Fossil Records and Formation

• Fossils are evidence of evolution

Fossil Record

• The fossil record includes all fossils discovered on Earth
• It contains millions of fossils representing thousands of species
• Most of these species are no longer alive
• The fossil record provides evidence that species have changed over time

Fossil Formation

• Fossils are the preserved remains or traces of ancient organisms

Fossil Formation Through Mineralization

• Minerals gradually replace the organic material in a fossil, preserving the structure over time
• Groundwater rich in minerals seeps into the remains
• Minerals crystallize and harden, effectively turning the organic material into stone

Fossil Formation Through Carbonization

• The organic material of a plant or animal is preserved as a thin film of carbon
• The remains are subjected to heat and pressure over time
• The volatile elements escape, leaving behind a carbon-rich residue that forms a fossil imprint

Types of Fossils

• Mold fossils are imprints or impressions in sediment when an organism decays
• Cast fossils are formed when a mold is filled with minerals or sediment, making a replica of the original organism
• Trace fossils are evidence of an organism's movement or behavior
• In rare cases, original tissues can be preserved in tar, ice, or amber

Determining Fossil Age

• Relative age-dating involves determining the order in which rock layers were deposited to find the relative age of a fossil
• Absolute age-dating is a method using radioactive decay to find the absolute age of a rock in years; best measured in igneous rocks

Fossils Over Time

• Scientists organize Earth's history into a timeline called the geologic time scale, dividing it into eons and eras
• Fossils mark time boundaries; different rock layers contain different fossils

Extinctions

• Extinctions occur when the last individual of a species dies due to environmental change
• A mass extinction is when many species become extinct within a million years or less

Types of Changes

• Sudden: Extinctions happen when environments change quickly
• Gradual: Species might become extinct when changes are not sudden

Mass Extinctions Events

• Ordovician: Death rate of 85%, caused by rapid global cooling and falling sea levels around 445 million years ago
• Devonian: Death rate of 70%, caused by asteroid impacts and rapid global cooling around 340 million years ago
• Permian: Death rate of 95%, caused by volcanic activity, increased methane and CO2, and rapid global warming around 250 million years ago
• Triassic: Death rate of 76%, caused by increased methane and CO2 and rapid global warming around 200 million years ago.
• K-T: Death rate of 80%, caused by asteroid impact, volcanic activity, and falling sea levels around 65 million years ago

Theory of Evolution & Natural Selection

• Charles Darwin developed the evolution theory based on natural selection

Natural Selection

• The theory describes how species change over time to adapt to their environment and compete for survival
• Organisms with traits suited to an environment survive, called "survival of the fittest"
• Traits giving a survival advantage are passed on through reproduction
• A species may become extinct if not fit for its environment or due to outside competition

Main Points of Natural Selection

• Individuals of the same species have diverse traits that contribute to their survival and reproduction
• Individuals with helpful variations grow and potentially form separate species if isolated

Variation & Adaptation

• Genetic differences/variations exist between individuals, leading to diversity
• Helpful variations are called adaptations, improving an organism's adaptation to its environment
• Organisms can become distinct from a common ancestor over many generations

Evidence of Evolution: Fossils

• Fossils can preserve organism structures, giving ideas of organisms from Earth's past
• The fossil record is incomplete due to rare conditions needed for preservation

Evidence of Evolution: Embryology

• Embryology, the study of embryos, shows that multiple Embryos exhibit similarities during early development

Evidence of Evolution: Structural Clues

• Homologous structures or similar body structures across many species can give clues about evolution
• Similarities between body structures indicate shared common ancestors

Evidence of Evolution: Vestigial Structures

• Vestigial structures are body structures that no longer function, but can provide information about evolution
• Vestigial structures are leftover remnants from ancestor species, indicating evolution
• Examples would be the tailbone and tonsils

Evidence of Evolution: DNA Clues

• Comparing DNA of different Species reveals evolutionary clues
• DNA similarities tell information about ancestry, mutation rates track changes, aiding in reclassifying species

Explore the fossil record as evidence of evolution, showcasing the changes in species over time. Learn about fossil formation through mineralization and carbonization, vital preservation processes. Discover how minerals replace organic material, and how carbon films create fossil imprints.