Bioresources of Assam HS 2nd year Biology Questions Answers AHSEC

Bioresources of Assam HS 2nd year Biology Questions Answers AHSEC: Bioresources of Assam is chapter 16 from HS second year AHSEC / Class 12 Science Biology. Here you can find Bioresources of Assam notes class 12 and Bioresources of Assam HS 2nd year Biology Questions Answers AHSEC.

Bioresources of Assam Biology AHSEC Questions Answers

Q1. What is ethnobotany ?

Ans: Ethnobotany deals with the relationship between plants and primitive people. It is concerned with the medical, religious uses of plants through the traditional knowledge of a local people.

Q2. Write a note on the plant resources of Assam.

Ans: Assam belongs to North East India and is one of the richest centres of biodiversity. It falls in the Indo-Malayan biodiversity hotspot. The forests of Assam are abundant in innumerable varieties of plants species, which include, timber plants, bamboo cane, medicinal plants, essential oil containing plants, gum and resin yielding plants.

Forests of Assam are also rich in orchids. Assam is also known for the origin of many varieties of plants in use. Rice, bamboo, banana, cane, citrus, orchid, ginger, etc. originated in Assam.

There are 8000 varieties of rice found in wild state. There are 63 varieties of bamboos, 10 varieties of citrus, 300 varieties of orchids, 66 aromatic plant varieties and a large variety of bananas found in this region. Assam along with North East accounts for 50% of the total plant biodiversity of India.

Q3. Write the scientific names and their families of three important timber yielding plants of Assam with their uses.

Ans: Scientific name of cinchona is Cinchona officinalis

The bark obtained from the plant contains quinine which is useful in treating malaria.

Scientific name of neem is Azadirachta indica

Neem is used as mosquito and insect repellant and therefore used while storing rice. It is also used as medicine in ayurveda and siddha due to its antibacterial, antifungal and sedative purpose.

Scientific name of Rauwolfia is Rauvolfia tetraphylla

An alkaloid called reserpine is obtained from rauwolfia and is used as anti hypersensitive drug which is used in ayurveda and unani as a medicine.

Bioresources of Assam AHSEC Important Questions

Q4. Write botanical & common name of three timber yielding plants of Assam.

Ans: The botanical and common names of 3 timber yielding plants of Assam are

Botanical name Common name

Shorea robusta Sal

Tectona grandis Teak

Dalbergia sissoo Sissoo

Gmelina arborea Gamhar

Q5. State the uses of (a) Rauwolfia, (b) Ipecac, (c) Cinchona. Mention their botanical name ?

Ans:

a. The plant Rauwolfia commonly known as ‘sarpagandha’ had been used as drug since ancient times. It roots were used as antidote for snake bite. It was used against various other diseases like fever, dysentery, intestinal pain, cholera, opacity of cornea. The alkaloid ‘reserpine’ isolated from the plant is used against high blood pressure, insomnia, schizophrenia, nervous breakdown and hypertension. The decoction of root is used to increase uterine contraction in labours.

Botanical name of the plant is Rauwolfia serpentina Benth.

b. The alkaloid ‘emetine’ obtained from the root of Ipecac is used for treatment of amoebic dysentery. It stimulates the liver and lowers blood pressure.

Botanical name of the plant is Cephaelis ipecacuanha .

c. Quinine, an alkaloid obtained from the bark of the Cinchona plant is one of the most important drugs known and it is the only adequate medicine for treatment of malaria. Quinine is also used as tonic and antiseptic. The other alkaloids obtained from the plant (quinidine, cinchonine and cinchonidine) are also used as medicine.

Botanical name of the plant is Cinchona officinalis.

Q6. What is sericulture ? What are the different types of silk producing insects found in Assam ?

Ans: Sericulture is the rearing of silk worms that produces the silk based on the quality of the silk and types of host plants, the silk moths can be classified into two different groups,

(a) Mulberry silk worm: The larvae of this moth mainly take the leaves of mulberry plants and the silk produced by them is known as mulberry silk. Bombyx mori is an important species of this group.

(b) Non-mulberry silk worms: The other silk producing moths are together known as non-mulberry silk moth. The important species of this type are

(i) Muga silk worm- Antheraea assama.

(ii) Eri silk worm- Philosomia ricini.

