Fossils

remains, traces, or imprints of once living organisms preserved in the earth's crust since some past geologic or prehistoric time. Fossa - hole, or to dig

Basic forms of fossils

Body fossils and Trace fossils

Body fossils (soft-bodied or skeletal)

exoskeletons, endoskeletons, or basal skeletons. Microfossils or macrofossils. Examples - Benthic foram, Planktic foram and Echinoid

Trace fossils in sediments

Signs of organic activity, burrowing, motion (tracks, trails), boring, footprints, recycling.

Fossilization

A random process, leaving many gaps in the documentation of evolutionary history

Conditions favoring fossil preservation

Possession of hard parts and quick burial around 3000 species of plants and animals live in a modern reef but only 75 are recognizable after death

Hard parts

Stand a much better chance of fossilization than do soft tissues, such as shell, teeth, and bony skeleton)

Quick burial

Helps prevent or retard the decay, scavengers can't disturb the remains (volcanic ash and tar pits)

Types of Fossilization

Unaltered remains and Altered remains

Unaltered Remains (1)

The hard skeleton of the organism or its soft part or both remains unchanged (soft parts). 1. Mammoth in the pleistocene glaciers of Siberia. 2. insect in amber in the oligocene deposits of Baltic province.

Unaltered Remains (2)

Hard Skeleton - Cenozoic shells which underwent little or no alteration of the original mineral substance.

Altered Remains

Soft parts decay and the hard skeletons are altered. Most fossils have undergone some degree of alteration since the death of the original organisms.

Five types of altered remains

Carbonization, Recrystallization, Replacement, Permineralization, Imprints (moulds and casts).

Carbonization

Removal of volatile constituents such as oxygen, hydrogen and nitrogen from the orgnanic compound leaving only carbon as a thin black film. (ex in Burguss shale, graptolites, fishes and plants

Recrystallization

Is the alteration of less stable inorganic compounds (aragonite) into more stable ones (calcite) without any chemical/compositional change.

Replacement

the original mineral of skeleton is dissolved and replaced by other mineral substances such as silica, pyrite, iron or dolomite. Dissolved by ground waters, and forms a replica of the original. (Petrified wood)

Permineralization

is the deposition of minerals in the interstices of skeleton. If the original organic material is porous, mineral matter carried by percolating solutions may be deposited in voids, without altering the original material. Ex bone pore spaces filled in with materials.

Imprints (Moulds and Casts)

Organic structure may leave an impression if it is pressed into a soft material that is capable of receiving and retaining the imprint such as clay. Impressions made by thin objects such as fish or leaves.

Mould

the impression of skeletal remains on rocks, may represent the external or internal surface of the organism.

Cast

if a mold is infilled with sediment or mineral, the infilling produces a cast. Can be artificial or natural (latex rubber, plaster of paris, dental wax, etc).

Main geological uses for fossil

Age, Correlation, Paleo-Environmental Analysis, and Record of life with Evolution.

The linnean taxonomic hierarchy

Kingdom, Phylum, Class, Order, Family, Genus, Species.

Prokaryote

cell represents the simplest grade of organization of life, in which genetic material (DNA) is not gathered together in a nucleus but distributed throughout the whole cell. Earliest life forms on Earth.

Eukaryotes

Organisms in which the genetic material is contained within a nuclear membrane, the name means "true kernel".

Three main domain paradigm of Woese

Prokaryotae which divides into Bacteria and Archaea and Eukarya.

Extinctions

99% of all species that existed are now extinct. The fossil record shows that extinction is the rule in the history of life. They are continual occurences in the history of life.

Mass Extinction facts

Periods during earths history where extinction rates have been greatly accelerated. Diversity of life is sharply reduced. Appear as sudden events but are likely to be gradual from a human perspective.

Five mass extinctions and how long ago they happened

Late Ordovician 440 mya Late Devonian 370 mya End Permian 245 mya End Triassic 210 mya End Cretaceous 65 mya