Vertebrate Biology

[ckstubbs]

Back in school after more than 10 years to finish a BSc in Biology. I am lost, and trying to recover, recoup what I was taught. I need help with the follwing experiment question

 

Design an experiment to determine the relationship of water properties & fish abundance (global).

Come up with a

- hypothesis

- 3-5 predictions and

- propose a way to come up with a collection of data.

 

Water properties I looked at

1. salinity

2. oxygen content

3. temperature

*(possibly) 4. pH

 

Proposed Hypothesis: The temperature will affect the salinity of the water and thus the abundance of the fish between a temperate and an arctic environ.

 

Shot down by lecturer: REASON - Looking at two variables at once.

Please help me to move on from here.

Edited February 13, 2011 by ckstubbs

[Blahah]

Hi, Firstly you don't need to post twice.

 

Secondly, you haven't given your experiment design, you only named the properties of water you looked at. Please describe the experiment you designed.

 

If your lecturer has said you looked at two variables at once, then that's probably the problem. You say you looked at 4 properties of water. To do this you would have to make sure that in each run, 3 of those variables were kept constant and one was varied. Then you can explore the effect of changing that variable. So for example if you wanted to look at sites with varying salinity, you would choose sites where OC, temp and pH were the same between all sites. Then you can map fish abundance between those sites and graph it against salinity.

 

If I were you, I'd think about what the primary difference is between temperate and arctic waters is. Is the the mean daily temperature? Is it the range of temperatures experienced over time (e.g. does the temp fluctuate more in temperate waters)? Is it salinity? Whatever you think characterises the difference between the two locations, look at that first.

[ckstubbs]

Thanks.

This experiment was not done yet. I have to design it and write it up and turn it in. The hypothesis I turned in after a 30 minute lab session was shot down due to 2 variables, the lecturer said. I am trying to design it and I do not know where to go after the first hypothesis.

 

Hi, Firstly you don't need to post twice.

 

Secondly, you haven't given your experiment design, you only named the properties of water you looked at. Please describe the experiment you designed.

 

If your lecturer has said you looked at two variables at once, then that's probably the problem. You say you looked at 4 properties of water. To do this you would have to make sure that in each run, 3 of those variables were kept constant and one was varied. Then you can explore the effect of changing that variable. So for example if you wanted to look at sites with varying salinity, you would choose sites where OC, temp and pH were the same between all sites. Then you can map fish abundance between those sites and graph it against salinity.

 

If I were you, I'd think about what the primary difference is between temperate and arctic waters is. Is the the mean daily temperature? Is it the range of temperatures experienced over time (e.g. does the temp fluctuate more in temperate waters)? Is it salinity? Whatever you think characterises the difference between the two locations, look at that first.

[Blahah]

OK, sorry I thought you were saying you had come up with a design.

 

So, my previous comment still stands. Choose one variable property. Then you need to find a dataset for global fish abundance and another one which gives you your property (e.g. world ocean temperatures). I wouldn't bother with salinity - it doesn't change that much in open ocean. Oxygen content will be closely related to temperature. pH also won't change much in the open ocean. Temperature would be a sensible thing to look at.

 

Edit: I didn't address the basic points of your assignment....

 

You might hypothesize that temperate oceans are more biologically productive than arctic oceans due to the effect of temperature.

 

This leads to the predictions that:

- there is a difference in temperature between oceans

- there is a difference in biological productivity between oceans

- with regards to fish abundance, a productive ocean should support a higher fish abundance, so there should be a greater fish abundance in the warmer ocean

- fish abundance in general should be correlated with ocean temperature, where all other properties of water are equal

 

And the method would involve finding datasets on the internet which tell you temperature of the ocean and fish abundance. They don't need to be from the same source. Then you just analyse whether your predictions are met by the data. Ideally you would compare sites where all the other properties of water which you identified are identical, with only temperature differing between the sites.

Edited February 14, 2011 by Blahah