Principles of Ecology BIOL3428 Exam 1 Study Guide PDF

Principles of Ecology BIOL3428 Exam 1 study guide Introduction Compare the different definitions of “Ecology” – which aspects of the definitions are common, and which are unique? How would you define ecology? ​ Ernst Haeckel (1866): "Comprehensive science of the relationship of the organism to...

Principles of Ecology BIOL3428 Exam 1 study guide Introduction Compare the different definitions of “Ecology” – which aspects of the definitions are common, and which are unique? How would you define ecology? ​ Ernst Haeckel (1866): "Comprehensive science of the relationship of the organism to the environment." ​ Charles Elton (1927): "Scientific natural history." ​ Eugene Odum (1963): "Study of structure and function of nature." ​ Herbert Andrewartha (1961): "Scientific study of distribution and abundance of organisms." ​ Robert Ricklefs (1973): "Study of the natural environment, particularly the interrelationships between organisms and their surroundings." ​ Charles Krebs (1972): "Scientific study of the interactions that determine the distribution and abundance of organisms." ​ Common aspects: Study of interactions between organisms and their environment. ​ Unique aspects: Some focus on natural history, others on functional dynamics, and some on evolutionary perspectives. ​ Definition: Ecology is the scientific study of how organisms interact with each other and their environment, influencing their distribution and abundance. What are the characteristics of a good hypothesis? What is a null hypothesis? What is the role of falsifiability in hypothesis testing? ​ Provides predictions ​ Must be testable and falsifiable ​ Null Hypothesis: A statement of no cause-and-effect (e.g., "There is no effect of light availability on the number of pine seedlings.") ​ Role of falsifiability: Essential for scientific inquiry; a hypothesis must be capable of being disproven with counterexamples. Evolution & Distribution of Organisms What are some factors that can drive evolution? ​ Mutation (creation of new alleles) ​ Gene flow (immigration/emigration) ​ Genetic drift (random changes, more severe in small populations) ​ Nonrandom mating (sexual selection) ​ Natural selection (differential survival and reproduction based on phenotype) What is the difference between a founder effect and a bottleneck effect? What types of populations may experience these events? How do these effects illustrate the broader concept of genetic drift? ​ Founder Effect: A new population established from a small subset of a larger population (e.g., polydactyly in Amish populations). ​ Bottleneck Effect: A drastic reduction in population size followed by expansion, reducing genetic diversity (e.g., Northern elephant seals hunted to near extinction). Principles of Ecology BIOL3428 Exam 1 study guide ​ Both illustrate genetic drift, where allele frequencies change by chance. What is the difference between Directional, Stabilizing, and Disruptive selection? Draw a graph showing the frequency of phenotype trait values before and after each of these three types of selection events. ​ Directional Selection: Favors extreme phenotypes at one end (e.g., finches with larger beaks in drought conditions). ​ Stabilizing Selection: Favors intermediate traits (e.g., synchronized hatching in birds). ​ Disruptive Selection: Favors extreme traits over intermediate ones (e.g., stickleback fish with distinct body types). What is the biological species concept? Describe three real-world examples where it may be difficult to use this concept to define a species. ​ Biological Species Concept (BSC): Groups capable of interbreeding to produce viable offspring. ​ Challenges: ○​ Asexual organisms (e.g., bacteria lack interbreeding potential). ○​ Hybridization (e.g., ligers and zonkeys exist but may not be viable). ○​ Species change over time (fossil records cannot assess interbreeding potential). What is Liebig’s Law of the Minimum, and how might it explain distributions of organisms? ​ Liebig’s Law of the Minimum: A biological process is limited by the scarcest resource available relative to its requirements What is Shelford’s Law of Tolerance, and how might it explain distributions of organisms? ​ Shelford’s Law of Tolerance: Organism distributions are limited by the factor for which they have the narrowest tolerance range. What is the difference between diffusion, jump dispersal and secular dispersal? Principles of Ecology BIOL3428 Exam 1 study guide ​ Diffusion: Gradual spread across hospitable terrain (e.g., invasive species like cane toads in Australia). ​ Jump Dispersal: Movement across large inhospitable areas (e.g., island colonization by birds). ​ Secular Dispersal: Slow diffusion over evolutionary time, leading to genetic divergence and speciation. What predictions does the ideal free distribution model make about how organisms are distributed across habitats? How does this differ from the ideal despotic distribution model? ​ Ideal Free Distribution: Organisms distribute themselves proportionally across habitats to maximize resources. ​ Ideal Despotic Distribution: More dominant individuals monopolize the