Need help with my homework...

[Reef of Eden]

Intro to Marine Bio

I'm having some trouble with an assignment I was given. I really feel stupid right now.

This is what is says:

All organisms in the aquatic environment must deal with the challenges of having their living tissues be denser than their surroundings. Proteins, organelles, muscle tissue, and most other things inside of cells are denser than the surrounding fluid (sea water).

* For this lab write-up, investigate the strategies used by three different organisms and explain their adaptations and/or behaviors used in dealing with these challenges. The three organisms will cover a wide size range, as the strategies involved tend to vary with this parameter. Use any combination of the book, magazines, the web, or other sources.

The organisms should fall in each of the three size classes:
1. Less than 1 cm in length
2. Between 1cm and 10 cm
3. Greater than 10cm



Please write up one paragraph on each of the organisms that:
1. Define that species particular challenges
2. Explains the morphological, physiological or behavioral strategy used to deal with the situation.
3. List the sources you used.



I've only had 3 classes so far, and I'm kinda at a loss as to where to even begin.

I'm not trying to ask anyone to do the assignment for me, I just so frustrated right now, I don't know what to do. And the last time I was given an assignment like this I just didn't even do it, because it was so beyond anything I even had learned., which is kind of the case right now.

 

[useskaforevil]

first think about what all organisms anywhere need to do. and then why it might be different for each size class. then think abotu what might be differnt in their surroundings, then think abot what might be different in an aquatic habitat.

also wahts the differnce between morphological and physiological?

 

[Reef of Eden]

<a href=showthread.php?s=&postid=11891345#post11891345 target=_blank>Originally posted</a> by useskaforevil
first think about what all organisms anywhere need to do. and then why it might be different for each size class. then think abotu what might be differnt in their surroundings, then think abot what might be different in an aquatic habitat.

also wahts the differnce between morphological and physiological?

first think about what all organisms anywhere need to do.
I guess in terms of being more dense than there surrounding, they all need to be buoyant?

Am I on the right path??

 

[hahnmeister]

Im not clear on what the exact challenge is regarding... is the challenge of density with regards to their bouyancy, or with regards to their internal organs/systems? I mean, for a fish, its an easy response... most fish just have a swim bladder, or if they dont (shark, goby), they need to swim or sink to the bottom. Not to mention, if its a crab... who cares if its denser than the surroundings... it walks on the bottom. So challnges with regards to bouyancy seems like a lame idea to me. If its with regards to the internal systems, its somewhat of an incorrect assumption that its a 'challenge' to be in surroundings that are less dense... its actually easier. Freshwater fish for instance, have less of a challenge to keep their tissues hydrated with water because all they have to do is swallow. Marine fish have to constantly swallow water to stay hydrated and their kidneys work alot harder to remove the salts/minerals.

I dont know if it applies, but you might want to look into the Bull Shark in the Gulf of Mexico. It is usually saltwater, but it can swim as far up the Mississippi as St. Louis by going into a 'recycle' mode where its kidneys recycle its own uric acid into its blood to keep its internal salinity constant. The challenge in this case, and for Salmon, is that its harder to keep your insides from 'leaking' through osmosis in freshwater than saltwater. Thats why I dont get the assertion that its somehow 'harder' for an organism to adapt to saltwater... its more the other way around.

 

[Reef of Eden]

<a href=showthread.php?s=&postid=11891606#post11891606 target=_blank>Originally posted</a> by hahnmeister
Im not clear on what the exact challenge is regarding... is the challenge of density with regards to their bouyancy, or with regards to their internal organs/systems? I mean, for a fish, its an easy response... most fish just have a swim bladder, or if they dont (shark, goby), they need to swim or sink to the bottom. Not to mention, if its a crab... who cares if its denser than the surroundings... it walks on the bottom. So challnges with regards to bouyancy seems like a lame idea to me. If its with regards to the internal systems, its somewhat of an incorrect assumption that its a 'challenge' to be in surroundings that are less dense... its actually easier. Freshwater fish for instance, have less of a challenge to keep their tissues hydrated with water because all they have to do is swallow. Marine fish have to constantly swallow water to stay hydrated and their kidneys work alot harder to remove the salts/minerals.

I dont know if it applies, but you might want to look into the Bull Shark in the Gulf of Mexico. It is usually saltwater, but it can swim as far up the Mississippi as St. Louis by going into a 'recycle' mode where its kidneys recycle its own uric acid into its blood to keep its internal salinity constant. The challenge in this case, and for Salmon, is that its harder to keep your insides from 'leaking' through osmosis in freshwater than saltwater. Thats why I dont get the assertion that its somehow 'harder' for an organism to adapt to saltwater... its more the other way around.

I couldn't agree with you more, but this is what I wrote for number three.

I figure its the challenges in regards to buoyancy.

