Earth Science Quiz on Early Atmosphere and Life

Life Through Earth's History

• The unit covers the history of life on Earth and Earth processes leading to life.
• It explores the interconnectedness of Earth, climate, and life for a holistic understanding.
• It includes an understanding of timescales.
• New vocabulary will be introduced throughout the unit.

What to Expect in This Unit

• History of life on Earth
• Earth processes leading to life and reciprocally life impacting Earth processes.
• Understanding the intertwined nature of Earth, climate, and life for holistic understanding of a timescale.
• Potential new vocabulary will be highlighted.

Phylogenetic Tree

• Diagram depicting species relationships and evolutionary history.

Geologic Time Scale

• Detailed chart visualizing Earth's history, spanning from its formation to the present.
• Includes major intervals like eons, eras, periods, epochs, and stages.
• Shows ages in millions of years ago (mya).

Earth's Formation

• First 50-100 million years post-formation characterized by intense heat, volcanic activity, and radioactive decay.

The Hadean

• The early period of Earth's history, marked by the moon's formation, ongoing cooling, and the slow formation of continental crust.

The Late Heavy Bombardment

• Meteorites and asteroids bombarded Earth due to a thin atmosphere at that time.
• Today, these objects burn up upon entering Earth's atmosphere.

Archean Volcanism

• Extensive volcanic activity led to considerable gas emissions during the early Precambrian.
• The atmosphere was primarily comprised of CO2, H2O, toxic gases like methane, ammonia H2, N2, and SO2.

Hydrosphere

• Earth's cooling allowed liquid water to form through precipitation from the atmosphere.
• The sources of surface water were outgassing from the Earth's interior and bombardment of icy comets and meteorites.

Faint Young Sun Paradox

• Early models suggested that the Sun was significantly weaker, causing Earth to be much colder and likely ice-covered.
• Evidence of liquid water existed as early as 4.4 billion years ago.

Two Explanations

• Greenhouse Effect: CO2, methane, and water vapor retained solar radiation, maintaining warmer temperatures.
• Lower Albedo: Oceans covered a larger portion of the Earth compared to today, absorbing more solar radiation and keeping Earth warmer.

Today's Atmosphere

• The atmosphere is crucial for protecting Earth from radiation, meteorites, and maintaining a stable temperature.
• It's composed primarily of nitrogen (78%), oxygen (21%), trace amounts of carbon dioxide, and other gases.

Archean Atmosphere

• An atmosphere dominated by CO2 (80%), with smaller amounts of H2, N2, and methane.
• The early atmosphere was strikingly different from today's, notably thin.

What Is Life?

• Life is defined biologically by processes including growth, metabolism, reproduction, and responding to stimuli.
• Chemically, the concept of life is intricately connected to organic molecules.
• Life fundamentally depends on carbon's capacity to form various bonds.
• Other perspectives on life, including philosophical, astrobiological, existential, and cultural, are also considered.
• Key building blocks of life include carbohydrates, nucleic acids, proteins, and lipids.

Evolution

• The heritable characteristics of biological populations change over successive generations.

Tree of Life

• A visual representation of the evolutionary relationships among all known living organisms, showing how different organisms arose from common ancestors.

Phylogenetic Tree

• A branching diagram illustrating the evolutionary relationships among biological groups.
• The arrangement reflects evolutionary divergence relationships with organisms derived from common ancestors, inferred using DNA information.

Cells of the 5 Kingdoms

• The five kingdoms contrast in their cell type (i.e., prokaryotic or eukaryotic), multicellularity, and energy acquisition strategies.

Prokaryote vs. Eukaryote Cells

• Prokaryotes are single-celled organisms with simpler internal structure, lacking a nucleus.
• Eukaryotes are typically larger and more complex, having membrane-bound organelles like a nucleus and mitochondria.

Single vs. Multicellular Organisms

• Single-cell organisms consist of a single cell.
• Multicellular organisms consist of multiple cells with specialized functions, providing complexity.

Autotrophs vs. Heterotrophs

• Autotrophs produce their food from sunlight (photosynthesis) or chemical sources (chemosynthesis).
• Heterotrophs depend on consuming food.

How Did Life Begin?

• Initially, life likely arose as a prokaryote autotroph.
• Chemosynthesis might have been the initial method for producing food, occurring in the absence of sunlight.
• Early environments like hydrothermal vents provided energy sources to support the beginning of life.

First Evidence of Life

• Chemical fossils (biomarkers and isotopic signatures).
• Fossil forms provide physical evidence, preserved depending on environmental conditions.
• Evidence from 3.2 billion years ago (Ga) marks some of the earliest known forms of prokaryotic life.

How Was Oxygen Produced?

• Early Earth's atmosphere contained little free oxygen.
• Oxygen production stemmed from photochemical oxidation and photosynthesis.

Stromatolites

• Stromatolites are layered mounds formed by cyanobacteria (photosynthetic bacteria).
• They are key evidence that photosynthetic life existed and made oxygen.

Great Oxygenation Event

• Marked a significant rise in atmospheric oxygen around 2.5-2.3 billion years ago.
• This event was catalyzed by cyanobacteria's oxygen production.
• . The increasing oxygen level from photosynthesizing organisms caused the formation of the Ozone layer.

Banded Iron Formations

• Formed when iron in water precipitated from oxidative processes related to the rise in atmospheric oxygen concentrations, about 2.5-1.8 billion years ago.

Redox Reactions

• The oxidation and reduction processes occurred as iron shifted from its ferrous state to ferric state with the addition of oxygen.
• These reactions produced a large-scale shift in Earth's conditions that facilitated further ecological development by increasing atmospheric oxygen.

The Proterozoic

• Characterized by abundant free oxygen and the rise of an ozone layer, enabling the transition to a habitable environment for diverse life forms.

Ancient Fossils: Oldest Eukaryotes

• Evidence of the earliest eukaryotes, showing advancements in cellular complexity.

Endosymbiosis in Eukaryotes

• Eukaryotic cells developed through the incorporation of ancestral prokaryotic cells (like mitochondria and chloroplasts).

Proterozoic

• Animals emerged at the end of the Precambrian during the Neoproterozoic.
• Evidence from worm burrows and fossils reveals animals' existence during this time.

The Ediacaran Fauna

• A group of soft-bodied, multicellular organisms.
• Found on various continents, with a notable presence in Australia

The Ediacaran Environment

• Multiple life forms, including jellyfish-like organisms and other soft-bodied creatures, inhabited the Ediacaran environment.

Cambrian Explosion

• A rapid diversification of life forms during the Cambrian, around 541 million years ago.
• A notable event in the increase in the complexity and diversity of fossil records including animals with shells.

Homework

• Students are assigned Precambrian life questions via Brightspace.
• In-class discussions will allow for comparing answers and clarifying any questions.

Test your knowledge on Earth's early atmospheric conditions and the origins of life. This quiz covers key concepts such as albedo, volcanic activity, and the characteristics that define living organisms. Explore how early Earth's environment has shaped our planet today.