February Test 2025

Key Concepts

Population Dynamics

• Density-Independent Factors

  • Example: Environmental events that affect population irrespective of size (e.g., drought, flood).

• Carrying Capacity

  • The maximum population size an environment can sustain without degradation.

  • As white-tailed deer population increases, potential effects include reduced carrying capacity due to resource limitation.

Growth Curves

• Exponential Growth vs. Logistic Growth

  • Exponential growth reflects rapid increase without resource limitations.

  • Logistic growth occurs when a population's size approaches carrying capacity, forming an S-shaped curve.

  • Limiting Resources: A limiting factor can cause population growth to slow as it nears carrying capacity.

Species Characteristics

• r-selected vs. K-selected Species

  • r-selected Species: Rapid reproduction, low parental care, high offspring mortality (e.g., bullfrogs).

  • K-selected Species: Longer development time, fewer offspring, higher survival rates (e.g., elephants).

Survivorship Curves

• Types of Survivorship Curves

  • Type I: High survival rates in early and middle life stages (e.g., humans).

  • Type II: Consistent mortality rate throughout life stages (e.g., some birds).

  • Type III: High mortality rates in early life, low in later years (e.g., many plants).

Ecological Concepts

• Resource Partitioning: Different species utilizing the same resource in varied ways to coexist.

• Sustainability Factors: Importance of carrying capacity and intrinsic growth rate in population dynamics.

• Impact of Agriculture on Ecosystems: Understanding soil types, erosion potential, and agricultural practices.

Soil and Agriculture

Soil Composition and Types

• Classification based on particle size: sand, silt, clay, loam.

• Soil Water-Holding Capacity: Influenced by the proportions of clay and organic matter.

• Soil Erosion Minimization: Best achieved using practices like no-till agriculture.

Agricultural Practices

• Polyculture: Planting multiple crop varieties in the same field to enhance biodiversity and resilience.

• Clear-Cutting in Forestry: Method involving uniform removal of trees, affecting ecological balance.

• Integrated Pest Management (IPM): Strategy incorporating biological, cultural, and chemical methods to control pests sustainably.

Environmental Change and Human Impact

Deforestation Effects

• Leads to problems such as increased erosion, loss of biodiversity, and altered local climates.

• Strategies to combat negative impacts include greenbelts and sustainable agricultural practices.

Demographic Transition Model

• Illustrates population growth through stages, analyzing fertility trends and societal development over time.

• Recognizes the importance of understanding total fertility rates and societal impacts on population growth.

Experiments and Data Analysis

Peony Seed Study

• Investigates germination rates under varying temperature and storage conditions, highlighting optimal conditions for seed viability.

Ecological Succession

• Primary vs. Secondary Succession

  • Primary succession begins on bare rock (lichens) and secondary succession occurs in environments where soil is already present (after disturbances).

  • Climax communities reflect stable ecosystems that can sustain themselves over time.

Important Implications for Conservation and Management

• Recognizing and managing biodiversity in ecosystems is vital to maintain environmental health.

• Understanding the role of different species, their interactions, and the impact of human activities on natural systems is crucial for sustainable practices.