Earth 7 - Dinosaurs

Midterm prep

Paleontology

The scientific study of fossils, which provides unparalleled insights into prehistoric life, evolution, and myriad other topics.

Scientific Method: four steps

1. Observe

2. Hypothesize

3. Predict

4. Test Predictions

Falsifiability

Hypotheses and the predictions scientists make must be vulnerable to being proven wrong.

Igneous Rocks

Form from melts (magma, lava) that cool and solidify. Only rarely preserve fossils (ash). We can often determine their ABSOLUTE ages.

Metamorphic Rocks

Underwent heating or pressure during their history, changing everything about them. Formed in places where rocks get carried to great depths (like seduction zones). Usually destroys any fossils that were in the rocks before pressure was applied (but rarely fossils can be found in them).

Sedimentary Rocks

Form from eroded pieces of other rocks (sediments) that accumulate in low lying areas. Sediments often bury organisms, preserving their remains. As sediments become rock, these remains become fossils. Often we can determine the RELATIVE ages of these rocks (not the absolute ages because that would just reveal the age of the sediments making up the larger rock). 

Fossil

Any evidence of ancient life. Form and are found with the following steps: Death → decay → burial → lithification → erosion. Two types: body and trace.

Body fossil

part of an organism (i.e. a tooth, limb, or whole specimen)

Trace fossil

evidence of an organism’s activity; evidence of an organism modifying its environment (i.e. a trackway, footprint, coprolite (fossilized feces), eggs, nests, burrows)

Lithification

Turning into rock (going from loose sediment to one rock)

Permineralization (Fossilization)

minerals fill in empty pore spaces in bones

Replacement (Fossilization)

new minerals replace original phosphate; the minerals already in the bone get replaced by new minerals, transforming it into something that can be preserved

Coprolite

Fossilized feces; example of a trace fossil

Relative dating

the age of rocks compared to other rocks

Absolute dating

the age of rocks in years

Relative Dating Principles

1. Original horizontality

2. Superposition

3. Faunal Succession

Superposition

Strata formed by the accumulation of rock particles, oldest are on the bottom and youngest on top. Rocks are deposited in a chronological sequence. Part of Relative Dating.

Faunal Succession 

Always the same sequence. Each group of organisms lived during a discreet time interval. This order is preserved in the rock record (ex: rabbits always appear after T. Rex). Thus fossils give us a sense of the relative age of rocks.

Original horizontality

Sedimentary rocks are deposited horizontally. If they are seen vertically now, they have been deformed by the earth’s crust. Part of relative dating.

Uniformitarianism

Physical processes observed today operated in the geological past. Modern processes help us unravel ancient events. Slow processes acting over vast timespans have helped shape earth’s surface on immense scales. 

Biostratigraphy

Using fossils to correlate rocks and determine their ages

Lithostratigraphy

Correlating rock types (sandstone with sandstone)

Simplified atomic structure

Each element has a specific number of protons.

Isotopes

Variants of the same element that have different numbers of neutrons. 2 kinds: Stable, Unstable

Radioactivity

Spontaneous changes (decay) in/of the structure of unstable atomic nuclei. Some isotopes are stable and others are unstable and break down over time. The break down is referred to as radioactivity.

Unstable Isotopes

Radioactive decay. One element (parent) will change into another (daughter) with more stable configuration.

Parent

unstable radioactive isotopes

Daughter Product

isotopes resulting from the decay of a parent

Half-life

The time required for one-half of the radioactive parent in a sample to decay into its daughter product. After one of these, half of the parent material will be represented. Usually an exponential decay process.

Darwin’s ideas

Common Descent with Modification; Natural selection

Common descent with modification 

All living organisms are related, descending from a single common ancestor

Natural Selection follows from three observations

Variation in a species; Different survival and reproduction; Heritability of Variation

Differential Survival and Reproduction

Often brutal in nature; some individuals have more offspring than others because their traits allow them to survive.

Heritability of Variation

Variation genetically controlled; Offspring resemble parents (exhibit similar variations); Certain traits will be eliminated and the species will move away from that trait because they stand out to a predator or some other cause of death. The survivors’ traits will live on and be inherited.

Cladograms

phylogeny or evolutionary tree; attempt to show the relationship between organisms

Taxa

single species or groups of species; represented by branches on a cladogram

Nodes

where branches join on a cladogram; represent the last common ancestor of those taxa; the hypothetical most recent common ancestor of everything that stems from that branch point. These are pivotal branch points on the evolutionary diagram. 