3. Shark

The shark lacks a swim bladder that most bony fish have, which makes it more prone to sinking than an ordinary fish. In order to combat sinking and maintain buoyancy sharks tend to have abnormally large and stiff pectoral fins in comparison to bony fish with swim bladders, and the upper lobe of the tail is much larger than the bottom producing lift. One part of the sharks body that is less dense than water is the oil in its liver, which creates buoyancy.

 

[hahnmeister]

But then its wrong... its actually easier for organisms to move in saltwater than freshwater (saltwater is denser and therefore you are more bouyant), and its easier to move in water than land... The proof? There are single celled organisms in fresh and saltwater that are able to move with great ease and little to no special 'adaptations' for it. I mean, the assertion of '...and most other things inside of cells are denser than the surrounding fluid' is true of all life forms including humans and birds unless they live in the earth/soil/rocks.

Due to the 'lack of clarity' from the requested assignment, I would seek further clarification of what you are supposed to do from the instructor. Those instructions arent very clear at all. I would be a turd and just write about three marine organisms that could care less about being 'denser than saltwater'... like a coral polyp, a small clam, and a large clam...lol. They have adapted by not adapting at all... they stay still and picked up photosynthetic/filter feeding methods to not need to move. I wouldnt say if their tissues are more or less dense than saltwater even... they could be the same, just with different contents... so whoop-d-doo.

 

[hahnmeister]

As far as sharks go, its a myth that they need to stay bouyant... many sharks rest on the bottom when sleeping, and many species LIVE on the bottom, so they could care less about being able to move. Dolphins and Whales... then its more true.

Interesting 'bouyancy'/mobility subjects:

1. Whales/Seals (blubber)
2. Gobies (rest on the bottom)
3. flambouyant cuttlefish (walks on its tenticles)
4. Kelp (gas sacks)
5. Chambered Nautilus (gas filled shell)
6. Octopods & their like (jet propulsion)
7. Remora (hitch a ride)
8. Plankton (who cares, go with the flow... yet shouldnt be discounted since a majority of everything in the ocean starts out as plankton)
9. Seahorses (monkey tail)
10. Man-O-war/other box jellies... heck, those are all 3 of your organisms in one... the gas bubble, tentlcles, etc... are considered 3 seperate organisms that grow together.
11. Flying Fish
12. Anything that doesnt swim... clams, corals, worms, crabs, etc.
12.5: anything that just doesnt move... duh.
13. swimming crabs
14. Feather Starfish (watch one swim and tell me that isnt cool).

The thing is, you might want to check into that whole idea that organisms are more dense than their surroundings in general. I dont think that is 100% true. Sure, parts of an organism might be more dense, but overall, many arent. Saltwater is filled with metals, salts, etc... it is heavier than pure water (which makes up more than 90% of what you are made of, and even more of most aquatic animals), so the argument could be made that 'parts of saltwater' are more dense than any organisms as well (like copper or iron in saltwater, or just pure sodium), but the point is that they both must be compared as a whole. Most organisms try to maintain a lower salinity level than their surrounding marine environment in order to function, so that alone makes them more bouyant. Some use gas bubbles, swim bladders, etc... but I dont know that that is a major adaptation... humans can float by just keeping air in their lungs, or if they have a high enough fat content... and those arent adaptations intended for a marine environment, unless you have read the 'naked ape' or any other articles about how its believed humans developed as a amphibian race of primate/ape. So heck, you could list humans on there as well... we have hands and feet suited for swimming, we can hold our breath, and our skin has very little fur to drag us down underwater. Note the fur on other apes faces up, yet the hair on our backs faces down as if to be more suited for swimming... makes you wonder, eh?

 

[Che]

If it were me doing the homework assignment, I would stick to simple.

1. Identify the organisms within the appropriate size range. I would use the textbook as much as possible and look at the body parts or morphological features that the book deems as interesting.

2. Identify the organisms challenges. From this point I would look for how these features are impacted by the area of interest to your professor - their density of organs and such.

3. As much as possible in subsequent organisms, use analagous features.

4. Make sure you answer all of the professor's questions: the morphological, physiological or behavioral strategy used to deal with the situation.

My best guess is that most issues will revolve around motility.

Good luck.

 

[greenbean36191]

I highly doubt this question has anything to do with buoyancy. As has already been pointed out, the question makes it clear that they're looking for adaptations that make marine species different than FW. The same tricks that work on FW work in salt. Also, the question specifically mentions problems at the tissue level and lower, which hints at an osmotic problem, not buoyancy.

Plus, in undergrad marine bio classes I can't think of another question that's asked more often than the question of osmoregulation in marine vs. fw species. I can think of maybe 2 times in 5 years that I ever had a question about how buoyancy was maintained and I can't even count how many times I got questions about osmoregulation.

 

[hahnmeister]

Thats what I was thinking too... thats more of a challenge. In which case, I would look at the Bull Shark.