Unit 3: Ecology

Unit 3: Population Ecology

Introduction to Ecology and Environmental Science

Overview of population ecology and its importance.

Phenomenon: Shrew Caravan

• Behavior: Shrews exhibit a unique behavior where a mother shrew forms a caravan by having her offspring hold onto one another to ensure safety while moving.

• Senses: They rely on strong senses of smell and hearing due to poor eyesight.

• Ecological Organization Level: Represents the organism level.

Levels of Ecological Organization

• Organism: Individual species.

• Population: Group of individuals.

• Community: Interaction between species.

• Ecosystem: Includes living organisms and their physical environment.

• Biome: A large geographical biotic unit.

• Biosphere: Parts of Earth that support life.

Population Dynamics

• Variation Among Species: Distribution varies; some populations are small and restricted, others are vast with large numbers of individuals.

Lesson Outline 01: Population Range and Abundance

• Population Range Definition: The size, shape, and location of the area occupied by a population.

• Environmental Limits: Species distributions are affected by environmental conditions.

• Organismal Adaptation: Organisms can only adapt to a certain extent due to energy costs in compensation for environmental variations.

Population Abundance

• Definition: The total number of individuals or biomass of a species present in a specified area.

• Population Sampling Method: Scientists use smaller sample plots in a study area to make generalizations about larger areas.

• Sampling Techniques: Essential for studying invasive and other species.

Lesson Outline 02: Population Spacing Definitions

• Population Spacing: Also known as Population Dispersion.

• Scale: Can be small scale (less environmental change) or large scale (substantial environmental change).

• Distribution patterns can be:

  • Random: Equal probability of occurrence.

  • Regular (Uniform): Uniformly spaced individuals.

  • Clumped: High local abundance separated by low abundance.

Population Density

• Definition: The number of individuals per unit area.

• Variation: Densities vary greatly and correlate with body size; smaller organisms tend to have higher densities.

Patterns of Density**

• Small organisms typically live at higher densities than larger ones.

• Generally, smaller animals exhibit higher population densities than larger species.

Survivorship Curves

• Type I: Mortality occurs primarily among older individuals.

• Type II: Constant survival rate throughout life.

• Type III: High mortality among young, followed by high survival rates.

Lesson Outline 04: Population Growth

• Growth Dynamics: Change in population size over time, affected by biotic and abiotic factors.

• Factors Influencing Growth:

  • Natality: Birth rates.

  • Mortality: Death rates.

  • Immigration: Individuals entering the population.

  • Emigration: Individuals exiting the population.

Population Growth Models

• Exponential Growth Characteristics: Rapid growth under ideal conditions, forming a “J” curve.

• Logistic Growth Characteristics: Growth levels off as resources become limited, forming an “S” curve.

Limiting Factors

• Density-Dependent Factors: Affected by population density, including biotic factors like disease and competition.

• Density-Independent Factors: Not affected by density, often abiotic, such as floods and extreme temperatures.

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