Page 113 - General and Inorganic Chemistry for Advanced Secondary Schools Students Book Form Five and Six

Biology for Secondary Schools

Questions researches particularly in the
(a) List down two observable features fields of physiology, genetics and
which show that these specimens evolution. Fruit flies (Drosophila
are arthropods. melanogaster) are among the
(b) What two external features insects used for this purpose.
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that distinguish a spider from a (f) Some insects are used in the
grasshopper? production of medicine. Such
insects include blister beetles
Advantage of arthropods that produce cantharidin which is
(a) They are used as food for human used for treatment of urinogenital
beings and other animals. They diseases.
are rich in protein and calcium (g) Some arthropods are scavengers
minerals. Example of edible and feed on rotten or decayed
arthropods are lobsters, prawns, materials, hence helping in
shrimps, edible grasshopper, and reducing wastes and ensuring
larvae of beetles and butterflies. nutrient circulation in the
(b) They are used for production of ecosystem. Examples of such
various substances. For example, arthropods are millipede and
honey bees produce honey, wax cockroaches.
and bee venom; silk worms (h) Some arthropods improve soil
produce silk that can be used for aeration and soil fertility. For
commercial purpose; and silk example, termites break down
from spiders is used to produce plant tissues and diplopods feed
surgical threads. on decaying plants and animals,
(c) They are used in biological thus improving soil fertility.
control of pests. Some arthropods (i) Some crustaceans are used for
have been used effectively as decoration purpose especially
predators to kill or control pests. crabs and crayfish.
For example, lady beetles are (j) Some arachnids, such as mites play
used to kill aphids. Aphids are the an important role in the formation
insect pests that transmit viruses of humus from decomposed leaf
to plants. litter and wood.
(d) Insects, such as bees and butterflies
are useful in agriculture as they Disadvantages of arthropods
act as pollinators. Many plants (a) Chilopods, such as centipedes
depend on insects for pollination. have venomous claws. They can
(e) They are used in scientific bite humans and other animals

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