IB Biology HL - Unit A2.1: Origins of Cells

Early Earth Conditions

Extreme conditions existed around 4 billion years ago.

Atmosphere Composition

Lacked oxygen, mainly methane and carbon dioxide.

Cause of High Temperatures in Early Earth

Volcanic activity and greenhouse gases.

UV Radiation

Intense UV radiation reached Earth's surface.

Volcanic Activity

Frequent eruptions contributed to chemical reactions.

Asteroid Bombardment

Impacts delivered materials and released energy.

Organic Molecule Formation

Carbon compounds formed under reducing conditions.

Energy Sources

Lightning, UV radiation, and volcanic heat drove reactions.

Cells

Smallest unit of self-sustaining life.

Characteristics of Life

Metabolism, reproduction, growth, and homeostasis.

Viruses

Non-living entities lacking metabolism and independent structures.

Catalysis

Simple organic molecules formed with energy input.

Self-Replication

RNA likely first molecule capable of self-replication.

Self-Assembly

Amphipathic molecules form vesicles in water.

Compartmentalization

Vesicles may have enclosed RNA and proteins.

Protocells

Primitive cells that could grow, divide, and evolve.

LUCA

Last Universal Common Ancestor of all life.

Spontaneous Origin Challenge

Difficult to observe cell origin directly today.

Reducing Conditions

Absence of oxygen favored organic molecule formation.

Chemical Reactions

Driven by environmental factors like heat and radiation.

First Living Cells

Evolved from self-assembled vesicles trapping biological molecules.

Miller-Urey Experiment

Simulated early Earth conditions to test organic molecule formation.

Amino Acids

Organic compounds formed in the Miller-Urey Experiment.

Vesicles

Membrane-bound structures formed from fatty acids.

Hydrophobic Barrier

Separates internal vesicle chemistry from external environment.

RNA

Presumed first genetic material capable of self-replication.

Ribozymes

RNA molecules that catalyze their own reactions.

Hydrothermal Vents

Proposed environment for LUCA's evolution.

Spontaneous Formation

Natural occurrence of structures from simple organic molecules.

Fatty Acids

Non-polar molecules that form micelles in water.

Micelles

Aggregates of fatty acids avoiding contact with water.

Spherical Bilayer

Structure formed by polar organic monomers and fatty acids.

Prebiotic Chemistry

Study of chemical processes leading to life formation.

Organic Molecules

Compounds essential for life, formed under early Earth conditions.

Peptide Bonds

Links formed between amino acids during protein synthesis.

Experimental Support

Evidence backing theories of life's origins.

Complex Molecules

Advanced structures arising from simpler organic precursors.

Atmospheric Composition

Uncertain makeup of early Earth's atmosphere affecting experiments.

Evolutionary Evidence

Data supporting the development of life from LUCA.

Domains of Life

Three branches: archaea, bacteria, and eukarya.

DNA

Molecule used for genetic information storage.

Enzymes

Proteins that catalyze metabolic reactions.

Lipid-based cell membrane

Structure surrounding LUCA's cells for protection.

Horizontal gene transfer

Gene exchange between organisms, not through reproduction.

Earth's age

Approximately 4.6 billion years old.

Date of First cells' evolution

Estimated between 3.5-4 billion years ago.

LUCA's estimated age

Approximately 3.5 billion years old.

Chemical evidence

Fossil-like structures indicating ancient life.

Biomarkers

Molecular fossils indicating past biological activity.

Stromatolites

Layered structures formed by photosynthetic bacteria.

Hydrothermal vents

Locations proposed for LUCA's evolution, rich in minerals.

Fossil evidence

Physical remains indicating past life forms.

Genetic evidence

Comparison of genes across organisms to infer LUCA.

Obligate anaerobe

Organism that does not require oxygen for survival.

Chemoautotroph

Organism that derives energy from inorganic compounds.

Thermophile

Organism that thrives in extreme heat environments.

Effect of Recognizing 355 shared genes across all life

ancient common ancestry between bacteria and archaea.

Carbon isotopes

Chemical signatures indicating biological processes in rocks.

Sedimentary rocks

Rocks containing preserved organic compounds and biomarkers.

Fossilized stromatolites

Ancient structures formed by microbial activity.

Deep sea vents

Proposed early habitats for life on Earth.

Molecular fossils

Organic compounds preserved in geological formations.