Lecture 4 BIOL 214

Rise of atmospheric oxygen

O2 atmosphere: 2.5 BYA

O2 supports multicellularity

Compression fossils

Made by pressure on sediment

plants and simple organisms - bc don’t break

Cast and mold fossils

inmpression made by organism that has hard exoskeleton

nice imprint

Permineralized fossils

cell structure not destroyed

deposit of minerals within cells

petrified wood

Unaltered Remains

insects “amber”

burrows or feces of animals; trace fossils

Three factors effecting fossil accuracy

Geography: deposition areas [lowland/ marines likely b/c deposition]

Taxonomic bias: bones and shells are amenable to fossilization [some animals make better fossils]

Temporal bias: Earth’s crust recycled, so older rocks are rarer [things too old can’t be identified]

Best Record of Fossils

Vertebraes

Why have Origins of higher taxa not been documented

• Organisms completely consumed

• Sediemtns form only sporadically

• Sediments must solidify into rocks

• ROcks must be exposed/ accessible

Species

temporally distinct parts of single evolutionary lineage, different forms

diff forms called CHRONOSPECIES (change in lineage = anagenesis)

Cladogenesis

speciation - splitting of lineage

Pseudo extinction / taxonomic extinction

lineage changes so much that its original name disappears

• contrasts with real extinction, in which a lineage fails to leave any descendants

Anagenesis

change so much now different species

chrono species for paleontologists

Identify chrono species and cladogenesis

A & B are different chrono species

A & C are different chrono species

B & C are different species from one another (cladogenesis)

Proterozoic Era Characteristics

• 2.5 BYA to 543 MYA

• prokaryotes and eukaryotic algae

640 MYA

Oldest fossils of multicelled animals age

Trace Fossils

First evidence of animal life appeared less than 1 BYA

• tracks, burrows, feces

Ediacaran Fauna

• 565-544 MYA

• best known Precambrian animals

• soft-bodied, lacking skeletons

• crept or stood upon the sea floor

• don’t fit modern phyla - sponges, jellyfish

• radial MAYBE bilateral symmetry

Ediacaran Fossils

• radial symmetry (sponges, jellyfish)

• dickinsoniana

Paleozoic Era: Cambrian Period

541 - 485 MYA

• “Cambrian explosion” started 530 MYA

• almost all of modern phyla and skeletonized marine animals appear on record

• explosion MAY have occurred 30 MYA or 5-10 MYA

• BURGESS SHALE

Cambrian Fossils: Trilobites

bilateral symmetry - more complex

appendages

segmentation

• Crustacean

Cambrian: Arthropods and worms

Onychophoran

Chordates

First vertebrates (jawless)

What precipitated the Cambrian Explosion

• diversification by increased O2 levels

• Vacant ecological habitats —> diversification

• Innovations related to multicellularity

• NOT ENTIRELY SURE

The split occurred pre-Cambrian

• primitive organisms (90% of Earth’s early history)

Diversification may have started…

Pre-Cambrian

Paleozoic Era: Ordovician (485-443 MYA)

Diversification with new classes

First land plants and jawed fish

ended with one of the largest mass extinctions

Early Devonian had…

The first terrestrial animals were arthropods

Oligotrophic

low nutrients in lake, low productivity, high oxygen levels

Late Devonian had…

The terrestrial vertebrates (tetrapod’s) had arisen

Devonian Period

Age of fish

massive emergence of aquatic species

Paleozoic: Carboniferous and Permian

widespread tropical swamp forests

gigantic dragonflies

reptiles

mammal-like reptiles

WORST extinction ever at the end of Permian

SLIDE 26 MUST KNOW

okay

Mesozoic Era

Triassic, then Jurassic, then Cretaceous

• dinos, mammals and birds

• mass extinction at the end

Eutherian mammals

mammals with placenta

• humans

Cenozoic Era: Paleocene epoch (66-56 MYA)

mammalian radiation after extinction of dinosaurs

Pleistocene Epoch (1.8 MYA to 10k YA)

quaternary period

glaciations

Origin and extinction of large mammals

modern humans

Holocene Epoch (10k to NOW)

Current time

agriculture

domesticated animals

digital watches

MIGHT be the worst mass extinction BC OF CLIMATE CHANGE

Extinction Definition

failure of lineage to leave any descendants

Background Extinction

within any group, the chance of extinctions is constant, but the rate may vary

Is smaller range or larger range better for taxa

A larger range because it is less vulnerable to habitat

What has caused mass extinction

climate change MOST LIKELY

What caused KT Extinction

asteroid

• impacted quartz —> lines on quartz

• existence of iridium —> none on earth