BIOL10004 Chapter 33: ESSENTIAL READING- Origins of life on earth (Chapter 33- 809–811, 816–819)

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jadebutterfly872

29 Jun 2018

School

University of Melbourne

Department

Biology

Course

BIOL10004

Professor

All

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ESSENTIAL READING: Origins of life on earth ( Chapter 33:

809–811, 816–819)

Fossils are a record in rocks of past life

Fossils are preserved remains of organisms

Trace fossils (dinosaur footprint, trilobite tracks, tubes of soft-bodied worms)

Chemical fossils (organic compounds produce by animals)

Hard parts fossilised (teeth, bone, external shells of animals, leaves, wood)

How do fossils form and where are they found?

Organisms must be buried in sediments of sand, silt or clay

Prevents decay

Sediments build up and squeeze out water

Physical compaction and chemical changes result in formation of sedimentary rocks

Sandstone, shale limestone

Limestone - fossils retain 3-D shape

Shale - highly compressed, flat fossils

Micro-spaces in bone wood filled with minerals

Heavier fossils than original remains

Fossil mould - rock itself forms impression around the organism

Fossil cast - a fossil mould filled by materials such as silica

Amber - insects trapped in amber, hardened resin conifers

Show wing venation, hairs and other fine details

Black shales - rich in organic matter, deposited on sea-floor, low oxygen

Carbonisation - carbon molecules stable and remain behind when mobile organic

compounds are lost during compaction

Geological Eras mark major events in evolution

Precambrian life

Precambrian era (before the Cambrian)

Two long periods of time

Archean eon (2500-4500 million Years ago) - Proterozoic eon (542-2500 million years ago)

Most Precambrian fossils found in black chert (Black substance from gels of silica

precipitated on surface of ancient sea-floors)

 Gels trapped primitive organisms and harden into rock

Archean Cherts in WA (3.3-3.5 Billion years ago) resemble modern bacteria and

cyanobacteria

Stromatolites - concentrically layered rocks

Formed by sediment trapped by successive growth of thin mats of cyanobacteria

Precambrian organisms were prokaryotes

Some were photosynthetic

Presence of pristane and phytane in black cherts, stable degradation products of chlorophyll

Banded iron stones - 1.8-2.3 billion years ago, rich iron oxides = high oxygen content

atmosphere

Increase oxygen - extinction of anaerobic forms of bacteria

Younger Precambrian rocks reveal small prokaryotes

Prokaryotes only recorded for next 2 billion years in fossil record

Ediacaran Fauna : evidence of multicellular organisms

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Document Summary

Essential reading: origins of life on earth ( Fossils are a record in rocks of past life. Trace fossils (dinosaur footprint, trilobite tracks, tubes of soft-bodied worms) Chemical fossils (organic compounds produce by animals) Hard parts fossilised (teeth, bone, external shells of animals, leaves, wood) Organisms must be buried in sediments of sand, silt or clay. Sediments build up and squeeze out water. Physical compaction and chemical changes result in formation of sedimentary rocks. Micro-spaces in bone wood filled with minerals. Fossil mould - rock itself forms impression around the organism. Fossil cast - a fossil mould filled by materials such as silica. Amber - insects trapped in amber, hardened resin conifers. Show wing venation, hairs and other fine details. Black shales - rich in organic matter, deposited on sea-floor, low oxygen. Carbonisation - carbon molecules stable and remain behind when mobile organic compounds are lost during compaction.

Related Questions

1. Refer to Figure 9.13. Which photo(s) (AâI) best illustrate(s) the methods of fossilization or fossil evidence listed
below? (Photos/letters may be used more than once.)
Petrification: The small internal cavities and pores of an original organism that are filled with precipitated mineral
matter. Photo(s):
Cast: The space once occupied by a dissolved shell or other structure is subsequently filled with mineral matter.
Photo(s):
Carbonization: Preservation that occurs when fine sediment encases delicate plant or animal forms and leaves a
residue of carbon. Photo(s):
impression: A replica of an organism, such as a leaf, left in fine-grained sedimentary rock. Photo(s):
Amber: Hardened resin of ancient trees that preserved delicate organisms such as insects. Photo(s):
indirect evidence: Traces of prehistoric life but not the organism itself. Photo(s):
ACTIVITY 9.6
Types of Fossils
A. Crustacean (shrimp) B. Fossilized wood C. Fossil bee
D. Fossil brachiopods E. Dinosaur track F. Trilobite fossil
G. Fossil dung H. Fossil spider I. Fossil fish

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BIOL10004 Chapter 33: ESSENTIAL READING- Origins of life on earth (Chapter 33- 809–811, 816–819)

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