for a correct explanation of how malaria is transmitted.)
Malaria is naturally transmitted by the bite of a female Anopheles
mosquito. When this species of mosquito bites an infected person, a small
amount of blood is taken, which contains malaria parasites (Plasmodium).
These parasites develop within the mosquito, and about one week later,
when the mosquito takes its next blood meal, the parasites are injected
with the mosquito’s saliva into the person being bitten. After a period of
between two weeks and several months (occasionally years) in the human
liver, the malaria parasites start to multiply within red blood cells, causing
symptoms that include a fever and headaches. In severe cases, the disease
worsens, leading to coma and death.(ii) Identify TWO environmental factors that contribute to the emergence of
malaria and explain how those factors influence the increase in the
incidence of the disease. (4 points maximum. 1 point for each correct
environmental factor, maximum of 2 points; 1 point for each correct
explanation of how each factor influenced the increase of the disease,
maximum of 2 points.)
Environmental factors that can contribute to the emergence of malaria
include:
- A decrease in the population of mosquito predators, which can increase
the mosquito population and the rate of transmission. - Genetic resistance to pesticides, which can also increase the mosquito
population and the rate of transmission. - Changes in the climate (e.g., global warming), which can increase the
number of suitable habitats, resulting in increased rates of transmission. - Changes in the current habitats (e.g., agriculture, logging), which can
increase the number of breeding sites. - An increase in the population density, which allows for a greater
opportunity for transmission. - The emergence of Plasmodia strains that are resistant to anti-malarial
drugs, which can then lead to an increase in the incidence and
transmission of malaria.
(iii) Describe biological control and provide ONE example of a biological
control method used for controlling the spread of the disease. (2 points
maximum. 1 point for a correct description of biological control and 1
point for a correct method for controlling the spread of malaria.)