Exam 2 Flashcards
11/4/24
Population
Group of individuals of the same species who live in the same area at the same time.
Population Ecology
The study of how and why a population changes over time.
Population Density
Number of individuals of a species per unit at a given time.
Population Dispersion
Spacing of a populations (Can be clumped, random, or uniform.
Niche
Organism’s place in the environment defined by physiological tolerances and resource requirments.
Two ways predator structure communities
Keystone predators
Trophic cascades
Time lags
Delays in the responses to births and deaths to an environmental change produce population cycles
Realized niche
Constrained by biological interactions among species
Three types of species interactions
Competitive, consumptive, mimicry
Competition
use of or defense of a resource by one individual that causes a reduction in that resource availability to another.
Competitive Exclusion
Two or more species with the same niche cannot coexist.
Intraspecific competition reduces resources in…
A density dependent manner; underlies the regulation of population size.
Interspecific population decreases…
The pop. of both species; may result in the ending of one species; upper hand goes to more efficient species.
Resource
Substance or factor that is consumed by an organism that supports population growth as it increases in availability.
Liebig’s law of minimum
Each pop. increases until the supply of a resource (limiting) becomes depleted, applies to resources that do not interact to determine population growth rate.
Interference Competition
Organism’s harm each other directly through physical force. Occurs when individuals defend resources in antagonistic behaviors.
Resource Competition
Occurs when individuals defend resources indirectly through mutual effects on the resource.
Allelopathy
Chemical competition, more often than not, plants do this.
Quantifying Competition in Plants vs. Animals
Plants = biomass; animals = numbers.
Plants = no escape from comp; Animals = can move away.
Range of Competitive Effects
Reduce growth + pop., reduce foraging, increase mortality (overgrowth comp), affect species diversity, drive resource partitioning (divergence in patterns of resource use).
Commensalism
An association between two species where only one is benefitted, other is unaffected.
Consumption
An ecological process in which energy flows from one to another.
Why care about predation?
Acts as a way to structure communities (trophic cascade, keystone predators), mechanism for natural selection, control species distribution or density.
Time lag
Delays in births/death rates as a result of environmental change which produces pop. cycles. Reproductive cycles, predator/prey interactions, amount of time to produce offspring.
Lotka-Volterra
Created equations for the isoclines of predator and prey interactions.
Population trajectory
Describes the joint cyclic changes of P and R counterclockwise.
Paradox Enrichment
Increases in food or nutrients destabilizes the system.
Three ways predators respond to prey…
Type 1: Individuals consume more prey as prey increases
Type 2: Predators can become satiated.
Type 3: Feeding is close to logistic curve; low feeding at low prey densities and higher at higher.
2 Types of Predator Response
Functional: Change in the rate of predation by an individual predator (search image, prey switching).
Numerical: Increase in the total number of predators (reproduction, aggregation).
Factors Influencing Stability
Stabilizing: Low predator efficiency, generalist predator, refugia.
Destabilizing: Time lags, highly efficient predator, specialists
Habitat loss
Major loss to habitat, all species affected, timespan for recovery is long.
Habitat degradation
Affects many but not all species, may be temporary.
Habitat Transformation/Conservation
Refers to process of change (natural or intentional)
Coral Reef Degradation
Increased level of CO2; in response, coral reefs will be pushed close to thermal limit, carbonate levels will drop below levels for coral accretion, increased bleaching/mortality/disease
Major causes of Habitat Loss
Agriculture (conversion to crops and livestock), extraction (mining, fisheries, forestry), development
Fragmentation (Habitat Loss)
1) reduction in habitat amount
2) Change in habitat configuration (increase in patches, decrease in patch size, increase in isolation)
Edge habitat impacted by…
Biotic factors -> Resource availability and species interaction.
Abiotic factors -> wind, solar radiation, changes vegetation structure
Edge effects on mammals are typically neutral or positive because…
Taller vegetation at the edge and increased foraging opportunities at the edge.
Can still be negative (ex. bush monkeys becoming hunted more easily with less areas to hide in).
Edge effects on birds
Specifically more negative because birds with nests on the edge are more likely to suffer from brood parasitism which reduces fledgling success.
Ways to access habitat quality
Preference: usage relative to availability; use density or presence/absence.
How Animals access habitat
Habitat imprinting, direct assessment, indirect assessment (presence of conspecifics, performance of conspecifics, cues)
Source
Areas where reproductive success is higher than mortality
Sink
Areas where mortality is higher than reproductive success
Metapopulations
Spatially isolated populations that are linked by the dispersal of individuals; set of local populations within some larger area where migration among patches is possible. Characterized by repeated extinctions and colonizations. Buffered by rescue attempts or recolonization after extinctions.
For persisting as a metapopulation, require these four aspects…
- Suitable habitat occurs in discrete patches that may be occupied by reproducing local populations.
- Even the largest local population is at risk of extinction.
- Habitat patches must not be too isolated.
- Dynamics of local populations must not be synchronized.
4 Types of Metapopulations
Classic, mainland/island, patchy pop., non-equilibrium
Succession
Pattern in temporal change in community composition. Change in species abundance due to extinction and recolonization.
Metapopulation Biology
Considers the size and isolation in patches with a uniform matrix
Matrix includes…
Movement of individuals, occupancy of patches, growth of populations
Corridor
A linear landscape element which serves as a linkage between historically connected habitats and is meant to facilitate movement between the two natural habitats.
Benefits of Corridors
Increases area, increase immigration, aids dispersal, allows range shift due to climate change, escape from fire or predation
Corridor information
data is limited on use and demography and genetic structure, effort and cost might be better used making larger reserves
Corridor hazards
provide avenue for catastrophes, entry route for exotics, may function as sinks, no buffer zone exposes migrants to danger, may facilitate poaching/trapping
Allee Effect
Mechanisms leading to a positive relationship
between fitness and density.
