Mount St. Helens is an active volcano located in the Cascade Range in southern W

Question

Mount St. Helens is an active volcano located in the Cascade Range in southern Washington, USA. In the morming of in 1980, volcano A experienced an earthquake which triggered a massive eruption. The eruption was the deadliest and most destructive volcanic event the history A in of the USA with magma and debris from the volcano covering vegetation, roads and building within an area of over 600km For ecologists, St Helens presented a unique opportunity to study animal and plant re-colonization of areas affected by the eruption. To study re-colonization of areas where vegetation had been completely covered by volcanic debris, ecologists studied the change in population density of lupine over fime. The population growth rate (low, medium and high) was calculated and plotted as a function of plant density in a particular area (see the following figure). Density plants/m) Which one of the five graphs aabeled would ustrate the same data points, but with population size number of in plotted as a A-E)below function

Explanation / Answer

Answer : D

In the graph, density vs population growth rate, at the initial stage plant density is low when growth rate is high and when plant density is high, growth rate has decreased. When density is high it means that there is no further space for new plant to grow so growth rate decreased. But it maintained that plant density that there is no decrease or increase and it is stable.

In the graph D, at the initial stage (time) population size is less but as time increased the population size gradually increased and becomes stable or constant

High growth rate = initial stage (time) = less density

Low growth rate = at some point of time = more density = no further space to occupy

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