Owl's life lab

Páginas: 6 (1410 palabras) Publicado: 9 de abril de 2011
Carlota Valencia
Professor: Earnshaw
BSC1005L
March, 05 2011

Owl's Life Lab

7. Click 4 times on the STEP button to advance the model by 4 weeks. Each week,
your assistant will catch and mark any adult owls that are caught in the net. At
the end of the 4 weeks, the nets will disappear and a box will appear telling you
how many owls were captured and marked. In the space below, recordthe
number of adult owls that are captured and marked. [Note that some of
marked owls may die before the end of the four weeks, so make sure to use the
number reported in the dialog box, rather than counting them on the screen.]

Number of marked adults: 64

9. To find the number of marked adults that remain at the end of the year, look at
the "Number of marked adults" item in the MarkerStatistics panel. This is the
number of adults you marked that survived. Record this number in the space
below. [Note that you should read the number from the Statistics panel rather
than counting the marked birds on the screen – some marked birds on the screen
may be hidden when you stop the model.]

Number of marked adults that survived: 56

10. To determine the annual survival rate foradults, divide the number of survivors by the number of owls that were marked. Record this adult survival rate in the space below, showing your calculations.

Rate: 56/64=87.5%

12. To sample the new patch of forest that appears, repeat steps 5 - 10. For the purpose of this lab, you can combine together your counts from both patches to get an average survival rate across the two patches.Record your data, calculations, and the resulting average adult survival rate from your samples in the space below.
Number of marked adults: 49
Number of marked adults that survive: 42

Rate of survive: 42/49=85.7%

13. Using the adult survival rate you just estimated, you can begin to make some important calculations. For example, let’s say you started with 1000 adult =spottedowls, but for some reason none of them could reproduce. How long would it take for the population to be reduced to half of its original size? Start by calculating the number of adult birds in year 1, using the annual survival rate you determined in the last step.

Adults in year 1 = Adults in year 0 x annual adult survival rate
Adults in year 1 = 49 x 85.7%=42


14. Complete thefollowing table to determine how long it would take for the population to be reduced to half of its original size. [Hint: your answer to the last question is the first entry in the table (i.e. Year 1 - Number of Adults) and the starting point for the next calculation.]

Year Number of Adults
1 49
2 42
3 35
4 31
5 27
6 23
7 208 17
9 14
15. Based on the values you recorded in the above table, how many years would it take for the population to be reduced to half of its original size?
It will take 9 years
17. Follow steps 5 - 12 to find the annual survival rate for the sub-adult owls. Note that the tags remain with the birds as they mature from sub-adults to adults, so if tagged birds disappear, itmeans they did not survive. Record -
Number of sub-adults that you marked: 20
Number of marked sub-adults that survived for one year: 17
Survival rate for sub-adults: 17/20=85%

18. The three numbers needed to calculate expected population growth rates are (1) the annual survival rate for adults; (2) the annual survival rate for sub-adults; and (3) the birth rate. You have already estimated thefirst two rates. The birth rate in this example is how many sub-adults are produced and survive per adult each year. You have not measured a birth rate yet, so you for now you must use a guess for what it might be. As a guess, say that the birth rate is 0.1, so that on average, one sub-adult is produced each year for every 10 adults. Summarize the 3 rates below:
Annual adult survival rate:...
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