NCERT Class 9 Science Lab Manual – Life Cycle of Mosquito

NCERT Class 9 Science Lab Manual – Life Cycle of Mosquito

EXPERIMENT

Aim
To study the life cycle of mosquito.

Theory
Mosquitoes

1. Insect family, Phylum-Arthropoda. There are 3,500 species of mosquitoes found throughout the world.
2. Vectors: Mosquitoes are vectors as they are carrier of pathogens that causes diseases.
3. Feeding Habit of Adult Mosquitoes: Both male and female mosquitoes feed on nectars, but the female mosquitoes feed on blood of many mammals as they need proteins and iron to develop eggs.
4. Some species feed at day time and some during dawn/dusk.
5. Detection of host: Female mosquitoes detect their host by detecting carbon dioxide from a distance.
6. Common diseases caused by mosquitoes: Yellow fever, Malaria, Dengue, Chickengunea.
7. Life span of adult Mosquito: Most male mosquitoes live only for a week and females live for about a month.
8. Importance of water: All mosquitoes need water to complete their life cycle. All female mosquitoes lay their eggs on water.

Metamorphosis

1. 1. The developmental stages of an adult mosquito, from its egg to an adult, is called metamorphosis.
   2. The length of the life cycle of mosquito is 30 days.
      

Materials Required
The preserved specimen showing different stages of life cycle of mosquito and a magnifying lens.

Procedure

1. Observe the given specimen carefully. Study the different stages of the life cycle of mosquito and note down the feature of each stage.
2. Draw diagram of the life cycle of mosquito.

Observation

1. Mosquito Egg Raft [I stage]
   The eggs are small, nearly 200-300 eggs sticking each other form a raft that floats on water and is about 1/4 inch long and 1/8 inch wide. This stage lasts for 24-48 hours.
   
2.  Larva [II stage]
   The larva emerges out from the egg within 48 hours.Larvae are commonly called ‘wrigglers’. They have a tube like body called siphon attached on their abdomen. They come to the surface of water at frequent intervals to breathe oxygen with the help of siphon. The larvae then wriggle down in water. They eat algae and small organisms in water.Larva sheds its skin four times (molting) the stages between molts is called instars.At the last instar, larva reaches a length of almost 1/2 inch and coils to form a pupa. This stage last for 7-14 days.
   
3. Pupa [III stage]
   The pupa formed from larva, floats in water. It takes oxygen through its two breathing tubes called “trumpets’.When the water is disturbed the pupa tumbles down and floats back on surface of water, so it is called “Tumblers”.This is hibernating stage when pupa does not eat and only rest/sleep. This stage last for 1-4 days.
   
4. Adult Mosquito [IV stage]
   The adult mosquito splits the pupa case and comes out on the surface of the water. It rests for sometime, until its body is dry and hard. It flies off in search of food.Male mosquito feeds on sugars, nectar from flowers.Female mosquito feeds on blood.
   

The common species of mosquitoes and diseases caused by them are:

Prevention and control: Destroy the breeding grounds . Kill the mosquitoes, isolate infected people,get vaccinated.

VIVA VOCE

Question 1:
Name the family and phylum of mosquito.
Answer:
Mosquitoes are from insect-family and Phylum is Arthropoda.

Question 2:
What are pathogens?
Answer:
The microscopic organism that causes diseases is called pathogen.

Question 3:
Which animal blood do they feed on?
Answer:
It feeds on blood of mammals.

Question 4:
Which stage is called wriggler?
Answer:
The II stage — Larva is called wriggler.

Question 5:
Name the stage where no feeding takes place in mosquitoes life cycle.
Answer:
Pupa stage is hibernating, when no feeding takes place.

Question 6:
Name the stage that is also called ‘Tumbler’.
Answer:
Pupa III stage.

PRACTICAL BASED QUESTIONS

Question 1:
What are vectors?
Answer:
Pathogen carrying organisms are called vectors, e.g., Mosquitoes.

Question 2:
Name the vector and pathogen that causes malaria.
Answer:
Pathogen – Plasmodium Vector – Female Anopheles.

Question 3:
Name any two diseases caused by mosquitoes.
Answer:
Dengue and Yellow fever – by Aedes aegypti

Question 4:
Why do female mosquitoes feed on blood?
Answer:
Female mosquitoes need proteins and iron to develop eggs hence, they feed on blood to fulfill their requirement.

Question 5:
What is metamorphosis?
Answer:
The various developmental stages seen in an organism from egg to an adult are called metamorphosis. It is the changes that occur in the various stages.

