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level: Level 1

Questions and Answers List

level questions: Level 1

QuestionAnswer
Monitoring how populations change in sizeFind effective ways of managing agricultural pests. Increase pop of rare, endangered species.
Population dynamicsNnow = Nthen + B - D + I - E How pop changes over time B= # deaths D= deaths I= immigrants E= emigrants
Unitary organismsForm, development, growth and longevity are highly determined and predictable. The zygote – from sexual reproduction –grows into a genetically unique organism
Modular organismsZygote develops into a unit of construction (a module) that then produces further, similar modules. Immobile; often reproduce asexually. Genet: Individual produced sexually is a genetic individual. Ramets: Modules produced asexually from the genet.
How to determine pop size1. Count total pop - sometimes impossible so you estimate: Extrapolate; Pop size=densityxarea 2. Estimate the density
Sampling methods1. Use quadrats 2. Index of relative density 3. Mark and recapture technique. r/N = m/n N= pop r= sample is caught n= sample recaptured m= # marked in recapture
Reproductive effortObjective is to maximise relative fitness. But extracts a cost to future reproductive success. NS optimises this trade-off
Species differ in their reproduction timingSemelparous species: First they invest energy in growth and development, then have a single and distinct period of reproduction, after they die. Iteroparous species: Repeated reproductive periods, they can be discrete or merge into a single period.
Basic Reproduction NumberR0 = Σ lxmx = ΣFx/a0
Passive dispersalMost plants, Non-exploratory, most seeds fall near parents, long range dispersal mechanisms: Wind, water etc
Active dispersalMobile animals. Maybe aided by passive means of transport. Range of factors can stimulate it: Crowding, food availability, temp
MigrationMass directional movement of animals from one location to another and back again (a return trip). Affect pop dynamics. Daily or seasonal migration.
What is competitionIs an interaction between individuals , brought out by a shared requirement for a resource. It leads to a reduction in a survivorship, growth and reproduction.
Population Biology: Concept 1Reproductive Rate R0 = Ng/ N0 N0= population time at0 Ng= population in the next generation
Population Biology: Concept 2Net reproduction rate RN= Nt/ N0 Nt= pop at the end of a time interval. When R0=RN, the time interval equals one gen. Pop growth when RN>1
Intraspecific comp.Results in an S-shaped pop curve
Pop growth in an unlimited env.dN/dt = rN dN= change in pop size dt= over time r= rate of change per individual (a constant) N= # of individuals
Carrying capacity KAvailability of resources (food, space, water) will limit population growth. The carrying capacity (K) is the maximum population size that can be supported by its habitat.
Scope for population growthK – N can be expressed as a proportion: (K-N)/K
Population growth in a limited environmentdN/dt = rN (K-N)/K
Logistic growth (model)As the population grows, density dependent changes in birth and death rates take effect, so dN / dt becomes zero. The curve is only an approximate for change of physical env, effects of predators, stochastic nature of birth/death rates.
Interference vs exploitation comp.Interference: individuals Interact directly, comp intensity may be high Exploitation: Do not interact directly, one individual is affected by the amount of resource that remains, comp intensity is linked to food availability.
The importance of density dependenceMany populations are at their carrying capacity. Competition depresses the growth and reproduction of individuals; it also increases mortality. A density dependent process
2 types of intraspecific comp.Scramble: Growth and reproduction are depressed equally across individuals as comp increases. Contest: Individuals deny their resources to others to share.
r and k speciesr: colonise disturbed land, poor comp. have strategies to exploit short lived and changeable envs, rapid growth and fast dispersal. k: low reproductive rate, good comp. Dominate in stable env, large and competitive species with slow pop. growth.
Different types of ecological interactions between 2 speciesPredation: One party benefits, the other incurs fitness costs Competition: Both parties suffer fitness cost Amensalism: One suffers and the other neither loses or wins Commensalism: One gains, the other neither loses or wins Mutualism: Both parties benefit
