Exam 3

• Ecology


  The scientific study of interactions among organisms and their environment
• Levels of Ecology


  • Organismal Ecology
  • Population Ecology
  • Community Ecology
  • Ecosystem Ecology
• Organismal Ecology


  • Focuses on how individual organisms adapt to their environment through physiological, biochemical, and behavioral means
• Population Ecology


  • Studies how groups of individuals of the same species live together, change, and evolve over time
• Community Ecology


  • Examines how collections of species interact and form functional communities
• Ecosystem Ecology


  • Investigates how energy flows and materials cycle through living and non-living parts of the environment
• Biotic factors


  All the living components of an ecosystem, such as plants, animals, fungi, and bacteria, which interact with each other and affect the ecosystem's structure and function
• Abiotic factors


  The non-living physical and chemical elements in the environment, like sunlight, soil, water, and temperature
• Forest ecosystem


  • Biotic components such as trees, animals, and microorganisms interact with abiotic components like sunlight, temperature, and soil quality
• Methods for measuring population density

  • Quadrats
  • Transects
  • Mark-Recapture
  • Remote Sensing
• Quadrats

  Used for sessile organisms; involves counting individuals within several small, randomly placed plots
• Transects


  Suitable for both sessile and slowly moving organisms; involves counting individuals along a line
• Mark-Recapture

  Used for motile organisms; individuals are captured, marked, and released, then recaptured to estimate total population size
• Remote Sensing


  Used for large or elusive animals, employing technology to estimate population size from afar
• Types of distribution patterns

  • Clumped
  • Uniform
  • Random
• Clumped distribution


  Individuals aggregate in patches, often due to resource availability or social interactions. This is the most common pattern in nature.
• Uniform distribution


  Individuals are evenly spaced, typically due to territorial behavior or competition for resources
• Random distribution


  The position of each individual is independent of others, usually occurring where resources are consistently available
• Life table


  Provides detailed reports of survival and mortality rates of a population at different ages
• Information provided in a life table

  • Survivorship (lx)
  • Mortality rate (qx)
  • Fecundity (mx)
• Calculating number dying (dx) and proportion alive (lx)

  1. dx = nx (number alive at start of age interval) - nx+1 (number alive at end of age interval)

  2. lx = nx/N0 (where N0 is the initial number of individuals)
• Types of survivorship curves

  • Type 1
  • Type 2
  • Type 3
• Type 1 survivorship curve

  High survival in early and middle life, followed by a steep decline in later life (e.g., humans)
• Type 2 survivorship curve

  Constant mortality rate throughout life (e.g., birds)
• Type 3 survivorship curve

  High mortality in early life, but those surviving the initial stages live much longer (e.g., oysters)
• Primary ecological events

  • Birth (natality)
  • Death (mortality)
  • Immigration
  • Emigration
• Birth rate (b)

  Number of births per individual per unit time
• Death rate (d)

  Number of deaths per individual per unit time
• Calculating change in population size

  ΔN=(Births+Immigration)−(Deaths+Emigration)
• Possible population growth patterns

  • r>0 (population grows exponentially)
  • r=0 (population is stable)
  • r<0 (population declines)
• Exponential growth

  Characterized by an increasing growth rate over time, leading to a J-shaped curve
• Logistic growth

  Growth rate decreases as the population reaches carrying capacity (K), resulting in an S-shaped curve
• Density-dependent factors

  Influence varies with population density (e.g., competition, predation, disease)
• Density-independent factors

  Impact does not vary with population size (e.g., weather events, natural disasters)
• Reproductive strategies

  • Semelparity
  • Iteroparity
• Semelparity

  Species reproduce once and then die (e.g., salmon, agave)
• Iteroparity

  Species reproduce multiple times over their life cycle (e.g., most mammals)
• Characteristics of r-selected and K-selected strategies

  • r-selected: High reproductive rate, low survivorship, adapted to unstable environments (e.g., insects)
  • K-selected: Lower reproductive rate, high survivorship, adapted to stable environments near carrying capacity (e.g., elephants)
• Human population growth has accelerated due to technological advances and improved health care
• The concept of carrying capacity for humans is complex, involving sustainable resource usage and environmental impact considerations