Activity 77: Ups and Downs Challenge How do scientists study the size of a population and predict future population changes?

Activity 77 Vocabulary: Ecologist: a person who studies living things in their environment. Fluctuation: continued change Population: Groups of individuals of a single species that live in the same place Introduced Species: a species living outside of its normal ecosystem

Getting Started Read Intro on E-32 -Disagree Anticipation Guide 1-14 (Before Column) + Agree -Disagree

Discuss in your Tables If you were a scientist interested in a particular species, what would you do to determine whether the species is successful in its environment? What kinds of observations would you make? What kind of data would you collect? Lets Read the Introduction on page 32!

In this activity… You are going to examine real data from lakes in northern Poland where zebra mussels have been found for over 150 years.

Doing the Activity- Part A Use SS77.1 “Ups and Downs” to create your graphs. Seats 1 & 3 graph 1959 to 1969 (Table 1) Seats 2 & 4 graph 1970-1979 (Table 2) Follow the procedure steps for Part A (Make sure to answer the questions on your SS 77.1) After Part A, please answer Analysis Question #1 in your notebooks.

Doing the Activity – Part B Follow Steps 5-8 and answer the questions in your notebooks. What overall trend do you see in the zebra mussel population between 1959 and 1979? Increase? Decrease? Same? Why?? Explain your thinking! **Mention specific years and population numbers in your analysis.

Part B In your journals… What overall trend do you see in the zebra mussel population between 1959 and 1979? Increase? Decrease? Same? Why?? Explain your thinking! **Mention specific years and population numbers in your analysis. When you are done answer analysis #2, 3, 5 and 6

Follow-Up How do ecologists know that they have sufficient data for a population over time?? In what ways might being able to predict future size of a population be useful??

Analysis #1 Answer A) It is impossible to judge whether this population has permanently increased or is merely fluctuating, and whether or not it will stay high or continue to fluctuate. The key point  predicting the future for this population remains guesswork, despite almost 20 years of data.

1b) Fluctuation similar to the one that occurred between 1959 and 1976 OR, the population could remain at a higher level, since the population remained steady from 1960-68. A complete die-out is unlikely, since the population has remained low, but constant for the last several years. On the other hand, a small population may be vulnerable to sudden environmental changes, which could occur at any time.

1c.)Additional information that could be helpful: Population data from the years before 1959 or after 1976 to see long term patterns The cause of the population crash between 1959-1960 Long term meteorological or water quality data Population data Key predator/prey species

2a) Factors that affect population size: Competition for resources Predation Changes in prey or plant food availability Temperature changes Increase/decrease in pH or rain and bodies of water Changes in wind and precipitation levels Human induced pollution 2b. Discuss how these changes could affect population size.

3. Practical factors that could interfere with the collection of this data: Expense of field study Availability of study site Weather Transportation Political boundaries, war, etc. Personal reasons of scientists running studies Unlike laboratory experiments, ecological data can not be re-created or collected at a later date. A well designed experiment would attempt to reduce variables and make the conclusions drawn from the data more reliable and valid. Collecting more data, especially in regular intervals such as a year, increases the quality of experimental conclusions.

5.) The additional data supports the hypothesis that the population will increase again and crash again repeatedly.

6.) a.) The number of zebra mussels in some parts of Lake Erie is 35 times as high as those described for the lakes in Poland b.) Graphs should start at 0 and go up, rapidly and perhaps exponentially.