Urban Ecology Theory Test #2 PDF

Urban Ecology Theory Test #2 Unit 6: Ecological Niche -​ Niche: the total requirements of a species for all resources and physical conditions which determine where it can live and how abundant it can be at any one place within its range -​ Niche dimensions: different bioti...

Urban Ecology Theory Test #2 Unit 6: Ecological Niche -​ Niche: the total requirements of a species for all resources and physical conditions which determine where it can live and how abundant it can be at any one place within its range -​ Niche dimensions: different biotic and abiotic variables that impact a species’ interaction with its environment Niche types Fundamental niche Realized niche -​ Resource dimensions and -​ Actual niche used due to organism could theoretically competition occupy in the absence of competition -​ Assumes presence of others is insignificant -​ The full range of conditions that allow a species to survive and reproduce, without the limitations of competition, predation, or other factors -​ Niche partitioning: a process where species divide up resources to reduce competition and coexist in the same environment -​ Generalist: species with broad niches; compete so there can only be a few leading to low diversity, cope better with changes in food supply  -​ Specialist: species with narrow niches; can coexist in the same habitat because they are not competing leading to high diversity -​ Niche overlap and breadth ★​ Niche breadth refers to generalist or specialist species ★​ Niche overlap refers to two or more species sharing same resources, predators, foraging space, soil type -​ Character displacement: an evolutionary process that occurs when similar species compete for resources in the same environment, resulting in the evolution of traits that reduce competition Unit 7: Spatial Pattern -​ Dispersal Vs Dispersion Dispersal Dispersion Movement or action of moving away Evenness of the population’s from a point in space distribution through space -​ Uniform, Aggregated, and Random distributions Uniform Aggregated Random Results from negative Small discrete groups An individual's position interactions among are formed, some is independent of individuals animals have social others; rare in nature groups meep morp  -​ Population density: a measurement of how many people live in a given area -​ Ecological density: the number of organisms in a population per unit of habitable land in a specific area -​ Variance/mean ratio: a statistical measure that characterizes the distribution of events or objects in time or space Unit 8: Community Ecology -​ Guilds: organisms who exploit a resource in a similar way -​ Community: a group of species that occupy a given area, interacting either directly or indirectly -​ Functional type: subsets of a community such as plants that photosynthesize using specific pathways -​ Zonation: spatial change in community structure Three Early Hypotheses for Defining Boundaries Between Communities Clements (Holistic) Gleason (Individualism) Whittaker (Hypothesis/Approach) -​ Frederic Clements -​ Individualism (1920‐ -​ Whittaker (1950s) -​ Organism concept ) -​ Broad‐scale of communities -​ Henry Gleason descriptions are -​ Super‐organism -​ Individualistic, or used for -​ Clear boundaries Continuum landscape -​ “climax” concept community community -​ “Fuzzy” structure boundaries -​ Great Smoky Mountains National Park Unit 9: Landscape and Succession Ecology Landscape: Mosaic of patches -​ Patch: Fundamental unit of a landscape, homogeneous units. Differ from their surroundings in structure (size and shape) and in species composition. Result from the interactions of factors: geology, topography, soils, and climate Landscape ecology: Study of the causes behind the formation of patches and borders and the ecological consequences of these spatial patterns on the landscape in space and time Matrix: In ecology, the matrix is the main landscape background that connects and encompasses patches. It can be a natural space or a modified environment, such as a city or farm. The matrix is important because it influences how species live and move, and it affects ecological stability and interactions Island Biogeography: ​ -​ The number of species established on an island represents a dynamic equilibrium between the immigration of new colonizing species and the extinction of previously established ones -​ Insular biogeography or, island biogeography, is a field within biogeography that examines the factors that affect the species richness and diversification of isolated natural communities -​ Theory created by E.O. Wilson and Rober MacArthur Concept involves -​ Colonizing or immigrating population -​ Extinction rate of species (loss through competition, etc.) -​ Species richness (S) -​ Turnover (T) (replacement of island species by colonizers) -​ Island distance -​ Island size Island Biogeography can be applied to Patches Other examples: -​ Mountaintops with their unique climate regime -​ Bogs with their unique flora -​ Small ponds and their unique aquatic organisms -​ Dunes and oases -​ Hosts as islands for parasites -​ Areas fragmented by human land use -​ Buildings, suburban, agricultural, “cottage country”. Can patches act like