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.

    Fossils (Fig 25.1) most frequently form from:

• organisms with hard parts - shells (Fig 25.1e), bones (Fig 25.1a) and (Fig 25.1b), exoskeleton
• organisms that are quickly buried in mud or sand (forms sedimentary rock)
• organisms trapped in amber (Fig 25.1g)
• 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 25.1c)
• 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 fossils.

    Aging bones and rocks

1. Relative Dating

    - Law of superimposition - sedimentary rock formation (fig 22.3)

    - Index fossils

    - Eras, periods within each era, and epochs within periods. Each marked by a large extinction episode.

   

2. Absolute Dating - radiometric dating. (Fig. 25.2)

        - Radioactive isotope

        - Half-life

        - Carbon14/12 (Carbon 14 degrades to nitrogen 14, but the comparison is done with carbon 12, which is stable)

        - Potassium-40 (degrades to calcium 40, then to argon 40)

Geologic History of Earth - (Table. 25.1). The Geologic Time Table

See cross-section of earth here and here.

    - solid inner core of iron & nickel
    - molten mantle
    - solid crust - 8-65 km thick

Continental drift (Fig 25.4)
    - plate tectonics (Fig. 25.3) (See links at end of lecture) (OH) and (OH)

   - types of boundaries (Image) (OH) and the mid-oceanic ridge (OH)

   - The mid-Atlantic ridge and the repeated reversal of the earth's magnetic field
    - convection cells in the mantle (OH) similar to those in boiling water (OH)
    - Pangaea

   - Where'd that Indian plate go?

    - 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 in:
    - the rising and falling of sea levels and the resultant changes in salinity
    - extension and retreat of ice (ice caps and glaciers)
Volcanos
    - 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
Meteorites (Fig 25.6)
    - caused "nuclear winters"
    - most important at end of Mesozoic (Cretaceous extinction - K-T boundary)

Mass extinctions (Fig 25.5)

A simple but interesting look at the origin of the earth and life from NASA.

Visit any time period at the Berkeley site. Lots of good pictures. Introduction to Evolution at Berkeley.

Geologic time table - simple one, complex one (you are not responsible for either one)

Major episodes in the history of Life (Fig 26.1) Clock analogy (Fig 26.2)

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 (A time line of the early years)

- atmosphere of early earth thought to contain:

         carbon monoxide

         carbon dioxide

         nitrogen

         water vapor

         BUT NO FREE OXYGEN, or just trace amounts
- atmosphere of present day
         78% nitrogen N2
         21% oxygen O2
         0.035% carbon dioxide CO2
          traces 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

- terrestrial synthesis - formation of monomers > polymers > protobionts (Fig 26.12) > primitive cells- abiotic synthesis

   - Miller-Urey (Fig 26.10)
    - shallow seas
    - hydrothermal vents             Hydrothermal vents in action
    - clay particles

    - bubble hypothesis

- 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 and autotrophic

The evolution of prokaryotes Early and modern prokaryotes (Fig 26.3)

- earliest fossils are 3.5 billion years old = stromatolites - Fossil (Fig 25.4c) & Modern
- evolved 3.6 bya - 4.1 bya
- 2.5-3.5 bya cyanobacteria (photosynthetic) (OH) & oxygen revolution

- evolution of photosynthetis (Fig 26.3)

PALEOZOIC ERA - Age of fishes 570-245 mya (Paleozoic Ocean Life - images) and a great trilobite site.

Cambrian Explosion. Timeline of the evolution of animal phyla (Fig 26.8)

    More on this here.
    - About 570-500 million years ago
    - Burgess shale (Fig 26.13)

Silurian - Invasion of Land

Devonian - first gymnosperms, insects

Carboniferous - those famous forests of the Carboniferous

Permian
    - Pangaea formed

   - Most recent data indicates there was probably an asteroid strike at that time also.
    - 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.

          Written by K.A. Grimm

MESOZOIC ERA - Age of Reptiles 245-65 mya. Discovery of dinosaurs.

Triassic
    - Radiation of gymnosperms, tree ferns, invertebrates & reptiles, including dinosaurs
Jurassic
    - map of earth at early Jurassic - about 200 mya

    - radiation of bony fishes, flying reptiles, some mammals
Cretaceous
    - 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 25.6)

    - a great K-T Boundary site, complete with a game to play and lots of info!

    - More on the impact theory of mass extinctions.

    - A great dinosaur site!

    - Hot-Blooded or Cold-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 here.

        by Bryan Goff, Central Connecticut State University

    - A NASA site on impact hazards of the future!

    - Levels of iridium in earth's strata.

    - OH of representative animals of the Mesozoic

CENOZOIC - Age of mammals 65-present

Ice Ages

Tertiary 65-2 mya
    - 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 extinct

    - The midwestern U.S., 16,000 years ago.
Human Impact
    - We've only been around a few seconds!! Geologically speaking.
    - Global climate change
    - Threats to biodiversity - humans causing another major extinction event?

    - OH for representative extinct North and South American mammals of the Cenozoic

Follow a fossil from finding to museum: http://www.dmnh.org/denverbasin2/fossil

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