Question to Think About
Some birds have a behavior known as "helping at the nest". A female bird will sometimes help another bird rear offspring rather than laying her own eggs and raising them. There are two different hypothese to explain this behavior. First, this may be an example of an altruistic behavior that can be explained by kin selection. Alternatively, this may be an example of a purely selfish behavior. It is possible that young inexperienced birds are not very good at raising offspring the first time they try and by helping another bird to raise offspring they may get practice that makes them better at rearing offspring later on.
1) Explain how you as a scientist would conduct a study to distinguish between these two alternative hypothese.
2) Should a female bird who is capable of raising three offspring on her own help her sister to raise her sister's offspring if helping her sister allows her sister to raise five more offspring? Be sure that you would be able to explain to someone else how you determined your answer.
If you post your answers to the blog then I will be able to take a look at them and you can also get some feedback from fellow students.
Old Exam Questions
Here are some examples of old exam questions dealing with altruism. See if you can figure out the correct answers (answers provided at the bottom of this post).
Researchers studying black-tailed prairie dogs conducted an experiment where they dragged a stuffed badger (a predator of prairie dogs) across the colony. They repeated the experiment 698 times over the course of 3 years. The researchers observed that individuals with no offspring in the colony gave a warning call 19% of the time whereas individuals with offspring in the colony called almost 50% of the time. Which of the following could explain why individuals with no offspring would ever call?
(a) group selection
(b) other squirrels will return the favor in the future
(c) they have other relatives in the colony
(d) a and b
(e) a, b, or c would explain this observation
Which of the following are examples of an altruistic trait?
(a) an African wild dog sharing food with other members of the group
(b) a female choosing to mate with a symmetric male
(c) a sterile worker bee helping her sister (the queen) to reproduce
(d) a and c
(e) neither a, b, or c
Further Reading
Here are links to a couple of articles you might want ot take a look at-
Altruistic behaviors http://www.eoearth.org/article/Altruistic_behaviors
Kin selection http://www.eoearth.org/article/Kin_selection
More advanced reading
One of the problems with introductory courses is that we have to cover so many topics that it is not possible to go into very much detail over any of them. If you are interested in learning more about kin selection and altruism the following article would be good to look at.
Kin selection: fact and fiction. http://westgroup.biology.ed.ac.uk/pdf/Griffin&West_02.pdf
Answers to the test questions: 1) c 2) d
For question #2, I think yes. The female bird would help her sister raise more children. The most important thing they would want to do is pass on genes to close relatives (kin selection). Since she's capable in raising children, having more would ensure that their offspring will survive and have lifetime reproduction success.
ReplyDeleteThen again, one can think that the bird with 3 kids of her own would be selfish and not help her sister. But since their relatives, and more traits would be passed on since there are 5 more offspring, the female bird can be altruistic and raise the additional kids with her sister to pass on genes.
Sorry I have been slow to respond to this comment. I just realized that people were responding on the blog. See the post I am adding.
DeleteThis comment has been removed by the author.
ReplyDeleteI disagree. the trick is to see the birds a vessels for genes to be passed on. The sisters share half of their genes with each other and with their offspring. Therefore, her sisters offspring share 1/4 of there genes with the female X. When the female bird helps her sister offspring we need to think of her as helping to pass on her genes. **note one unit of genes is equivalent to her passing on 100% of her genes.** If each of her sisters offspring is passing on 1/4 her genes then helping her sister raise 5 kids is helping pass on 1.25 units of her genes. If the female raises 3 of her own offspring then she is helping to pass on 1.5 units of her genes. When we compare the two scenarios it is clear by helping raise her own children she is helping to pass on more of her genes.
ReplyDeleteFYI: I used Hamilton's rule
DeleteYes, Hamilton's Rule is the way to go.
DeleteYes, Hamilton's Rule is the way to go.
DeleteYes, we need to use Hamilton's Rule to answer this question. We need to figure out the costs, benefits, and degrees of relatedness.
ReplyDeleteC = 3 babies (the babies she could have made if she reproduced herself)
B = 5 babies (the extra babies her sister produces with her help)
r = 1/2
be altruistic if
5 x 1/2 > 3
because 2.5 is not greater than 3 the animal should be selfish in this case.
Does this make sense?
Yes, we need to use Hamilton's Rule to answer this question. We need to figure out the costs, benefits, and degrees of relatedness.
ReplyDeleteC = 3 babies (the babies she could have made if she reproduced herself)
B = 5 babies (the extra babies her sister produces with her help)
r = 1/2
be altruistic if
5 x 1/2 > 3
because 2.5 is not greater than 3 the animal should be selfish in this case.
Does this make sense?
This comment has been removed by the author.
DeleteYes it makes sense.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteI do not understand why my number are different than yours. I think the benefit is 1.5 because each of the three children has 1/2 their mom's genes. The sister birds offspring only have 1/4 of the moms genes. SO the number i get are 1.5>1.25
ReplyDelete