Question 6:
How do female mosquitoes detect their host?
Answer:
Female mosquitoes detect their host by detecting carbon dioxide from a distance.

Question 7:
Name any four places in your house where mosquitoes can breed.
Answer:.
Flower vase with stagnant water, cooler, refrigerator tray behind fridge and empty pots with water.

Question 8:
What is the life span of male and female mosquitoes?
Answer:
Male mosquitoes’ life span – A week.
Female mosquitoes’ life span – A month.

Question 9:
Give the importance of water for mosquitoes.
Answer:
To complete the life cycle water is essential as for first three stages of metamorphosis water is essential.

Question 10:
Name the three stages of life cycle of mosquito where water is essential.
Answer:
I stage – egg, II stage – larva, III stage – pupa.
All 3 stages occur in water.

Question 11:
Give the time taken by female mosquito egg to hatch.
Answer:
It takes 24-48 hours depending on the temperature of water.

Question 12:
What is siphon in Larvae?
Answer:
It is a tube like structure attached to the abdomen of larvae and helps in breathing oxygen from air.

Question 13:
Explain ‘Moulting’ and ‘Instars’.
Answer:
Shedding of skin by larvae is called moulting, this happens four times.
The stages of larvae between molting is called Instars.

Question 14:
State the life span of each stage of mosquito.

Question 15:
Why do female mosquitoes inject saliva into the host body before sucking the blood?
Answer:
The female mosquito saliva contains anti-coagulants which prevents host blood from clotting and keeps the flow of blood normal. So, that it can feed on the blood.

Question 16:
Suggest any two preventive measures for the control of spread of mosquito diseases.
Answer:

1. Do not allow water to stand in your locality, near house.
2. Use mosquito repellants to keep them away.
3. Get vaccinated.

NCERT LAB MANUAL QUESTIONS

Question 1:
Why is it important to study the life cycle of mosquito?
Answer:
The mosquitoes cause severe diseases and by studying their life cycle we can prevent their growth.

Question 2:
At which stage in the life cycle of a mosquito, moulting takes place?
Answer:
In the larval stage.

Question 3:
Why does only the female mosquito require a blood meal?
Answer:
It is only the female mosquitoes that lay eggs and for the formation of these eggs they need proteins and iron from blood.

Question 4:
What are the conditions that are helpful for breeding of mosquitoes?
Answer:
Wet and warm conditions are favourable for the breeding of mosquitoes.

Question 5:
Suggest three measures to check the breeding of mosquitoes.
Answer:
To check the growth of mosquitoes following measures can be taken:

1. Do not allow any stagnant water to collect in the vicinity.
2. Put layer of cheap oil like kerosene on the water so as to prevent the metamorphosis of larvae into adult mosquitoes.
3. Fumigate the area with mosquitoes.

MULTIPLE CHOICE QUESTIONS (MCQs)
Questions based on Procedural and Manipulative Skills

Question 1:
The Phylum of mosquitoes is
(a) Insect
(b) Annelid
(c) Arthropoda
(d) Aedes.

Question 2:
Mosquitoes carry disease causing organisms, such mosquitoes and organisms are respectively called.
(a) Vectors and Pathogens
(b) Pathogens and Vectors
(c) Anopheles Protozoa
(d) Aedes Virus.

Question 3:
What is correct about the biting habit of mosquitoes?
(a) they bite during day time
(b) they bite only during night time
(c) they can bite at anytime
(d) depends on the species and feeding habit.

Question 4:
The female mosquito lives for
(a) a year
(b) a week
(c) a month
(d) a day.

Question 5:
The insect responsible for the cause of chickengunya is
(a) Anopheles
(b) Aedes aegypti
(c) Culex tarsalis
(d) none of these.

Question 6:
The Protozoa that can cause malaria is
(a) Plasmodium malaria
(b) Plasmodium ovale
(c) Plasmodium vivax
(d) all of these.

Question 7:
When the malaria parasite enters the human blood, it multiplies in
(a) lungs
(b) kidney
(c) liver
(d) spleen.

Question 8:
The Pathogen of malaria multiplies in the mosquito body in the
(a) abdomen
(b) gut
(c) both (a) and (b)
(d) none of these.

Question 9:
An effective way to control the mosquitoes is
(a) kill the adult mosquitoes
(b) kill the mosquito larvae
(c) destroy the eggs in the water
(d) kill only the female mosquitoes.

Question 10:
The larvae and pupae are also known as
(a) wriggler and tumbler respectively
(b) tumbler and wriggler respectively
(c) siphons and trumpets respectively
(d) trumpets and siphons respectively.

