Biology 570
Discussion Questions

Birch, LC. 1948.  The intrinsic rate of natural increase of an insect population.  Journal of Animal Ecology 17: 15-26. 


 



Write short answers to each of these questions, using information gleaned from the paper.  Bring typed answers to class and be prepared to talk about them in groups of 10.
 

  1. What kind of organism was Birch studying?  What sort of life cycle does it have?

  2. What information did Birch need in order to calculate the net reproductive rate R0?

  3. Which entries in the life table (Table 1) did he actually measure and which entries did he estimate from published data on another species?  What are the 4 columns in the table?

  4. From the bibliography references, what was the type of organism used in the estimate of the missing life table data, and how different was it from the animal Birch was studying?

  5. Does the estimate of R0 seem reasonable?  Are organisms in nature likely to grow this fast?  Think about what Birch says on p 17 in relation to this.

  6. On p 19 Birch goes through all kinds of contortions to calculate Se-rx lx mx = 1.  Specifically, he multiplies both sides of this equation by e7 or approximately 1100.  Why did he do this, and would there be any reason to do so if you were using your calcuator to do this analysis?

  7. What is table 2 about?

  8. Birch argues on p 20 that adult survival is not very important to his estimates of r.  What if he were off by a factor of 10 in some of his estimates of lx, say l 4.5 were 0.087  or l 14.5 were 0.045 ?  Do you think that either one would make a difference?

  9. In section 6, Birch shows the results of some experimental manipulations of rice weevil populations.  What were the experimental treatments?  How did they differ from the conditions described for Table 1?

  10. Compare the lx and mx values in Tables 1 and 5. What similarities and differences are there?

  11. What is Birch trying to say with Table 6?