BGY3402 Principles of Ecology: Sub-disciplines and Autecology

Overview and Sub-disciplines of Ecology

Topic Objectives: After completing this module, students should be able to accomplish the following outcomes: * Identify and understand the various sub-disciplines in ecology. * Comprehensive understanding of the concept of autecology. * Explain the primary study focuses within the field of autecology. * Understand the fundamental concept of synecology. * Differentiate clearly between autecology and synecology.
Sub-disciplines Categorized by Methodology: * Field Ecology: The collection of information outside a laboratory setting, conducted in the natural field. * Quantitative Ecology: The application of advanced statistical tools and numerical analysis to various problems within the field of ecology. * Theoretical Ecology: The development of ecological theory, typically utilizing mathematical and/or computer modeling tools.
Sub-disciplines Categorized by Taxon: * Animal Ecology: The scientific study of relationships between living animals and their environment. * Plant Ecology: The study of environmental effects on the abundance and distribution of plants. * Insect Ecology: The study of how insects interact with their surrounding environment. * Microbial Ecology: The study of the relationship of microorganisms with their environment.
Sub-disciplines Categorized by Spatial Scale: * Global Ecology: The study of the global sum of all ecosystems on Earth. * Macroecology: The study of relationships between organisms and their environment at large spatial scales. * Microecology: Often refers to microbial ecology or the ecology occurring within a microhabitat.
Sub-disciplines Categorized by Levels of Organization: * Organismal Ecology: Studies how individual organisms meet environmental challenges. * Population Ecology: Examines factors affecting population structure and dynamics. * Community Ecology: Focuses on interactions between different species, such as competition and predation. * Ecosystem Ecology: Studies the flow of energy and the cycling of materials between biotic and abiotic components. * Landscape Ecology: Analyzes the spatial patterns, mechanisms, and the exchange of energy across multiple ecosystems. * Biosphere Ecology: Examines regional and global interactions and the functioning of the entire biosphere.

Concepts of Autecology

Definition of Autecology: * The study specifically focused on an individual or a single species in relation to its environment, whether internal or external. * Odum (1959) classified autecology specifically as "species ecology." * Example: Studying the mangrove tree of species $Rhizophora$ sp. in relation to its coastal or estuarine environment. * Typical focus areas include the nutrition, growth, reproduction, development, and life history of individual species within an environment.
Key Features of Autecology: * Studies one species or one individual at a time. * Focuses on behavioral, physiological, and morphological adaptations. * Examines ecological niches, tolerance limits, survival strategies, and reproductive patterns. * Determines how environmental conditions influence the growth, development, and distribution of the subject.
Scope of Autecology Focus Areas: 1. Response to environment. 2. Range of tolerance. 3. Energy balance. 4. Habitat selection. 5. Spread of organisms. 6. Animal behavior.

Response to Environment

Habitat and Environment: * Environment/Habitat: Consists of the physical and chemical components existing around an organism. * Terrestrial Habitats: Includes forests, grasslands, and deserts. * Aquatic Habitats: Divided into Marine (coastal, offshore, ocean) and Freshwater (pond, lake, river). * Sub-habitat (Microhabitat): Describes the small-scale physical requirements of a particular organism or population.
Factors Affecting Range of Tolerance: * Abiotic Factors: Consist of physical and chemical properties in the environment. * Biotic Factors: The relationships with other individual organisms existing in the same environment.
Key Abiotic Factors and Responses: * Temperature: Influences metabolic rate and determines species distribution. Example: Tropical species cannot survive in cold climates. * Light: Essential for photosynthesis; influences plant growth and animal behavior. Examples: Shade-tolerant plants versus sun plants. * Soil Characteristics: Includes nutrients, texture, moisture, and $pH$ . Example: Certain plants grow only in acidic soils. * Salinity: Particularly important in aquatic ecosystems. Example: The difference between freshwater fish and marine fish.
Types of Responses to Environment: * Physiological Responses: Internal body adjustments. Examples: Sweating in humans, antifreeze proteins in fish, osmoregulation in marine animals, and seed dormancy. * Morphological Responses: Structural adaptations. Examples: Thick fur in Arctic mammals, waxy leaves in desert plants, and buoyancy structures in aquatic plants. * Behavioral Responses: Changes in behavior. Examples: Migration, hibernation, burrowing, and circadian rhythms.

