The History of Life on Earth

Macroevolution

Major changes in life above the species level in earth’s history

Origin of First Cells

When earth was hot, mostly ocean with volcanic gases & low O2 (3.5 bya)

Earliest Evidence of Life

Oldest cell fossils are prokaryotes

• in stromatolite formation (3.5 bya)

• Layered mates of prokaryotes & minerals

Adaptive Radiation

• Adaptive radiation has occurred small-scale in isolated island groups

• Historically, major radiations followed with mass extinctions

Novel Features

• Novel features are features that evolved gradually

• Novel features is result of many small function improvements

  • change = better adaptation but for same use

    Ex: complex squid eyes

Exaptation

• adaptations to different uses

  Ex: Hair (insulation) —>porcupine quills (defense)

Regulatory Genes

Regulatory Genes control when, where, & which expressed

• single mutations may affect expression of many genes during development

  Ex: DNA Coding for Transcription factors affects transcriptions for many proteins.

Heterochrony

Heterochrony is evolutionary change in form due to change in rate or timing of developmental events

• a change in growth rate of parts can produce a new final shape

  Ex: Premature children

Paedomorphosis

Paedomorphosis is a change of timing produces a sexually mature adult with juvenile features

The Fossil Record

Fossils are remnants, casts, or traces of organisms

What do fossils tell us ?

• anatomy, habitats, diet, lifestyle, activity, genetic info (DNA)

Hadean Eon

Planet formed 4.6 bya

• molten rock surface, no liquid water

Archean Eon

• crust cooled, solidified, 3.8 bya

• Condensed water formed global ocean

• Tectonic plates shift

• First life ! Prokaryotic cells

Proterozoic Eon

• eukaryotic life began 2.1 bya

• Continents form as islands merge

• First multicellular life

Paleozoic Era

• Cambrian explosion of animal diversity

  • Ex. Age of Fishes, First land vertebrates

• Ends with Permian Mass Extinction (Volcano) THE BIG ONE

Mesozoic Era

• Age of Dinosaurs & reptiles

• Cone bearing seed plants dominate

• First mammals & birds

• Breakup of Pangaea ( climate change, allopathic speciation, species distribution)

Cretaceous Mass Extinction

• Mesozoic Era ends (meter, Yucatán peninsula)

Cenozoic Era

• major diversification of mammals, flowering plants, insects, birds

• First humans