Question 11:
Which family of mosquitoes does not drink blood?
(a) Anophelinae
(b) Toxorhynchites
(c) Aedes
(d) Culicinae.

Question 12:
The disease not spread by mosquito bite
(a) Malaria
(b) Yellow fever
(c) Chickengunya
(d) Cholera.

Question 13:
The number of species of mosquitoes are
(a) 15,000
(,b) 2,500
(c) 2,000
(d) 3,500.

Question 14:
Both male and female mosquito obtain their food from
(a) sugar
(b) blood
(c) nectar from flowers
(d) grass sap.

Question 15:
Anopheles mosquitoes are the only species known to
(a) carry malaria
(b) carry dengue
(c) suck blood
(d) lay eggs.

Question 16:
Apart from malaria for which diseases mosquito acts as vector?
(a) Encephalitis
(b) Filariasis
(c) Yellow fever
(d) all of these.

Question 17:
Mosquito eggs can survive for
(a) one day
(b) one year
(c) one month
(d) five year.

Question 18:
One female mosquito during her life span can lay
(a) 100 eggs
(b) 1000 eggs
(c) 2000 eggs
(d) 1000-3000 eggs.

Question 19:
According to the WHO the malaria deaths that occur worldwide in a year is
(a) 1.5-2.7 lakh
(b) 1.5-2.7 million
(c) 15-27 lakh
(d) 15-27 million.

Question 20:
Life span of male & female mosquito is
(a) Male – 1 year, Female – 2 years
(,b) Male – 1 month. Female – 1 year
(c) Male – 1 week, Female – 1 month
(d) Male – 1 day, Female – 1 week

Question 21:
The only mosquito that lays its egg on damp soil is
(a) Anopheles mosquito
(b) Aedes mosquito
(c) Culex tersalis mosquito
(d) None of these

Question 22:
Eggs hatch into larva of mosquitoes within
(a) 48 days
(b) 48 weeks
(c) 48 hours
(d) 8 days

Question 23:
The raft of eggs layed by mosquito has approximately
(a) 200-300 eggs
(b) 20-30 eggs
(c) 2000-3000 eggs
(d) 100-200 eggs

Question 24:
Larva of mosquitoes breath through……………and eat…………
(a) siphon ; algae
(b) siphon ; algae & small organisms
(c) skin ; algae
(d) skin ; small organisms

Question 25:
The disease caused due to vectors carried by Aedes aegypti is
(a) Dengue
(b) Yellow fever
(c) Chickengunya fever
(d) all of the above

Questions based on Observational Skills

Question 26:
After the fourth molt, mosquito larva changes into
(a) pupae
(b) tumblers
(c) both (a) and (b)
(d) none.

Question 27:
The pupae breathe through
(a) trumpets
(b) siphon
(c) molts
(d) wriggler.

Question 28:
The correct order for stages of mosquitoes life cycle are
(a) egg, nymph, adult
(b) egg, pupa, larva, adult
(c) egg, larva, pupa, adult
(d) egg, larva, adult.

Question 29:
How many legs do mosquitoes have?
(a) three
(b) four
(c) five
(d) six.

Question 30:
The main sections of mosquito body are
(a) head, thorax, abdomen
(b) head, thorax, wings
(c) head, abdomen, wings
(d) head, abdomen, tail.

Question 31:
The adult mosquito breathes through
(a) lungs
(b) gills
(c) air sacs
(d) spiracles.

Question 32:
The diagram shows the life cycle of a mosquito, the missing stages (i) and (ii) are __

(a) (i) pupa (ii) larva
(b) (i) larva (ii) pupa
(c) (i) tumbler (ii) wriggler
(d) (i) tumbler (ii) pupa.

Question 33:
Which of the given feature the pupa does not show?
(a) tail
(b) wing
(c) mouth
(d) abdomen.

Question 34:
The given diagram shows the stage of mosquito, also called

(a) wriggler
(b) Tumbler
(c) raft
(d) instars

Questions based on Reporting and Interpretation Skills

Question 35:
Mosquitoes stab two tubes into the skin one is to inject saliva other one is
(a) to inject coagulants
(b) to suck blood
(c) hold the hole open
(d) extract soft tissue.

Question 36:
The mosquitoes spread malaria but the only role it plays is
(a) grows parasite larvae in the gut
(b) passes germs from dirty water to humans
(c) deposits faeces into a person’s skin
(d) acquires parasite from one human and pass it to another.