(iii) Tassar silk worm- Antheraea paphia.

Bioresources of Assam Biology chapter 16

Q7. How can you distinguish a muga cocoon from an eri cocoon ?

Ans:

Eri cocoon

• The cocoons are hanged from the twig by a peduncle.

• The cocoons are formed on the upper portion of the plant.

• The cocoon has an open end through which the moth comes out.

• The eri-cocoon has to be spinned instead of reeling as it is an open mouthed cocoon.

Muga cocoon

• The cocoons are formed in between two dry leaves. The cocoon has a small peduncle.

• The fully grown larvae descend to the base of the tree to form the cocoon.

• The chrysalid secretes an alkaline solution which dissolves the cocoon shell to form an aperture for the moth to emerge.

• The cocoons selected for spinning are kept over low fire for killing the chrysalid present inside the cocoon.

Q8. How the muga cocoons are spinned ?

Ans: The cocoon selected for spinning are treated over low fire for a reasonable period and then kept in sunlight for about 2-3 days. Then the cocoons are boiled in an alkaline solution made of certain leaves and straw for about 15 to 30 minutes to remove the glue of the cocoon and to make the silk filament weak. The reeling of the muga cocoon is carried by keeping the cocoon in lukewarm water in a basin. The spinning is done by muga reeling apparatus namely ‘bhir’, ‘muga pedaling bhir’, etc.

Q9. Describe the life history of muga silk worm that you have studied ?

Ans: The life cycle of muga silk worm consists of four stages, namely, (a) Egg (b) Larva (c) Pupa covered but cocoon & ( d) Moth.

A moth needs 48-52 days in summer and 145-150 days in winter to complete the life cycle. The muga worm is a multivoltine species and it breeds 4-5 broods in a year.

(a) Egg- A female moth after mating lays about 250 eggs. Deposition of eggs may continue for three to four days. The eggs are oval shaped with a hard chitinous shell. The eggs are provided with a brown glue which help these to stick to the surface.

(b) Larva- In normal temperature and humidity, the eggs hatch within 9 or 10 days. Normally hatching takes place at dawn. The newly hatched larva possesses black and yellow stripes alternately. In successive moulting it changes its colour and becomes bigger in size. The full grown larva is green in colour but the colour of the head is brown. Soon after hatching the larva disperses in search of food. The larva complete their level all stage within one to three months.

The larvae moults four times and so there are five stages in the larval development. The silk glands are situated at the anterior part of the body. It is a large gland, tubular in appearance and occupies two-third of the body. When the larva gets matured, it wonders aimlessly and prepares itself to form the cocoon.

(c) Pupa- The full frown larvae descend to the base of the tree, ceases to feed and excretes a fluid accompanied by excreta. It then moves aimlessly to find a suitable apace for spinning the cocoon. The larva forms the cocoon in between two dry leaves. The cocoon formation is completed in three or four days and the larva is completely covered by the cocoon. The cocoon has a small peduncle. After the completion of the cocoon, the larva transforms into pupa which is brown in colour. The duration of the pupal stage varies in different seasons.

(d) Moth- After about two or four weeks, the chrysalid emerges as moth normally during the dusk. The head of the chrysalid secretes on alkaline solution which dissolves the cocoon shell and the moth emerges through this aperture. The emerged soon after emergence, the body of the moths are hardened and wings are expanded (the colour of the wing of male moth is deep brown while it is light coloured in female). The male moth is active flier and it searches the passive female for mating. The mating generally starts from night fall and continues till next day and unpairs in the next evening. After mating the moths remain inactive for a day. After unpairing the female moth lays about 250 eggs for 3-4 days.

Bioresources of Assam HS 2nd year Biology Solution

Q10. Describe the life history of eri silk worm that you have studied.

Ans: The life cycle of eri silk worm (Philosomia ricini) is completed through four stages:

(a) Eggs (b) Larva (c) Pupa in cocoon & (d) Adult moth.

The cycle is completed in 44-48 days in summer and takes about 85-87 days in winter.

(a) Eggs: The eggs are oval shaped with medium size and are covered by a hard chitinous white or creamy coloured shell. A female moth after copulation lays about 300-500 eggs in cluster which may continue for 3-4 days. The hatching of eggs takes place after about 10 days but it depends on the temperature of the environment.

