Biology paper 3

[Mahdi]

Negative feedback is simply a process by which different internal conditions of the body are controlled. Such as level of circulating hormones to maintain homeostasis.

 

[natsume hyuga]

Anytime x)



Implications doesn't mean BAD things. It just means advantages/disadvantages. The implications of self pollination are:
- No pollinating agent is required
- Less variation as there is no exchange of genetic material from different plants
- Is much faster then cross pollination
- Much higher chance of pollination
- Plants are unable to colonize new areas as the pollen grains are not transferred from one plant to the next.

Advantages of cross pollination are:
- Results in variation
- Plants are able to colonize new areas as pollen grains are spread by pollinating agents.

Thanks alot, but one thing.. colonise in new areas, isnt that for the advantages of seed dispersal?

 

[Incognito]

Thanks alot, but one thing.. colonise in new areas, isnt that for the advantages of seed dispersal?

Various plants such as weeds are unfavourable. If they colonise new areas such as farms they may grow there, creating competition for food and light for the crops. Which might lead to a lower crop yield. Thus it may be a disadvantage.

 

[ZainH]

Thanks alot, but one thing.. colonise in new areas, isnt that for the advantages of seed dispersal?

You see, if they are cross pollinated then while the insects are carrying pollen grains, or they are being dispersed by wind , they have chances of landing in new areas. If its self-pollination , since it requires no pollinating agent.. most of the plants would grow near the parent plant which would increase competition. So colonizing new areas is an ADVANTAGE of cross-pollination.

 

[Dsilentkila]

Negative feedback is basically taking neccessary measures to maintain a condition.
Such as body temperature, if it goes higher then normal the brain sends impulses to the sweat glands to produce sweat.

thnks browski, ur great

 

[dana xP]

guys i need help in a question,,,,,,
( describe how negative feed back is involved in the control of body temperature)
and its for 3 marks !!!

 

[Dsilentkila]

not really good in bio, but from my understanding of negative feedback u could go like...
The receptors in the skin send impulses to the brain when the body temp is above(or below) normal , the brain sends impulses to effectors to act in order to(oppose the change and) bring back the temperature to normal. For example sweat glands will be stimulated to produce more sweat or vasodilation occurs in arterioles close to the surface of the skin ( so that more heat is lost through radiation).

 

[igcse student 5558]

When do u guys have the exam ?!

 

[cool girl]

Can some 1 here post paper 3 bio variant 2 oct/nov 2011 with marking schemes plz i need it urgently
thnx in advance

 

[cool girl]

When do u guys have the exam ?!

tomorow at 9

 

[natsume hyuga]

tomorow at 9

which variant?

 

[igcse student 5558]

Country !?!? Variant !!!

 

[ZainH]

thnks browski, ur great

Anytime x)

When do u guys have the exam ?!

Tomorrow at 2:45.

 

[Lost_Life]

does anyone have october/novemeber 2001 paper32 mark scheme bio?

 

[ZainH]

does anyone have october/novemeber 2001 paper32 mark scheme bio?

Just a tip, back in 2001 the syllabus wasn't the same. There are less stuff now, try solving papers from 2006-2011! x)

(Don't got the mark scheme, sorry)

 

[Dsilentkila]

guys i need help in a question,,,,,,
( describe how negative feed back is involved in the control of body temperature)
and its for 3 marks !!!

this one is strainght out of the notes out of http://www.xtremepapers.com/community/threads/igcse-physics-chemistry-biology-notes.14611/
"Negative feedbackis where, when the hypothalamus has made your skin take action to increase heat loss, info about this is fed back as the drop in blood temperature is sensed, so the hypothalamus stops the skin taking action to lose heat.""

 

[Lost_Life]

i know but there is this question that got me puzzled i just want to know the answer!!!!

 

[Lost_Life]

hey, how does dialysis machine work?
im sooooooooooooooooooooooooooooooooooooo stressed i have biology and french continuous writing on the same day!! my hand will fall off!!!!

 

[whitetiger64]

Can anyone plz explain nitrification and nitrogen fixation?
Thank you!

 

[ZainH]

Can anyone plz explain nitrification and nitrogen fixation?
Thank you!

Oh me too please, those are my worst topics..