Population Ecology Lecture Notes

Population Ecology Overview

Fundamental Concepts in Population Ecology

• Population Ecology: Study of how biotic (living) and abiotic (non-living) factors influence the abundance, dispersion, and age structure of populations.

Key Definitions

• Population: A group of individuals of a single species living in a specific area.

• Density: The number of individuals per unit area or volume.

• Immigration: Arrival of new individuals from other areas.

• Emigration: Departure of individuals from a population.

• Dispersion: The pattern of spacing among individuals within the population's boundaries.

Distribution Patterns

• Allows individuals to maximize access to resources.

• Influenced by:

  • Resource Distribution: When resources are unevenly distributed, populations may cluster.

  • Social Behavior: Grouping behavior influenced by social structures.

  • Territorial Behavior: Results in spacing among individuals.

Population Growth Models

1. Exponential Growth

   • Occurs under ideal conditions with unlimited resources.

   • Characterized by a J-shaped curve.

2. Logistic Growth

   • Describes how population growth slows as it nears its carrying capacity (K).

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

3. Boom and Bust Cycles

   • Some populations exhibit regular boom-and-bust cycles, e.g., Snowshoe hare and Lynx populations.

Density-Dependent Regulation Factors

• Increased population density intensifies competition for resources, lowering birth rates.

• Pathogens: Spread more rapidly in densely populated areas.

• Predator-Prey Dynamics: As prey populations grow, predators may feed preferentially on that species.

• Toxic Waste: Accumulation can lead to population size regulation.

Demographic Patterns

• Zero Population Growth (ZPG): Occurs when the birth rate equals the death rate.

• The Demographic Transition: A shift from high birth and death rates to low birth and death rates, often correlated with improvements in health care and education.

Life History Traits

• Define an organism's schedule of reproduction and survival.

• Studied often through a Cohort: a group of individuals of the same age.

• Survivorship Curves: Graphical representation of mortality rates at different ages.

• K-selection vs. r-selection:

  • K-selection: Traits advantageous at high densities; young need care (e.g., elephants).

  • r-selection: Traits that maximize reproductive success; young require little or no care (e.g., fish).

Parental Support Strategies

• Altricial Species: Young require significant care (e.g., birds).

• Precocial Species: Young are relatively independent at birth (e.g., deer).

• Mating Systems:

  • Monogamy: One partner, maximizing offspring survival.

  • Polygyny: One male mates with multiple females.

  • Polyandry: One female mates with multiple males (rare).

Age Structure and Population Growth

• Age structure significantly influences population growth rates.

• It is the relative number of individuals of each age within a population.

Global Carrying Capacity

• Questions arise about how many humans the biosphere can support.

• Ecological Footprint: The total land and water area required to sustain a person, city, or nation, highlighting sustainability issues in population ecology.