Interspecific competitionCompetition between individuals of different species for a shared, limited resource. Individuals undergo a reduction in fecundity, growth or survivorship as a result of interference or resource exploitation. Minus-minus interaction
AllelopathyA mechanism for interference competition seen in plants and microbes. Secondary metabolites that affect growth, survivorship and fecundity. -ve allelopathy is important for interference comp: Plant compounds released into the soil inhibit growth of competitors.
Principles 1: Competition and asymmetry,1: Competition and asymmetry: Interspecific competition is often asymmetric, This can lead to 1 species excluding another through competition 2: Environmental conditions influence competitive ability 3: Competing species co-exist
Principle 2: Environmental conditions influence competitive abilityA mathematical model of interspecific competition. Expressions to describe the relationship between 2 species using the same resource.
Competitive exclusion principleIf 2 competing species coexist in a stable environment, they do so as a result of niche differentiation. If there is no differentiation, or it is precluded by the habitat, one species will exclude the other. Competitive exclusion occurs when the realized niche of the superior competitor completely fills the fundamental niche of the inferior competitor.
Invasive speciesNon native species accidentally or deliberately introduced to an area outside of its natural range, which establishes and spreads and causes economic, environmental / ecological damage. Reasons: The displace native species, damaging effects through predation and transmit pathogens. Native species do not have time to adapt.
PredationHerbivores, Carnivores and Omnivores. Predators are agents of mortality, with potential to regulate prey populations.
True predatorsInvariably kill their prey by immediate attack, and consume several prey in their lifetime.
Methods of obtaining foodAmbush, Stalking and Pursuit
GrazersConsume only part of each prey item. Do not usually kill prey, especially in short term. Attack several or many prey in their lifetime
ParasitesConsume only part of each prey item. Do not usually kill prey, especially in short term. Attack one or very few prey items; form intimate association with their prey.
Predations affects:Individuals: have high fitness cost on prey Populations: regulate population of both predator and pop Communities: som affect structure of communities
Lotka-Volterra prey equationdN/dt=rN-aPN a= search and attack efficiency P= # of predators N= # of prey
Lotka-Volterra predator equationdP/dt=faPN-qP P=# pf predators N=# of prey f= predator efficiency at converting food to offspring a= search and attack efficiency q= predator mortality rate aPN= rate of food consumption
L-V model predicts mutual population regulation and assumptionsPrey increase when predator abundance is low, but decrease when it is high. The converse is true for predators. This density dependence is not direct but rather time-delayed Predators have a max. feeding rate but model assumes not max. Predator-prey pops do not exist as isolated pairs Interaction influenced by env.
Ecological concepts: 1. Predator Functional ResponsesLooks at effects on prey consumption of : predator satiation and ability to detect prey. It describes the relationship between the per capita rate of prey consumption and the number or density of prey. 3 Basic Patterns: Type I. - The rate of consumption per predator is proportional to prey density (no saltation), passive predator. Type II. - The rate of prey consumed per predator increases rapidly, then plateaus with increasing prey density, most common. Type III. - S shaped curve: predator response to prey is depressed at low prey density.
Ecological Concepts: 2. Foraging for prey involves decisions about allocation of time and energy. "Optimal foraging Theory"All prey do not offer the same energy. Predators must weight up the cost. Profitability: energy content-cost to acquire/time taken to acquire
Five Desicions1. Choosing between habitats. 2. Potential energy intake & need to avoid predators. 3. How long to stay in a feeding patch? 4. Effects of competing predators in the same habitat. 5. What’s the optimal diet.
Other Ecological Concepts3. Predators influence prey through nonlethal and lethal effects 4. Physical conditions mediate predation 5. Infection can make hosts more susceptible to predation 6.Predator-prey interactions: a major evolutionary force: Predator-prey interaction is dynamic, Predators evolve efficient tactics for acquiring prey, prey evolve wide variety of methods of defence. 7. Predator prey populations don’t exist as isolated pairs