best habitats, forcing subordinates into lower-quality areas. Population Growth Parameters What is a population? How might this be difficult to define in modular versus unitary organisms? ​ Definition of a Population: A group of individuals of the same species in a given area. ​ Modular organisms: Can be difficult to define due to clonal reproduction (e.g., coral colonies). ​ Unitary organisms: Distinct individuals (e.g., birds, mammals). What’s the difference between absolute density and relative density? ​ Absolute Density: Number of individuals per unit area. ​ Relative Density: Comparison of population densities without exact numbers. Review some of the methods discussed for measuring density. Which method might you pick for populations of sunflowers? For songbirds? For Galapagos tortoises? ​ Sunflowers: Quadrat sampling. ​ Songbirds: Point counts. ​ Galapagos tortoises: Mark-recapture method. Say you capture 25 snails and mark their shells with a small dab of nail polish. Three days later, you capture 50 snails in the same area, and 15 of those are marked. What’s your estimate of the total population size of snails? ​ Mark-Recapture Example Calculation: ​ 1st capture: 25 marked ​ 2nd capture: 50 total, 15 marked ​ Population estimate (N) = (M × C) / R = (25 × 50) / 15 = 83 Review the assumptions that must be met to accurately estimate population size with mark-recapture. How might each of those assumptions be violated in the real world? ​ No immigration/emigration. ​ No births/deaths. ​ Marked individuals mix randomly. ​ Marks do not affect survival. Principles of Ecology BIOL3428 Exam 1 study guide ​ Capture probability remains constant. What is the difference between density and dispersion? What are the three different major types of dispersion patterns in a population? ​ Density: Number of individuals per unit area. ​ Dispersion: How individuals are spaced within the area. ○​ Clumped (e.g., school of fish) ○​ Uniform (e.g., territorial birds) ○​ Random (e.g., wind-dispersed plants) Life Tables Review the parameters in a standard life table. Make sure you know how to calculate the columns and rows if you are given initial information (such as the number alive at the beginning of each stage, and births in each stage). Practice by filling in this table: # of x nx lx dx qx bx lxbx xlxbx births 0 250 0 1 120 0 2 110 55 3 86 240 4 21 3 5 0 0 USING TABLE: What is the average # of progeny produced per individual in this population? (Same as R0) ​ USING TABLE: What is the generation time if this population breeds continuously? What about if generations are discrete? ​ USING TABLE: If this population has discrete generations, and x is in years, what would be population # be in 24 years? (Use the 250 as your starting #) ​ USING TABLE: In contrast, if this population breeds continuously and has overlapping generations, then what would the population # be in 24 years? (Use the 250 as your starting #) ​ USING TABLE: Why do you suspect that continuously breeding populations with nondiscrete generations grow faster than those with discrete generations? ​ Principles of Ecology BIOL3428 Exam 1 study guide Draw type I, II, and III survivorship curves. Make sure to label your axes appropriately. Provide an example of an organism that fits each type. Limitations on Population Growth Draw a graph showing the difference between geometric and logistic growth. What is the equation for simple logistic growth? What assumptions does this model make about populations? ​ What is density dependence? How is density dependence important for the logistic growth model? ​ Density dependence refers to the effect that population density has on birth rates, death rates, and overall population growth ​ In the logistic growth model, density dependence is a key factor that limits population growth as the population approaches the carrying capacity (K) of the environment. What is an equilibrium model? What is dynamic equilibrium? Why might equilibrium be hard to achieve in the real world? Principles of Ecology BIOL3428 Exam 1 study guide ​ equilibrium model assumes that populations and ecosystems reach a stable state over time where birth and death rates (or resource inputs and outputs) are balanced. In this model, populations stabilize around a carrying capacity (K) due to density-dependent regulation, and the system remains relatively constant unless disrupted ​ dynamic equilibrium refers to a system that fluctuates around an equilibrium point due to ongoing births, deaths, immigration, and emigration. While the population size may vary over time, it tends to return to a stable state rather than increasing or decreasing indefinitely. ​ In real-world ecosystems, true equilibrium is difficult to achieve due to several factors: ○​ Environmental Variability: Climate change, natural disasters, and seasonal changes constantly alter resource availability and population dynamics. ○​ Species Interactions: Predation, competition, mutualism, and disease outbreaks create fluctuations in population sizes. ○​ Human Impact: Habitat destruction, pollution, hunting, and introduced species disrupt natural balances. ○​ Stochasticity (Random Events): Random