Biology Forums - Study Force

A group of children at a birthday party sit around a table covered with pieces of candy. Each
child must gather candy, one piece at a time, as fast as possible. No child is permitted to impede the
access of another child to the remaining candy on the table. When the table has been cleared, the child
with the most pieces of candy is declared the winner. This is an example of:
A. interference competition
B. exploitation competition
C. none of the above

What's the positive and negative benefits for inducible defense and constitutive defense.

Last but not least, does anyone know about the story about the cactus moth and the prickly pear (are native in South America)? My question is what might happen if the cactus moth were inadvertently eliminated from South America?

I would say (B) exploitation competition because the description mentions that:


Which indicates that there is no interference. Interference competition is a form of competition that involves a fight or other active interaction among organisms.

yea, thats what I got. not sure about the other 2 questions

When the cactus moth (Cactoblastis cactorum) was introduced into Australia as a biological control agent for prickly pear cacti, populations of the prickly pear were much reduced, but not eradicated. Today, both the prickly pear and the cactus moth can be found at low levels in Australia.

If the moth were removed, the prickly pear cacti would grow uncontrollably because you eliminate the predation.

thanks howard. I tried searching for this, where did you find it?

I searched my old notes, it was on a review we once had, not sure if it's accurate though.

Then you prob have most of the answers I'm looking for...Are these other questions I asked similar to what's on your review? If so, can I checked my answers with you? I don't have the key to my review study guide.

It was a PDF with questions only, never wrote the answers on the computer :( If I had them, I would've sent them to you already :P

What other questions do you have, I could probably help.

Here are some of the other questions I just want to check. Not sure with the answers....


1) Some plant chemical defenses are inducible; the plant increases its production of toxic or unpalatable substances after being damaged by an herbivore. How does an inducible defense benefit the plant, compared to a constitutive defense that is present at all times?

Inducible defense is less costly. Produced when needed whereas constitutive defense is too costly to maintain when herbivory is light or absent.

Actually, i also wanted to know, what's the negative side of inducible defense and positive side of constitutive defense.

2) Not all species of acacia form mutualistic partnerships with ants. In a setting where herbivore pressure on acacias is low, why might the ant-acacia mutualism not have arisen?

maybe no pressure from herbivore?


3) Ecologists have developed elegant theories, coupled with mathematical models, which enable us to determine when two competitors, or a predator and prey, can coexist. Are these theories and models readily transferred to the community level? Why or why not?

I think yes. does it have something to do with indirect or direction interaction?

4) This question was from the other post I took out of:
The Finnish scientist Cajander observed that, in northern Europe, Scots pine typically occurs on unproductive sites, those that are either wet and acidic or dry and basic. However, under forestry management, this species performs best on productive sites, those that are fertile and have intermediate moisture conditions. Discuss this discrepancy between the observed distribution of Scots pine and its performance in cultivation.

Don't know about 1.

For (2), why would the acacia plant form a mutualistic relationship with ants if there are no herbivores? Why would you need the ants to scare away herbivores if there aren't any. Make sense?

For (3), I would say no because there are many factors in a large community, too many interacting populations to keep track of - keep in mind that abiotic factors can vary dramatically depending on the climate or weather conditions.