fossil assemblages with very narrow ranges can be used by examining overlapping range

Geological Time Scale

A time scale that was built using fossils. It shows how life has changed through time.

Fossil Correlation

We can match strata in different locations using fossils (and fossil assemblages) found within rock units

Absolute Age Dating

Providing an actual numerical age of rock or event by radiometric dating

Radiometric Dating

Uses the concept of radioactive elements having a consistent decay rate, and therefore serves as a "clock." Involves measuring the ratio of parent vs. daughter isotopes

Radioactive Decay

Spontaneous decay (change) to another type of atom that emits radiation (alpha or beta decay). Must change the number of protons. Often occurs with an unstable isotope of an atom.

Isotopes

Atoms of the same element with varying numbers of neutrons. In general, the more neutrons, the more unstable the isotope.

Alpha Decay

Loss of 2 protons and 2 neutrons, atomic mass goes down by 4

Beta Decay

Extra neutron emits 1 electron, becomes a proton, mass stays same, # of protons goes up by 1

Parent (Atom)

Original atom before radioactive decay occurs

Daughter (Atom)

New atom after radioactive decay occurs

Half-Life

The length of time it takes for half of the parent isotope to decay to the daughter isotope. Different isotopes have different half-lives: short half-lives are useful for dating relatively young rocks, and long-half life isotopes are useful for dating older rocks.

Lithostratigraphy

The relationship of one body of rock to another, each layer is a different rock type

Chronostratigraphy

The temporal relationship between rock units, each layer is a different age

Biostratigraphy

The method of relative age dating that utilizes the presence of fossil organisms found within strata, each layer contains a different fossil assemblage

Conditions of Preservation

Presence of hard parts (shells, bones, teeth); rapid burial by sediment (remove most of the oxygen, protection from scavengers), which eventually lithifies into sedimentary rock. If an organism gets buried very rapidly after death, or buried alive, in environments that discourage scavenging and disturbance by burrowers, complete and articulated organisms can be spectacularly preserved.

Preservation Biases

Geographic Environment, Organisms, Time. Normally only hard parts of organisms are preserved; preservation of soft tissue is very rare

Common Types of Preservation

Permineralization, recrystallization, replacement of original hard part by a new mineral, carbon films or impressions, casts or molds, trace fossils

Permineralization

When minerals like quartz or calcite crystallize in pore spaces of a fossil

Preservable groups

8 classes of 6 phyla of 111 classes of 36 animal phyla that have a chance at preservation due to their hard parts. The classes are corals, brachiopods, mollusca (snails, clams), trilobites, echinoderms (crinoids), and vertebrates

Hard Part Composition

Most commonly composed of either calcium carbonate (calcite/aragonite) or calcium phosphate

Taphonomy

The study of everything that happens to an organism between death and fossilization. It includes decay, disarticulation, transport, fragmentation, accumulation, sorting, burial, and disturbance

Lagerstatten

German for "motherload". Exceptionally well-preserved fossil deposits. Two types; Konzentrat and Konservat.

Konzentrat-Lagerstatten

A fossil deposit that is exceptional in terms of the quantity of fossils that have been preserved.

Konservat-Lagerstatten

A fossil deposit that is exceptional in terms of the quality of fossils that have been preserved.

Fossilization

Under certain special circumstances, the chemistry surrounding (and within) the decaying organism can favor the early precipitation of minerals (such as pyrite, calcium carbonate, calcium phosphate, and others) that will allow the organism's soft tissues (or their outline) to be preserved. Needs to outpace decay in order to occur.

Exceptional fossilization can...

Provide information on animals normally known only from their fossilized hard parts

Reveal otherwise unknown organisms

Provide a more complete picture of ancient ecology (generally 70 to 90% of marine animals and all of the plants have very little chance to be preservable in most marine ecosystems)

Show the evolutionary history of soft-bodied groups, and of soft-part characters of known groups

Trace Fossils/Ichnofossils

Not the preserved remains of an organism, but the preserved activity of an organism, often in the form of molds and casts. The preserved burrows, footprints and trackways produced as an organism moves, rests, and feeds. Dinosaur trace fossils can provide information on anatomy, social behavior, feeding strategies, how they moved and at what speed.

