Page 135 - Biology_Form_3

Biology for Secondary Schools
5. Feedback mechanisms are critical in
regulation, functioning through either
positive or negative feedback loops.
Negative feedback reduces the impact
of a stimulus, helping to restore normal
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conditions, such as in temperature
and blood sugar regulation. Positive
feedback amplifies the initial stimulus,
as seen in childbirth and blood clotting. by promoting glucose uptake by cells
6. Thermoregulation is the ability of
organisms to regulate body temperature
to remain stable despite environmental
fluctuations. Endothermic animals,
like mammals and birds, maintain a
constant internal temperature through 10. Imbalances in regulatory mechanisms
mechanisms such as sweating and
shivering. Ectothermic animals, such
as reptiles and amphibians, adjust their
body temperature behaviourally by
basking in the sun or seeking shade.
7. In response to cold temperatures, the
body conserves heat through processes
like vasoconstriction, which reduces
blood flow to the skin, and shivering,
which generates heat through muscle
activity. In contrast, in hot conditions,
mechanisms such as sweating and
vasodilation help dissipate excess Choose the most correct answer.
heat, preventing overheating. Some
animals also engage in behavioural 1.
adaptations such as panting and
licking to regulate body temperature.
8. Osmoregulation ensures the balance
of water and salts in the body to
maintain proper cell function. It
is controlled by hormones such as
antidiuretic hormone (ADH), which 2. Tissue fluid contains the same
regulates water retention in the
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BIOLOGY FORM 3 FINAL EDITED 16.09.2025.indd 128
BIOLOGY FORM 3 FINAL EDITED 16.09.2025.indd 128
KAMISHNA
kidneys. Aldosterone also plays a role
in maintaining sodium and chloride
ion levels, helping to stabilize osmotic
pressure.
9. Blood sugar regulation is primarily
controlled by insulin and glucagon,
hormones produced by the pancreas.
Insulin lowers blood glucose levels
and converting excess glucose into
glycogen. Glucagon raises blood sugar
levels by breaking down glycogen into
glucose, ensuring a constant supply of
energy.
can lead to disorders such as diabetes
mellitus, characterized by high
blood sugar levels due to insufficient
insulin production. Hypoglycemia,
or low blood sugar, can result in
dizziness, confusion, and even loss of
consciousness. Effective regulation of
physiological processes is crucial for
maintaining health and overall body
function.
Revision exercise 5
Beta cells in the islets of Langerhans
secretes__________.
(a) glucagon
(b) insulin
(c) thyroxine
(d) aldosterone
composition as blood but
lacks__________.
Student’s Book - Form Three
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