Week 1 - Biodiversity and History of Life

bio 2

Importance of Organismal Diversity

• Organismal diversity is integral for ecosystem resilience, productivity, and long-term stability. Its loss can lead to fragile ecosystems that are more prone to collapse.

• Supports ecosystem services critical for human survival such as:

  • Pollination: Essential for the reproduction of many plants/environments, which in turn supports food systems.

  • Nutrient Cycling: Critical for maintaining soil health and fertility, allowing for sustainable agriculture and natural ecosystems.

  • Climate Regulation: Diverse ecosystems help stabilize climate by absorbing carbon dioxide and regulating temperature.

• Provides vast resources for human use including food, medicine derived from various species, and raw materials (fibers, timber).

Key Biodiversity Studies (Tilman et al.)

• Location: Cedar Creek Ecosystem Science Reserve, Michigan.

• Research Focus: Investigated species richness in various experimental grassland plots.

• Key Findings:

  • Increased biodiversity correlated with higher plant biomass production, leading to more robust ecosystems.

  • Enhanced CO2 absorption efficiency observed with greater biodiversity, emphasizing the ecological value of plant variety.

• Conclusion: Biodiversity has a direct positive impact on ecosystem productivity and stability, rendering diverse ecosystems more capable of withstanding disturbances.

Impact of Grass Species on Productivity

• Increased diversity in grass species leads to greater primary productivity and biomass accumulation.

• This diversity also enhances resilience against drought conditions, showcasing the benefits of polyculture systems in agriculture.

Ecosystem Services and Human Benefit

• Studies reveal that higher biodiversity levels correlate with improved ecosystem services, directly benefitting humanity (e.g., ranging from clean air and water to pollination of crops).

Species Count

• Approximately 1.5 - 1.75 million species have been described scientifically, but many remain unnamed or misunderstood.

• Well-known groups: Include butterflies, flowering plants (angiosperms), and vertebrates like mammals, birds, reptiles.

• Poorly understood groups: Encompass microbes such as bacteria, nematodes, fungi, and mites.

• Estimates: Suggest around 8.7 million species exist on Earth, with a significant number classified as insects and plants.

Pyramid of Diversity

• Most multicellular organisms are represented by insects, illustrating their vast diversity.

• Significant extant species include:

  • Insects: Estimated at 8,750,000 species.

  • Plants: Approximately 320,000 known plant species.

Interpreting Data: X-Y Plots

• Skills Check:

  • Explanatory Variable: lizard size (cm)

  • Response Variable: lizard running speed (m/s)

• Students will learn to plot data trends from experiments involving various lizard populations to analyze relationships.

Geological Events and History of Life

Major Geological Events

• Earth's Formation: Approximately 4.6 billion years ago (bya), initiated conditions for life.

• Cooling Phase: Around 4.0 billion years ago saw the formation of liquid water essential for life.

• Oxygenation Event: Major oxygenation events around 2.5 billion years ago drastically altered Earth's atmosphere and led to aerobic life forms.

• Early Earth Conditions: Characterized by extremely high temperatures and significant volcanic activity, ultimately leading to oceans conducive for life's emergence.

Hypotheses for the Origins of Life

• Miller-Urey Experiment:

  • Demonstrated that organic molecules (amino acids) could be synthesized under simulated early Earth conditions, supporting biogenesis theories.

• Hydrothermal Vent Hypothesis: Suggests that life may have originated in nutrient-rich, energy-exploiting environments deep under the sea, around hydrothermal vents.

Major Events in Life's History

• First unicellular life: Emerged approximately 3.8 billion years ago, setting the foundation for all life forms.

• First multicellular life: Occurred around 1.2 billion years ago, indicating increased complexity in biological forms.

• Colonization of land: Began approximately 500 million years ago, a critical step for terrestrial ecosystems.

• Dinosaurs: Dominated the planet from 230 million to 65 million years ago, shaping ecosystems before their extinction.

• First humans: Emerged approximately 2 million years ago, showcasing rapid development and adaptability of species in the evolution continuum.

Fossil Record and Fossilization

Fossilization Process

• Death of Organism: Organisms with hard parts (bones, shells) have higher chances of fossilization.

• Decay: Soft tissues decompose rapidly, favoring preservation of hard structures.

• Burial: Rapid sedimentation enhances preservation rates.

• Mineralization: Minerals infiltrate and replace organic material over time.

• Compaction and Cementation: Layers harden and become rock formations through geological processes.

• Uplift: Geological activity exposes fossils at the Earth's surface over millions of years.

Types of Fossils

• Trace Fossils: Provide evidence of behaviors like tracks, burrows, and coprolites (fossilized feces), offering insights into past life.

Dating Fossils

• Relative vs. Numerical Dating: Different techniques used to determine age and sequence of fossil deposition.

  • Relative Dating: Establishes a timeline of events or relative ages without specific ages.

  • Numerical Dating: Assigns numerical ages to fossils/rocks through various methods.

  • Key Dating Methods:

    • Uranium-Lead Dating: Applicable for dating rocks from 10 million years to 4.6 billion years.

    • Potassium-Argon Dating: Useful for dating specimens from 100,000 years to 4.6 billion years.

    • Carbon-14 Dating: Effective for more recent fossils (up to 100,000 years) with a half-life of 5,730 years.

Limits of Fossilization

• Factors Influencing Fossilization:

  • Organisms with hard body parts have higher fossilization success rates.

  • Rapid entombment in sediment enhances preservation likelihood.

  • Environmental conditions such as aquatic versus arid habitats significantly impact decay processes.

Eons and Eras in Geological History

Overview

• Precambrian: Characterized predominantly by single-celled life forms that paved the way for complex organisms.

• Phanerozoic: An era marked by an explosion of diverse multicellular life forms, represented by animal and plant phyla.

Proterozoic Era Highlights

• Cambrian Period:

  • Known for major diversification of animal life leading to complex ecosystems.

  • Key adaptations such as complex body plans, hard shells for protection, and efficient locomotion evolved during this period.

Mesozoic Era Highlights

• Dominant Species: Often referred to as the Age of Reptiles, where dinosaurs thrived alongside the first birds.

• Ended with a mass extinction event 66 million years ago that brought significant changes to the Earth's biodiversity.

Cenozoic Era Overview

• Dubbed the "Age of Mammals," this era saw the diversification of mammals into various niches alongside flourishing bird and flowering plant populations.

• Human evolution occurred during this era, showcasing a remarkable biological adaptation and environmental influence on species development.

Evolution by Changes in Regulation

• Tetrapod Limb Evolution: Regulatory changes in Hox genes were crucial for the development of limbs from ancestral fin-like structures, illustrating adaptation over time in response to environmental challenges.

Visual Summary of Deep Time and Life on Earth

• This section will examine Earth's age, environmental conditions, and the life forms evolving through time, demonstrating the intricate processes that have led to current biodiversity.

• Key Factors:

  • Climate changes, influenced by atmospheric variations (e.g., CO2 and O2 levels), played significant roles in life evolution.

  • Fossils serve as vital records providing insights into organic evolution and the diversity of life past and present.