islands? -​ “Any patch of habitat isolated from similar habitat by different, relatively inhospitable terrain traversed only with difficulty by organisms of the habitat patch may be considered an island; in this sense much of the biotic world is insular, for habitats are often not homogeneous but rather are arranged as patches in a crazy quilt. Consequently, any model of island biology should be relevant to small scale, local systems, as well as to larger ones” (Simberloff, 1974) Boundary: A place where the edge of one patch meets the edge of another a)​ Narrow and abrupt b)​ Wide with a transition zone (ecotone) a) and b) Straight c)​ Convoluted d)​ Perforated Inherent edges: the result of natural features of the physical environment such as rock outcrops, changes in underlying rock, etc Induced edges: are the result of natural or man‐made disturbances ‐ fires, storms, roads, pastures, logging, etc. ‐ if left alone they will go back to their original state (succession) Transition Zones (Ecotone): In ecology, a transition zone is a geographical area where different biotic components, or sets of taxa, can coexist and interact. These areas are also known as ecotones or boundaries. -​ Environmental conditions in transition zones enable certain plant and animal species to colonize border environments -​ Borders blend elements from all adjacent patches and offer unique habitats with relatively easy access to adjacent communities -​ The edge effect is the phenomenon where edge communities are often quite diverse -​ Edge species are those restricted exclusively to the edge environment Ecological Succession: The process of change in the species structure of an ecological community over time. The time scale can be decades (for example after wildfire), or even millions of years after a mass extinction. Unit 10: Predation Density dependence, Lotka-Volterra model for predation, Rosenzweig-MacArthur Model. Numerical and Functional response, types of functional responses, types of defenses, warning coloration, batesian vs. mullerian mimicry, types of hunting, optimal foraging theory Predation: The consumption of all or a part of another living organism (the prey) by another (the predator) Density Dependent Regulator -​ Predators as a source of density-dependent regulation on the mortality of the prey population -​ Prey as a source of density-dependent regulation on the birthrate of the predator population The Lotka–Volterra model is a simplification of real life situations ​ Several assumptions made by the model: ​ Food supply of the predators depends exclusively on the target prey population (i.e., single prey models) ​ Prey population has sufficient food at any time ​ Rate of change of either population is proportional to the size ​ Genetic adaptation and disease have little or no effect on the population ​ Predators have a limitless appetite ​ Stochastic events do not influence the model ​ Other interactions (e.g., competition) are ignored Predators can change in four ways as prey numbers increase 1)​ Numerical Response: Increase the number of predators through immigration and/or reproduction ​ 2)​ Aggregate Response a)​ An increase in prey will cause predators to concentrate in certain areas (spatial)​ 3)​ Developmental Response a)​ Predators will change the amount of prey consumed as they age and reach maturity​ 4)​ Functional Response: ​ The greater the number of prey, the more the predator will eat ​ This is the relationship between the per capita predation rate (number of prey consumed per unit time) and prey population size There are three types of functional responses -​ Type I: Predation is constant and is independent of prey density -​ Characteristic of passive predators (filter feeders) -​ All of the time allocated to feeding is spent searching  -​ Type II: The per capita rate of predation increases in a decelerating fashion up to a maximum rate that is attained at some high prey density -​ Most common for predators -​ Type III: Rate at which prey are consumed is low at first, increasing in a sigmoid fashion as the rate of predation reaches a maximum -​ Initial rate of prey mortality increases with prey density Hunting Tactics Ambush hunting means lying in wait for prey to come along -​ Low frequency of success but it requires minimal energy -​ Ex: Frogs, crocodiles, lizards, certain insects Stalking is a deliberate form of hunting with a quick attack -​ Search time is great but pursuit time is minimal -​ Ex: Herons, some cats Pursuit hunting involves minimal search time (the predator usually knows the location of the prey) but considerable pursuit time -​ Ex: Hawks, lions, wolves, insectivorous bats Cryptic Coloration: Deception by resembling their prey, chemical poisons, and other means to lure and capture prey -​ Ex: Alligator snapping turtle (cryptic coloration and worm-shaped tongue Coordinated and Communal Hunting: Each individual within a group must synchronise their actions (over space and time) in order to target prey -​ Ex: Wolves, lions, and orcas Optimal Foraging Theory: Natural selection favors efficient foragers -​ Helps predict behaviors exhibited while searching for food -​ Based on energy obtained (calories), as well as energy spent searching for prey