Chapter 44 Population Ecology

Definition of Ecology: The study of interactions between organisms and their physical environment.
Key Terms: - Habitat: The specific place where an organism lives. - Population: All individuals of a species within a particular area at a specific time. - Species: Groups of similar organisms capable of interbreeding and producing viable offspring. - Community: All populations of different species interacting in a specific locale (e.g., coral reef). - Ecosystem: A community interacting with its physical environment, where variables like sunlight play a role. - Biosphere: The zones of Earth’s soil, water, and air that support life.
Nature of Modern Ecology: It is predictive rather than merely descriptive.

Demography: Statistical study of populations, encompassing: - Population Density: The number of individuals per unit area. - Population Distribution: The pattern in which individuals are dispersed across a given space. - Growth Rate: The change in population size over time.
Limiting Factors: Environmental elements that determine organism habitat and potential population size (e.g., oxygen levels affecting trout vs. carp).

Patterns of Distribution: - Clumped: Individuals grouped in patches. - Random: Individuals are spaced unpredictably. - Uniform: Individuals are evenly distributed.
Changing Distribution: Not static; can evolve due to various factors (e.g., desert shrubs maturing leading to changes in patterns).

Natural Increase (r): Rate calculated as the number of births minus the number of deaths in a population annually.
Biotic Potential: The maximum reproductive capacity of a population, influenced by: - Survival rate of offspring. - Competition levels. - Reproductive age and frequency. - Presence of diseases and predators.
Mortality Patterns: - Cohort: Group of individuals born simultaneously. - Life Tables: Used to understand survivorship rates across specific intervals.

Types of Survivorship Curves: - Type I: High survival rates until old age. - Type II: Constant mortality rate regardless of age. - Type III: High mortality at young ages.
Age Distribution Grouping: - Prereproductive: Before reproductive age. - Reproductive: Capable of reproduction. - Postreproductive: Past reproductive age.
Age-Structure Diagrams: - Illustrate population trends (increasing, stable, or decreasing based on age distributions).

Factors Influencing Population Size: - Density-Independent Factors: Natural disasters affecting populations regardless of density. - Density-Dependent Factors: Effects grow as the population density increases (e.g., competition, predation).
Carrying Capacity (K): The maximum number of a species that can be sustained by an environment, influenced by resource availability.

Life History Components: - Births per reproduction, age of reproduction, lifespan, and survival probability throughout lifespan.
r-selection vs K-selection: - r-Selected Populations: Opportunistic species in unstable environments, producing many offspring with minimal parental care (e.g., insects, annual plants). - K-Selected Populations: Equilibrium species in stable environments, producing fewer offspring with higher parental investment (e.g., large mammals, birds of prey).

Historical Population Growth: Reached over 8.0 billion; exponential growth began post-1750.
Population Milestones: - 1800: 1 billion - 1930: 2 billion - 1974: 4 billion

Characteristics of More-Developed Countries (MDCs): Slower population growth, higher standards of living, demographic transitions leading to stabilization.
Characteristics of Less-Developed Countries (LDCs): Rapid population growth, lower standards of living, population policies promoting family planning and education.

Population size and resource consumption metrics critically impact environmental health.
Types of Overpopulation: - Due to growth (common in LDCs). - Due to increased resource consumption (common in MDCs).

Key Characteristics of Unsustainability: - Major alterations to ecosystems, reliance on nonrenewable resources causing pollution, excessive water use, soil degradation from modern practices.
Steps Toward Sustainability Include: - Shift to renewable resources, biodiversity conservation, adopting practices from natural ecosystems to achieve balance in resource use.