Unit 8 University Ecology Study Guide
Topic 1: Responses to the Environment
Foundational Interactions: Interactions between complex living organisms lead to significant changes in communities and ecosystems.
Learning Objectives:
Explain how behavioral and physiological responses relate to internal/external environment changes.
Explain how behavioral responses affect fitness and population success.
Ethology and Behavioral Ecology:
Ethology: The study of how evolutionary processes shape inherited behaviors and how animals respond to specific stimuli.
Behavior: An animal's response to an internal or external stimulus. It is governed by both nature (genetic factors) and nurture (environmental factors), allowing for survival and reproduction subject to natural selection.
Understanding Behavior (Causation):
Proximate Cause: Explains "how" a behavior occurs or is modified. It looks at the immediate stimulus triggering the behavior and how the "nurture" component (experiences during growth) shapes the response.
Ultimate Cause: Explains "why" a behavior occurs in the context of natural selection. It looks at how the behavior helps the animal survive and reproduce, focusing on the "nature" or evolutionary/genetic basis.
Example Analysis (Zebras): When zebras graze, some stay "on guard." If a guard makes a warning call, the group flees.
Proximate Cause: The auditory stimulus of the warning call triggers a flight response.
Ultimate Cause: Increased survival for the group; the behavior prevents predation, ensuring the population's reproductive success.
Innate vs. Learned Behaviors:
Innate Behaviors: Developmentally fixed, automatic, and consistent behaviors that do not need to be learned; they are essentially "hard-wired."
Fixed Action Patterns (FAP): A sequence of unlearned acts linked to a sign stimulus (external cue). These actions are unchangeable and carried out to completion once triggered.
Example: Stickleback fish exhibit FAPs when seeing the red belly of another male fish.
Learned Behaviors: Behaviors shaped by experience and the environment.
Imprinting: A long-lasting behavioral response to a specific individual, occurring during a "sensitive/critical" period early in life (e.g., ducklings following their mother).
Spatial Learning: Establishing memories based on the spatial structure of surroundings. Organisms may use landmarks or form a cognitive map.
Associative Learning: Associating one environmental feature with another (e.g., a predator associating the bright color of a Monarch butterfly with a foul taste).
Social Learning: Learning through observing and imitating others (e.g., chimpanzees learning to crack nuts with stones by watching elders).
Responses to Environmental Stimuli:
Biological Clock: Internal mechanisms that regulate the timing of physiological processes and behaviors independently of environment, though often synced with environmental cues.
Circadian Rhythm: Internal rhythm following a roughly -hour cycle, regulating sleep, feeding, and hormone release.
Diurnal: Most active during the day.
Nocturnal: Most active during the night.
Crepuscular: Most active at dawn or dusk.
Directed Movements:
Taxis: Directional movement toward (positive) or away from (negative) a stimulus.
Phototaxis: Response to light.
Chemotaxis: Response to chemical signals (e.g., bacterial cells moving toward sugars).
Geotaxis: Response to gravity.
Kinesis: A non-directional change in the rate of movement or frequency of turning in response to a stimulus.
Migration: A regular, long-distance change in location triggered by environmental cues such as the sun's position, Earth’s magnetic field, or celestial cues.
Example (Monarch Butterflies): Migrate miles from Canada/USA to Mexico. Benefits include survival in warmer climates; costs include high energy expenditure and risk of death.
Plant Responses:
Phototropism: A growth response where plants grow toward (or away from) a light source.
Photoperiodism: Changes in physiological activity in response to day length (e.g., flowering only in specific seasons).
Soil Composition: Soil pH affects nutrient availability and phenotype expression (e.g., Hydrangea blooms are blue at pH and pink at pH ).
Defense Mechanisms:
Physical: Thorns or trichomes (small hair-like structures).
Chemical: Production of toxins or volatile organic compounds. Lima bean plants release chemicals when damaged that warn neighboring plants to produce their own defensive compounds.
Communication:
Signals: Stimuli generated and transmitted between animals, subject to natural selection.
Visual: Behaviors or traits that can be seen (e.g., peacock feathers, bird courtship dances, lizard pushups for dominance).
Auditory: Sounds used to attract mates (male songs) or warn of predators (meerkat alarm calls).