Corpolites

Fossilized feces

Gastroliths

Stomach stones

Steps Involved in Collecting Fossils

1. Planning

2. Prospecting

3. Collecting

4. Preparing and Curating

Structure of the Earth

Inner core - solid, mostly metallic iron

Outer core - liquid, mostly iron

Mantle - solid, mostly silicate rocks, flows over geologic time

Asthenosphere - solid, mostly silicate rocks

Lithosphere - cool, strong top layer, mostly silicate rocks (crust is the brittle uppermost part of the lithosphere; oceanic crust and continental crust have different compositions and origins)

Rock Types

Igneous, Metamorphic, Sedimentary

Igneous Rock

Rock formed from cooling of molten material (magma)

Metamorphic Rock

Already-formed rocks that have undergone change by heat and/or pressure

Sedimentary Rock

Rock formed on the Earth's surface from the products of weathering and erosion

Plate Tectonics

Proposed by Alfred Wegener. Driven by circulation within the mantle. The level of tectonic activity has changed overtime, and can in turn effect sea level (by lifting oceanic crust and displacing the oceans onto the continents) and global climate (more volcanism increases the amount of the greenhouse gas CO2 in the atmosphere). The lithosphere is broken into plates that move relative to one another; earthquakes and volcanoes primarily associated with plate tectonic boundaries.

Plate Boundaries

Convergent (subduction zones, collisions), Divergent (continental rifts, spreading ridges), Transform (fault)

State of the Earth during the Late Triassic

Earth is dominated by the unified landmass Pangaea. Similar biotas around the world (within climatic constraints), and more extreme climates.

State of the Earth during the Late Jurassic

Pangaea has begun to breakup while the southern continent of Gondwana remains.

State of the Earth during the Late Cretaceous

Almost modern distribution of continents, supercontinents have broken up. Relatively high sea levels, and fragmented continents result in a more moderated climate

Effects of Tectonics on Climate

The lay out of the continents, position of mountain ranges, and height of sea level as controlled by tectonics will affect global atmosphere and ocean circulation patterns

Descent with Modification

The concept that organisms have changed and modified their morphology (morph - shape; ology - the study of) through each succeeding generation

Classification of Organisms

Done according to a system devised by the Swedish naturalist Carolus Linnaeus. Hierarchical system ranking organisms in groups of decreasing size: Kingdom, Phylum, Class, Order, Family, Genus, species. Individuals referred to by italicized generic (genus) and specific (species) name. Any name in the hierarchy - representing a group of organisms - is considered a taxon (plural taxa). Originally based solely on overall similarities between organisms, and not on relationship

Homologous Anatomical Structures

Can be traced back to a single original structure in a common ancestor

Analogous Anatomical Structures

Structures with different origins that may perform similar functions

Phylogenetic Systematics

The technique by which relationships between organisms can be inferred using unique features of organisms and depends upon the hierarchical distribution of "characters" in organisms

Cladogram

Branching diagrams that show hierarchies of diagnostic characters. Use character hierarchies to establish clades or monophyletic groups. Derived characters are "diagnostic" and specifies an evolved condition of that character in a descendent, and are evidence of monophyletic groups. Primitive or ancestral characters specifies the condition of a particular feature in the ancestor

Parsimony

The explanation with the least necessary steps is probably the best one

Phylogenetic Definition

Define a group by considering two of its members, and then defining it as all organisms stemming from the most recent common ancestor of those two organisms

Charles Darwin

Didn't come up with evolution, but had the idea that evolution was driven by Natural Selection

Natural Selection

The process whereby organisms better adapted to their environment tend to survive and produce more offspring. DNA information (genes) is read to produce RNA, which in turn is read to produce proteins; proteins are then responsible for both organic structure and process; changes in DNA then is reflected as changes to structure and process; the farther the relationship between organisms, the more changes. As natural selection acts on a population with genetic variability ("morphospace"), it will "push" the makeup of the population in a certain direction, which over many generations can result in major evolutionary change. Gradual evolutionary change over time can be seen in fossils as a result of natural selection.

Parallel Evolution

Unrelated organisms experiencing similar selective pressures may evolve similar characteristics and might occupy similar ecological niches

Speciation

Occurs when different populations change in different directions enough that they can no longer interbreed

Phylogenetic Trees

Show the past history of speciation, and eventually separation of entire taxa

Evolutionary Processes

Developmental change, isometric/allometric scaling in ontogeny, fusion of bones/structures

Neoteny

Advancing reproductive maturity; enabling reproduction before adult features develop

Isometric Scaling

Happens when proportional relationships are preserved as size changes during growth or over evolutionary time.

Allometric Scaling

Happens when proportional relationships are NOT preserved as size changes during growth or over evolutionary time.

Vestigial

A structure that is present in an organism but no longer serves its original purpose

Evidence of Monophyly of Life on Earth

Life is united by many characters, including...

