Which of these following scenarios is caused by the Allee effect? O The chytrid fungus devastates Amphibian populations world-wide. Smaller populations are more likely to be extirpated when the...

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Extracted text: Which of these following scenarios is caused by the Allee effect? O The chytrid fungus devastates Amphibian populations world-wide. Smaller populations are more likely to be extirpated when the pathogen is introduced, because they have less genetic variability and therefore a smaller likelihood to have individuals that are naturally resistant to the fungus. After a big disturbance in forests, such as fire, many seeds germinate and seedlings compete for space, light and resources. K-selected species produce fewer, but larger seeds that are initially outnumbered by the numerous seeds and resulting seedlings of r-selected species. The initial advantage of r-selected species of occupying more locations and therefore by random chance also better locations, is later overcome by the K-selected species' higher competitive ability. Therefore, for the first years to decades, r-selected species dominate areas that experienced severe disturbances, while in mature forests, K-selected species dominate. O The emerald ash borer, a beetle whose larvae live and feed under the bark of ash trees and eventually kill-off the tree by girdling it while feeding, is decimating ash trees. Ash trees occurring in medium to high densities experience particularly high attack rates and are likely to be wiped out completely, while isolated individual ash trees that have no ash neighbors have a higher chance to be missed by the ash borer and survive. Corals rely on external fertilization when gametes (sperm and eggs) are released into the sea in large quantities and have to meet at random chance. When coral densities drop due to coral bleaching and die back, external fertilization becomes inefficient, few zygotes form, and coral populations further decline or go extinct.