Sister groups

The branches stemming from the same node; also known as closest relatives

pruning

a way to simplify cladograms; You can combine branches like this only when the more inclusive category that you form is a clade (or monophyletic taxon) that includes all of the descendants of a common ancestor

Evolutionary Novelties

Defining character, derived character, advanced character, diagnostic feature/character = the same thing as this; a novel character that other organisms lack, derived from a common ancestor 

Homologous Characters

similar because they were inherited from common ancestor (ex: Arms, legs, fins, and wings in these groups are superficially different, but their unequivocal underlying similarity is indicative of their shared ancestry)

Convergent Characters

Similarities not inherited from a common ancestor (independently acquired); ex: Last common ancestor of butterflies and birds lacked wings. Wings arose independently.

Secondary Loss

A feature was developed and then a species lost that feature. An evolutionary novelty appeared and then was lost later. Ex: Snakes are tetrapods, their ancestors had limbs, but they lost those limbs later

Paraphyletic groups

Ancestor + SOME descendants = BAD (artificial, incomplete branch on evolutionary tree); A group that includes an ancestor and some but not all of its descendants

Monophyletic Groups (aka Clades)

Include ancestor + ALL descendants = GOOD (real/natural, complete branches on evolutionary tree)

Oldest clear evidence of life

Fossil Stromatolites; Bacterial body fossils (sulphate reducers?)

Fossil Stromatolites

Layered colonial structures or rocks; Formed in shallow waters as microorganisms (cyanobacteria) trap sediment → microbial mats! preserved from 3.5 million years ago

Bacterial body fossils

 single celled organisms that were preserved; preserved from 3.5 million years ago

The Great Oxidation 

Several lines of evidence for influx of O2 into atmosphere/oceans around 2.5 Ga; Some argue that Cyanobacteria photosynthesized to push higher O2 levels into the atmosphere

Cyanobacteria

formed stromatolites; the ONLY organisms to ever “invent” the ability to photosynthesize and produce oxygen. 

3 Domains of Life

Bacteria, Archaea, Eukarya 

Endosymbiosis

how organisms went from prokaryotes to eukaryotes; Aerobic bacteria became incorporated into an ancestral eukaryotic cell, becoming the mitochondria. at the same time, photosynthetic bacterium was engulfed in these protoeukaryotes and they became the chloroplasts

“Snowball Earth” Global Glacinations

earth became completely covered in ice at the end of the Precambrian (even the oceans froze over)

Paleozoic Era

Begins with an explosion in animal diversity; Plants and vertebrates transition to land; Beginning: Cambrian, End: Permian

Mammals

Generally small-sized in Mesozoic. Ecologically diverse, but not dominant. Diversify rapidly in the Cenozoic.

Cambrian Radiation of animals

includes first vertebrates; Most animal body plans appear in the fossil record near the base of the Paleozoic

Cambrian

earliest slice of time after Precambrian; start of the paleozoic

Arthropods

Include crustaceans, trilobites, insects, and arachnids. They are the most diverse of all animal groups (making up ~80% of all animal species alive).

Vertebrate

a large group of animals distinguished by the possession of a backbone or spinal column

Gnathostomes

Vertebrates with jaws; “Jaw Mouths”

Gill arches

Used for filter feeding and respiration; later evolved into the bones of the jaw

Chondrichthyes

Sharks, rays, skates, chimeras; “Cartilage fish"; Because their skeletons are not ossified, they are very rare in the fossil record

Osteichthyes

Ray-finned “fish,” fleshy-limbed vertebrates; characterized by more bone in the skeleton and air sacks (like lungs)

Ray-finned “fish”

Actinopterygii; These fish have little needles of bone running from the ends of the fins to the body wall

Fleshy-limbed Vertebrates

Sarcopterygii; They have flesh and muscle at the bases of their limbs/fins

Tetrapods

Four-limbed vertebrates with fingers that can walk on land; Four limbs with fingers; Vertebrae with struts; Robust hips; Stapes

Four Robust Limbs

with digits; used in locomotion & grasping; a tetrapod novelty

Vertebrae with struts

helps keep the backbone rigid on land, since weight is no longer supported by the water; tetrapod novelty

Robust hips

attach to the spine, supporting more weight; firm skeletal connection between hind limb and vertebral column; tetrapod novelty