Range of Tolerance

Basic Principles: * Abundance or distribution is regulated by environmental factors. * Optimal Range: Organisms have optimal survival conditions within critical minimal and maximal thresholds. * As a population is exposed to extremes, survival rates drop until reaching a zone of death. * Example: Polar bears thrive in low temperatures but die from overheating in the tropics; giraffes thrive in African savanna heat but freeze in the Arctic.
Laws of Tolerance and Limitations: * Shelford’s Law of Tolerance (1911): Proposed by American zoologist Victor Ernest Shelford. It states that an organism's success is based on a complex set of conditions, where each organism has a minimum, maximum, and optimum environmental factor that determines its success. * Liebig’s Law of the Minimum: When a process depends on several different factors, the speed of the process is determined by the slowest (minimum) factor. Example: Photosynthesis is limited by low light in the morning/evening even if $CO_2$ and water are abundant.
Tolerance Zones: * Zone of Optimum: Favors maximal reproductive success and survivability. High rates of growth and feeding. * Zones of Stress: Regions flanking the optimal zone where organisms can survive, but reproduction is usually not possible and growth/feeding are slow. * Zones of Intolerance: Outermost regions representing extremes where organisms cannot survive, leading to the death of individuals and loss of population.
Tolerance Terminology (Prefixes): * Eury- (Wide Range): * Eurythermal: Can tolerate a wide range of temperatures. * Euryhydric: Wide range of water tolerance. * Euryhaline: Wide range of salinity tolerance. * Euryphagic: Wide range of food sources. * Euryecious: Wide range of habitat selection. * Steno- (Narrow Range): * Stenothermal: Narrow temperature tolerance. * Stenohydric: Narrow water tolerance. * Stenohaline: Narrow salinity tolerance. * Stenophagic: Narrow food range. * Stenoecious: Narrow habitat selection. * Note: Organisms with wide tolerance for one factor may have narrow tolerance for another. Widely distributed organisms typically have wide ranges of tolerance.
Adaptation Strategies for Environmental Change: 1. Dormancy: Growth and activity are temporarily stopped. 2. Hibernation: State of inactivity and metabolic depression in animals. 3. Aestivation: Inactive state in response to very hot or dry conditions. 4. Migration: Traveling long distances to find new habitats. 5. Acclimation: Organism adjusting to change to survive physical and biological stresses. 6. Phenotypic Plasticity: Ability to change phenotype in response to environment. Examples: $Eumaeus\,atala$ butterfly color changes between winter and spring; $Ranunculus\,aquatilis$ (water crowfoot) having both broad aerial leaves and narrow submerged leaves.
Applications of Tolerance [Plants]: * Halophytes: Salt-tolerant plants; may be stressed in freshwater. * Glycophytes: Non-salt-tolerant plants (most land plants); damaged by high salinity which makes water uptake difficult or toxic. * Sun-loving vs. Shaded: Sunflowers (high light intensity) vs. forest understory plants like $Calathea$ (low light). * Water Availability: Xerophytes (cacti) tolerate low water; Paddy requires high humidity and waterlogged soils.
Applications of Tolerance [Animals]: * Corals: Reef-building species have an optimal growth range between $20\,^{\circ}C$ and $30\,^{\circ}C$ . They rely on photosynthetic zooxanthellae algae. Zooxanthellae cannot survive below $18\,^{\circ}C$ or above $50\,^{\circ}C$ . Excess heat causes algae to leave, resulting in coral bleaching. * Temperature Regulation: Homeotherms (regulate internal temperature) can occupy wider ranges than non-regulators. * Food Availability: Specific food requirements limit distribution and may drive seasonal migrations.

