Origin of Life

Identify biological events (origin of groups, mass extinctions) that occurred in the geologic record. Describe the uses and limitations of the fossil record, using examples. Describe continental drift and plate tectonic. Explain the impact of Permian and Cretaceous extinctions. Describe events leading to adaptive radiation. Outline the hypothesised sequence of events leading to life.

Polymer

A large molecule with repeated units of the same structure

• Nucleic acids, proteins, and polysaccharides

Characteristics of Life

• Organization

• Homeostasis

• Metabolism

• Response to Stimuli

• Adaptation

• Reproduction

Organization

Structurally composed of one or more cells

Homeostasis

The maintenance of an internal environment despite external variations

Metabolism

A system of management of energy and materials via chemical reactions

Response to Stimuli

Response to stimuli via changes in growth, alteration of chemical reactions, or movement

Adaptation

The ability to change over time in response to the environment

Reproduction

The ability to produce new individual organisms

Virus vs Viroid

• Both are infectious and parasitic

• Virus is composed of genetic material (DNA or RNA) encased in protein shell

• Viroid is composed of a short strand of circular RNA

Evidence for and against viruses and viroids being life forms

For:

• Have nucleic acids for replication

• Show signs of adaptation

Against:

• They lack metabolism, homeostasis, and rely on host cell

3 main eons of the geological records

• Archaean Eon

• Proterozoic Eon

  • Precambrian: prokaryotic life form

• Phanerozoic

  • Paleozoic, Mesozoic, Cenozoic eras

  • Multicellular, eukaryotic life forms

Fossils

Preserved remains or evidence of organisms that lived in the past

Where are fossils found

Sedimentary rocks through accumulation of materials such as mud, silt, and sand

Functions of fossils

• Direct evidence of life forms and events in the past

• Calibration of phylogeny

Fossilization

A process of organic and inorganic materials related to organism is preserved in the geological record

Fossilization Process

• Organism or its remains are buried in sediments

• Materials of organisms are replaced by mineral

• Strata are removed, exposing the fossilized remains or traces of the remains

Organisms are more likely to be fossilized with following features:

• Having existed for a long time

• Widespread and large populations

• Having “hard” tissues such as bones and teeth

• Near area where rapid burial can occur

• Few if any decomposing organisms

Body Fossils

Actual remains of the organisms after being replaced by minerals.

Preserved fossils

Actual remains of the organisms with some percentage of organic materials.

• Sub-fossils have high percentage of organic materials.

Cast

Sedimental in-fills of a space previously occupied by organisms.

Molds

Fossilised imprints of organisms.

Trace fossils

Records of biological activities left by organisms.

Relative Dating

A sequence of fossil from old to young corresponding to the sedimentary strata.

• Numerical number is typically absent

• Based on geological principles on sedimentary rock formations

Index Fossil

• Widespread organisms to connect strata between localities

• Endemic organisms that only appeared for a short amount of time

• Assist in relative dating

Limitations of relative dating

• Sedimentary strata are incomplete

• Sedimentary strata can be distorted and even inverted

Absolute dating

Using geological or biological evidence to estimate a numerical age before the present

Categories of absolute dating

• Radiometric

• Dendrochronology

• Amino acid racemization

Radiometric dating

Dating based on the decay of radioactive isotopes

Dendrochronology

Dating based on growth in tree rings

Amino Acid Racemization

Dating based on the generalized process of protein decay after death

Half-life

The time required for 50% of atoms in a given amount of isotope to decay

Continental Drift

The landmass of the Earth moves substantially over geological time

Effects of continental drifts

• Changes of oceanic circulation

• Changes in eustatic sea level

• Plate tectonics drove the changes in where continents were located

  • Mountains and valleys

  • Supercontinent

  • Catastrophes

  • Introduction of mineral-rich fluids

Plate Tectonics

Crusts of the Earth move and collide to reshape the Earth’s landscape

• Crusts are classified into continental and oceanic plates

  • Oceanic plates lie under oceans

  • Continental plates have rock mass above and below sea

  • Epicontinental sea refers to the body of water above the continental plate

Formation of Pangea Environmental Effects

• Epicontinental sea shrunk, and number of shallow water habitats were reduced

• Inland climate became cooler and drier

Pangea’s Implications on Evolution

• Slow habitat changes meant that adaptations were gradually accumulated, eventually new habitats were created and existing habitats were removed

• As continents drifted, isolation of land masses could’ve lead to allopatric speciation

• Gene flow could’ve occurred due to temporary land mass connection

Extinction

The last individual of a species is dead, or its survival cannot be considered beyond reasonable doubts

• 98% of known species are extinct

Mass Extinction

The elimination of a large number of species throughout Earth, as a result of global environmental changes.

• Usually defined as over 75% of known species were lost in a short period of geological time.

• Five mass extinction events have been recognized in Earth’s history