and handling the prey -​ Maximum net rate of energy gain = optimal diet and foraging efficiency Predatory Defenses: Wide range of characteristics to avoid being detected, selected, and captured by a predator Type of Defense Description Chemical Defense -​ Alarm pheromones induce flight reactions in members of the same and related species -​ Odorous secretions repel predators -​ Storage or synthesis of toxins and poisons Cryptic Coloration -​ Includes colors and patterns that allow prey to blend into the background Object Resemblance -​ Common among insects Flashing Coloration -​ May distract and disorient predators or it may serve as a signal to promote group cohesion Warning Coloration -​ Animals that are toxic to predators or use chemical defenses -​ Bold color patterns that serve to warn would-be predators Batesian Mimicry -​ An edible species mimics the “Red next to yellow, you’re a dead fellow, inedible species (the model) red next to black, you’re a friend of -​ Butterflies and snakes Jack!” -​ Mimicry is not limited to color pattern (rattle-like sound) Mullerian Mimicry -​ Similar color pattern shared by many unpalatable or venomous species -​ Effective because the predator has to be exposed to only one of these species before learning to stay away from all other species with the same warning color patterns Protective Armor -​ (Shells, quills) is used by some animals for defense Behavioral Defenses -​ A wide range of behavioral defenses is known to help prey avoid or escape predators -​ Alarm calls -​ Living in groups -​ Changing foraging behavior -​ Distraction displays -​ Predator Satiation: Most offspring are produced in a short period of time Mechanical Defenses -​ Hairy leaves, thorns, spines discourage feeding -​ The cellulose in lignin content make most plant tissues a low-quality food Unit 11: Competition Intra vs Interspecific Competition Intraspecific Interspecific Occurs among individuals or groups Occurs among individuals or groups of the same species of different species -​ Initially effects growth and -​ Each competitor has their own development intraspecific factors going on -​ Later affects individual survival -​ Affects populations of 2+ species adversely and reproduction Six types of Interspecific Competition Consumption Occurs when one species Ex: different animal inhibits another by species competing for consuming a shared acorns resource Preemption Occurs when the Ex. sessile organisms like occupation by one barnacles individual precludes establishment by others Overgrowth Occurs when one Ex: overgrown organism grows over vines/plants another and inhibits access to an essential resource Chemical interaction Involves the production Ex: allelopathy in plants of chemical growth inhibitors or toxins released by an individual Territorial Results from the behavioral exclusion of others from a defended territory Encounter Results during non Ex: scavengers fighting territorial meetings over a carcass Mechanisms of competition Competition type When does it occur Effects Scramble competition Occurs when individuals Exploitative and passive indirectly interacts with one another but affect the availability of shared resources (e.g. grazing herbivores) Contest competition Results when individuals Interference, aggressive directly interact and prevent others from occupying a habitat or accessing resources within it (e.g. bird species nesting sites) Apparent competition Occurs indirectly Linked to predation between two species which are both prayed upon by the same predator Home range: the area that an animal normally uses during a year -​ Size varies with food resource availability, mode of food gathering, metabolic needs, body size, gender, age, diet/niche Gause experiment: G. F. Gause examined competition between Paramecium aurelia and P. caudatum Competitive exclusion principle: “competing species cannot coexist within the same ecological niche” -​ If population A increases the least bit faster than population B, then A will eventually outcompete B (B will become extinct) However… -​ Species can compete for two resources and can coexist when 2 conditions are met -​ The habitat must be such that the one species is more limited by one resource and the other species is limited by the other resource -​ Each species must consume more of the resource that more limits its own growth. -​ In extreme cases, we see examples of how competitive pressures have led to niche partitioning. de Wit replacement series: method for comparing effects of intraspecific and interspecific competition in plants Lotka Volterra: Δ𝑁 = 𝑟𝑁 ((𝐾 – 𝑁)/𝐾) -​ 𝛂 = competition coefficient that quantifies the per capita effect of species 2 on species 1 -​ 𝛃 = competition coefficient that quantifies the per capita effect of species 1 on species 2 For species 1: 𝛂N2 and for species 2: 𝛃N1 -​ N1 = population size of species 1 -​ N2 = population size of species 2 Model for competition: two species using the same resources in the same territory -​ Each occupies a niche but both spend time in the same area -​ American bison and black tailed prairie dogs Resource partitioning: process in which different species in an ecosystem divide up resources to avoid competition and coexist Unit 13: Biodiversity