BI107 A2 Quiz 5 Review Session

Quiz 5 Review Updates

  • Review Session: Conducted by Dr. Spilios.

  • Structure: Content review followed by Q&A.

  • Engagement: Questions can be sent through chat in real-time.

  • Study Groups: Encouraged for peer interaction and understanding validation. The session is tailored but not exhaustive of all topics.

Levels of Organization

Community

  • Definition: Populations of various species that interact in a shared environment.

  • Complexity: Illustrated by the ant video during lectures.

  • Interactions: Encompasses biotic interactions in a given area.

Ant and Fungi Community

  • Relationship: Ants and fungi interact in a complex manner.

    • Types of Fungi:

      1. Beneficial Fungi: Cultivates food for ants.

      2. Parasitic Fungi: Threatens beneficial fungi.

  • Bacteria: Carried by ants help inhibit parasitic fungi.

  • Yeast Impact: Indirectly feeds on bacteria and can harm beneficial fungi.

Food Chains and Food Webs

  • Interdependence: Organisms evolve in response to one another, creating complexity.

  • Energy Flow:

    • Arrows in diagrams indicate the direction of energy transfer.

    • Trophic levels depend on the energy source.

  • Dynamic Nature: Food chains/webs evolve over time due to abiotic factors.

Abiotic Factors Influencing Communities

  • Significant Factors: Including elevation and seasonal changes.

Temporal Turnover

  • Key Causes:

    1. Ongoing colonization and local extinction.

    2. Post-disturbance environment changes.

    3. Global climate shifts.

Colonization and Extinction

  • Mechanisms:

    1. Species may occupy new habitats (dispersal).

    2. Local extinctions can reshape community structures.

Natural Disturbances

  • Effects: Natural disasters can dramatically alter community makeup.

  • Succession: The predictable changes in community composition after disturbances.

Global Climate Change Impacts

  • Long-term Factors: Geological and climatic changes that gradually influence communities.

Energy Flow in Communities

  • Efficiency: Energy transfer is not perfect; only about 10% moves up trophic levels.

  • Energy Loss Reasons:

    • Indigestible matter.

    • Waste excretion.

    • Not consumed.

Community Structure

  • Niche Definition: The specific physical and biological conditions a species occupies.

  • Ecological Role: Enhances species diversity in communities.

Species Diversity

  • Components:

    1. Species Richness: Total different species present.

    2. Relative Abundance: Distribution proportions among species.

  • Diversity Assessment: Utilizes Shannon Diversity Index to evaluate community structure.

NPP Relationship with Species Richness

  • Observations: NPP influences species richness but there is a saturation point where this is negligible.

Trophic Structure

  • Impact of Species Abundance Changes: Can create cascading effects through food webs.

    • Example: Absence of sea stars increases muscle populations, reducing overall species diversity.

Patterns in Diversity

  • Geographical Variation:

    • Higher diversity observed near the equator due to stable climates and high solar energy.

    • Hypotheses for this phenomenon include:

      1. Stability permits ongoing evolution.

      2. Higher productivity supports diverse communities.

      3. Habitat variation increases ecological niches.

Regional Species Diversity

  • Diversity Patterns:

    • Highest at the equator.

    • Influenced by land area and distance to other habitats.

Island Biogeography Theory

  • Definition: Species number on an island relates to colonization and extinction rates.

  • Parameters:

    • Colonization: Affected by island proximity to mainland.

    • Extinction: Influenced by island size.

Population Dynamics

  • Population Defined: Individuals of a species within a specific area and time.

  • Ecological Study Focus: Population density and dynamics.

  • Growth Rate Dynamics: Calculated using established models (BD Model, BIDE Model).

Life Tables

  • Usage: Measure populations and demographic events over time.

  • Fecundity: Number of offspring per surviving female determines population growth potential.

Life History Strategies**

  • Limited resources lead to life history trade-offs between quality and quantity of offspring.

  • Example: Frogs produce numerous offspring; whales care for fewer but invest significant resources.

Population Growth and Limits**

  • Multiplicative Growth: Natural communities show exponential growth until limited by resources (carrying capacity).

  • Carrying Capacity (K): Maximum population size an environment can sustain.

Density-dependent Factors

  • Examples:

    1. Resource availability decreases with more individuals.

    2. Increased intraspecific competition as population density rises.

    3. Predator pressures increase with population density.

    4. Pathogen spreads more easily in denser populations.

Human Population Trends**

  • Exponential growth model due to agriculture and technology.

  • Key Observations:

    1. r value decline since 1963.

    2. Transition from high fecundity to higher life expectancy.