History of Life on Earth
This lecture has links to many websites that contain supplemental
information which I hope may be of interest to you. You are not
responsible for the information at these sites on the exams but
I hope you will take a look at some of them.
Fossils - relics or impressions of organisms from the
past, preserved in rock.
25.1) most frequently form from:
- organisms with hard parts - shells (Fig
25.1e), bones (Fig
25.1a) and (Fig
- organisms that are quickly buried in mud or sand (forms
- organisms trapped in amber (Fig
- Many of the parts found have been hardened by petrification,
which occurs when minerals dissolved in groundwater seep into
the tissues of dead organisms and replace organic matter. (Fig
- other fossils are replicas, casts from molds
left when corpses were covered by mud or sand.
- tracks (Fig
25.1f) and coprolites
Paleontology - the study of
Aging bones and rocks
- 1. Relative
- - Law of superimposition - sedimentary
rock formation (fig
- - Index fossils
- - Eras, periods within
each era, and epochs within periods. Each marked by a
large extinction episode.
- 2. Absolute Dating - radiometric dating. (Fig.
- - Radioactive
- - Half-life
- - Carbon14/12
(Carbon 14 degrades to nitrogen 14)
- - Uranium
238 (degrades to lead 206) - only for dating volcanic rocks
- - Potassium-40
(degrades to calcium 40, then to argon 40)
Geologic History of Earth -
25.1). The Geologic Time Table
See cross-section of earth here
- - solid inner
core of iron & nickel
- molten mantle
- solid crust - 8-65 km thick
Plate tectonics (Fig.
25.3) (See links at end of lecture)
- - convection cells
in the mantle (OH) similar to those in boiling water (OH)
- - types of boundaries
(Image) (OH) and the mid-oceanic ridge (OH)
- - Continental
- - Pangaea
- - The mid-Atlantic
ridge and the repeated reversal of
the earth's magnetic field
- - Where'd that Indian
- - California
- into the sea? The San Andreas fault - a map and a picture.
- Wegener's evidence (1) Africa and S. America (2) biogeograpy (3) glacial deposits
- - See drawings
from 1858 by Antonio Snider-Pellegrini before and after the breakup of Pangaea, which was not even
named until 1912 (by Wegener).
Alternation between hot & cold climates which resulted
- the rising and falling of sea levels
and the resultant changes in salinity
- extension and retreat of ice (ice caps
- caused "nuclear winters"
- possibly caused mass extinction at
end of Permian when Pangaea formed
- - some formed
at areas other than boundaries. See map of earth's hot spots and creation of Hawaii
- caused "nuclear winters"
- most important at end of Mesozoic (Cretaceous
extinction - K-T boundary)
- - recently
implicated in Permian extiction also
- Mass extinctions (Fig
A simple but interesting look at the
of the earth and life from NASA.
time period at the Berkeley site. Lots
of good pictures. Introduction to Evolution at Berkeley.
Geologic time table - simple
one (you are not responsible for either one)
Major episodes in the history of Life (Fig
26.1) Clock analogy (Fig
Precambrian - From
the earth's creation to the beginning of the Paleozoic. also look at this site
Universe 10-20 byo
Solar system 4.5-5 byo
Earth (OH) - 4.6 byo
- - atmosphere of early
earth thought to contain:
NO FREE OXYGEN, or just trace amounts (reducing environment)
- atmosphere of present day
carbon dioxide CO2
of rarer gases
Origin of life - life began 3.5-4.0 bya
Eukaryotes evolved about 2.1 bya and multicellular eukaryotes
evolved by 1.2 bya
Image of early earth
Origin of life by chemical evolution
- abiotic synthesis
- - terrestrial synthesis - formation
of monomers > polymers > origin of self-replication
molecules > protobionts (Fig
26.12) > primitive cells
- - Miller-Urey (Fig
- shallow seas
vents in action
- clay, sand, rock particles
- - extraterrestrial - comets,
asteroids, meteors (Panspermia)
- - a lecture on origin of life by Dr. Taggart
A good article
on the origin of life by Christian de Duve in the American Scientist
Define prokaryotic, eukaryotic, heterotrophic
The evolution of prokaryotes
Early and modern prokaryotes (Fig
- - earliest
fossils are 3.5 billion years old =
- Fossil (Fig
26.4c) & Modern
- evolved 3.6 bya - 4.0 bya
- 2.0-3.5 bya cyanobacteria (photosynthetic) oxygen
- - evolution of photosynthesis (Fig
Precambrian Extinction - huge extinction event probably
caused by severe glaciation.
ERA - Age of fishes 543-245 mya
Ocean Life - images) and a great trilobite
- Cambrian Explosion. Timeline of the evolution of animal
- More on this
- About 570-500 million years ago
- - most major
animal phyla appeared during this time
Ordivician - Invasion
of Land - plants,
animals and fungi
Devonian - first amphibians, insects
Carboniferous - those famous
forests of the Carboniferous
- Pangaea formed
- - Most recent data
indicates there was probably an asteroid strike at that time
- extinction of about 90% of marine and
70% terrestrial species. Possible causes.
- - The Permian
Reef Complex (Delaware Basin) of West
Texas - A virtual tour of a Texas site.
by K.A. Grimm
ERA - Age of Reptiles 245-65 mya. Discovery
- - OH of representative animals of the Mesozoic
- Radiation of gymnosperms, tree ferns,
invertebrates & reptiles, including dinosaurs
- map of earth at early Jurassic - about 200 mya
- - radiation
of bony fishes, flying reptiles, some mammals
- very warm, sea levels high, radiation
of flowering plants, dinosaurs, small mammals
- Extinction of Dinosaurs (K-T boundary) (Big blank place on this page - keep scrolling!)
- ended 65 million years ago, most think
caused by asteroid impact (OH) (Fig
- - a great K-T
Boundary site, complete with a game
to play and lots of info!
- - More on the
theory of mass extinctions.
- - A great dinosaur site!
- - Hot-Blooded
- - A satellite
image of the Yucatan impact site of
that giant asteroid.
- - An alternative
theory of the extinction of the dinosaurs, gradualism, is presented
by Bryan Goff, Central Connecticut State University
- - A NASA site
hazards of the future!
- - Levels of
iridium in earth's strata.
CENOZOIC - Age of mammals 65-present
- - OH for representative extinct North and South
American mammals of the Cenozoic
- Climate cooler, sea levels lower,continents
near current positions
- Radiation of birds, mammals, flowering
plants and insects.
Quartenary 2 mya - present
- Cold clilmate, repeated glaciations,
sea levels low
- Humans evolve, many large mammals go
- - The
midwestern U.S., 16,000 years ago.
- We've only been around a few seconds!!
- Threats to biodiversity - humans causing
another major extinction event?
Follow a fossil from finding to museum:
La Brea Tar Pits: http://www.tarpits.org
Links for plate tectonics
from USGS: http://pubs.usgs.gov/publications/text//dynamic.html
from Berkeley: http://www.ucmp.berkeley.edu:80/geology/tectonics.html
from Dinosauria: http://www.dinosauria.com/dml/maps.htm