Paleo Final

fossilization process

organism death, scavenging and microbial decay, sedimentation and burial, lithification (cementing and compacting), discovery and analysis

biotic factors that affect fossilization process (5)

bioturbation, hard v soft body parts, habitat preference and behavior, geographic range, abundance

abiotic factors that affect fossilization process (5)

biostratinomy (storm reworking), anoxic conditions, sedimentation rates, enviro conditions (T, pH, salinity), erosional v depositional

how to get exceptional preservation

anoxic conditions, rapid burial, lake stratification (anything to reduce scavenging and decomposition)

what makes lagerstatten exceptional

fully articulated, soft parts, colors preserved

how can we use lagerstatten

can tell us what’s missing in the normal fossil record, can provide key evolutionary steps (ex. first bird), can tell habits (ex. mating ground)

alterations that can occur in lagerstatten

compaction, flattening, permineralized/replaced

how to measure preservation probabilty

\# observed ocurrences-2/# possible occurrences -2

which orgs have high preservation probabilities

abundant, biomineralized, live in a habitat with sedimentation

what gets preserved

biomineralized parts like bones, teeth, shells

what doesnt get preserved

soft tissues and parts like fur/hair and feathers

what does a low preservation probability mean

lower chance of being preserved and therefore sampled and studied

how to calculate which periods of time had the best preservation probability

\#preserved + sampled/# extant

the fidelity of the fossil record

how accurately does the fossil record reflect the environment the fossils come from

different methods to measure the fidelity of the fossil record

compare lagerstatten to normal deposits (what % will get preserved under normal conditions), live dead analysis (do the live and dead agree or was there change), live fossil analysis (do extant taxa have a fossil), or preservation probabilities

what are the 3 biodiversity metrics

species composition, relative abundance, species richness

species composition

the species that are there

relative abundance

how many of one species vs all of the taxa

species richness

\# species in a community

time averaging

events that occurred at separate times appearing to occur simultaneously in the fossil record

TA is affected by

sedimentation rates, bioturbation, reworking, filters of fossilization

what is low TA and what does it look like

a short time between the fossils in a rock; looks like a lot of sediment, articulated fossils, life positions

what is high TA and what does it look like

a long time between fossils in a rock; looks like a lot of fragments and disarticulation, few sediments, lots of reworking, variety of remains

how to determine TA in the lab

radiocarbon dating

degrees of time averaging

ecological census (snapshot), within habitat (one habitat’s community), environmental condensation (mixing habitats), biostratigraphic condensation

when is time averaging bad

when trying to reconstruct a community and its interactions but you don’t know if everything lived together

how is time averaging good

can be telling of geologic processes like low sed rates, can show disagreements among communities and see how when or why change occurred

live v dead analysis

measures how biologically similar are live and dead samples

live dead disagreements and how they occur (ex)

when the live and dead samples don’t match; they occur when a change occurred and shifted environmental conditions and therefore the biological makeup (ex. eutrophication, bottom trawling)

how can live dead disagreements occur in the absence of human activity

if the enviro change occurred for a long time (ex. MS river), dead communities may not have caught up to recent enviro change because they average out over decades/centuries, live snapshot may be different (ex. geese/seasonal variation)

how is live dead analysis affected by sampling and how to account for it

dead samples are much bigger bc they’ve accumulated over time so they show more diversity (the more you look the more you find); account for dead sample size by using rarefaction (how many would i have found if my n was)

global biodiversity

calculated by # genera through time from fossil evidence

errors in the biodiversity database: rock area

different areas could have had sediments eroded, metamorphosed, etc that destroyed them or not all areas have sedimentation

errors in the biodiversity database: uneven sampling

site accessibility, the more you look in 1 area the more you find, if temperate areas were evenly sampled we might have a less distinct gradient

errors in the biodiversity database: lithification bias

older fossils tend to be molds or casts not unlithified like younger fossils; can tell more about morphology from younger

errors in the biodiversity database: preservation bias

divers soft-bodied orgs not preserved, less aragonite and therefore calcite in the past

errors in the biodiversity database: pull of the recent

including extant taxa in diversity curves will extend fossil species’ ranges and make current diversity way higher than fossil

errors in the biodiversity database: environmental bias

not comparing similar conditions or enviros

how to minimize errors in biodiversity database

standardize paleobio data by enviro type, rock type, similar age ranges

how can there be so many paleobio errors but they still compare to expert data

the errors are randomly distributed so they average out over time, might affect regional but not global biodiversity data

what processes drive the fossil record and what are those processes functions of

driven by burial and sedimentation from depositional environments, which are a function of climate and tectonics

spatial and temporal variation in the fossil record depend on

where basins are and how often they are created

erosional v depositional environment

more sediment removed from land v sediment added to the land

how can sediment characteristics reconstruct past environments

sedimentary structures (ripples, mudcracks), grain size can tell us relative depth, iron content/oxidation can tell us oxygen content

fossil record and sea level rise

the shore becomes depositional and a part of the fossil record so less sediment is being delivered to the sea floor, which increases its time averaging. the grain size at the shore decreases from sand to mud

fossil record and sea level fall

grain size at shore increases from mud to sand but it becomes an erosional environment so the fossils that were there are now gone, making it an unconformity. sediment delivery to the floow increases and reduced time averaging

