Page 197 - Biology_F5

Biology for Advanced Level Secondary Schools

Advantages of Arthropods examples include locusts and the
(a) Insects such as bees and butterflies caterpillars of butterflies and moths.
are useful in agriculture; as they act (d) Some arthropods are parasitic to
as pollinators. Many plants depend on mammals. Typical examples of such
insects for pollination. arthropods are ticks, jiggers, and

(b) They are used in industries for bedbugs, which grip themselves on
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production of honey and wax human skin and suck blood.
materials; example honey bees.
(c) Insects are used in biological control 3.7.5 Phylum Chordata

of pests; in certain cases, insects have This is among the major phyla of kingdom
been very effective predators to reduce Animalia. The phylum comprises all
the number of pests. For example, lady animals that at some point during their
beetles are used to kill aphids (the pest lives, possess a hollow nerve cord and
insects that transmit viruses to plants). notochord.
(d) Many arthropods are used as food; General characteristics of phylum
they are a good source of protein for Chordata
humans and other animals. Examples (a) They have a notochord at some stages
include shrimps, lobsters, crabs, edible of their development. Notochord is a
grasshoppers, locusts, and many larvae stiff, flexible rod located dorsally to the
of beetles and moths. gut and ventrally to the nerve cord. In
(e) Insects are used in research and vertabrates the notochord is replaced
biological studies. by a vertebral column (backbone)
(f) Insects such a as butterflies are valued during adulthood.
for their beauty. (b) They have visceral clefts, which are
(g) Many arthropods are used as indicators slits perforating the body wall in the
of the environmental quality. pharynx. They are useful in fishes
and tadpole larva of amphibians for
Disadvantages of Arthropods gas exchange, as they use gills. In
(a) Some insects are vectors of animal adult amphibians, reptiles, aves and
and plant diseases. For example, mammals, the visceral clefts never
mosquitoes carry Plasmodium, which develop gills.
causes malaria, and tsetse flies carry (c) They have post-anal tail at some stages
Trypanosoma, which causes sleeping of their development.
sickness to human beings. Whiteflies (d) They have a dorsal hollow nerve cord
carry Tomato yellow leaf curl virus,
which causes chlorosis in plants. found above the notochord and below
(b) Some arthropods such as scorpions the epidermis. In higher chordates,
and centipedes can bite human beings, the anterior part forms a brain and the
release their venom causing severe posterior part forms a spinal cord.
pains. (e) They have ventrally positioned heart,
(c) Some arthropods destroy crop plants; which is a pumping organ that pumps

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