Species Definition Strengths Limitations Concept Morphological A species is a group of - Useful for - Subjective Species organisms that share fossils and and prone to Concept similar physical organisms misinterpret characteristics where ation. (morphology). reproduction - Cryptic data is species look unavailable. identical but - Easy to apply are with clear genetically physical traits. distinct. Biological A species is a group of - Focuses on - Not Species individuals that can reproductive applicable to Concept interbreed and produce isolation and asexual viable, fertile offspring, but gene flow. organisms. are reproductively isolated - Useful for - Hard to use from other groups. studying for extinct speciation species. processes. - Hybrids complicate its use. Genetic Species A species is a group of - Objective and - Requires Concept organisms that share high relies on advanced genetic similarity and measurable genetic distinct genetic markers. genetic data. analysis. - Can identify - Genetic cryptic species. differences may not always reflect reproductive isolation. Ecological A species is a group of - Highlights Overlapping Species organisms that occupy the ecological niches can Concept same ecological niche and adaptations. blur interact with the - Useful for distinctions. environment in a similar understanding way. species’ Requires environmental extensive roles. ecological data. Phylogenetic A species is the smallest - Incorporates - May Species group that shares a evolutionary over-split Concept common ancestor and has history. species into unique genetic or - Applies to both smaller morphological traits. sexual and groups. asexual - Requires organisms. detailed phylogenetic data. Evolutionary A species is a lineage of - Emphasizes - Difficult to Species organisms evolving evolutionary define Concept independently, maintaining processes and practical unique characteristics over history. boundaries. time. - Applies - Requires broadly across comprehensi different taxa. ve historical and genetic data. Example: Wolves, Dogs, and Coyotes ​ Under the Biological Species Concept, wolves, dogs, and coyotes might be considered one species because they can interbreed and produce fertile offspring. ​ Under the Morphological Species Concept, their physical differences might classify them as separate species. ​ Under the Phylogenetic Species Concept, their evolutionary lineages and genetic differences could also distinguish them as separate species. Post 2020 Global Biodiversity Framework (COP 15) -​ « 30 X 30 » initiative (protection and management of 30% ecosystems by 2030) -​ By 2021 50 countries, by 100 over 100 countries Keystone Species: Has a disproportionate impact on the community relative to its abundance -​ The removal of a keystone species initiates changes in the community structure and often results in significant loss of diversity -​ Otters eating urchins that eat kelp Singapore Index -​ Cities that have applied the Singapore Index have found that: -​ Facilitated capacity-building in biodiversity conservation -​ Indicators function as biodiversity conservation guidelines -​ Quantitative scoring assists in setting priorities for conservation actions and budget allocation. Species Richness Diversity Definition Richness Alpha Diversity The diversity within a Measured as species single, localized habitat richness (number of or community species in a given area) -​ Shannon and Example: Counting Simpson can also species in a forest plot be used for richness and evenness Beta Diversity The difference in species Not directly a richness composition between two measure. or more habitats or Quantifies the extent of communities species turnover or variation between sites Example: Comparing species between a forest and grassland Gamma Diversity The total diversity of a Often measured as landscape or larger species across all region that encompasses habitats in the region multiple habitats or communities Example: Counting all species across a forest, grassland, and wetland Species Accumulation Curve -​ Cumulative species count against year a)​ New World grasses b)​ Gymnosperms c)​ Ants (by decade) d)​ Mosses e)​ Ferns f)​ Lycopods g)​ British flora h)​ Birds of the world Species Richness (S): -​ The count or the number of species occurring within the community Relative Abundance -​ Represents the percentage each species contributes to the total number of individuals of all species Simpson Index -​ Based on the probability of finding a second individual in a sample will be from the same species as the first -​ Influenced by common species rather than species richness. The addition of extra species makes little difference Shannon-Wiener Index (Abundance-based diversity index) Review Questions: 1. Community disturbance can vary in intensity, scale and frequency. Discuss these terms. Community disturbances are events that can disrupt the functions of a community directly altering resource availability, dynamics between populations, and ecosystem processes. Intensity refers to the severity of the disturbance and its effects on a community. Low intensity disturbances have temporary small scale effects which allows for a community to recover quickly and easily. High intensity