Ecology Fundamentals and Organismal Ecology

Ecology - Fundamentals

• Ecology studies the relationships between organisms and their environment.
• Interdependence: Species survival depends on other living things and non-living components.
• Models represent ecological systems. Earth is the largest ecological system.
• Ecosystem encompasses all organisms and non-living components in a specific area.
• Community includes all interacting organisms in an area, excluding non-living factors.
• Population consists of all organisms of one species within a given area.
• Organism is an individual animal.

Organismal Ecology

• Focuses on individual species and their relationships with the environment.
• Autecology studies an individual's relationship with its environment, emphasizing life history and behavior adaptations.
• Synecology examines groups of organisms and their environmental relationships (community and ecosystem ecology).
• Organisms are classified as unitary or modular.

Unitary vs. Modular Organisms

• Unitary:
  • Deterministic form (predictable development).
  • Continuous, predictable growth.
  • Highly mobile.
  • Governed by genes.
• Modular:
  • Indeterminate form (variable development).
  • Unpredictable development.
  • Sedentary or less mobile.
  • Highly influenced by the environment.

Species Definition

• A species is a group of interbreeding individuals reproductively isolated from other groups.

Environment

• Includes everything external to the organism, both abiotic (non-living) and biotic (living).
• Environmental factors:
  • Resource: consumed or used up by organisms (e.g., light, nutrients, water).
  • Condition: influences organisms' functioning but is not consumed (e.g., temperature, pH).
• Habitat is the organism's physical address, including biotic and abiotic factors.

Niche Concept

• Niche describes an organism's role or way of life.
• It's not a place, but the conditions and resources needed for survival.
• Fundamental niche represents the full potential of an organism.
• Realized niche considers competition and predation, limiting the organism's role.
• Generalists use a wider variety of resources, while specialists have narrow resource requirements, higher extinction risk.

Abiotic Factors: Light

• Visible light (400-700 nm) is the primary energy source.
• Factors influencing light effects: intensity, quality, periodicity, and direction.
• Fate of light: transmission, reflection, refraction, absorption, scattering.
• Light as a condition: circadian rhythms, photoperiodism, phototropism, phototaxis.
• Light as a resource: photosynthesis (PAR).
• Shade is a resource depletion zone.

Abiotic Factors: Light Utilization in Plants

• Heliophytes (sun plants) thrive in full sun, high intensity.
• Sciophytes (shade plants) are efficient at low light.

Abiotic Factors: Temperature

• Temperature measures average kinetic energy. Heat is the transfer of energy between systems.
• Macroclimate describes large-area weather, while microclimate changes over small areas. 
• Temperature affects organisms through response curves.
• Organisms are classified by temperature tolerance (thermophiles, mesophiles, psychrophiles).

Responses to Temperature

• Poikilotherms (variable body temperature) are often ectotherms (heat from the environment).
• Homeotherms (constant body temperature) are usually endotherms (heat from metabolism).
• Adaptations to extreme temperatures include insulation, evaporative cooling, and adjustments to freezing points.
• Organisms may enter torpor, hibernation, or estivation during extreme conditions.

Law of Tolerance

• An organism's ability to survive depends on its tolerance to physical and chemical factors.
• Response curves show tolerance ranges; optimal conditions allow reproduction.
• Multiple curves illustrate responses to factors that are essential, toxic, or both. 

Ecosystem Components: Biotic Roles

• Producers (autotrophs) make their own food (photoautotrophs use light, chemoautotrophs use chemicals).
• Consumers (heterotrophs) obtain energy from producers or other consumers.
• Herbivores feed on producers; carnivores feed on other consumers. Omnivores consume both plants and animals.
• Decomposers (detritivores, scavengers, saprophytes) break down organic matter, recycling nutrients.

Feeding Relationships

• Trophic levels represent energy transfer levels in food chains, webs, and pyramids.

Abiotic Factors: Water & Nutrients

• Water is both a condition and a resource.
• Organisms are largely composed of water, requiring hydration for metabolism.