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