Population Growth Activity: A Simulated Tide pool

There is a page in your lab manual in Lab 2 that represents a 100 square meter intertidal area (tidepool) – use this diagram for this activity. This page simulates the habitat for a variety of marine plants and animals, among them various algae and sea urchins. The date is December 31. Answer the following questions about the algae and urchin populations. You will need to print out the page in order to answer the following questions for your lab report.

1.What is the density of the algae? (Count each of the algae symbols, placing a small check next to one that you have counted or alternatively you could write a number so that you don’t double count). Record your density of algae number here: ______

2.What pattern best describes the dispersion of algae? What factors in the environment might cause this pattern?

3.The sea urchin population consists of adults (some of which died during the year) and young (which have been born during the year).

  1. What is the total size of the adult sea urchin population (live animals only)? ______
  1. What is the density of the entire population (including young urchins too)? ______

Note: Density implies that area has been taken into account (m2). Reduce to lowest common denominator.

4.At the beginning of the year (January 1) the urchin population consists of all the adult urchins plus those that died during the year. What was the size of the population at the beginning of the year? This does not require area.

5.What is the sea urchin death rate (D)? This is the number of dead urchins divided by the total alive at Jan 1. Recall that death rate is a percentage.

d = ______

6.Using the population size total from question 4 (for your denominator), determine the birth rate (B) for the sea urchin population. Recall that birth rate is a percentage.

b = ______

7.What is the annual growth rate (R) for the sea urchin population? ______

8.At the current rate of growth, how many sea urchins will there be in this 100 square meter area in five years? Do you think this likely? Why?

Hint: G = (r) x (Number of individuals in year)

Use this calculation 5 times, assuming the same r found in #7

and you will need to adjust for a new total number in the entire

population for each interval.

Record your G for year 5 here: ______

Evaluate: Is this number realistic for an area of 100 m2? ______

Keep in mind that an urchin is about the size of a baseball.