Earth's Geological Eras and Paleontological Insights

Understanding Earth's Ancient History

Key Concepts in Paleontology

Paleobiogeography: Species Distribution and Migration

• Defining the largest possible precision divergence geographic areas of species and fossil groups.
• Understanding their migrations.

Barriers to Migration

• Weather patterns
• Prevailing winds
• Ocean currents
• Differences in temperature and salinity
• Presence of rivers
• Areas of dense vegetation
• Mountain ranges

Paleontological Basis: Evolution Through Time

• Variation of organisms over time.
• Intermediate or transitional forms.
• Synthetic forms.
• Progressive vestigial organs.

Stratigraphic Paleontology: Fossils and Strata

• Characteristic fossils in specific strata.
• Fast-moving species.
• Wide area dispersion.
• Abundance in the layers.

Earth's Geological Eras: A Timeline

Cenozoic Era (0-65 Million Years Ago)

• Glaciations.
• Quaternary and Tertiary periods.

Mesozoic Era (65-225 Million Years Ago)

• Separation of Pangea.
• Age of Reptiles.
• Flowering plants emerge.
• Periods: Cretaceous, Jurassic, Triassic.

Paleozoic Era (225-570 Million Years Ago)

• Collision of the Americas to form Pangea.
• Periods: Permian, Carboniferous, Devonian, Silurian, Ordovician, Cambrian.

Precambrian Era (570-4600 Million Years Ago)

• Characterized by igneous and metamorphic rocks.
• 100% marine life.

Detailed Eras and Evolutionary Milestones

Precambrian Era: Earth's Earliest Beginnings

• Formation of the planet and primitive atmosphere.
• Impacts of meteorites and volcanic activity.
• Modification of the primitive atmosphere.
• Appearance of photosynthesis.
• High temperatures.
• Earliest evidence of life (potentially extraterrestrial or chemical origin, thermophilic or hyperthermophilic environment).
• Certainties: Unicellular, heterotrophic, anaerobic life forms.
• Increase in atmospheric oxygen.
• Emergence of eukaryotic cells.
• Appearance of the Metazoan group.

Paleozoic Era: Diversification of Life

• Existence of Pangea.
• Greater development of life forms.
• Explosive radiation of marine animals without a spinal column.
• Evolution of the skeleton.

Early Paleozoic: Marine Invertebrates (Cambrian-Silurian)

• Dominance of invertebrate marine organisms.

Late Paleozoic: Conquest of Land (Devonian-Permian)

• Conquest of the terrestrial environment.
• Cambrian: Appearance of jawless fish (agnathans) and the spine.
• Devonian: Jawed fish evolve, amphibian evolution begins.

The Conquest of Land: Key Adaptations

• Body fully supports its weight.
• Efficient breathing mechanisms.
• Adaptations to avoid dehydration.
• Permian: First appearance of reptiles.

Evolution of Plants

• Silurian: Plants had no leaves, stem photosynthesis, reproductive structures at the apex.
• Devonian: Gymnosperms, ferns, mosses appear.
• Cretaceous: Angiosperms emerge.

Evolution of Insects

• Silurian: First appearance of insects.
• Cretaceous: Significant proliferation of insects.

Mesozoic Era: Age of Reptiles and Fragmentation

• Beginning of the fragmentation of Pangea.
• Starts and ends with mass extinctions.
• Increase in biodiversity.
• Significant development of cephalopods.
• Great development of ferns and gymnosperms.
• Onset of warm-blooded organisms.

Cenozoic Era: Age of Mammals and Modern Life

• Age of mammals.
• Diversification of angiosperms and decline of gymnosperms.
• Abundance of insects.
• Evolution of humankind.