answer

Brown trout are fish that may migrate, or repeatedly travel between habitats. Brown trout that live in oceans often migrate to lakes or rivers to reproduce. To reach the place where they reproduce, the trout may need to pass through many different areas. Some areas are harder for trout with certain body lengths to pass through. A longer trout may struggle to swim through a shallow stream. A shorter trout a brown trout with its body length shown ay struggle to jump over a large dam or waterfall. If ; the trout cannot pass through these areas, they may be unable to finish migrating. Trout that do not finish migrating are less likely to reproduce. The graph below describes an isolated population of brown trout over a time period long enough for natural selection to occur. The graph shows body length measurements for a representative sample of the population at the start of this period and for another representative sample at the end. At the start of this time period, the brown trout's environment changed. Body length (cm) Sample at Si | i i meme a end 34 38 42 46 50 54 58 62 66 70 74 78 82 86 Describe how the brown trout population changed over this time period. Use the theory of natural selection to construct a possible explanation for this change. The average body length * in the population. This suggests that trout with shorter bodies were * likely to reproduce after the population's environment changed. This may have occurred because the environment changed to have significantly * dams. So trout with shorter bodies were more likely to * migrating