Evolution and the Fossil Record

Week 3

Definition of a fossil

any trace left by an organisms that lived in the past

( ): , ( ) and ( ) , ( ) , often including preserved skin, muscle, bone, hair, and internal organs

Preserved remains

amber

freezing

intact remains of animals

( ): when dissolved minerals carried by ground water fill the tiny cellular spaces of plants and animals. The dissolved minerals crystallize and produce rocks in the shape of the animal or plant. Shape is preserved but the composition is altered permineralization is the process by which petrification occurs

permineralization

( ): record behavior instead of form. Dinosaur trackways can tell us about the animal’s stride length and we can estimate max speed. Other trace fossils are coprolites, burrow or den. In some rare cases the trace is preserved with the animal.

trace fossils

( ): natural casts form when flowing water removes all of the original bone or tissue leaving just an impression in sediment. Minerals fill in the mold, recreating the original shape of the organism very common for marine organism with shells

molds and casts

what is taphonomy?

study of the fossilization process

taphos = ( )

burial

what factors contribute to the difference between what was once alive and its representation in the fossil record?

-Hard parts preserve more easily

-Abundance: common species have higher probability to be preserved

-Environmental: some environments offer better preservation

-Age of the bedrock: modern rocks are more accessible and better preserved

-Human activity: geographic, taxonomic and morphological

geological time scale, hierarchy divided into ( ), ( ), ( ), ( ), and ( )

eons

eras

periods

epochs

stages

each interval on the geological time scale is defined by what?

a suite of diagnostic fossils and bounded by extinctions of varying severity

Life evolved on a world that was changing itself, primer driver is ( ) which did what

plate tectonics

rearranges continents and oceans

changes in climate

( ) :

( ): ancient life

( ): middle life

( ): recent life

phanerozoic

Paleozoic

Mesozoic

Cenozoic

( ) : layered sedimentary formations that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral “microbial mats”. In turn, these mats build up layer by layer, growing gradually over time.

stromatolitesstroma

( ) are a major constituent of the fossil record of the first forms of life on earth. They fist appeared in the fossil record during the Archean eon 3.4 billion years ago, nearly two-thirds of earths existence. They peaked about 1.25 billion years ago and subsequently declined in abundance and diversity, so that by the start of the Cambrian they had fallen on 20% of their peak.

stromatolites

( ) still form today. However, modern formations do not boast nearly as many shapes or sizes, with far smaller diameters in the columnal formations. Part of this has to do with competition: when stromatolites first evolved, they had none. Those that exist now have to contend with food competition with other aquatic organisms that stromatolites allowed to evolve in the first place, a generational struggle that stromatolites are on the losing side of -> potential explanation for their decrease during the Cambrian! Fossilized stromatolite from Western Australia Modern stromatolites in Shark Bay, Western Australia

stromatolites

( ) is the primary criteria to infer evolutionary relationships among organisms preserved in the fossil record (DNA unavailable most of the time)-Morphospecies

morphology

The ( )-( )

-First evidence of macroscopic life: 565-544 Ma

-Lichens, algae, and forms that are not currently present on earth

-experts agree that the Ediacaran fauna included sponges, jellyfishes and comb jelly relatives.

-bilaterally symmetric animals? probably but no good fossil record (only some trace fossils seem to point towards it)

Ediacaran biota

End of the Proterozoic and Precambrian

( )

-Astonishing variety of large and complex bilaterally symmetric animals

-Arthropods, mollusks, vertebrates, and echinoderms

-several chordates: jawless vertebrates with notochord

-exceptionally preserved site: Lagerstatte (BC, Canada)

-earliest members of virtually all major animal lineages appeared relatively suddenly in the fossil record, at the same time, in geographically distant parts of the globe

The burgess Shale fauna- Cambrian

What caused the Cambrian Explosion?

-Cyanobacteria are among the earliest living forms on Earth

-Cyanobaterica are photosynthetic organisms-p

The difference between ribozymes and ribosomes

a ribosome is a biological machine that utilizes a ribozyme to translate RNA into proteins. Ribosome=the whole organelle, ribozyme=the RNA piece that catalyse

( ) is different than ( ) - A petrified/ permineralized fossil has the organic material replaced with minerals and mold is created by the organism dissolving within rock leaving a cavity, then minerals filling in the space form a cast, permineralization is actually replacing the original material, whereas a cast/mold is the impression of the original materal, which is perhaps

What times do we have to remember?