how are sedimentation and TA related

inversely

biological species method

individuals in the same species can naturally breed an produce viable offspring

morphological species method

species with similar morphologies are closely related

which species method can you use for fossils and why

morphological because you cant breed fossils

problems with using morphology in the fossil record

cant preserve all aspects of morphology (ex. color, toxicity), the same species could have variable morphology (pseudo) or identical morphologies might belong to different species (cryptic)

how do pseudo species affect the fossil record

splitting into more species than there are, can result in underestimating geographic range and overestimating species richness

how do cryptic species affect the fossil record

lumping multiple species into one, can overestimate geographic range size and underestimate species richness

phylogeny

species that are closely related in the phylogenetic tree are similar/have similar characteristics

principle of parsimony

favor the simplest hypothesis that is consistent with the data and has the fewest assumptions/least independent gains and losses of traits

problems with using phylogeny

hard to know which traits to look at, close relatedness might not always be obvious (ex. elephant shrew)

synapomorpy

shared derived character

sympleisiomoprhy

shared primitive trait (ex. mammal hair)

convergent evolution

independent gain of traits, often due to enviro pressures (ex. dorsal fin)

where is most biodiversity

low latitudes, warm coast areas, lowlands

what are the different biodiversity gradients

latitudinal, elevational, bathymetric

biodiversity gradient is controlled by (5)

temp, climate stability, oxygen, amount of sunlight and therefore primary productivity

niches

n-dimensional volume with biotic and abiotic variables defining tolerance ranges of species

fundamental v realized niches

where a species could live in principle v where they actually live

how to reconstruct niches

sediment structures and grain size, skeletal morphology (teeth for diet), co-occurring species (webs), indicator taxa (corals)

how to reconstruct biotic interactions

gut and coprolite content, related extant species observation, nitrogen isotopes (bioaccumulation), functional morphology (teeth), bioerosion

cambrian explosion

presence of biomin skeletons, large bodies, and new body plans (ex. segmented, molting)

Cambrian explosion had an increase in \[\] and not \[\]

disparity not diveristy

possible explanations for the Cambrian explosion (5)

predator prey arms race (triggered by inc oxygen and therefore body size), end glaciation of great unconformity dumping minerals like iron and calcite into water, transgression=more oceans=more niches, transition orgs not preserved or gradual orgs eroded

Ordovician radiation

increase diversity after cambrian explosion but not disparity (filling in gaps)

limiting biodiversity factors everywhere

temp, food availability, habitat heterogeneity

cambrian fauna

trilobites, inarticulate brachiopods, hyolith mollusks, primitive crinoids, biomin sponges

paleozoic fauna

brachiopods, bryozoans, corals, crinoids, gastropods and bivalves, fish

devonian fauna

first forest (tree like ferns), 1st terrestrial vertebrate

cretaceous fauna

dinosaurs, birds, first flowering plants

modern fauna

mammals, large bodied orgs, humans, no trilobites, no brachipods

what allowed for diversification of modern fauna

diversified after end-permian extinction since mammals were less vulnerable to extinction selectivity and were able to rebound and take over abandoned niches and the mesozoic marine revolution

mesozoic marine revolution

predators became more active so prey adapted new morphologies like thick and spiny shells and then predators adapted to become shell crushing and boring (evidence includes boreholes)

evolution

change in heritable traits of populations over genera

how to measure evolutionary change

measure change in mean trait value in population over time

steps for natural selection

variation in population to be acted upon, different survival and reproduction rates based on trait variation, traits are heritable through generations

biological fitness

ability to contribute offspring to the next generation

directional evolution and ex

selection in favor of 1 extreme (ex. fur color from gray to white)

stabilizing selection and ex

selection against extremes (ex. human birth weight)

disruptive selection and ex

selection for both extremes (ex. beak shape due to competition)

random walk (no selection)

no preference, all forms equally successful but survival is “random”, always results in increased variability

anagensis

evolution throughout the whole species (like directional and natural selection)

cladogensis

evolution associated with branching/speciation

punctuated equilibrium

cladogenesis with long periods of stasis then rapid morphological change

what could cause stasis (6)

enviro change is within species tolerance, species tracks change, broad species tolerance, OR change in morpho traits not preserved (color), no continuous/gradual data, small windows of preservation

mass extinctions

outliers of extinction rate relative to adjacent time intervals/background rate

characteristics of mass extinctions

global in scale, major shift in taxon composition, evenness, and dominance

mass v background extinction

different intensities/scales, background is more deterministic (trait based) while mass is more stochastic (random)

identifying mass extinctions in the rock record

limestone fossil content (reduction in diversity or abundance), reef gap, stromatolite resurgence (no grazers), body size decrease, stress-tolerant weedy taxa present

triggers v kill mechanisms

triggers are the overarching change and the kill mechanism actually causes death (ex sea level rise v habitat loss)

end permian extinction triggers v kill mechanisms

volcanism, siberian traps, slowed ocean circulation v rising co2, ocean acidification, warm t, ocean stratification, anoxia/euxinia

end ordovician extinction triggers v kill mechanisms

glaciation, regression, increased albedo v reduced sunlight and productivity, habitat loss

triassic-jurassic mass extinction triggers v kill mechanisms

volcanism v increase co2, increase t, ocean acidification

end cretaceous mass extinction triggers v kill mechanisms

transgression, greenhouse climate, bolide impact v anoxia, decreased temp gradient, bolide and impacts (tsunamis, sun blockage)

are all mass extinctions the same? ex.

no the impacts arent always comparable (ex. pt extinction killed 96% marine inverts and 70% land verts but the end ordo only lost some groups not the major clades, allowing them to survive and radiate post-extinction