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An Overview of AHSEC Class 12 Biology Notes for 2025
| Name of Board | AHSEC |
| Class: | Assam Board Class 12 |
| Subject: | AHSEC Class 12 Biology |
| Number of Chapter: | 14 |
| Chapter Name | Bioresources |
| Content Type: | Text, Images and PDF Format |
| Academic Year: | 2024-25 |
| Medium: | English |
| Available Solution Link: | AHSEC Class Biology Notes |
AHSEC Class 12th Biology Chapter: 14 Bioresources
A. FILL IN THE BLANKS. (1 mark each)
1. Natural resources are the products of _____and ____.
Ans. Vegetation and Wildlife and
2. Out of 400 varieties of total Indian orchids, Assam is the home of nearly_____ orchid varieties.
Ans. 293
3. About_____ nos of alkaloids have been isolated from the parts of Rauwolfia plants.
Ans. 20
4. Quinine and cinchonine are obtained from_____plant.
Ans. Cinchona
5. Wood is the secondary tissue produced by the_____ tissue of large trees.
Ans. Xylem
6. The sericogenic insects belong to the order ______
Ans. Lepidoptera
7. The female muga moth lays about_____ Kharika. eggs on
Ans. 250
8. Pebrine is caused by_______.
Ans. Nosema bombycis.
9. Kasseru is______ food plant of eri silkworm.
Ans. host.
10. Increase in concentration of toxicant at successive trophic levels is known as_____
Ans.: Biomagnification.
11. Major component of natural resources produced from Plants and Animals are called______
Ans. Fossil fuels
12. Role of Plants in controlling rainfall, soil erosion, pollution etc. ultimately maintain the_______of our environment.
Ans. Balance
13. Alkaloid reserpine obtained from the plant_____ _____.
Ans.: Rauwolfia serpertina.
14. A popular drug ‘Vaska’ prepared from_____and used as______
Ans.: Adhatsda Vasica, Cough expectorant
15. Botanical name of Sal tree is______.
Ans. Shorea robusta.
B. TRUE OR FALSE (1 mark each)
1. Plants provide food, clothes and shelter to the human.
Ans. True
2. Quinine, quinidine, cinchonine are the important and adequate medicines used to promote strength and vigor.
Ans. False
3. Medicines obtained from Atropa belladonna is used to get relieve from pains of cardiac muscles and palpitation of heart.
Ans. True
4. Heart wood and sap wood of teak plant are white and golden yellow respectively in colour.
Ans. False
5. Gmelina arborea is the botanical name of Indian redwood (sisso) belonging to family Verbenaceae.
Ans. False
6. Sericulture is an important cottage industry of Assam.
Ans. True
7. The primary food plant of Bombyx mori is castor.
Ans. False
8. The eggs of silk moth are washed in 2% formalin for disinfection.
Ans. True
C. VERY SHORT ANSWER QUESTIONS: (1 MARK EACH)
1. What is natural resource?
Ans. All components of natural origin found in the atmosphere hydrosphere and lithosphere which support life and are needed for survivobility and prosperity are called natural resources.
2. What do you mean by Biological hot spot?
Ans. Biological hot spot are the areas of high endemism and very high levels of species richness.
3. What are the genetic resources of forest?
Ans. Trees, shrubs or any other woody vegetation.
4. Who first described the plant Rauwolfia?
Ans. Benthum
5. What do you understand by rain forest?
Ans. The forests which occur in equatorial and subequatorial regions which receives abundant rainfall, bright sunshine, warmth and high humidity for optimum plant growth.
6. What is sericulture?
Ans. Sericulture is the rearing and management of silk worms.
7. Write the name of the family to which Mulberry silk moth belongs.
Ans. Bombycidae.
8. Write the scientific name of mulberry silk moth
Ans. Bombyx mori.
9. Describe the precautionary measures to be taken in muga silkworm rearing..
Ans. 1) Sualu leaves are better for rearing the muga larvae in earlier stage. So rearers maintain some sualu plant along with some som plants for rearing of larva.
