Long Answer Type(a) Nerve impulses to the adrenal medulla regulate the release of epinephirine, blood Ca++ level regulates secretion of parathyroid hormone, and a hormone from the anterior pituitary gland stimulates the release of cortisol by the adrenal cortex.
If the gland is stimulated then the hormone is released and if it is not stimulated, no hormone is released. The level of stimulation determine the level of response. The situation is slightly more complex when hormone are released in response to a chemical stimulus such as another hormone or glucose. In such instance, secretion is controlled by a negative feedback mechanism. The presence of the appropriate chemical in the blood stimulus the release of the hormone. As the hormone level rise the amount of stimulating chemical in the blood drops. As a result of this, the endocrine gland receives less stimulation and so the Hormone level drop. This kind of feedback mechanism is very common, and it gives a senstive level of control which can be constantly adjusted to the needs of the body.
(a) Explain four measures to control population explosion.
(b) Write the causative agent and main symptoms of the following diseases
(i) Tuberculosis (ii) Tetanus
(iii) Hepatitis (iv) Malaria
(c) Write two differences between benign tumour and malignant tumour.
(a) Define:
(i) Vestigeal organs
(ii) Sympatric speciation
(iii) Mutagens
(iv) Biogeography
(b) Archaeopteryx is considered a connecting link between reptiles and birds. Justify the statement by giving two characteristics of each group.
(c) Give two differences between natural selection and artificial selection.
a) Write four characteristics that have developed during human evolution.
(b) What are stem cells? Write two applications of stem cell in medical treatment.
(c) Mention three basic ways to conserve plant resources.
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