(b) Larva: After hatching the larvae tend to remain together. It is about one centimeter in length and grown to 8 centimeter when mature. The newly hatched larva possesses a black coloured head and the body becomes yellow in colour but gradually changes to green yellow. The larva matures in 17 to 45 days which depends on the environmental temperature and humidity. On moulting, the integument of the head breaks on the sides and the larva comes out with a new integument. The larva possesses long tubular silk glands which are responsible for production of silk. The silk gland secretes the silky substances to form the cocoon where the larva transforms into a chrysalid.

(c) Pupa: The larva of last instar before moulting ceases feeding and transform into a chrysalid. The larva excretes silky substance after settling in a crevice and spins the cocoon, which is completed in 3-4 days. Inside the cocoon, the larva transforms itself into a brown coloured chrysalid. The essential organs of the moth are then formed and the body is covered by a hard integument. Diapause may occur in this stage. The colour of the chrysalid turns black before the emergence of the moth.

(d) Moth: The moth emerges from the chrysalid form after about 2 week. The moth comes out through the open end of the cocoon normally in morning houses. After sometime they fully stretch their wings. The body of the male moth measures 2.5cm while that of female is 3cm. After stretching the wings, the male finds out the female for mating which lasts about 24 hours. During mating, the moth remains motionless. The male unpairs in next evening and after this the female lays the eggs, normally during the night.

Q11. How the eri-silk thread is spinned from the cocoon ?

Ans: The eri-cocoon has to be spinned instead of reeling as it is an open mouthed cocoon. The moth emerges from the cocoon through the open mouth without disturbing the cocoon and its fibre. For spinning, cocoon are first cleaned off the pupal and moulted skin, otherwise it will spoil the quality of the eri thread. The cocoons are then boiled in alkaline solution made traditionally from ashes of certain leaves or straw for 2-3 hours. Soda and potash solution are used commercially. Boiling is done for removing the gum like substances from the cocoon. After boiling the cocoons are wrapped in a green leaf for 3-4 days. These are then washed with sufficient amount of water and dried. The well dried cocoons can be preserved for a long time for spinning.

Bioresources of Assam class 12 Science, Biology

Q12. What are the host plants of eri-silk worm ?

Ans: Eri worm is polyphagus and feeds on leaves of a variety of plants. Castor plants are the most important host plant of Eri. Between two varieties of castor plant, seed is preferred to green. Besides, the leaves of Kesseru, Tapioca, Gomari, Payan, Gulancha, etc. are also used in eri-culture.

Q13. How many instars are found in the larval development of eri silkworm ?

Ans: Five instars are found in the larval development of eri silk worm.

Q14. Why the eri cocoons are spinned instead of reeling ?

Ans: The eri cocoons are spinned instead of reeling because they are open mouthed worm. The moth emerges from the cocoon through the open mouth without disturbing the cocoon and its fibers.

Q15. Name the important diseases of silk worm. Write the symptoms of the diseases and also mention the control and preventive measures.

Ans: Two important diseases of eri silk worms are

(i) Flacherie locally known as ‘mukhlaga’.

(ii) Pebrine locally known as ‘phutukia’.

(iii) Grasserie locally known as ‘Phula rog’.

(iv) Muscardine.

Q16. Name some pests of eri silk worm.

Ans: The important pest of eri silk worm is ‘Tachind’ fly. Some other pests are ants, wasps, hornets, cockroaches, lizards and rats.

Q17. Why muga silk is known as “queen of silk” ?

Ans: Commercially the muga silk is more costly and also the colour of the thread is golden yellow which is unique to the species. So muga silk is known as “queen of silk”

Q18. What are the different host plants of muga silk worm ?

Ans: Muga silk worm is a polyphagus species and feeds on variety of plants. The most common host plants are ‘som’ and ‘sualu’. The secondary host plants are ‘Mijankari’, ‘Digloti’, ‘Bagri’ and ‘Bajramani’.

Q19. Name the different stages found in life history of muga ?

Ans: The life cycle of muga silk worm consists of four stages namely

(i) eggs (koni)

(ii) larva (polu)

(iii) pupa covered by cocoon (leta) and

(iv) moth or adult (chakari).