1 Animals and plants have internal communication systems that allow information to pass between different parts of their bodies, and so help them to respond to changes in their external and internal environments. 2 Mammals keep their internal environment relatively constant, so providing steady and appropriate...

Stomata have daily rhythms of opening and closing and also respond to changes in environmental conditions to- allow diffusion of CO­2­- regulate water loss by transpiration Stomata open due to: Stomata close due to: high light intensitylow concentration of CO­2­  darknesshigh concentration of CO­2­ low...

The presence of glucose and ketones in urine indicates that a person may have diabetes. If the concentration for these rises above the renal threshold, then not all glucose has been absorbed from the filtrate in the proximal convoluted tubule --> so will be present in the urine.A large quantity or long-term presence...

Insulin and glucagon work together as part of a negative feedback system. As a result of glucagon secretion, the liver releases extra glucose to increase the concentration in the blood. Muscle cells do not have receptors for glucagon and so do not respond to it.This is question 9, taken directly from the specimen paper...

The blood glucose concentration is regulated by negative feedback control mechanisms.Blood glucose concentration should remain at a fairly constant value of about 100 mg glucose per 100 cm3 of blood.If blood glucose concentration falls well below this level, the person is said to be hypoglycaemic. Cells do not have enough...

Osmoregulation is the control of the water content of body fluids. It is part of homeostasis, the maintenance of a constant internal environment. It is important that cells are surrounded by tissue fluid of a similar water potential to their own contents, to avoid too much water loss or gain which could disrupt metabolism....