fluctuations in birth and death rates, genetic drift, and extreme weather events can push populations away from equilibrium. What is the theta logistic model? What assumption does it relax compared to the simple logistic model? How might this make better predictions about population dynamics for some organisms? ​ theta logistic model is a modification of the simple logistic growth model that introduces a shape parameter (θ\thetaθ) to adjust how population growth rate responds to population size relative to carrying capacity (K) ​ The simple logistic model assumes that density dependence affects population growth in a linear way—meaning that as population size increases, the rate of growth declines smoothly and proportionally ​ Better Reflects Species-Specific Growth Responses: Some species experience weak density dependence at low densities but strong effects as they approach carrying capacity (e.g., large mammals with social structures). Others experience strong regulation even at low densities (e.g., species with high competition for limited resources). ​ Accounts for Delayed Feedbacks & Behavioral Adjustments: Some populations may not experience immediate growth restrictions at high densities due to time lags in resource depletion, dispersal, or social interactions. ​ Improves Modeling of Real-World Populations: Many populations do not follow the strict linear assumptions of the simple logistic model. The theta logistic model provides a more flexible, realistic framework to predict population dynamics. What does it mean if the Theta logistic model is concave or convex? What predictions would be made in either case about rates of population recovery after a disturbance (compared to the simple logistic model)? ​ Concave (θ 1θ>1) ○​ Density dependence is weak at low population sizes but increases sharply as NNN nears KKK. ○​ Populations can recover quickly from low numbers because growth remains high until densities approach KKK. ○​ Example: Species that experience Allee effects, where low densities promote faster growth due to cooperative behaviors (e.g., pack hunting, social structure). ​ Concave (θ 1θ>1) → Faster Recovery: ○​ After a disturbance, populations can rebound quickly because density-dependent regulation remains weak until they approach carrying capacity. ○​ This can lead to more rapid population booms compared to the simple logistic model. Behavioral ecology What are Tinbergen’s 4 behavioral ecology questions? Which are proximate and which are ultimate questions? Try to come up with an example of a species/scenario/behavior that aligns with each of the four questions (from species and systems we’ve talked about in class, in the book, or your own knowledge) ​ Mechanism (Proximate Cause) - How is a behavior produced? (e.g., neurological control) ​ Development - How does a behavior develop? (e.g., learned or innate) ​ Function (Ultimate Cause) - What is the adaptive value? (e.g., fitness consequences) ​ Evolution - What is the evolutionary history? ​ Examples: ○​ Stickleback fish exhibit fixed action patterns triggered by red coloration. ○​ Geese imprint on the first moving object they see (often their mother). Describe how the example of the sticklebacks explains the difference between fixed action patterns and a sign stimulus. How would these concepts apply to the example of geese imprinting (i.e., what is the fixed action pattern, and what might be the sign stimulus in that scenario)? ​ Stickleback Example: Fixed Action Patterns vs. Sign Stimulus ○​ Fixed Action Pattern (FAP): A fixed sequence of instinctual behaviors that is stereotyped (occurs the same way every time) and once triggered, is usually carried out to completion. ○​ Sign Stimulus: A specific external cue that triggers the fixed action pattern. ​ Stickleback Example Principles of Ecology BIOL3428 Exam 1 study guide ○​ Fixed Action Pattern: Male sticklebacks exhibit aggressive territorial behavior when they see another male entering their nesting territory. This response is automatic and consistent. ○​ Sign Stimulus: The red belly of another male stickleback is the key trigger. Even if an object is unrealistic but has a red underside, the male stickleback will still attack. ​ Geese Imprinting Example ○​ Fixed Action Pattern: Following the first moving object they see after hatching. Once initiated, this behavior is irreversible and persists as the gosling follows the "mother" (even if it's not a biological parent). ○​ Sign Stimulus: The first moving object (typically the mother goose, but could be a human or even an inanimate object). ​ Comparison: ○​ Sticklebacks: A repeated behavior (aggression) triggered by a specific feature (red belly). ○​ Geese: A one-time learning event (imprinting) triggered by a broad stimulus (first moving object). Optimal foraging models predict when a predator will switch from one prey to another. Describe the different reasons why real-world observations of foraging behavior may not match model predictions. ​ Predicts when an organism will switch from one prey to another based on energy gains vs. handling time. Life history strategies What are the fundamental metrics that are measured in