Question

5. Due to changes in river direction after erosion, a wooded area has become significantly drier. Before the river changed direction, a small understory plant, Biologus twohundredica, grew to an average height of 7.12 cm. Afterthe river shifted, many Biologus t wohundredica plants perished. The victims had an average height of 9.12 cm. The survivors had an average height of 4.12 cm. a. What is the selection differential for this population? b. Write an example of a selection differential for a less intense selective event on the same trait

Answer 1

Answer .(1)

This is the effect of rechannelisation of river in riparian zone.

Earlier riparian vegetations were well adapted to environmental conditions . Plants which were having tall character were most affected . Short height plants were able to adjust to rechennalisation of river. The re channelisation of river created dried conditions leading to reduction in ground water levels , increased herbivory by cattle like animals and less sediment deposition that cost plants heavily . So short height plants with average value of 4.12 cm were having survival advantages over other types of plants . Small height plants are allowing more light absorption in crowded conditions .

Ans .2 Another similar example can be seen in North America where Willow plant (smilax ) height is affected due to rechannelisation of some rivers . These rivers were rechannelised to avoid flooding .