152 NATURAL SELECTION 



[Born at Shrewsbury in 1809; educated at Edinburgh and 

 Cambridge ; naturalist on board the Beagle (1831-6) ; published 

 his greatest work, The Origin of Species, in 1859 ; died 1882.] 



EXERCISES 



1. Mention some ' changing conditions of life '. 



2. Illustrate the ' struggle for life * in the case of wrens, 

 rabbits, &c. Explain ' geometrical rate of increase 1 as exem- 

 plified in wild animals with which you are acquainted. Mention 

 all the causes you can think of as likely to shorten the life of 

 a sparrow, or a deer, or a trout, &c. 



3. How may the increase of voles, constituting a plague, be 

 accounted for ? What might be the effect of shooting all the 

 owls and hawks in a district upon other organic life, and upon 

 human welfare or comfort ? What is meant by the ' balance of 

 nature ' ? 



4. May there be variations in the structure or habits of wild 

 animals that are not ' useful ' to them ? How might they arise ? 

 What would be their ultimate effect? How is it that some 

 species of animals are now extinct ? 



5. How has domesticity interfered with natural selection ? Is 

 it always true that only the fittest survive ? Is the strongest the 

 fittest ? What more than strength is required to render an 

 animal 'fit'? 



EXPLANATION OF SOME BOTANICAL 

 TERMS 



anther, the top of a stamen: it contains pollen. 

 axil, the angle between a leaf and the stem. 

 bract, a small leaf or scale at the base of a flower stem. 

 caducous, falling off" early. 



calyx, cup or outer case of a flower : its parts are sepals. 

 corolla, the inner part of a flower, next the calyx, usually 

 brightly coloured : its parts are petals. 



