Week 12 notes for extinction happens

  • Understanding Extinction

    • Extinction is a natural process, occurring irrespective of human activity.
    • Natural selection continues regardless of our contributions to the environment, eliminating species that are not suited for survival.

  • Nature of Extinction

    • Extinction is characterized as permanent and inevitable; once a species is extinct, it cannot be revived by evolution.
    • All species, including humans, are eventually subject to extinction due to natural processes (e.g., solar changes).

  • Dinosaurs and Extinction Events

    • Dinosaurs thrived for millions of years, spanning various geological periods.
    • They were widespread and highly diverse, leading to questions about how they could all go extinct simultaneously.
    • The extinction boundary (Cretaceous-Paleogene) is marked in geological records by a significant drop in certain species, including dinosaurs.
    • Other major extinctions have occurred, but the dinosaurs' demise is particularly well-known.

  • Cretaceous and Paleogene Periods

    • The boundary between the Cretaceous and Paleogene signifies a mass extinction event.
    • Different types of sediment (strata) represent changes in fauna and flora across time.

  • Hypotheses for Dinosaur Extinction

    • Numerous hypotheses exist regarding the cause of the dinosaurs' extinction, including:
    • Extreme climate changes which may disrupt ecosystems.
    • Volcanic activity, especially extensive eruptions, contributing to atmospheric changes.
    • Asteroid impact causing immediate catastrophic consequences.
    • Disease and pandemics, though unlikely to wipe out such diverse species globally.
    • Natural fluctuations and human activity (e.g., pollution) exacerbate current extinction trends.

  • Key Concepts in Extinction

    • The idea of “anthropogenic” effects refers to human-caused changes impacting ecosystems.
    • Examples of endangered species today include polar bears and white rhinos, primarily due to habitat loss, climate change, and hunting.
    • Case studies of species that have gone extinct due to human actions include dodo birds and passenger pigeons.

  • Climate Change and Carbon Dioxide

    • Atmospheric composition primarily consists of nitrogen (78%) and oxygen (21%).
    • Carbon dioxide levels influence the heating of the Earth and ecosystems; current levels around 430 parts per million (PPM) have raised concerns about climate stability.

  • Volcanic Activity and Its Effects

    • Volcanic eruptions release gases and particulates that can cause climate changes (e.g., cooling or acid rain).
    • The concept of volcanic ash, comprising pulverized rock, plays an essential role in understanding historic extinction events.

  • Asteroid Impact Hypothesis

    • A significant asteroid (~6 miles in diameter) is theorized to have struck the Earth, causing massive destruction and changing the environment drastically.
    • The kinetic energy of the impact was immense, comparable to the release from atomic bombs, leading to widespread fires, ash clouds, and disruption of the food chain.
    • The aftermath resulted in starvation as food sources diminished.

  • Survivability Factors Post-Impact

    • After the extinction event, larger animals were more likely to die due to higher food demands.
    • Smaller animals and those capable of burrowing (e.g., certain mammals) had higher survival rates, showing adaptation strategies to climate and environmental shifts.

  • Evidence of Impact Events

    • Geological evidence includes shocked minerals, iridium anomalies (common in meteorites but rare on Earth), and glass particles formed from high-energy impacts.
    • These markers help identify and validate theories regarding mass extinction events and environmental changes.