Question 37:
What is the incorrect statement for mosquitoes?
(a) Mosquitoes are attracted to dark colours.
(b) Mosquitoes can smell your scent and carbon dioxide you exhale.
(c) A female mosquito will continue to bite until it has collected enough protein.
(d) Mosquitoes spread disease by feeding on an infected host and then biting a human.

Question 38:
Female mosquitoes feed on blood because
(a) It does not feed on anything else.
(b) It needs protein to grow bigger in size
(c) It needs protein and iron to develop eggs
(d) It needs calcium and iron to develop eggs

Question 39:
Female mosquitoes detect host by
(a) colour of clothes they wear
(b) colour of light they emit
(c) body colour of the host
(d) detecting carbon dioxide released by host

Question 40:
The non-feeding or resting stage of mosquito life cycle is
(a) larva
(b) Pupa
(c) Adult male mosquito
(d) Adult female mosquito

Question 41:
The length of the life cycle of mosquito is
(a) 30 weeks
(b) 30 days
(c) 30 hours
(d) 30 months

Question 42:
To prevent the clotting of human blood the mosquito injects the anti-coagulant in human body that is
(a) Mosquitoes blood
(b) Mosquitoes saliva
(c) Mosquitoes enzyme
(d) none of these

Question 43:
Female mosquitoes feed on blood of
(a) Human being
(b) cow
(c) dog
(d) all of the mammals

Question 44:
Shedding of skin by larvae is called
(a) Wriggling
(b) Instar
(c) Moulting
(d) Tumbler

SCORING KEY WITH EXPLANATION

1. (c) Mosquitoes are insects and belong to phylum arthropoda.
2. (a) Vectors are carriers of disease causing micro-organism called pathogens.
3. (d) Different species of mosquitoes have different feeding habits.
4. (c) Female mosquitoes lifespan is around 30 days.
5. (b) Aedes aegypti causes chickengunya.
6. (d) All the given Plasmodium causes malaria.
7. (c) Malaria parasite multiplies in liver of human body.
8. (b) Malaria parasite multiplies in gut of mosquito body.
9. (b) Larvae can be easily killed.
10. (a) Larvae are called wrigglers and pupae are called tumblers because they show this movement in water.
11. (b) Not all species of mosquito drinks blood.
12. (d) Cholera is a water borne disease caused by bacteria.
13. (d) Around 3,500 species of mosquitoes are found all over the world.
14. (c) Male and female mosquito sucks nectar from flowers.
15. (a) Anopheles mosquito spreads malaria.
16. (d) Mosquito are carriers of many pathogens that causes the diseases in human.
17. (d) Egg of mosquito are found to be survived for 5 years.
18. (d) Female mosquito in its life span can lay 1000- 3000 eggs.
19. (b) 1.5 to 2.7 million is the number of death caused due to malaria, in the data of WHO.
20. (c) Adult male can survive for 1 week and female mosquito for 1 month.
21. (b) Aedes mosquito lays egg on moist soil.
22. (c) Hatching of larvae takes 48 hours from the egg of mosquito.
23. (a) Raft of eggs have 200-300 eggs in it.
24. (b) Larvae breathe through siphon and eat algae or small organism in water.
25. (d) Aedes aegypti is a carrier of many types of pathogens that can cause all the given diseases.
26. (c) Mosquitoes larva changes into pupae, its also called tumblers.
27. (a) The pupae breathe through trumpets which are breathing tubes.
28. (c) Egg- larva – pupae – adult is the life cycle of mosquito.
29. (d) Mosquitoes have 6 legs.
30. (a) The body of mosquito is divided into 3 parts, head – thorax – abdomen.
31. (d) Spiracles are small breathing pores on mosquito body.
32. (b) Egg- larva – pupae – adult is the life cycle of insect.
33. (c) Pupa do not feed, has no mouth.
34. (b) This is a pupa also called tumbler due its movement.
35. (b) One tube of mosquito injects saliva to prevent blood clotting and the other tube sucks the blood.
36. (d) Mosquitoes are carriers of disease.
37. (a) Mosquitoes are not attracted to dark colours.
38. (c) Female mosquitoes need iron and protein to lay eggs.
39. (d) The heat is released due to the release of carbon dioxide gas which helps mosquito in detecting the mammals.
40. (b) Pupa is the non feeding stage of mosquito.
41. (b) Mosquito can survive for around 30 days.
42. (b) Mosquito saliva prevents the blood from clotting.
43. (d) Female mosquito feeds on blood of mammals.
44. (c) Shedding means moulting.

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