Tactile: Physical contact (e.g., primate grooming, the "waggle dance" in honeybees to communicate food distance and direction).
Electrical: Specialized cells generating electric fields to locate prey (e.g., sharks, rays).
Chemical: Pheromones emitted to affect others of the same species. Some cause immediate behavioral changes (ant trails), while others have long-term effects (queen bee cuticular hydrocarbons maintaining hive rank).
Mating and Cooperation:
Sexual Selection: Natural selection for mating success resulting in differential reproductive success.
Mating Systems: Can be monogamous or polygamous (polygyny or polyandry).
Courtship Rituals: Ensure species compatibility and allow females to evaluate mate quality.
Cooperative Behavior: Benefits the group and increases overall fitness.
Pack/Herd Behavior: Increases prey capture (hunting) or reduces individual risk (foraging).
Altruism: Selfless behavior where an individual reduces its own fitness to increase the fitness of others in the population.
Example (Naked Mole Rats): Non-reproductive members sacrifice themselves to protect the breeding queen and kings.
Topic 2: Energy Flow Through Ecosystems
Ecosystem Foundation: An ecosystem is the sum of all organisms in an area and the abiotic factors they interact with.
Biotic Factors: Living or once-living components.
Abiotic Factors: Nonliving chemical and physical properties.
Laws of Thermodynamics in Ecology:
First Law: Energy cannot be created or destroyed, only transformed. A net gain in energy results in storage or growth; a net loss results in mass loss and death.
Second Law: Every energy transfer increases the entropy of the universe.
Metabolic Rate: The total amount of energy an animal uses per unit of time.
Measurement: Heat loss, oxygen () consumption, or carbon dioxide () production.
Relation to Mass: Smaller organisms have a higher metabolic rate per unit of body mass compared to larger organisms. (e.g., one gram of mouse tissue burns more calories than one gram of elephant tissue).
Body Temperature Regulation:
Endotherms: Use thermal energy from metabolism to maintain a homeostatic body temperature.
Ectotherms: Lack internal mechanisms; regulate temperature behaviorally (moving into sun/shade).
Trophic Levels and Energy Flow:
Energy Transfer: Energy flows in one direction and cannot be recycled. Matter/nutrients cycle through biogeochemical pathways.
Primary Producers (Autotrophs): Utilize light energy (photosynthesis) or chemical energy (chemosynthesis) to synthesize organic compounds.
Heterotrophs: Rely on autotrophs for energy.
Primary Consumers: Herbivores.
Secondary Consumers: Carnivores that eat herbivores.
Tertiary Consumers: Carnivores that eat other carnivores.
Quaternary Consumers: Top predators with no natural enemies (Apex predators).
Decomposers/Scavengers: Decomposers (fungi, bacteria) get energy from detritus (nonliving organic matter) and recycle small inorganic molecules back to producers.
Primary and Secondary Production:
Primary Production: Amount of light energy converted to chemical energy.
Gross Primary Production (GPP): Total primary production.
Net Primary Production (NPP): minus the energy used by producers for their own respiration ().
Secondary Production: Amount of chemical energy in consumer food converted to new biomass.
Transfer Efficiency: Transfer between trophic levels is approximately efficient.
Biogeochemical Cycles:
Water Cycle: Vital for all life; involves evaporation, condensation, precipitation, and transpiration (water vapor leaving plants through stomata).
Carbon Cycle: Essential for organic compounds. Processes include photosynthesis, cellular respiration, decomposition, and combustion. Higher atmospheric from human activity leads to ocean acidification and climate change.
Nitrogen Cycle: Essential for amino acids, proteins, and nucleic acids. Atmosphere is the largest reservoir ().
Fixation: gas converted to Ammonia () then Ammonium ().
Nitrification: Production of Nitrates.
Assimilation: Organisms taking in nitrogen.
Ammonification: Production of Ammonia from waste/dead matter.
Denitrification: Returning nitrogen to the atmosphere.
Phosphorus Cycle: Important for nucleic acids, phospholipids, and . Weathering rocks release Phosphate () into soil/water.
