Simutext Flashcards
Geometric growth assumes
- unlimited resources and low predation
- one reproductive event per time step
- species can undergo geometric growth but not for long
Geometric growth model applies to…
- populations that are not limited by their growth
- to organisms that reproduce once a year like annual plants, some fish, ungulates (caribou, elk, etc) so that all individuals are added to pop at once
- short term population projections even with finite resources
Where did soybean aphids come from
China, and we don’t know how
parthenogenetically
Ability to reproduce without fertilization. Females can essentially clone themselves. This method of reproduction can be a means to rapidly increase population size or take advantage of stable conditions.
Soybean Aphids
- some can fly and disperse to other crops
- some stay on same plant whole life
- aphid population can go up to 15 generations in one summer
Exponential growth equation
- used for species where generations overlap
- can model species growth for a short period of time
Larger species tend to have…
populations that grow more slowly because larger organisms take more time to accumulate resources in order to grow and reproduce.
Species that can grow exponentially
pests, exotics, pioneers, and humans
Examples of logistic growth
Paramecium (Gause), sheep on Tasmania
Proportional impact of disease is lower at…
lower populations sizes
Density independent factors
have same impact on both small and large populations
Ex. roadkill, storms, fires, floods
Density dependent factors
food, space, light, predation, disease, parasitism
ex. song sparrows will have reduced birth rates and increased death when populations are overcrowded because they spend too much time protecting territories
How does the value of P affect the overall rate at which patches go extinct in a metapopulations?
When P is high (most patches occupied) there will be a high extinction rate because there are many patches total that have the potential to go extinct.
Patch occupancy is highest when…
Patches are larger (lower extinction rate) and closer together (higher colonization rate)
Classic metapopulation as defined by Levins
Each patch is identical and all patches continually go through rounds of extinction and recolonization (non-threatened species like marbled salamander and Glanville butterfly)
How do roads decrease metapopulation survival
cutting off dispersal
Extinction risk occurs when
populations become small and/or isolated because by chance many aphids die at once and in small pops this can cause extinction
Why are the effects of demographic stochasticity more apparent in small populations?
If, for example, randomly there is a spike in births or deaths in a population, it leads to unexpected growth/decline. It is unlikely for coincidences to happen in large populations.
Allee effects
Problematic for social animals at low density, but also for finding mate, and pollen dispersal if flowers are too far apart.
Butterfly effect
Lack of long-term predictability (deterministic chaos) relates to sensitivity to initial conditions; small changes to initial conditions amplify in the long run
Deterministic chaos is common with
small, unmanaged populations with super high growth rates but can occur even when environmental and demographic conditions do not change.
Most common source of variability in real world?
Damped oscillations; population initially overshoots K, falls under dramatically but with time the amplitudes of the oscillations diminish. Famous ex. Lemmings.
Parameters c and e pertain to… but affect…
individual patches
the dynamics of overall colonization and extinction