Possession of RNA and DNA

Cell membranes composed of lipids

A genetic code all keyed to the exact same amino acids

Cells that function using the same metabolic pathways

Phylum Chordata

Means "Nerve-Cord Bearing." Cambrian-aged Pikaia, pharyngeal gills, notochord, nerve cord.

Cephalochordata

Modern member of Chordata Amphioxus, segmentation of body wall, upper and lower nerve and blood vessel branches, and many newly evolved biochemical metabolic pathways

Vertebrata

Name refers to joints in the spine, mineralized internal skeleton divided into discrete elements

Gnathostomata

Vertebrates with true jaws

Osteichthyes

Divided into Actinopterygii (ray-finned fishes), Sarcopterygii (lobe-finned fishes). Lobe-finned fishes share homologous characters with Tetrapoda - shoulder girdle and 3 primary limb bones

Tetrapod

Defined as the clade containing salamanders, mammals, and all descendants of their most recent common ancestor; diagnosed by the appearance of 4 limbs with a distinctive arrangement of bones; skeletal plan with:

Vertebral column sandwiched by paired forelimbs and hind limbs

Limbs attached to column by groups of bones called girdles

Head composed of skull and mandible (lower jaw)

Tail

Amniota

Defined as the monophyletic group that includes birds, mammals, and all the descendants of their most recent common ancestor; Characterized by the invention of a special membrane for the egg-bound, developing embryo called an amnion that allows gas exchange but retains water, and enabled vertebrates to become fully terrestrial

Major groups of the Amniotes

Anapsids, Synapsids, Diapsids

Anapsids/Anapsida

Amniotes with no post-orbital temporal fenestra (openings in the skull roof behind the eyes), originally believed to include Chelonia (turtles) but now looks to only be extinct groups

Synapsids/Synapsida

Amniotes with a single temporal fenestra, "mammal-like reptiles" (e.g. Dimetrodon), and the mammals

Diapsids/Diapsida

Amniotes with two temporal fenestrae, defined as the monophyletic group that includes birds, lizards, and all the descendants of their most recent common ancestors

Lepidosauromorpha

Word meaning "scaly lizard-shaped," is composed of snakes, lizards, the tuatara, and a number of extinct lizard-like diapsids, including the large marine mosasaurs

Archosauria

Teeth in sockets, antorbital fenestra (hole in front of eye socket); Crurotarsi (crocodiles, alligators, Protosuchus) and Ornithodira

Ornithodira

Contains 2 sister clades Pterosauria (flying reptiles, very diverse, many ate fish; Pterodactyl, Rhamphorhynchus, Quetzalcoatlus) and Dinosauria

Diagnostic characters of the Dinosauria

Defined as Triceratops and Passer (sparrow), and all members of the clade descended from their most recent common ancestor. Diagnosed by

1. Elongate deltopectoral crest on humerus (upper arm)

2. Perforate acetabulum (hip socket)

3. Fibula contacts ≤ 30 % of astragulus (ankle)

4. Epipophyses (bony projections) on cervical (neck) vertebrae

5. Asymmetrical 4th trochanter (projection for muscle attachment) on femur (thighbone).

Unlike earlier tetrapods, dinosaurs had a fully erect posture, leg joints that limited movement to a single plane

Dinosauria Sister Clades

Saurischia, Ornithischia

Saurischia

Lizard-like hip or pelvis, with pubis directed anteriorly (forward), and slightly downward

Ornithischia

Bird-like pelvis, at least a part of the pubis runs posteriorly

Dinosauromorpha

Appear in the Middle and early Late Triassic, where the true Dinosauria appearing in the late Upper Triassic of South America, and spreading globally and completely taking over from this group by the very end of the Triassic

Evolution of Feathers (Stages)

Type 1) simple, hollow, cylindrical filaments (hair-like)

Type 2) tufts of elongate multiple filaments

Type 3) filament tufts align in a single plane while also developing barbs and barbules

Type 4) "closed" vane with interlocking barbs and barbules, providing a rigid structure ("contour" feather)

Type 5) vane becomes asymmetrical (e.g. a flight feather)

Feathers

The finding of Archaeopteryx eventually revolutionized our understanding of dinosaur-bird relationships thanks to John Ostrom. This trait, thought once as a diagnostic character for birds, now seems to be a diagnostic character for Dinosauria, and maybe even originating further back. Therefore, they did not evolve specifically for flight. Their original purposes were likely for insulation (as hair is for mammals), and for display (species recognition and sexual selection) and may have originated from sensory hairs in the skin