Topics 3 & 4: Population Ecology and Growth
Population Dynamics:
Density: Individuals per unit area/volume. Determined via counting or sampling/extrapolation techniques.
Dispersion Patterns:
Clumped: Gathered in patches (common for resource access or protection).
Uniform: Evenly spaced (often due to territoriality).
Random: Unpredictable spacing (rare).
Demography: The study of vital statistics (birth/death rates).
Survivorship Curves:
Type I: Low death rate early, high death rate later (e.g., Humans in the US).
Type II: Constant death rate over lifespan.
Type III: High death rate early, low death rate for survivors.
Population Growth Models:
General Growth Equation:
= change in size, = change in time, = birth rate, = death rate.
Exponential Growth: Occurs under ideal conditions with unlimited resources; results in a J-shaped curve.
Equation:
= maximum per capita growth rate.
Logistic Growth: Growth rate approaches zero as the population size () reaches the carrying capacity (); results in an S-shaped curve.
Equation:
= Carrying Capacity (maximum sustainable abundance supported by resources).
Life History and Regulation:
K-selection (Density-Dependent): Selection for traits advantageous at high densities near carrying capacity.
r-selection (Density-Independent): Selection for traits that maximize reproductive success in low-density environments.
Density-Dependent Regulation: Factors like competition, predation, waste accumulation, territoriality, and disease that change birth/death rates as density increases.
Density-Independent Regulation: Factors like weather, climate, and natural disasters that affect population size regardless of density.
Topics 5 & 6: Community Ecology and Biodiversity
Community Structure: Measured by species composition and diversity.
Niche: An organism's role or "job."
Fundamental Niche: Niche potentially occupied without constraints.
Realized Niche: Niche actually occupied due to competition/predation.
Interspecific Interactions:
Competition (-/-): Two or more species compete for the same resource.
Competitive Exclusion Principle: Two species cannot coexist permanently in the same niche; one will eventually eliminate the other.
Niche Partitioning: Differentiation of niches that enables similar species to coexist.
Predation (+/-): Predator kills and eats prey.
Cryptic Coloration: Camouflage.
Batesian Mimicry: Harmless species mimics a harmful one.
Müllerian Mimicry: Two or more harmful/bad-tasting species mimic each other.
Herbivory (+/-): Organism eats part of a plant/alga.
Symbiosis: Direct contact between species.
Parasitism (+/-): Parasite derives nourishment from host.
Mutualism (+/+): Both species benefit.
Commensalism (+/0): One benefits, other unaffected.
Facilitation (+/+ or 0/+): Positive effect on another species without intimate contact.
Biodiversity:
Species Richness: Total number of different species.
Relative Abundance: Proportion of each species in the community.
Simpson’s Diversity Index:
= total number of organisms of a particular species.
= total number of organisms of all species.
Communities with higher diversity are more resilient to environmental changes.
Keystone Species: Species whose impact on the community is disproportionately large relative to their abundance. Their removal often causes ecosystem collapse (e.g., coral in reefs, bees as pollinators).
Topic 7: Disruptions in Ecosystems
Adaptation and Fitness:
Heterozygote Advantage: When the heterozygous genotype () has higher fitness than either homozygote (e.g., sickle cell trait providing protection against malaria).
Mutations: Random sources of variation; environmental pressures (like pesticides) do not cause specific mutations for resistance, but rather select for them if they exist.
Invasive Species: Species introduced to new ranges, often by humans. They exploit new niches free of predators/competitors and outcompete native species.
Ecological Succession:
Primary Succession: Occurs on entirely new, lifeless habitats (e.g., after a volcanic eruption).
Secondary Succession: Occurs where an existing community has been disturbed but soil remains intact (e.g., after a fire).
Human Impact:
Biomagnification: Toxins (like flame retardants or heavy metals) increase in concentration at higher trophic levels because they do not break down easily. Top predators accumulate the highest concentrations.
Eutrophication: Nutrient runoff (Nitrogen/Phosphorus) causes algal blooms. Algae block sunlight, leading to plant death and oxygen depletion by decomposers, creating "dead zones" where aquatic life cannot survive.
Disturbances: Geological (volcanoes, earthquakes) and meteorological (hurricanes, floods) events shift habitats and trigger migration or successional changes.