Download Parental Care Model: r-Selected and k

Parental Care Model: r-Selected and k-selected species
APES
Purpose/Problem:
Organisms have different life strategies in the natural world. Scientists spend much of their time and money conducting research on
the various aspects of these strategies. One such strategy is parental care. While some organisms have a few young and care for
these young, other organisms have many young and do not care for those young. Differences will occur in these populations relating
to energy parents expend (taking care of young vs. having more young), survival of young (parents there to protect vs. young on their
own), and the overall population dynamics (many young introduced at one time vs. a few young introduced at one time). A model of
these two different parental care strategies can be developed using bubbles.
Materials:
Bubble wand
Bubble solution
Stopwatch
Pen/Pencil for collecting data
Procedure:
Each group of students (3) has a time period in which to blow bubbles with no parental care. This is done by one person blowing a
bubble, one person timing until the bubble pops and one person recording the data. The individual recording the data is also to pick
the bubble to time and watch that bubble (usually more than one bubble is blown at a time and it is important to randomly pick a bubble
as it’s blown – DO NOT wait to see which bubble lasts the longest!!). Bubbles are left to “survive on their own”. They are timed until
they pop or can not be seen any longer (out of bounds, too high, etc). A second time period is then given to students in which bubbles
are blown and given parental care. The group is now responsible for assisting the bubbles in staying “alive”. This is done by wafting
the bubbles in the air by hands or blowing. These bubbles are also timed until they pop or cannot be seen any longer. Bubbles from
either group are still “alive” if on the ground or a surface but still not popped. Bubbles may not be placed back on the wand.
Data:
Trial
Time (s) Random Bubble
Survived without care
Time (s) Chosen Bubble Survived
with care
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Analysis Questions:
1) Create a T-chart comparing the differences between r and k selected species.
2) Give 2 examples of each and explain why you chose those examples.
3) Graph the data (number survived vs. time). Graph both sets of data to make a double line graph. Remember axes.
4) Were your bubbles with parental care r or k selected?
5) Explain why endangered species are more likely to be k selected species.
6) Given current environmental conditions, if you had a choice would you rather be an r-strategist or a K-strategist?
Explain your answer. What implications does your decision have for your current lifestyle?
Analyze the survivorship graph and explain which organisms, according to THIS graph, are r selected and/or k selected.
7) What does parental care have to do with these curves?
8) Which curve would be typical of an organism that experiences
high predation as small individuals but when they are adults are
more able to avoid most predators?
9) Are large mammals type I, II or III on the survivorship curve
graph?
10) Which type of survivorship curve reflects a large loss of young?