disturbances such as environmental catastrophes can devastate a community in its entirety resulting in significant or permanent changes to community structure. Scale refers to the spatial extent of the disturbance from local to widespread. Small scale disturbances can be beneficial and can often enhance biodiversity within the ecosystem. For example, a tree falling in a forest resulting in localized gaps which allow sunlight to reach the understory. Large scale disturbances can cause great loss in biodiversity and disrupt entire ecosystems. Frequency refers to how often a disturbance occurs. Frequent disturbances can prevent certain species from establishing themselves within a given environment. Infrequent disturbances can result in long periods of stability allowing slow-growing or long-living species to flourish and dominate. 2. Contrast between bottom-up and top-down control in the structure of a food web. Bottom-up control refers to the influence of resource availability on the structure and dynamics of the food web. It emphasizes the availability of energy and nutrients. Biomass such as herbivores and predators are restricted by the scarcity of sunlight, nutrients, and water. Energy and resources flow upward from the base. Changes in primary production (due to nutrient addition/reduction) thus propagate throughout the entire food web. For example, in aquatic environments, nutrient availability such as nitrogen and phosphorus determine the growth of species such as phytoplankton, which impacts zooplankton, which impacts fish and so on. Top-down Control refers to the influence of consumers on the structure and dynamics of the food web. This control originates from higher trophic levels which cascade downward through the food web. It focuses on predation and grazing wherein predators regulate prey species abundance which affects lower levels (e.g. herbivores and primary producers). Predator populations create cascading effects via the controlling of herbivore abundance. Less herbivory allows plants to flourish. Removing an apex predator can lead to overabundance of herbivores which may result in overgrazing and loss of vegetation. 3. Contrast Clements and Gleason views on community organization. -​ Interdependence: Clements saw strong interdependence among species, while Gleason believed species interact loosely, driven by individual needs. -​ Succession: Clements’ model predicts a fixed endpoint, while Gleason's allows for variability based on environmental and stochastic factors. -​ Community Boundaries: Clements described sharp boundaries, whereas Gleason saw gradual transitions. While both views contributed to ecological theory, Gleason's individualistic concept is more widely accepted today. Ecologists recognize that species' distributions are primarily driven by abiotic factors (e.g., temperature, moisture) and biotic interactions, with community composition being dynamic and variable over time. However, elements of Clements' perspective, such as the idea of interdependence in some ecosystems, remain relevant in specific contexts like mutualistic relationships. 4. What type of mechanical and chemical defenses have plants evolved to deter herbivores? Mechanical defenses -​ Physical barriers: thorns and spines, trichomes, thick bark/cuticle -​ Movement based defenses: Mimosa pudica(Sensitive plant): leaves that fold or collapse when touched making the plant less appealing or accessible -​ Structural traits: ★​ Tough leaves and sclerenchyma cells ★​ Leaf shape and orientation Chemical Defenses -​ Toxins like alkaloids (nicotine caffeine morphine) which poison/deter herbivores by interfering with their physiological processes -​ Digestibility reducers -​ Repellents and irritants (essential oils, latex, resins) -​ Induced chemical responses 5. Create a simple data set of species and counts of organisms of two locations. Compare the biodiversity indices using the Simpson index of diversity. Species Count (location A) Count (location B) Species 1 30 10 Species 2 50 10 Species 3 20 10 Species 4 0 10 Species 5 0 10 Species 6 0 10  ​ Location A: Simpson Index = 0.62 ​ Location B: Simpson Index = 0.83 Conclusion: Location B has a higher Simpson Index of Diversity, indicating greater biodiversity than Location A. This is because Location B has an even distribution of species, while Location A is dominated by one species (Species 2). 6. Distinguish between a dominant and a keystone species. -​ A dominant species is the most abundant species within a given ecosystem, often controlling availability of resources. -​ A keystone species has a disproportionately large effect on its ecosystem despite its abundance not necessarily being high. This is because they play crucial roles in maintaining the structure of an ecological community and influencing interactions of other species. Key Difference: The influence of dominant species arises from their abundance or biomass, whereas the influence of keystone species comes from their ecological roles, which are often vital for ecosystem stability and diversity. 