2) The larvae should be protected from dust and smoke.
3) Overcrowding of larvae should be avoided.
10. Define spinneret.
Ans. A spinneret is a tube like structure on a larva’s lower lip that contains the spinning apparatus (the silk glands) of the larva.
11. When did the Air (Prevention and Control of Pollu- tion) Act came into force in India?
Ans.: 1981
12. What are major necessities of human life provided by plants?
Ans. The major necessities of human life provided by plants are-
(i) Plants provide food of various kinds such as cereals, pulses, etc.
(ii) Plants provide fibres e.g., Jute, Cotton.
(iii) Plants provide oxygen.
(iv) Plants also provide various medicines.
13. What is the botanical name of Cinchona plant?
Ans. Cinchona officinalis
14. Why Neem plant is called wonder plant?
Ans. Neem plant is called wonder plant because every part of the plant body i.e., stem leaf, flower, bark has some medicinal property.
D. SHORT ANSWER QUESTIONS (2 MARKS EACH)
1. What is the causative organism and symptoms of Flacherie?
Ans. The causative organism of Flasherie is a virus.
Symptoms Flacherie is mostly prevalent in muga culture during summer. The infected larva soon die and sometimes the entire brood is completely destroyed. The infected larva cannot spin the cocoon properly and most of the larva die before spinning the cocoon.
2. What measures are to be adopted when the culture is infected by flacherie.
Ans. When the culture is infected by flawcherie, to prevent it, overcrorousding of the larvae must be prvented. The disease free seeds should be reared only. The larvae should be provided with tender leaves as far as practicable and it should be kept away from sun and rain.
3. What are the species of commercially reared Tasar silkworm. State the name of two food plants of Tasar silkworm
Ans. Antheraea paphi, Antheraea mylitta Food plants → Oak and Sal plants.
4. Give the systematic position of muga silkworm.
Ans. Muga Antheraea assama Primary host plant Eri Philosomia ricini Primary host Som and Sualu Castor plant.
5. According to scientific name and one primary host plant of muga and ari silkworm.
Ans. (i) Mulberry silk worm (Bombyx mori) Family Bombycidae
(ii) Muga silk worm (Antheraea assama) Family – Saturnidae
(iii) Eri silkworm (Philosomia ricini) Family Saturnidae
(iv) Tasar silkworm (Antheraea paphia) Family Saturnidae
6. Give the scientific name and one primary host plant of muga and eri silkworms.
Ans. Phylum – Arthropoda
Class – Insecta
Order – Lepidoptera
Family – Saturnidae
Genus – Antheraea
Species – assama.
7. What are the different silkworms cultured in Assam commercially.
Ans. Mulberry silkworm, Muga silk worm, Eri silkworm and Tasar silkworm.
8. Give the botanical name mentioning their family names of the two plants whose roots are used for preparation of medicines.
Ans. (i) Rauvolfia serpentina Family Apocyanaceae
(ii) Cephaelis ipecacuanha (ipecac) Family Rubiaceae
9. “Assam is a land of biological hot spot” Give reasons.
Ans. Assam is a constituent unit of the Eastern Himalayan biodiveristy region, one of the two biodiversity hot spots in the country. The climatic condition and wide variety of physical features witnessed in Assam have resulted in a diversity of ecological habitats such as forests, grasslands, wetlands which harbour and sustain wide ranging floral and faunal species, Because of this biodiversity Assam is considered as a land of biological hot spot.
10. What is ethnobotany? How it is related. to medicinal plants?
Ans. Ethnobotony is the scientific study of the relationships that exists between people and plants.
Traditional knowledge related to bioresources is knowledge accumulated by various local communities, tribesmen and medical practitioners over long period of history regarding the use in medicine. Ethnobotanists reveal the locally important plant species and the traditional knowledge related to its for the discovery of crude drugs or medicine. In this way ethnobotany is related to medicinal plants.
