Practice Population Problems

Closed population - define:

1. A bacterial culture has an intrinsic rate of increase (r_c) of 12%/hour.  A  microbiologist has estimated the population to be 1,957,039 in a petri dish. How many bacteria will there be in the next hour?  How long will it take for the culture to double in size (note that the units are in hours, not years)?

2. A forest ecologist is monitoring the tree population in a small woodlot.  He has determined that the current population of trees is 1285.  He also know that for every 100 trees, an average of twenty-six seeds survive to becoming a tree in ten years.  He also knows that for every 100 trees, 5 will die in ten years.  What would be the projection for the number of trees in the woodlot in 10 years?  in 20 years?

Open population - define:

3. The resource biologist at Chincoteague National Wildlife Refuge wants to calculate how many horses from the Virginia side of Assateague Island should be rounded up  at the Volunteer Fire Department Horse Auction in July.  The current population is 112.  On average, each year 25 horses are born into the population and 8 die.  An average of 2 horses break through the fence  and immigrate from the Maryland  side.  How many horses should be removed from the population (emigration) to keep it stable?

4. The population of mice in a prairie is estimated to be 476 in 2002.  In an average year, 46 mice are born per 100 mice, 53 die per 100, 17 per 100 move into the the prairie from the adjacent habitat and 12 per 100 move out.  What is the intrinsic rate of growth (r_c), what is the annual population growth (r_o), and what is the net migration rate? Is this population growing, stable or declining?

Also, look at the population pyramids for these countries at:

http://www.census.gov/ipc/www/idbsum.html

and describe them as expanding, stable, diminishing, or transitional or maybe they just defy description.    Good luck!

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Last revised: Wednesday, 11 April 2007