7. How are species richness and species evenness different? -​ Species richness: the number of different species present in a particular area -​ Species evenness: measures the relative abundance of each species in a given area and describes how evenly individuals are distributed among species -​ Species richness tells how many species are present. Species evenness tells how balanced the populations of those species are. 8. How have urban areas negatively affected urban biodiversity? How about positively? Negative -​ Habitat destruction and fragmentation -​ Pollution -​ Introduction of invasive species -​ Climate change and urban heat island effect -​ Barriers to movement Positive -​ Creation of new habitats -​ Biodiversity conservation initiatives -​ Adaptation opportunities? -​ Increases awareness and education -​ Urban farming and pollinator habitats 9. Distinguish the terms edge, border and ecotone. -​ Edge refers to a boundary between ecosystems or habitats. -​ Border generally refers to a defined, often territorial boundary. -​ Ecotone is a specific, biodiverse transitional area between two ecosystems. 10. How do patch size and isolation (distance to neighboring islands) influence patterns of species diversity in cities? How would you test this? -​ Patch size: Larger patches generally support more species due to the availability of more resources, microhabitats, and space for species to establish territories. Larger areas tend to have greater habitat complexity, which supports more ecological niches. Smaller patches, in contrast, are more likely to have limited resources, higher vulnerability to disturbances, and lower species richness. -​ Isolation: The distance between patches influences species dispersal. Patches that are more isolated from others may experience lower species diversity due to reduced gene flow and limited opportunities for species to colonize. In contrast, patches that are closer together are more likely to facilitate the movement of species, which can help maintain higher species diversity. Could be tested by conducting a survey wherein several urban green spaces of different sizes and degrees of isolation are identified. 11. How is the coexistence of many species in the same habitat compatible with the existence of interspecific competition? -​ species can utilize different resources or occupy different niches within the environment, reducing direct competition. This phenomenon is known as niche differentiation or resource partitioning. -​ In interspecific competition, different species compete for the same limited resources, such as food, water, or space. However, when species evolve strategies to exploit different aspects of the environment (such as different times of day for  foraging, or different food sources), they can coexist more effectively. This can be achieved via ★​ Spatial partitioning ★​ Dietary differences ★​ Behavioral adaptations Thus, while interspecific competition does occur, these adaptations allow species to coexist by minimizing competition for the same resources. 12. If you observe a species in the wild, are you observing its fundamental or realized niche? When observing a species in the wild, you are observing its realized niche. This refers to the actual conditions under which the species lives, including its interactions with other species, competition, and resource availability. In contrast, the fundamental niche represents the full range of environmental conditions and resources a species could theoretically occupy in the absence of limiting factors like competition, predation, and disease. Therefore, the realized niche is the subset of the fundamental niche that the species actually occupies in the wild. 13. In both predation and parasitism, one organism (species) derives its energy and nutrients from consuming another organism. What is the difference between the two processes? Predation: ​ Involves one organism (predator) killing and consuming another organism (prey). ​ The interaction is usually brief and ends with the death of the prey. ​ Example: A lion hunting and eating a zebra. Parasitism: ​ Involves one organism (parasite) deriving energy and nutrients from another organism (host) without immediately killing it. ​ The interaction is typically long-term, and the host may or may not die as a result. ​ Example: A tapeworm living inside a mammal's intestines 14. In the Lotka-Volterra model of interspecific competition, one outcome leads to the species coexisting. What circumstance is necessary for this outcome? Coexistence occurs when the intraspecific competition (competition within the same species) is stronger than interspecific competition (competition between different species). ​ This happens when: ○​ The competition coefficients (α and β) are relatively small.  ○​ Each species has a competitive advantage in its niche, allowing them to coexist at equilibrium. 15. Spring ephemerals and trees live in the same habitat. How do their respective niche and habitat compare?​ Habitat: Both spring ephemerals (short-lived flowering plants) and trees share the same forest habitat. Niche: ​ Spring ephemerals occupy a temporal niche, thriving in the early spring before trees leaf out and block sunlight. They capitalize on the sunlight and resources available during this brief period. ​ Trees have a long-term niche, utilizing sunlight, water, and nutrients throughout the growing season once they leaf out. This differentiation allows them to coexist despite living in the same habitat. 