the field of life history theory? How do these differ from their individual counterparts? ​ Fundamental Metrics in Life History Theory ○​ Age of Maturity: When an organism first reproduces. ​ Population-level metric: Average age of first reproduction across individuals in a species. ​ Individual-level counterpart: The specific age when a particular organism reproduces for the first time. ○​ Lifespan (Longevity): How long an organism typically lives. ​ Population-level metric: The average lifespan of individuals in a population or species. ​ Individual-level counterpart: The actual lifespan of a single organism. ○​ Fecundity (Reproductive Output): The number of offspring an organism produces. ​ Population-level metric: Average reproductive output per individual over its lifetime. ​ Individual-level counterpart: The exact number of offspring produced by one organism. ○​ Survivorship Curves: Patterns of mortality across different age groups. ​ Population-level metric: Classifies species into Type I (low early mortality), Type II (constant mortality), or Type III (high early mortality). Principles of Ecology BIOL3428 Exam 1 study guide ​ Individual-level counterpart: A single organism’s likelihood of surviving to each life stage. ○​ Parental Investment: The amount of energy and resources devoted to offspring. ​ Population-level metric: Average time/energy spent per offspring across individuals in a species. ​ Individual-level counterpart: The actual care provided by a single parent to its offspring. ​ How These Metrics Differ from Individual Counterparts: ○​ Life history theory generalizes these traits to make comparisons across species and populations rather than focusing on individual variation. ○​ Population-level metrics help predict evolutionary trade-offs (e.g., should an organism reproduce early with many offspring or later with fewer, better-supported offspring?). ○​ Individual-level differences contribute to variation within a population, but life history theory looks at how selection shapes these traits over generations. What is the potential importance of body size for a life history strategy? What might be the potential trade-offs of waiting to reproduce only after you reach a larger body size compared to another species that reproduces earlier? ​ Growth vs. reproduction (larger body size can enhance fitness, but delays reproduction). ​ Semelparity: One large reproductive event (e.g., salmon). ​ Iteroparity: Multiple reproductive events over time (e.g., humans, elephants). Review the circle/line/cross diagrams depicting different life history strategies. What are the variables shown in those graphs that determine fecundity and, ultimately, fitness? What could you change in a given diagram to increase the fitness of that strategy? ​ Key Variables in These Graphs: ○​ Circles – Represent individual organisms in a population. ○​ Solid Lines – Represent births (number of offspring produced). ○​ Dashed Lines – Represent winter survival (overwintering success of individuals). ○​ Wavy Lines – Represent summer survival (survival through favorable seasons). ○​ Crosses – Represent deaths (mortality events). ​ How These Variables Determine Fecundity and Fitness: ○​ Fecundity (Reproductive Output): Determined by the number of solid lines connecting individuals to offspring. ○​ Juvenile Survival: If many offspring die young (crosses appearing early in life), overall fitness is reduced. ○​ Adult Survival: If adults survive multiple reproductive seasons (fewer crosses in mature individuals), they may have higher lifetime reproductive success. ○​ Trade-offs Between Reproduction & Survival: High fecundity strategies may result in lower parental survival (more crosses among adults), while lower fecundity strategies may allow higher offspring survival. ​ How to Increase Fitness in a Given Strategy: ○​ Increase Offspring Survival: Principles of Ecology BIOL3428 Exam 1 study guide ​ Reduce the number of crosses at early life stages (Type I survivorship curve). ​ Increase parental investment (e.g., fewer, well-provisioned offspring). ○​ Increase Adult Longevity: ​ Reduce adult mortality (fewer crosses among adults). ​ Shift investment from early reproduction to long-term survival and future reproduction. ○​ Adjust Reproductive Timing: ​ If delaying reproduction allows for larger size and more offspring, shifting births to later life stages may improve fitness. ​ Conversely, if early reproduction is beneficial (e.g., high juvenile mortality), increasing early-life births may help. ○​ Optimize Seasonal Survival: ​ Ensure more individuals survive winter (dashed lines) and summer (wavy lines) to maintain long-term population stability. Describe the differences between the r-selection/K-selection model ​ r-selected species maximize reproduction, K-selected species maximize efficiency at carrying capacity. Experimental design What is the difference between a mensurative study and a manipulative experiment? Why might a manipulative experiment have more power for hypothesis testing? ​ Mensurative: Observational, no direct manipulation (e.g., studying species distributions). ​ Manipulative: Directly altering variables to