Question

15. Read the following and answer any four questions from 15(i) to 15(v) given below:
Ecological Indicators
The presence of dragonflies can reveal changes in the water ecosystems more quickly than studying other
animals or plants. In fact, from the nymph to the adult stage, the dragonfly has a significant, positive
ecological impact Dragonfly eggs are laid and hatched in or near water, so their lives impact both water
and land ecosystems. Once hatched, dragonfly nymphs can breathe underwater which enables them to eat
mosquito larvae, other aquatic insects and worms, and even small aquatic vertebrates like tadpoles and
small fish and in the air. Adult dragonflies capture and eat adult mosquitoes. Community wide mosquito
control programs that spray insecticides to kill adult mosquitoes also kill dragonflies.
i. The approach to biological control includes:
Import and release of an insect pest to a new area to provide hosts for natural enemies
b. Import and release of natural enemies from the native home of an alien insect pest that has
invaded a new area
Preservation of natural enemies (predators & parasitoids) that are already established in an
a.
area
d.
Use of insecticides to reduce alien insect pests to establish new equilibriu
position
11.
Two diseases less likely to occur in a region with plenty of dragon flies are
a
Yellow fever and amoebic dysentery
b.
Malaria and Yellow fever
C.
Anthrax and typhoid
Cholera and typhoid
d.
111.
a
Dragonflies indicate positive ecological impact as-
The presence of dragonflies indicates polluted water.
b Dragonitx nymphs selectively eat mosquito larvae.
They help to decrease the probability of diseases spread by vectors.
d Dragonfly do not cause any harm to beneficial species.
The most effective stages in the life cycle of Dragonfly that eradicate mosquitoes are
a. Larvae and Adult
b. Caterpillar and Adult
C.
IV.
c. Nymph and Adult
d. Pupa and Adult
V
Assertion: Releasing dragonflies in areas where there is an outbreak ef malarial diseases can be an​

Answer 1

Answer:

(i) c. Preservation of natural enemies (predators & parasitoids) vectors.

(ii) b. Malaria and Yellow fever

(iii) c. They help to decrease the probability of diseases spread by mosquitoes, horseflies and deer flies.

(iv) c. Nymph and Adult

(v) c. Assertion is true statement, but reason is false.

Answer 2

Answer

As per the statements, the answers are

i) option a. Preservation of natural adversaries( bloodsuckers & parasitoids) vectors.

ii) option b. Malaria and yellow fever

iii) option c. they help to drop the probability of conditions spread by mosquitoes, horseflies etc.

iv) option c. Nymph and Adult

v) option c. The assertion be a true statement, but the explanation is false.

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