Zadanie 1j, Paper 2, maj 2024, TZ1, Biologia IB HL

A hypothetical grassland investigation examines how herbivorous field mice affect runner grasses and tall tussock grasses. The mice normally obtain food from one of the grass types. Replicated plots were monitored with mice present or excluded. The first dataset gives mean biomass from 2006 to 2010. Error bars throughout show standard deviations.

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A later experiment measured change in the volume occupied by one tussock-grass species over two growing seasons.

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Predatory birds that hunt small rodents from vegetation visited the later study but were absent during the first experiment. Fifteen plots were surveyed for vegetation cover and bird visits.

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In another month-long experiment, predators had access to all plots. Researchers measured changes in tussock-grass root biomass and plant volume with and without mice.

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Finally, plots contained three levels of tussock-grass cover as well as the plants normally eaten by the mice. Birds could visit freely. Feeding frequency and mouse mortality were recorded over three weeks.

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