EXERCISE 90 



HOW KAPIDLY MAY PLANTS AND ANIMALS INCKEASE UNDER ENTIRELY 



FAVORABLE CONDITIONS? 



Materials. Ears of corn ; heads of wheat or oats ; seed pods of any common plants ; data 

 regarding number of eggs laid by a robin and a toad. 



Directions. Determine how rapidly given plants or animals would increase in given lengths of 

 time, if all seeds should grow each year in case of plants or if all the young of animals should 

 mature. 



It is suggested that each pupil perform but one or two of the determinations given below, and 

 that the results of all determinations be made available to the entire class. 



a. Indian corn. Count the rows and number of grains in a row on one ear. Estimate the 

 number of grains on the ear. Calculate the descendants in the fifth generation. 



b. Wheat. Ascertain the number of grains in a head and suppose that there are five heads to 

 each plant. Calculate the number of grains in the fifth generation. 



c. Robin. Assuming that a female robin will lay four eggs and that one half of the new birds 

 will be females, calculate the number of robins at the end of ten years if all eggs hatch and no 

 birds die. 



d. Toad. A female toad may lay as many as 11,000 eggs. Assuming 8000 as a fair average 

 and that one half the young toads will be females, calculate the number of toads from a sirtgle 

 pair at the end of four generations if all the eggs hatch and no toads die. 



Additional problems. Assuming that an average toad will weigh a quarter of a pound, what would 

 be the weight of the four generations of toads according to the above estimate? 



Why do not plants or animals really increase as rapidly as indicated by the above calculations ? 



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