PRELIMINARY STAGE
2013
Osei Tutu SHS
Yaa Asantewaah SHS
MfantsiMan Girls
QUESTION
Which structure in insects removes waste products?
ANSWER: Malpighian tubules
EXPLANATION
Malpighian tubules remove nitrogenous waste (as uric acid) and assist osmoregulation in insects.
PRACTICE QUESTIONS
1. Where do the Malpighian tubules open in an insect?
ANSWER: At the junction of the midgut and the hindgut.
2. What is the main nitrogenous waste excreted by insects?
ANSWER: Uric acid.
3. Why is uric acid a suitable excretory product for insects?
ANSWER: It is insoluble and non-toxic and is excreted with very little water, so water is conserved.
4. From which fluid do the Malpighian tubules extract waste products?
ANSWER: The haemolymph (blood).
5. In which body cavity do the Malpighian tubules lie?
ANSWER: The haemocoel.
6. Which part of the insect gut reabsorbs water from the tubule contents?
ANSWER: The rectum.
7. Apart from excretion, state one other function of the Malpighian tubules.
ANSWER: Osmoregulation (regulating the water and salt balance of the body).
8. How are the Malpighian tubules different from the mammalian kidney tubules in where they end?
ANSWER: Malpighian tubules end blindly in the haemocoel, while kidney tubules are attached to a filtering glomerulus and lead to a collecting duct.
9. How do the wastes leave the body after being emptied into the gut?
ANSWER: They are voided through the anus together with the faeces.
10. What is the term for animals that excrete uric acid as their main nitrogenous waste?
ANSWER: Uricotelic.
11. Name two other groups of animals that excrete uric acid.
ANSWER: Birds and reptiles.
12. Which class of arthropods, other than insects, also has Malpighian tubules?
ANSWER: Arachnids (e.g. spiders).