11. How and why almost all animals including human are directly or indirectly depend on plants for survival?
Ans. Plants are the sources of food for all other organism. Man depends upon plants not only for food but also for many other materials on which his culture and civilization depend. Other organisms also depend upon plants for food and shelter. Plants are useful for maintaining natural balance. They increase fertility, check soil erosion, conserve soil water, reduce the effect of flood and desertification.
12. What are the cellular constituents of commercial tim- `ber?
Ans. In commercial timber the outer region of the wood is of light colour and is known as sapwood, while the inner region is of dark colour and is known as heartwood. The heartwood is filled with tannins, oils, m gums, resins etc. is hard and durable. The heartwood usually takes good polish and can be put to various uses.
13. Write the botanical names of any two medicinal plants from which cough expectorant is prepared.
Ans. Two plants from where cough expectorants are prepared are-
(i) Adhatoda vasica (Vasak)
(ii) Glycyrrhiza glabra (Jastimadhu)
(E) SHORT ANSWER QUESTION (3 MARKS EACH)
1. Give the scientific names mentioning their families of three popular and important timber yielding plants of Assam.
Ans. Sal- Shorea robusta Family Dipterocarpaceae
(ii) Teak Tectona grandis Family Verbenaceae
(iii) Sissoo Dalbergia sissoo Family Leguminosae
2. Write the scientific names with their utility of the following plants.
Ans. (a) Rauvolfia Rauvolfia serpentina.
Utility: Reserpine isolated from this plant is used against high blood pressure, insomnia schizophrenia, nervous breakdown and hypertension. Juice of leaves is use to remove opacities of the cornea.
(b) Cinchona Cinchona officinalis
Utility: Quinine is one of the most important drugs obtained from the bark of cinchona trees. It is very bitter, white granular substance. It is the only adequate medicine for treatment of malaria. In addition to its quinine is also used as tonic and antiseptic.
(c) Teak Tectona grandis
Utility: It is the main building material of our country. It is extensively used in house building, bridge building and for making railway sleepers, furniture etc.
(d) Sal Shorea robusta
Utility: It has extensive use in making piles, beams, planking, bridge building and boat making. It makes excellent frame for doors and windows. The resin is used as increase. The barks are used to prepare some kinds of dye.
(e) Indian red wood (sissoo) – Dalbergia sissoo.
Utility: It makes high class wood for furniture and cabinet Because of its strength, elasticity and durability it is used for making wooden frameworks, agricultural implements, boats, railways sleepers etc.
(f) Neem Azadirachta indica
Utility: Neem leaves are used to treat leprosy, chicken pox and also in curing neuromscular pains. Neem has antibacterial properties that help in fighting against skin infections such as acne, psoriasis etc. Neem extracts also help in treating diabetes. Neem oil extracted from the seeds has insecticidal properties due to which it has been used for pest control. Flowers are used for elimination of intentional worms. Bark is used as analgesic curative of fever.
3. Why eri silkworm is called polyphagous? State the different food plants of eri silk worms.
Ans. Eri silkworm is called polyphagous because it feeds on leaves of variety of plants.
Castor plant is the most important host plant of eri. Two varieties of castor plants red and green are used though red in usually preferred. The leaves of ‘Kesseru’, ‘Barkesseru’, Tapioca, Gomari, Payan and Gulancha are also used in sericulture. In Assam, host plants are not normally cultivated in organized manner but the rearers keep some host plants in their home for ericulture.
4. Write briefly how muga silk is obtained from the cocoon.
Ans. The cocoons are kept over low fire for a reasonable period (about an hour) thereby killing the chrysalid present inside the cocoon. The treated cocoons are then kept in sunlight for two or three days. Then the cocoons are boiled in an alkaline solution for about 15-30 minutes to remove the glue of the cocoons. The boiling in alkaline solution makes silk filament weak, Along with the alkaline solution, some other substances such as ‘owtenga’, simalu bark etc are also added to facilitate easy reeling. The reeling of the muga cocoon is carried by keeping the cocoon in lukewarm water.
