history of life

Oldest known rocks 4.5 mil years ago (moon rocks)

• radiometric dating

  • moon formed from earth during heavy bombardment

Oldest rocks found on Earth

4.06 vya

• plate tectonics and subduction melts oldest rocks

Heavy bombardment kept Earth very hot

no life could form

Most likely, life arose

multiple times; all but one went extinct

One lineage persisted to give rise to all life today, known as

LUCA - last universal common ancestor

What does it mean to be alive?

• possess a genotype

• possess phenotype (protein structure ex)

• evolve

• acquire energy

• replicate

Evidence of life was found in rocks in Greenland from

3.7-3.85 bya

Chemical fossils

remains of chemicals created by life

What chemical fossils exist on the Greenland rocks

granite globules with life-like 12C and 13C ratio

• controversial

• prior to this life was inhabitable bc oceans vaporized

Life appears to have arose ____once Earth habitable

quickly

How did life begin?

• building blocks of organic molecules synthesized from abiotic chemical reactions

• formation of polymers with replication ability outside of life

• at some point RNA and ribozymes developed

  • RNA world idea

• formation of DNA (information) and proteins (work)

  • chicken and egg

Catalytic RNA

store information and can perform work

Ribozymes

RNA enzymes that possess genotype and phenotype

Oparin-Haldane model of life beginning

1. assembly of building block

2. assembly of polymers

3. membrane and energy source

Early earth’s environment may not have been good for synthesis of

building blocks

Heavy bombardment

many meteors and comets hit Earth

Meteorites found with

organic compounds inside

• amino acids (gly, ala, glu, val, pro) at high concentrations

How do we thing the compounds for life were delivered to Earth?

interstellar dust with gentle delivery - meteors burn up with heat

The fossil record preserves time stamped trace of living past including a

record of macroevolution (morpho change, speciation, and extinction)

Morphospecies

recognizing species based on anatomy and morphology

Taphonomy

study of fossilization process

How is morphology biased in fossil record?

hard parts preserve better than soft parts

How does abundance create bias in fossil record?

common species are more likely to be found than rare ones

How does environment create bias in fossil record?

characteristics of place make fossilization more or less likely (i.e. sea floor vs mountain)

How does geology create bias in fossil record?

fate and accessibility of rocks with fossils

• prob good ones on seafloor we cannot get

How do humans create bias in fossil record?

go to same collection sites

fossil

any trace left by an organism that lived in the past

What are some ways fossils can be preserved?

• amber

  • plant resin traps organisms and hardens

  • minimal alteration, rare, and primarily insects

• freezing

  • minimal alteration, rare

  • tissue, fur, DNA

• special environments

  • 2000 year old human cadavers in peat bogs

    • very anorexic

    • almost look like modern presevation

  • 100k dried giant ground sloth dung; dry conditions

permineralization/replacement

• organsims buried in sediment

• dissolved minerals either replace original mineral content or precipitate in or around it

• preserves shape, sometimes internal details

Natural molds and casts

• organismal remains decay when buried in sediment

• preserves surface shape but no internal details

Trace fossils

• record behavior/signs instead of body form

• footprints, trackways

  • burrows and dens (infilling by sediment makes cast

Coprolites

fossilized feces

geologic time scale

intervals ordered by relative age

• rocks placed in older to younger (bottom to top seq)

  • time interval spans are not equal

radiometric dating

measures the decay of specific radioactive elements

• decay measured the half lives of the atoms

• ½ of parent atom decay into daughter atoms

• ratio of parent to daughter tells us how many half lives have passed

Fossils contain only

sedimentary rocks

Radiometric dating only works for

igneous rocks (created by cooling of magma (volcanic)

precambrian life

tiny, anaerobic, marine, evidence of cell division 3.6 bya

• oxygen in atmosphere from cyano

• evo of eukaryotes in this time (1.8 bya)

Fossil evidence of eukaryotes

1.8 bya

• chemical fossil evidence suggest earlier (2.7 bya)

Evolution of eukaryotes

single celled for first 1 bya

evolution of multicellularity

development of cell adhesion

• arose independently 6 times

Ediacaran

first unequivocal evidence of macroscopic (multicellular) life

565-544 mya - end of proterozoic era

What were animals in Ediacaran?

sponges, jellyfish, comb jellys

• no hard parts, small, simple morhpolgy

• mostly impression fossils

• no predation really

• evidence of early bilaterians (bilaterally symmetrical animals)

  • blastomeres of cleaving embryo similar to athropods

  • trace fossils

Cambrian explosion

540 mya

• most animal phyla appeared rapidly in this era

There are no _____ in the fossil record before Cambrian

modern phyla

Why did life explode in Cambrian?

increase in oxygen levels in atmosphere

• more energy available to life (ETC)

• promoted diversification

Paleozoic life (after cambrian)

• early vertebrates

• nautiloids and ammonoids

• fishlike vertebrates

• on land

  • tiktaalik, winged insects, giant millipedes, no flowering plants but lycophtes

What was the Burgess Shale (505 mya)?

has rich ocean fauna from Cambrian

• many soft bodied forms

• molluscs, segmented worms

• many unusual and hard to classify

• larger, bilateral animals with segmentation (1 cm)

• early chordates (jawless vertebrates

• diversity of feeding strategies, evolution of predation

What life was found in late Devonian?

first terrestrial vertebrates

Carboniferous

hot, tropical climate with many swamps

• giant lycophyte trees, ferns, horsetails, no flowers

• spore reproduction

• first winged insects, giant millipedes adn dragonflies

  • more oxy = more aerobic resp = more effecient

End permian mass extinction

during permian the continetns all amassed into the supercontient pangea

• mountain building (appalachians)

  • sea level lowest in earth history

• 80% marine invertebrates and 50% genera extinct

• rapidly = 60-200k years

• caused by volcanic eruptions in Siberia

The largest mass extinction event was

end permian mass extinction

Mesozoic life is the

age of reptiles = triassic, jurassic and cretaceous

Pangea breaks up in mesozoic, forming

Tethys sea (between asia and africa

laurasia (northern land masses)

gondwana (southern land masses)

Mesozoic ended with the K/T mass extinction (K/Pg) which

killed the dinosaurs

• 15% of families, 47% of geenra of marine inverterates

  • many mammal lineages went extinct

Cenozoic world starts to resemble modern world, where

mammals and birds greatly diversified

Only 3 mammal groups survived the K/Pg mass extinction, what were they?

monotremes, marsupials, eutherian mammals

True or false: Most modern mammal orders arose after the KT boundary

False; diversified after though

glacial refugia

sites of favorable conditions during glaciation

transitional forms

species with a mix of features: some ancestral traits and some derived traits found in descendants

archaeopteryx

145-150 mya

• found in germany

• discovered after publication of Origin

• crow sized

• skeleton is reptile like, but have modern-like feathers

Birds are derived from

theropod dinosaurs

• earliest birds were most likely bipedal carnivores

stasis

no change

evolutionary changes

consistent directional changes in morphology over time

background extinction

average rate of extinction over time