Energy Balance

Thermodynamic Principles: * 1st Law: Energy can be transformed but not created or destroyed. $\text{Total potential energy} = (\text{Potential energy used for work}) + (\text{Heat produced})$ . * 2nd Law: No process is $100\%$ efficient; some energy is always lost as heat.
Energy Balance Equation: * $\text{Energy Gain} = \text{Energy Loss}$ * If Gain > Loss, body temperature rises. If Loss > Gain, body temperature decreases. * Ecological Energy Budget: $C = P + R + U + F$ * $C$ : Energy consumed. * $P$ : Production (growth and reproduction). * $R$ : Respiration. * $U$ : Excretory waste. * $F$ : Fecal loss.
Diversity of Energy Use: * Autotrophs: Transform sunlight into organic molecules via photosynthesis. Formula: $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$ . * Heterotrophs: Gain energy via respiration. * Aerobic: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy}$ . * Anaerobic: $C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 6CO_2 + \text{energy}$ . * Photosynthetic Bacteria: Green or purple sulfur bacteria; do not release oxygen and use sulfur compounds as electron donors. * Auxotrophs: Autotrophic bacteria requiring specific organic compounds (thiamine, Vitamin $B_{12}$ , biotin). * Chemosynthetic Autotrophs: Obtain energy from the oxidation of inorganic compounds. * Non-sulfur Bacteria: Metabolic opportunists switching between modes based on light and oxygen.
Thermoregulation Strategies: * Endotherms: Generate internal metabolic heat (mammals, birds). Stable temperature, high energy demand. * Ectotherms: Rely on external environmental heat (reptiles, amphibians, insects). Low metabolic rate, temperature varies with environment; utilize behavioral basking.

Habitat Selection and Spread

Habitat Selection: The process by which organisms choose environments to maximize survival and reproduction. Choice is not random. * Abiotic factors: Temperature, moisture, light intensity, soil type. * Biotic factors: Food availability, predation risk, competition, presence of conspecifics (members of the same species).
Habitat Strategies: * Generalist Species: Occupy many habitat types, broad tolerance (rats, cockroaches, crows). * Specialist Species: Require specific conditions, narrow niche (coral reef fish, pandas, koalas).
Ontogenetic Habitat Shift: Using different habitats during different life phases. * Insects: Larvae on specific host plants; adults have a wider range. * Amphibians: Eggs and larvae in aquatic habitats; adults in terrestrial habitats.
Spread of Organisms (Dispersal): * Passive Dispersal: Moved without own locomotion. Agents include Wind (Anemochory), Water (Hydrochory), and Animals (Zoochory). * Active Dispersal: Organisms move using their own energy. Allows for habitat selection. * Ideal Free Distribution (IFD) Theory: Individuals distribute themselves based on resource availability, assuming they move freely and know habitat quality. * Mechanisms: Movement of propagules (seeds/spores), Migration, Colonization, and Range Expansion. * Study Methods: Field surveys, mark-recapture, Radio/GPS tracking, stable isotopes, genetic markers, and habitat suitability modeling.

Animal Behavior (Ethology)

Ethology: The scientific study of animal behavior. * Focus on natural conditions: Foraging, mating, defensive skills in wildlife. * Unnatural circumstances: Captivity, where natural skills may be lost.
Behavior in Autecology: * Behavior is an immediate, flexible, and often reversible response to environmental stimuli. * It is the "first line of response" to stress, allowing organisms to avoid unfavorable conditions or exploit resources without structural changes. * Ecologists use behavior as an early warning indicator of environmental stress (e.g., changes in feeding due to pollution or migration shifts due to climate change).

Synecology

Definition: The study of groups of organisms belonging to different species in relation to their environment. It is typically habitat-based. * Includes population ecology, community ecology, and ecosystem ecology. * Focuses on community characteristics, successional changes (dispersion, colonization), and interrelationships between species.
Comparison: Autecology vs. Synecology: * Autecology: Known as species ecology; focus on a single individual, species, or population; attempts to discover distribution, development, nutrition, and physiology. * Synecology: Focus on more than one species; study of groups of organisms in respect to habitat; concerns higher levels of organization (population, community, ecosystem).