5. “Assam is very rich in sericogenic resources”. Explain the statement.
Ans. The north eastern region of India occupies an important position in sericulture map of India, Sericulture practice is mostly confined to the Brahmaputra valley and its surrounding areas. The climate and general environment of Assam is well suited to ericulture. The congenial atmosphere helps the cultivation of the host plants and availability of the serigenous insects. Traditional varieties of silk culture include eri, muga, mulberry and Tassar. Eri and muga are considered to be of indigenous origin. The muga silk is known for its fine sheen and golden colour is used by the local silk weaving industry and this has contributed to the development of muga culture in the silk.
6. “Forests are full of future genetic resources”. Explain the statement.
Ans. Forests are the most important natural resources for man. It has immense value to human civilization. Forests resources will never get exhausted and will continue for ever if proper scientific management and conservation practices are followed to increase its productivity. About 80% of food is got from 20 plants. Worldwide about 25,000 species of plants are being used in traditional medicines, Forest resources are also the basis for large scale wood production to satisfy the worldwide need for timber and paper. Apart from these various other economically important things are abtained from the forests which will help the human civilization to survive not only today but in futuer also. Thats why it is said that forests are full of future genetic resources.
7. Describe a case study of integrated Waste Water Treat- ment.
Ans. Integrated waste water management was done by utilising a mix of artificial and natural processes in the town of Arcata situated along the northern coast of California Collaborating with biologists from the Humboldt State University, the towns people created an integrated waste water treatment process within a natu- ral system. The cleaning occurs in two stages-
(a) The conventional sedimentation, filtering and chlorine treat- ments are given. After this stage lots of dangerous pollutants like dissolved heavy metals still remain..
(b) Secondly the biologists developed a series of six connected marshes over 60 hectares of marshland. Appropriate plants, algae, fungi and bacteria were seeded into this area which neutralize, absorb and assimilate the pollutants. Hence, as the water flows through the marshes it gets purified naturally.
8. Discuss the anatomical characters of timber produced from teak and hill teak. Mention their botanical names.
Ans. Teak Tectona grandis Anatomical characters- Timber is fairly hard, exceedingly du- rable and strongly scented. It takes a high polish. It contains an oil that acts as a preservative of the timber. The sapwood is white and the heartwood dark golden yellow, but gradually turns dark brown.
Hill teak: Cedrus deodara Anatomical characters : The wood is light yellow brown in colour and has a characteristic odour.
LONG ANSWER QUESTION (5 MARKS EACH)
1. Describe the life cycle and rearing of muga silk moth.
Ans. The life cycle of muga silk moth consists of four stages.
(i) Eggs: A female moth after mating lays about 250 eggs. The eggs are oval shaped with a hard chitinous shell. The eggs are provided with a brown glow which helps the eggs to stick to the surface. The eggs are collected and washed with 2% formaline to prevent the pebrine disease.
(ii) Larva: In normal temperature and humidity, the eggs hatch within 9 or 10 days. Soon after hatching, the larva disperses in search of food. The larva complete their larval stage within one to three months. The larva moults four time. So there are five stages in the larval development. Moulting of skin takes place at an interval of four or five days.
In rearing the newly hatched larvae are placed on the tender leaves of dwarf host plants. The larvae starts feeding on the tender leaves of sualu plants. When all the leaves are eaten up the larvae descend to the base of the tree. All this stage the larvae are collected by ‘Chaloni’ to be hanged to a new tree. The process continues till the larva are fully matured and prepared themselves to form the cocoon.
(iii) Pupa: The full grown larvae descend to the base of the tree, ceases to feed and excretes a fluid accompanied by excreta. The cocoon formed is completed in 3 or 4 days. After the completion of the cocoon, the Larva transforms into pupa.
