187 research outputs found
A papĂr- Ă©s a szĂĄmĂtĂłgĂ©p alapĂș tesztelĂ©s összehasonlĂtĂł vizsgĂĄlata kĂŒlönbözĆ ite paramĂ©terek mentĂ©
A mérés-értékelés IKT eszközökkel való tåmogatåsa képes lehet a
folyamat teljes Ă©s valĂłdi megreformĂĄlĂĄsĂĄra. A felelĆssĂ©gteljes
åttéréshez azonban pontos informåciókkal kell rendelkezni arról,
hogy a médium megvåltoztatås, hogyan befolyåsolja az
eredmĂ©nyeket. Ez egyrĂ©szt indokolt a korĂĄbbi papĂ alapĂș
eredmĂ©nyekkel valĂł összehasonlĂtĂĄs vĂ©gett, mĂĄsrĂ©szrĆl nem lehetnek
håtrånyosan érintett tanulói körök (Molnår, 2010; Lent, 2009). Jelen
tanulmĂĄny az itemek kĂŒlönbözĆ paramĂ©tereinek szempontjĂĄbĂłl
vizsgĂĄlja a mĂ©dia befolyĂĄsolĂł erejĂ©t a matematika mƱveltsĂ©gterĂŒleten
elsĆtĆl hatodik osztĂĄlyig
Population dynamics of epiphytic orchids in a metapopulation context
Background and Aims Populations of many epiphytes show a patchy distribution where clusters of plants growing on individual trees are spatially separated and may thus function as metapopulations. Seed dispersal is necessary to (re)colonize unoccupied habitats, and to transfer seeds from high- to low-competition patches. Increasing dispersal distances, however, reduces local fecundity and the probability that seeds will find a safe site outside the original patch. Thus, there is a conflict between seed survival and colonization.
Methods Populations of three epiphytic orchids were monitored over three years in a Mexican humid montane forest and analysed with spatially averaged and with spatially explicit matrix metapopulation models. In the latter, population dynamics at the scale of the subpopulations (epiphytes on individual host trees) are based on detailed stage-structured observations of transition probabilities and trees are connected by a dispersal function.
Key Results Population growth rates differed among trees and years. While ignoring these differences, and averaging the population matrices over trees, yields negative population growth, metapopulation models predict stable or growing populations because the trees that support growing subpopulations determine the growth of the metapopulation. Stochastic models which account for the differences among years differed only marginally from deterministic models. Population growth rates were significantly lower, and extinctions of local patches more frequent in models where higher dispersal results in reduced local fecundity compared with hypothetical models where this is not the case. The difference between the two models increased with increasing mean dispersal distance. Though recolonization events increased with dispersal distance, this could not compensate the losses due to reduced local fecundity.
Conclusions For epiphytes, metapopulation models are useful to capture processes beyond the level of the single host tree, but local processes are equally important to understand epiphyte population dynamics
Az online projektmunka Ă©s megvalĂłsĂtĂĄsĂĄnak eszközei - Az oktatĂĄsi cĂ©lĂș közössĂ©gi hĂĄlĂłzatok hasznĂĄlatĂĄnak praktikus kĂ©rdĂ©sei
A tanulmĂĄny fĂłkuszĂĄban a projektmĂłdszer oktatĂĄsi terĂŒleten valĂł felhasznĂĄlĂĄsa ĂĄll. Ez a mĂłdszer a tanulĂĄs tanulĂĄsĂĄra nevel egy olyan problĂ©mamegoldĂł algoritmus elsajĂĄtĂtĂĄsĂĄval, ahol a konkrĂ©t cĂ©l elĂ©rĂ©se mĂĄsodlagos szerepet tölt be. A mĂłdszer hatĂ©konysĂĄgĂĄt növeli az IKT-, illetve online eszközök bevonĂĄsa. A cikkben ilyen mĂłdszerek Ă©s lehetĆsĂ©gek szisztematikus ĂĄttekintĂ©sĂ©t olvashatjuk
A papĂr- Ă©s a szĂĄmĂtĂłgĂ©p alapĂș tesztelĂ©s összehasonlĂtĂł vizsgĂĄlata kĂŒlönbözĆ item paramĂ©terek mentĂ©n
A mérés-értékelés IKT eszközökkel való tåmogatåsa képes lehet a
folyamat teljes Ă©s valĂłdi megreformĂĄlĂĄsĂĄra. A felelĆssĂ©gteljes
åttéréshez azonban pontos informåciókkal kell rendelkezni arról,
hogy a médium megvåltoztatås, hogyan befolyåsolja az
eredmĂ©nyeket. Ez egyrĂ©szt indokolt a korĂĄbbi papĂ alapĂș
eredmĂ©nyekkel valĂł összehasonlĂtĂĄs vĂ©gett, mĂĄsrĂ©szrĆl nem lehetnek
håtrånyosan érintett tanulói körök (Molnår, 2010; Lent, 2009). Jelen
tanulmĂĄny az itemek kĂŒlönbözĆ paramĂ©tereinek szempontjĂĄbĂłl
vizsgĂĄlja a mĂ©dia befolyĂĄsolĂł erejĂ©t a matematika mƱveltsĂ©gterĂŒleten
elsĆtĆl hatodik osztĂĄlyig
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