measure responses (e.g., changing light availability to study seedling growth). What is the difference between a dependent and independent variable? ​ Independent Variable (X): ○​ The variable that is manipulated or changed by the researcher. ○​ Represents the cause in a cause-and-effect relationship. ○​ Example: Amount of sunlight given to plants in a growth experiment. ​ Dependent Variable (Y): ○​ The variable that is measured to determine the effect of the independent variable. ○​ Represents the effect in a cause-and-effect relationship. ○​ Example: The height of the plants after different amounts of sunlight exposure. Why are replication, randomization and independence important for experiments? ​ Replication - Ensuring results are repeatable. ​ Randomization - Avoiding bias. ​ Independence - Ensuring results are not influenced by external factors. ​ Controls: Principles of Ecology BIOL3428 Exam 1 study guide ○​ Negative Control: No treatment applied. ○​ Procedural Control: Ensures the method itself doesn’t affect results. What is the role of an experimental control in a manipulative experiment? What are the differences between negative and procedural control groups? ​ An experimental control is used in a manipulative experiment to provide a baseline comparison for evaluating the effects of the independent variable ​ Negative Control Group: ○​ A group that does not receive the experimental treatment. ○​ Used to confirm that any observed effects are due to the manipulation of the independent variable and not due to external influences. ○​ Example: If testing the effect of fertilizer on plant growth, a negative control would be a set of plants that receive no fertilizer to compare against treated plants. ​ Procedural Control Group: ○​ A group that undergoes the same procedures as the experimental group, but without applying the actual experimental treatment. ○​ Used to account for any effects caused by the method itself, rather than the independent variable. ○​ Example: If testing the effect of a cage on fish feeding behavior, a procedural control would involve placing an empty cage in the environment to ensure that the cage itself is not affecting the results. Terms​ Review the following terms: Null hypothesis: No cause-and-effect Phenotype vs genotype: expressed statement. Statistically testable and could be characteristics vs. genetic makeup rejected in favor of alternative hypothesis Natural selection: differential survival and Alternative hypothesis: tentative explanation reproduction of individuals due to differences in for observed patterns formatted as a cause and phenotype effect statement Founder effect: establishment of a new Falsifiability: information can be used to reject population from small subset of larger hypotheses population Fitness: relative ability to survive and reproduce Bottleneck effect: large reduction in population viable offspring size followed by expansion leading to a reduction in genetic diversity. Allele frequencies Adaptation: trait(s) of an individual that are altered increases fitness Principles of Ecology BIOL3428 Exam 1 study guide Allopatric speciation: geographic isolation from Sign stimulus: essential part of a stimulus that parent population leads diergence and elicits a response speciation Imprinting: a limited phase during development Sympatric speciation: speciation in the absence that is the only time when certain behaviors can of geographic separation be learned Genetic drift: change in allele frequency of a Habituation: response to stimuli decreases with population by chance; small populations are exposure affected the most Latent Learning vs Insight: improvement Carrying capacity: the maximum number of through repetition vs natural problem-solving individuals that can be sustainably supported in Semelparity: species that reproduce once, then a habitat die. leads to discrete growth Emigration: the act of leaving a habitat or Iteroparity: species that reproduce multiple region with the intent of living elsewhere times, leads to overlapping generations Ideal free distribution: population density Negative control: a group that does not receive increases in ‘best’ habitat, resources decline. any treatment. No response is expected Eventually habitat quality becomes equal to ‘lesser’ habitat Procedural control: a control group that tests of the method for imposing a treatment causes a Ideal despotic distribution: territorial, response itself, regardless of whether you aggressive individuals occupy best habitats, manipulate the independent variable subordinated forced into lesser habitats. Fitness lower in poorer habitats Independent variable: the “cause” in the hypothesis. This variable changes and it is the Jump vs. secular dispersal: movement across variable that is manipulated large distances vs. diffusion over significant time, evolutionary change occurs during process Dependent variable: the “effect” in the hypothesis. This variable changes in response to Ethology: study of animal behavior the independent variable and what would be Fixed action pattern: behaviors performed by measured. all members of one sex of one species in a stereotypical pattern