(iv) Moth: After about two to four weeks, the chrysalid emerges as moth. The head of the chrysalid secretes an alkaline solution which dissolves the cocoon shell. Through this aperture the moth emerges. The male moth is active flier and its searches the female moth for mating. The mating generally starts from nightfall and continues till next day and unpair in the next evening. After mating the moths remain inactive for a day. After unpairing the female moth lays the eggs. for three to four days.
2. Write a note on disease of silkworm mentioning the causative organism of each disease.
Ans. The diseases of silkworm are
(i) Pebrine (locally called phutukia): It is caused by a protozoa namely Nosema bombycis. The larva generally gets infected from the shell of the eggs. So, it is inherited from the infected mother. The disease may also spread by infected leaves of the host plants. When infected the larva becomes weak and the silk glands are not properly developed. The disease can be prevented by keeping the live cocoons in a temperature of 34°C at the prepupal stage for about 16 hours. It can also be prevented by heating the eggs after deposition in 40°C in a hot water bath for 20-30 minutes. Also washing the eggs with 2% formal and by eliminating the disease infected moth in rearing prevents the disease.
(ii) Flacherie (locally called mukhlaga): Caused by a virus followed by a secondary bacterial infection. The infected larva soon die and sometimes the entire brood is completely destroyed. The infected larva cannot spin the cocoon properly and most of the larva die before spinning of the cocoon. To prevent this disease over crowding of the larvae must be prevented. The disease free seeds show be reared only. The larvae should be provided with tender leaves and its should be kept aways from sun and rain.
3. Describe the life cycle and rearing of muga silk moth.
Ans. The life cycle of muga silk moth consists of four stages.
(i) Eggs: A female moth after mating lays about 250 eggs. The eggs are oval shaped with a hard chitinous shell. The eggs are provided with a brown glow which helps the eggs to stick to the surface. The eggs are collected and washed with 2% formaline to prevent the pebrine disease.
(ii) Larva: In normal temperature and humidity, the eggs hatch within 9 or 10 days. Soon after hatching, the larva disperses in search of food. The larva complete their larval stage within one to three months. The larva moults four time. So there are five stages in the larval development. Moulting of skin takes place at an interval of four or five days.
In rearing the newly hatched larvae are placed on the tender leaves of dwarf host plants. The larvae starts feeding on the tender leaves of sualu plants. When all the leaves are eaten up the larvae descend to the base of the tree. All this stage the larvae are collected by ‘Chaloni’ to be hanged to a new tree. The process continues till the larva are fully matured and prepared themselves to form the cocoon.
(iii) Pupa: The full grown larvae descend to the base of the tree, ceases to feed and excretes a fluid accompanied by excreta. The cocoon formed is completed in 3 or 4 days. After the completion of the cocoon, the Larva transforms into pupa.
(iv) Moth: After about two to four weeks, the chrysalid emerges as moth. The head of the chrysalid secretes an alkaline solution which dissolves the cocoon shell. Through this aperture the moth emerges. The male moth is active flier and its searches the female moth for mating. The mating generally starts from nightfall and continues till next day and unpair in the next evening. After mating the moths remain inactive for a day. After unpairing the female moth lays the eggs. for three to four days.
4. Explain why northeast region of India specially Assam is regarded as very rich in plant resources.
Ans. The region is characterised by diverse physiography ranging from plains, plateaus and mountains with associated valleys. The region receives moderately high rainfall and the average minimum and maximum are 1650 mm and 6320 mm respectively. Assam is a part of both Himalaya as well as Indo-Burma biodiversity hotspots in the world. It forms a unique biogeographic province encompassing major biomes recognized in the world. It has the richest reservoir of plant diversity in India because of its climatic condition and location. All types right from the grassland, meadows, marshes, swamps, scrub forest, mixed deciduvous forests, humid evergeen forests are found here. The varied forest types found in the region are home to numerous plants. These all reasons make Assam rich in plant resources.
