Biodiversity Loss, Extinction, and Earth Sciences: Causes, Paleontology, and Geology

Causes of Biodiversity Loss

Principal causes of the loss of biodiversity include habitat change, habitat destruction, climate change, the introduction of invasive species, overexploitation, and pollution.

Loss of biodiversity: a decrease in the relative abundance of species and the extinction of species.

Extinction

Extinction: a species is considered extinct when it has not been recorded for at least 50 years (for example, the Pleistocene mammoth and the dodo, which disappeared in the 1600s). The highest extinction rates occur on islands, which are highly vulnerable ecosystems. Island species have difficulty competing, have low adaptive capacity, and lack defenses against predators; when new predators are introduced, they become highly vulnerable to diseases.

Endemic Species and Hotspots

Endemic species: a species that is naturally found in one specific geographic location and nowhere else.

Biodiversity hotspot: a region with a high concentration of biodiversity.

Ecosystems with the greatest degree of endemism: oceanic islands, lakes, and mountain summits.

Vulnerable Species

Vulnerable species: species with a restricted geographic distribution, a small population size, low genetic variability, and an absence of mechanisms that allow the expansion of their genes.

Principal Extinction Factors

Principal extinction factors: habitat fragmentation and loss, overexploitation of species, introduction of species, ecosystem disruption, loss of genetic variability, the loss of rainforest on the coast of Madagascar, the introduction of exotic species, and overexploitation of species.

Consequences of extinction: loss of species and disruption of trophic interactions.

Geology

Geology is the study of the Earth, including its solid rocks, minerals, the origin of oceans and mountain basins, and the continents that force the change of climate. It covers the history of Earth and of life on Earth, including bodies related to life, and the way the environment has changed over time. It also studies the origin of land and water resources, underground water, precious stones, construction materials, energy minerals, landslides, earthquakes, volcanic eruptions, tsunamis, and other bodies in the solar system.

Specialties of Geology

Specialties: soil mechanics, hydrogeology, environmental geology, sedimentology, regional geology, paleontology, geochemistry, crystallography, and geophysics.

Geophysics studies the physics of the Earth, such as discontinuities and the propagation of seismic waves.

Mineralogy studies minerals, their internal structures, chemical composition, and classification.

Petrology studies the origin, formation processes, and composition of rocks.

Petrography, a branch of petrology, describes rock content, mineral content, and texture.

Geochemistry studies the distribution and abundance of elements in different parts of the Earth's crust.

Structural geology analyzes the tectonic structures of the Earth's crust and the forces that produce folding, fractures, and mountains.

Historical geology studies the formation epochs of the Earth from its origin to the present.

Paleontology studies past life from geological epochs, including fossils, their classification, and their recognition, which helps improve knowledge of evolution.

Hydrogeology investigates the quantity and quality of underground water found beneath the land surface.

Economic geology focuses on the exploration of metallic and non-metallic deposits.

Environmental geology searches for sectors contaminated by natural and human processes.

Time is a continuous, non-spatial dimension in which events occur; the past is irreversibly succeeded by the present, which flows toward the future.

Geological Principles

Uniformitarianism principles: superposition means that more recent upper strata lie above older lower strata.

Horizontality? Sedimentary strata were originally deposited horizontally. Layers of rock form continuous, three-dimensional bodies.

Metamorphism is the change in the constitution of a rock that occurs after its consolidation and crystallization.

Faunal assemblage refers to the set of fossil life found in an interval, where each stratum represents one individual time.

Faunal succession corresponds to the vertical succession of rock sequences.

Correlation means that two different rocks exposed in different places that contain the same faunal assemblage are of the same age.

Inclusion, related to metamorphism, is when a rock is included in another rock that is older.

Discontinuities:

• Angular unconformity: an older folded series is overlain by a modern series at an angle.
• Erosive unconformity: the older part is partly eroded before the younger series is deposited on an irregular surface.
• Nonconformity: an eroded surface separates two types of rock formed at different times.

Paleontology

Paleontology is the science that studies fossils. Fossils are evidence of life that is often more than a million years old. A paleontologist describes the fossil, determines what data it provides, and identifies the era in which it lived.

Fossilization process: chemical transformations in which organic material is replaced by minerals.

Normal fossils are remains of a body.

Impressions or imprints are not part of an organic body but the mark left by it in the earth.

Chemical fossils are substances in rocks that indicate the presence of a body that could not otherwise be fossilized.

Geochemical fossilization:

• Putrefaction (decomposition of soft organic matter): oxidation destroys organic compounds with the release of gases. Reduction occurs anaerobically through the action of bacteria that reduce sulfur compounds.
• Mineralization (deposition of minerals within the interstices or hard parts): carbonation replaces organic remains with calcium carbonate in the form of calcite; silicification is substitution by colloidal silica solutions; pyritization is substitution by iron sulfide; phosphatization is substitution by calcium phosphate; carbonization is substitution by carbon, typical of plants and arthropods.

Early paleontological research: current living organisms serve as references for studying extinct ones through comparative anatomy, organic correlation, and relative chronology, based on the superposition of strata.

Paleontological findings: the duration of geological epochs and species has been limited. The differences between fossil faunas and present-day animals are considerable, and older animals were often more primitive. The appearance of a biological group, its existence, and its extinction occurred without interruption, with each species arising in space and time, coinciding with other pre-existing species. The geographic distribution of biological groups changed over time, and the paleontologist works exclusively with morphological species.

Branches of Paleobiology

Paleobiology studies fossils as biological organisms, based on current principles, comparative anatomy, and organic correlation.

Paleoecology interprets ancient environments and studies the environmental conditions in which organisms lived.

Biofacies are sets of paleontological characteristics that reflect the ecological conditions existing during the formation of a stratum.

Paleoethology reconstructs the behavior of an organism.

Paleophysiology can deduce whether organisms were warm-blooded and other physiological processes.

Paleoneurology studies the cranium to infer intelligence.