Stapes

Sound doesn’t travel as efficiently in the air as in water, so this bone connects the eardrum to the inner ear, to help transmit sounds; touches the eardrum and the opening of the inner ear to help transfer sound; tetrapod novelty

Seeds

The evolution of these was related to new modes of fertilization that did NOT require water; help prevent desiccation; allow plants to germinate under ideal conditions; allowed plants to become more fully terrestrial

Amniotes

Synapsids and reptiles; evolutionary novelties: Amniotic Egg, Internal fertilization, Waterproof skin, Complex lungs

Amphibious

animals spent much if not most of their lives in water (with short excursions to land); tied to water for reproduction and early development; use metamorphosis

Metamorphosis

the process undergone by developing amphibians as they go from fertilized eggs to fully developed animals

Amniotic egg

self-contained egg with membranes of various functions (like the amnion, which is the membrane that holds the water and embryo developing in the water); an amniote evolutionary novelty

Internal Fertlization

as opposed to spawning, amniotes deliver sperm directly into the mother (a consequence of the self-contained egg); an amniote evolutionary novelty

Spawning

releasing sperm and eggs directly into water

Waterproof Skin

Keeps amniotes from desiccating; minimizes water loss and allows animals to live away from water

Mesozoic

Beginning: Triassic, Middle: Jurassic, End: Cretaceous. End-Permian Extinction occurred right before this era.

Complex lungs

an amniote evolutionary novelty; allowed amniotes to take in more oxygen to fill their increased energy requirements from being active and living on land

Eukaryotes 

organisms with an advanced cell structure, including a nucleus, organelles (like the mitochondria) and chloroplasts (where photosynthesis takes place) 

Anapsid

a skull condition with no temporal fenestrae. This is an ancestral condition (i.e., early tetrapods and early amniotes had this condition)

Reptiles

Evolutionary Novelty: B-keratin scales; two types: early anapsid and diapsid

Diapsids

Have two temporal fenestrae; includes: turtles (secondary loss of temporal fenestrae), “lizards” & kin, and archosaurs; fenestrae developed convergently

Synapsids

One temporal fenestra; mammals included in this category; fenestra developed convergently

Archosaurs

Includes: crocodiles & kin, Pterosaurs, and Dinosaurs. Evolutionary novelties: Thecodonty, Antiorbital fenestrae, Mandibular fenestrae, Parental care

Thecodonty

the roots of the teeth completely encircled by bone; convergent with mammals; an archosaur evolutionary novelty

Antiorbital fenestra

a hole (fenestra) in the front part of the skull, just anterior of the eye; not seen in crocodiles or other current archosaurs; an archosaur evolutionary novelty

Mandibular fenestra

a hole (fenestra) in the lower jaw; an archosaur evolutionary novelty

Parental care

animals with this generally invest a lot of time in incubating eggs or hanging out near their nest then providing nourishment to their young; an archosaur evolutionary novelty (developed convergently from mammals)

End-Permian extinction

Earth’s most severe extinction event; ~80% of all marine species went extinct, ~70% of all terrestrial vertebrate species became extinct; between the Permian (Paleozoic) and Triassic (Mesozoic); caused by formation of Pangea and Volcanic eruptions

Formation of Pangea

Contributed to the End-Permian extinction; lowered the sea level, changed weather patterns, created more dry land, removed some shallow marine environments

Volcanic eruptions

Contributed to the End-Permian extinction; Siberian traps flood basalts ~250 Ma. 3-4 million km^3 of lava - enough to cover Earth in 20+ ft of basalt all in Siberia

Ornithodires

Dinosaurs and Pterosaurs; running adaptations including Mesotarsal ankle and Digitigrade stance

Mesotarsal ankle

All motion takes place between the tarsals; The tibia and fibula are attached to the ankle bones, making a hinge-like motion; an ornithodire evolutionary novelty 

Digitigrade stance

ankles are held off the ground and they walk on their digits; Only digits and phalanges strike the ground; an ornithodire evolutionary novelty

Plantigrade stance

ankle bones strike the ground during a step. Digits on ground.

Unguligrade stance

walking on the tip of one's digits (i.e. hooved animals)

Pterosaurs

“Winged lizard”; most of the wing comes off of 1 elongated finger bone; a type of ornithodire

Dinosaurs

Evolutionary Novelties: Erect posture and narrow-tracked gait (including the following morphological change: opening in hip socket bordered by a bony upper ridge (lip) Upright Femur, Femur with inturned head); an ornithodire