Pre-Cambrian (Eon)

Phanerozoic (Eon)

Paleozoic (Era)-Cambrian (first Epoch)

Mesozoic (Era)

Cenozoic (Era)

The Great Oxidation event explained

4 billion years ago the atmosphere had a very low percentage of oxygen (organisms with anaerobic metabolism)→about 3 billion years ago cyanobacteria: photosynthesize and release O2→that happening over 200-300 million years increased O2 level in the atmosphere→ the O2 accumulated in the Ocean and started escaping into the atmosphere→ this wiped out much of the Earth’s anaerobic life→ rise of organisms using O2 in respiration → higher metabolic rates=larger, more complex organisms (Cambrian fauna explosion)

( )

-before the ( ), plants evolved in the Ordovician and insects began exploiting resources on land in the Silurian

-transition from water to land brought stronger joints, enlarger rib attachments and pelvic modifications

-loss of fin rays-replaced by digits

-limb modification (not an immediate change, most early tetrapod spend most of the time in the water)

The Fish-Tetrapod transition-Devonian

Devonian

( )

-Theropods, bipedal carnivorous dinosaurs includes birds as its living descendants

• have hollow bones

• a subgroup possess a furcula (fused clavicles-wishbone in modern birds)

• Feathers-even on those that could not fly

  • Flight hypotheses (ground up (more likely)/trees down)

The dinosaur-Bird transition-L

( )

-synapsid lineage-transition from reptile like form in the carboniferous to the earliest mammal by the early Jurassic

-evolution of the jaw-started with the temporal fenestra

• enlarged dentary

• bony secondary palate that separated breathing and chewing

-evolution of the mammalian ear

• two bones in the jaw were reduced and incorporated in the middle ear

• lower jaw hinge

The Origin of Mammals- Early Jurasic

Bilaterally symmetry- likely in the ( )

pre-Cambrian

( )-higher O2

• The most species-rich lineages of animals alive today were all present in the ( )

Cambrian Explosion

Cambrian

Transition from water to land for vertebrates

• ( ) modification

limb

Evolution

Fossils doument how the types of species on ear

Mass extinction: ( )

when global extinction rates rise significantly above background levels in a geologically short period of time (interval time: span of a million years, over 60% of living species at that moment went extinct)

Background extinction: ( )

the extinction rate is in background levels (the longer a species

The longer a species exists the more likely?

Extinction rates changes are constant within ( ) but largely change between ( )

clades

Mass extinctions are the result of?

catastrophic episodes of environmental change

( ): High-impact extinction

-Hypothesis: collision of an enormous (mountain size) asteroid on Earth

-Evidence: anomalous concentrations of the element Iridium in sediments

• Rare on earth but common asteroids and other extraterrestrial objects

-Evidence: presence of shocked quartz particles and microtektites produced by intense, short-term pressure

-Impact: the collision provoked intense acid rain, global cooling, massive earthquakes and tsunami

Cretaceous-Paleogene (K-Pg)

( ): The biggest of the Big

-Hypothesis: large-scale volcanic activity combined with low oxygen levels ands runaway greenhouse conditions

-Evidence: massive fluctuations in the global carbon cycle → environmental instability

-Evidence: oceanic anoxia

-Impact: most taxa took long time to diversify

• First~10 million years of the Early Triassic were a dead zone

-Taxa extinct: trilobites, most brachiopods, some archaic groups of tetrapod

• Radiation of echinoderms and precursors of dinosaurs

Permian-Triassic

Since 1600 about ( ) species have become extinct

1100

Habitat loss due to ( )

expanding human populations

Current extinction rates is ( ) to ( ) times the background extinction rates

100 to 1000

At current rates, in the next 100 years ( ) of species might disappear

60%

( ) can now be estimated from molecular clocks

Divergence

The molecular clock is ( ) specific. Different ( ) and ( ) regions (i.e., coding vs. non-

When we are creating a phylogeny using a molecula

Comparing ( ) under a specific model of evolution, along with at least one fossil-calibrated point

minimum and maximum divergence time estimates (confidence interval)

DNA

The most effective fossilization processes are ( ), ( ), ( ) and ( ).

• rapid burial of organics remains in water-saturated environments

compression

impression

casting

permineralization

Most of the major animal lineages present today first appear during the ( )

Cambrian

( ) is the most spectacular of a series of adaptive radiations in the phanerozoic

• Adaptive radiations can be triggered by key morphological adaptations or ecological opportunity

The Cambrian Explosion

( ) are characterized by the rapid disappearance of a large percentage of species biodiversity

Mass extinctions

There are 5 major extinctions and the best known is the ( )-caused by the impact of a massive asteroid

K-pg

( ) and ( ) species are less likely to go extinct

widely distributed

abundant

We are likely undergoing a sixth mass extinction due to ( )

human-caused habitat loss