Ecology Exam Review Notes

Unit 8: Ecology Review

Food Webs and Energy Flow
  • Food Web: Illustrates the flow of energy between different organisms. Include:
    • Producers
    • Primary Consumers
    • Secondary Consumers
    • Decomposers
Communication and Species
  • Communication affects species interactions and behaviors. Examples include:
    • Visual Signals: Used in animal mating rituals (e.g., bright feathers).
    • Chemical Signals: Used in plant communication during droughts.
Density-Dependent Factors
  • Factors affecting population growth based on density:
    • Competition for Resources: Increased density leads to competition for limited resources.
    • Predation: Higher density can lead to increased predation rates.
    • Disease: High density can facilitate the spread of disease.
Density-Independent Factors
  • Factors affecting populations regardless of density:
    • Natural Disasters (e.g., hurricanes, wildfires).
    • Climate Changes (e.g., drought).
    • Human Activities (e.g., habitat destruction).
Calculating Species Diversity
  • Simpson's Diversity Index:
    • Formula: D = 1 - \frac{\sum (n/N)^2}{N}
    • $n$ = total number of organisms of a particular species
    • $N$ = total number of organisms of all species
Species-Species Interactions
  • Mutualism: Both species benefit (e.g., bees and flowers).
  • Commensalism: One species benefits, the other is unaffected (e.g., barnacles on whales).
  • Parasitism: One species benefits at the expense of another (e.g., ticks on mammals).
  • Predation: One organism (predator) eats another (prey).

Unit 8: Ecology - Responses to the Environment

Enduring Understanding
  • Timing and coordination of biological mechanisms involved in growth, reproduction, and homeostasis depend on organisms responding to environmental cues.
Behavioral and Physiological Responses
  • Phototropism: Directional growth of plants towards light.
    • Hormone involved: Auxin, which accumulates on the darker side of the plant to promote growth towards light.
    • Effects of mutations that prevent phototropism can lead to reduced survival in varying light conditions.
  • Taxis and Kinesis: Movement responses in animals toward (taxis) or away (kinesis) from stimuli.
  • Hibernation: Metabolism slows to save energy during low food availability.
Environmental Cues and Plant Responses
  • Photoperiodism: Plants' ability to respond to changes in lengths of day and night.
    • Long-day plants require longer daylight to flower.
    • Short-day plants require shorter daylight.

Unit 8: Energy Flow Through Ecosystems

Energy Acquisition Strategies
  • Autotrophs: Convert energy from sunlight or chemical sources.
  • Heterotrophs: Rely on consuming other organisms for energy.
Metabolism and Size
  • Smaller organisms usually have higher metabolic rates per unit body mass.
  • Net gain in energy results in growth; loss results in death.

Unit 8: Population Ecology

Growth Dynamics
  • Exponential growth occurs when resources are abundant, leading to rapid increases in population size.
  • Logistic growth considers carrying capacity $(K)$, where population growth slows as resources become scarce.
Population Limiting Factors
  • Density-dependent factors: Include predation and disease.
  • Density-independent factors: Include natural disasters and climate changes.

Unit 8: Community Ecology

Community Structure
  • Measured by species composition and diversity.
  • Interactions among populations (e.g., competition, predation, and symbiosis) influence community dynamics.

Unit 8: Biodiversity

  • Biodiversity impacts ecosystem resilience and health.
  • Keystone species: Maintain the structure and balance of an ecosystem.
  • Changes in biodiversity can lead to ecological imbalances, exemplified by keystone species extinction.

Unit 8: Disruptions to Ecosystems

  • Invasive Species: Negatively influence native species dynamics by outcompeting them for resources.
  • Human Impact: Accelerates ecosystem changes via habitat destruction and introduction of pollutants.
  • Geological and meteorological events can also lead to changes in communities and ecosystems.
  • Natural selection favors traits that enhance reproductive fitness and survival