Qualification > Sciences
IGCSE BIOLOGY DOUBTS HERE !!!!
WARRIOR:
--- Quote from: Deadly_king on October 02, 2010, 07:13:30 am ---Importance of diffusion of gases :
Carbon dioxide and Oxygen diffuse in and out of leaves. They are required for both respiration and photosynthesis (the two most important processes for life to occur).
Diffusion of solutes :
Transport of materials. Water or the solution acts as transport medium. Example : blood
Water as a solvent :
1. This is important as it allows ions and polar molecules to move freely within itself. Some specific ions are essential for survival of plants (e.g). They dissolve in water to get it specific cells.
2. Oxygen and carbon dioxide diffuse within a layer of moisture around mesophyll cells in order to get in. It facilitates diffusion.
Hope it helps :)
Again water acts as a transport medium.
--- End quote ---
+ rep thx!
Deadly_king:
--- Quote from: ~Vin~ on October 02, 2010, 07:27:35 am ---Thanks a lot King. Do you mind if I add exactly same stuff to the bunch of bio notes?
--- End quote ---
Not at all Vin. Am just glad being able to help :)
You're welcome guys :)
acash09:
Hey guys, can someone explain to me the meaning of negative feedback? Its in the homeostasis lesson about the hypothalamus.
Is it needed in any other lesson for the 2010 exams?
Much appreciated.
Acash09
nid404:
--- Quote from: acash09 on October 09, 2010, 04:39:31 pm ---Hey guys, can someone explain to me the meaning of negative feedback? Its in the homeostasis lesson about the hypothalamus.
Is it needed in any other lesson for the 2010 exams?
Much appreciated.
Acash09
--- End quote ---
This is a small part of the syllabus and I've hardly come across any questions when I was doing my igz but you need to know what negative feedback is.
Homeostasis is the maintenance of constant internal conditions. It is often controlled be negative feedback There are six different things which need to be kept constant
Removal of carbon dioxide
Removal of urea
(Of these two we don’t need any of them, they are constantly being produced by the body and we need to constantly get rid of them.)
Ion content
Water Content
Sugar content
Temperature
Amount of thyroxin
(We need these four in certain amounts, and too much can be dangerous.)
The hypothalamus (or thermoregulatory gland) is located just above the pituitary gland. It contains sensors which monitor blood temperature and water content, and send nerve impulses to the pituitary gland. It also monitors carbon dioxide which is removed by the lungs in exhaled air. The kidneys control water content (via ADH) and ion content of the blood. The pituitary gland produces ADH for the kidneys, while the skin helps control the body temperature by sweating and raising hairs. The muscles can shiver to increase temperature. Finally the liver and pancreas work together to keep the blood sugar levels correct.
The pituitary gland secrets thyroid stimulating hormone, and the more secreted the more thyroxin is made. However, if too much thyroxin is made then it goes back to the pituitary gland and tells it to stop making so much thyroid stimulating hormone.<< when there is excess of a certain hormone, the hormone acts as an inhibitor in itself and stops its own production..This is negative feedback.
MKL:
--- Quote from: Garfield on October 10, 2010, 08:15:39 am ---This is a small part of the syllabus and I've hardly come across any questions when I was doing my igz but you need to know what negative feedback is.
Homeostasis is the maintenance of constant internal conditions. It is often controlled be negative feedback There are six different things which need to be kept constant
Removal of carbon dioxide
Removal of urea
(Of these two we don’t need any of them, they are constantly being produced by the body and we need to constantly get rid of them.)
Ion content
Water Content
Sugar content
Temperature
Amount of thyroxin
(We need these four in certain amounts, and too much can be dangerous.)
The hypothalamus (or thermoregulatory gland) is located just above the pituitary gland. It contains sensors which monitor blood temperature and water content, and send nerve impulses to the pituitary gland. It also monitors carbon dioxide which is removed by the lungs in exhaled air. The kidneys control water content (via ADH) and ion content of the blood. The pituitary gland produces ADH for the kidneys, while the skin helps control the body temperature by sweating and raising hairs. The muscles can shiver to increase temperature. Finally the liver and pancreas work together to keep the blood sugar levels correct.
The pituitary gland secrets thyroid stimulating hormone, and the more secreted the more thyroxin is made. However, if too much thyroxin is made then it goes back to the pituitary gland and tells it to stop making so much thyroid stimulating hormone.<< when there is excess of a certain hormone, the hormone acts as an inhibitor in itself and stops its own production..This is negative feedback.
--- End quote ---
You need to be able to describe the function of the kidney in removing urea/excess water for Core, and need to be able to outline the structure of the kidney and structure + functioning of the nephron for Supplement, including the role of the renal capsule and the tubule.
Only negative feedback loops for maintenance of temperature in skin (Core) and maintenance of glucose content via insulin/glucagon (Supplement) are needed for IGCSE. At least that's what it says on the 2010 Syllabus.
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