16. The Lotka-Volterra model of predation-prey dynamics suggests mutual control between predator and prey populations that result in the two populations oscillating through time. Why does the predator population lag behind the prey population? -​ The predator population lags because it depends on the prey population for energy and reproduction. When prey populations increase, predators benefit, but it takes time for them to reproduce and grow in number. When predator populations grow, they reduce prey numbers, causing a decline in prey availability. Predators then decline due to starvation or reduced reproduction rates. This time delay creates a lag between the peaks and troughs of prey and predator populations, resulting in oscillations. 17. What conditions must be established before a researcher can definitively state that two species are competing for a resource? Is establishing that two species overlap in their use of a resource a sufficient condition to determine that interspecific competition is occurring? To definitively state that two species are competing for a resource, the following conditions must be met: 1.​ Shared, Limiting Resource: The species must rely on the same resource, and that resource must be in limited supply. 2.​ Negative Impact on Fitness: The use of the resource by one species must reduce the availability of the resource for the other, thereby decreasing the fitness (e.g., growth, reproduction, or survival) of both species. 3.​ Experimental Evidence: Demonstrations of reduced performance (e.g., population size, growth rate) of one species in the presence of the other  provide strong evidence of competition. Controlled experiments can manipulate resource availability or species presence to confirm this. Is Overlapping Resource Use Sufficient? No, simply observing overlap in resource use is not sufficient. For example, two species might use the same resource but at different times or in non-limiting quantities, meaning competition is not occurring. Clear evidence of negative interactions is necessary to confirm interspecific competition. 18. What is meant by functional response in predation?​ A functional response describes how a predator's rate of prey consumption changes with prey density. There are three types: 1.​ Type I: Predation increases linearly with prey density until a saturation point. Common in filter feeders. 2.​ Type II: Predation rate rises quickly at low prey densities but slows as prey density increases, reflecting handling time and predator satiation. 3.​ Type III: Predation is low at low prey densities (due to prey hiding or lack of predator search efficiency), increases sharply at intermediate densities, and plateaus at high densities. Example: ​ A wolf eating deer might show a Type II response: it consumes more deer as their population increases, but its consumption levels off when it becomes full or when hunting and handling take more time. 19. What is meant by numerical response in predation? A numerical response refers to changes in predator population size in response to changes in prey density. Predators can respond in two ways: 1.​ Reproductive Response: Increased prey availability leads to higher reproduction rates in predators, causing a population increase. 2.​ Aggregative Response: Predators move into areas with higher prey density, increasing their local abundance. Example:  ​ A population of foxes may grow as rabbit populations increase because more food allows for better survival and reproduction. 20. What is niche breadth? Explain how inter- and intraspecific competition interact to influence niche breadth? Niche breadth refers to the range of resources or conditions a species can use or tolerate in its environment. It represents the ecological versatility of the species. Interspecific Competition: ​ Reduces niche breadth due to competitive exclusion, where species are forced to specialize in narrower resource ranges to avoid direct competition. ​ Example: Two bird species might split resources by one focusing on insects from tree trunks and the other on leaves. Intraspecific Competition: ​ Occurs within a species, as individuals compete for the same resources. ​ Can lead to resource partitioning within the population (e.g., different age groups or sizes using different resources). 21. Why is the diversity of species different between an edge and the habitat next to it? How is it different? ​ Edge: Boundary between two ecosystems with unique conditions (higher light, temperature fluctuations, wind exposure). ​ Higher Species Richness: Edges support species from both adjacent habitats and edge specialists. ​ Lower Specialist Abundance: Interior species (specialists) are less abundant at edges due to harsher conditions. ​ Increased Generalists: Generalist species, tolerant of various conditions, are more common at edges. ​ Interior Habitat: Supports more specialized species adapted to stable conditions. 22. Watch the following video (https://www.youtube.com/watch?v=3h- TfH1wrfI&feature=emb_logo). In competition models, is seen in class equal to 12 or 21 ? What happens when 21 < 1 ? What happens when 12 = 21 ?