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nish
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PostSubject: answer this Fri Jan 23, 2009 2:15 pm

Very Happy
we often see algae floating during day and they sink during night in a pond
why does this happen?????????????? Cool Cool Cool Cool Razz Razz Razz Razz Razz Razz Razz Razz Razz
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Candy
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PostSubject: Re: answer this Fri Jan 23, 2009 2:21 pm

Quite Interesting Wait for A few Seconds I am searching The Answer
Very Happy Smile
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PostSubject: Re: answer this Fri Jan 23, 2009 2:30 pm

The Reason Why They Float is Here : bounce
Some blue-green algae can float to the surface under these
conditions having access to all the light in the top waters (photic region) and
nutrients in the top and bottom waters. This allows the
algae to flourish and bloom. Some other algae are motile
and can swim to the photic region under these conditions.


Many other factors play a role in the formation of blue-green algal blooms
including temperature, salinity, zooplankton grazing, pH and turbidity.
Algae vary considerably in size, shape, and growth form.

They can be:



  • Single celled
  • Many celled - either colonially or as filaments of cells; or
  • Elaborate plant bodies with differentiated cell types



Main habitat preferences are:



  • Free floating in the water column (planktonic). These comprise the
    microscopic unicellular algae and colonial and filamentous algae,
    known as "phytoplankton".
  • Growing as a film on rocks on the bottom (benthic) or on plants
    growing in the water (epiphytic). These may be single celled or
    small colonial and filamentous species.
  • Growing out into the water column but attached to a substrate at one
    point. These comprise the larger filamentous algae, and macroalgae
    (eg. seaweeds).
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nish
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PostSubject: Re: answer this Fri Jan 23, 2009 2:33 pm

THI IS A 2 MARK QUES
I WANT 2 POINTS only
please be specific
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Anu..i luv icse...:)
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PostSubject: Re: answer this Sat Jan 24, 2009 12:46 am

even we had the same question....i think it's like this:

during daytime, photosynthesis occurs, releasing O2 and filling up aerenchyma and thus, increasing the buoyancy?

at night no photosynthesis so, it sinks....

well..its a guess!!! i dunno whether its ryt or wrong!! Razz
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nish
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PostSubject: Re: answer this Sat Jan 24, 2009 7:19 pm

Very Happy i think during day time O2 IS GIVEN OUT , O2 IS LIGHT SO THEY RISE
during night CO2is produced which is heavy bounce bounce Very Happy Very Happy Very Happy Exclamation Exclamation Exclamation Exclamation Exclamation Exclamation Exclamation
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PostSubject: Re: answer this Fri Jan 30, 2009 3:57 pm

so...wats the ryt answer?
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jOhNy
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PostSubject: Re: answer this Sat Jan 31, 2009 11:11 pm

hey wait...is this topic related to our syllabus Question Question Question
if yes...someone plzz explain it in a simple 2 lines.
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PostSubject: Re: answer this Sun Feb 01, 2009 9:30 pm

yeah it is there...thts y i'm scratching my head for it Suspect

wait till we figure out an answer...then we ll explain in 1 simple line only cat
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jOhNy
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PostSubject: Re: answer this Sat Feb 07, 2009 11:07 pm

hey anu...u still scratching ur head?? confused plzz explain this in 2 lines..
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Anu..i luv icse...:)
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PostSubject: Re: answer this Sat Feb 07, 2009 11:17 pm

still dont know the answer....ask your intelligent frnd and get an answer!!! the answers will be out by monday or tuesday..i'll ask my teacher, as i had got this question in preparatory
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jOhNy
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PostSubject: Re: answer this Sat Feb 07, 2009 11:34 pm

hey..stop harrasing my 'intelligent' friend.just kidding lol!
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PostSubject: Re: answer this Sat Feb 07, 2009 11:43 pm

not harrasing...make use of intelligence!! Twisted Evil
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PostSubject: Re: answer this Thu Feb 12, 2009 11:52 pm

my answer is correct...i verified with maam

so, john, read my answer again...its just two lines.
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vallabh
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PostSubject: Re: answer this Wed Feb 18, 2009 9:59 pm

what kind of sense is that??
o2 is given out and because it is light the algae rises ???????
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PostSubject: Re: answer this Wed Feb 18, 2009 11:31 pm

vallabh....check out my answer...not nish's...he just guessed like me.....so, there is nothing compulsory that guesses should be sensible na!! scratch lol!
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ambili
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PostSubject: Re: answer this Fri Feb 20, 2009 4:39 pm

pls give the final ans..........
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PostSubject: Re: answer this Fri Feb 20, 2009 6:40 pm

arre....ambili...i told na....my answer is correct ...check it....i have given it here only in previous comment
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PostSubject: Re: answer this Fri Feb 20, 2009 6:42 pm

"during daytime, photosynthesis occurs, releasing O2 and filling up aerenchyma and thus, increasing the buoyancy

at night no photosynthesis so, it sinks...."
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jOhNy
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PostSubject: Re: answer this Fri Feb 20, 2009 8:30 pm

but which chap of our syll is this topic related??
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PostSubject: Re: answer this Fri Feb 20, 2009 9:15 pm

mm...good question...though i dont know the answer for it!! Very Happy but, i gt this ques in the pre board....but, i cant rely on my teacher,,she is good for irrelevant things only!!

maybe this is related to photosynthesis in aquatic plants? its not in syll!!
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JiGaR
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PostSubject: Re: answer this Mon Mar 16, 2009 9:08 pm

Hello,
I think I have d ans.... Wink
this is coz of sum property of plants known as phototropism...
it exists for unicellular organisms as well...
if you remember that when plant is kept in a dark room with one window from where it recieves sunlight ...it bends/grows in that direction ...
in the same way algae (rather all unicellular organisms) not only have the property of growing in that direction but even moving in that direction... hence they rise up... Exclamation

same relative terms exists:
-> chemotropism .....towards water
->thermotropism.....towards heat eg: folding of mimosa leaves..[Note: 2 reasons for folding of mimosa: turgidity or thermotropism]

Best Of Luck! What a Face
---$@% Jigar %@$--- bounce bounce
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PostSubject: Re: answer this Mon Mar 16, 2009 9:36 pm

thankyou....but this isnt in syllabus...but still, helpful
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abhi_1993
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PostSubject: Re: answer this Mon Mar 16, 2009 10:09 pm

uh...if the ans about phototropism is rite...den i think it is in our syllabus...cuz we hav turgor...and phototropism is a type of turgor
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Arya Nair
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PostSubject: Re: answer this Mon Mar 16, 2009 11:17 pm

i haven't read about phototropism in the text(it is there?)
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