5 Discuss briefly giving your views how plant resources of Assam can be utilized for economic development of the people.
Ans. During the course of evolution of human civilization man gradually gathered experience of the use of various type of plants for various purposes. Scientific knowledge is essential for identification and utilization of various plants and plant products. It is also essential to improve the quantity and quality of the products and their sustainability. The various ways how plant resources can be utilized for economic development are
(i) Drugs and Medicines: Many important therapeutic medicines can be developed from plant materials. In traditional medicines thousands of plants are used in preparation of drugs. A number of drugs from traditional medicine system can be scientifically examined to find out the important biochemical. And more potent medicines can be prepared by chemically modifying the therapeutically useful plant biochemicals.
(2) Fibres: Natural fibres are obtained from Cotton, Jute, Flax, hemp etc. which are used in industries for making different articles.
(3) Timber: Forest trees of Assam has lots of timber value and are very expensive. So if it is properly utilized and timber industry is developed then it will help in economic development of the people.
(4) Tannins: Bark of trees provide a number of products. It is being increasingly used as a larger lasting substitute for peat but two traditional benefits are tannins and bost for rope making. Tannins are astringent asidic substances used in treating leather and formation of inks and dyes.
(5) Oils and resins: Essential oils are extracted from a variety of forest plants such as rosha grass, sandal wood etc. Trees also provide resins and latex. Resins yield turpentine and similar products, white latex is the raw material for rubber.
Thus the plant resources available in Assam is scientifically used for preparation of above mentioned products, then it will help in the economic development of the people.
6. State briefly how water pollution can be controlled?
Ans. For controlling water pollution there are come preventive measures and some curative measures-
1. Preventive measures-
(a) Proper disposal of sewage should be done so that it does not find its way into water bodies.
(b) Oil spill should be prevented.
(c) discharge of effluents into rivers, lakes and sea should be strictly prohibited without treatment.
(b) Abuse of water must be checked.
2. Curative measures
(a) Using septic tanks, waste water treatment plants, sewage treatment plants etc. to reduce the waste products present in water.
(b) For drinking purposes water is purified through various steps including biological treatment and disinfection.
(c) Industrial water can be made less polluted before discharge by biological treatment using water hyacinth. Water hyacinth has remarkable capacity to accumulate poisonous metals including ra- dioactive wastes.
(d) Certain strains of bacteria can reduce the oil spill effect and can use up cyanides and heavy metals if judiciously used.
7. Discuss in brief giving their botanical names, parts used and purposes of uses of any five medicinal plants uti- lized in traditional practices by ethnic groups.
Ans. Five medicinal plants utilized in traditional practices by ethnic groups are-
1. JASTIMADHU
Botanical name: Glycyrrhiza globra
Parts used: Underground stems and roots.
Purpose of use: It is used as a remedy for coughs, bronchitis, asthma and certain urinary troubles. It is also supposed to produce a healing effect in gastric ulcers.
2. INDIAN ALOE :
Botanical name Aloe barbadensis
Parts used Leaves
Purpose of use After removal of skin from the leaf, they are given to persons suffering from fevers, constipation, joundice, sheumatism, certain skin diseases etc. It is regarded valuable for piles. The leaf juice is used for removal of intestinal worms in children.
3. CHIRETTA
Botanical name: Swertia chirayita
Parts used Stem (dried plant)
Purpose of use: It is stomachic, antihelmentic, laxative, antidiarrhoeic. It is a good remedy for bronchitis, asthma and liver ailmerts. It can be used for skin discases.
4. VASAK
Botanical name: Adhatoda vasica
Past used fresh leaves, root.
Purpose of use: Useful in ailments like bronchitis, asthma, fever, jaundice. Leaves and roots are antispasmodic and very good for treatment of coughs.
5. OPINUM PAPPY
Botanical name: Papaver somniferum
Part used dried latex
Purpose of use Opinum are widely used for relieving pain and are considered valuable as hypnotics. It is also used for treat- ment of diarrhoea and also used as a diaphoretic.
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Last Words on AHSEC Class 12 Biology Chapter: 14 Bioresources
The Chapter 14 of AHSEC Class 12 Biology deals with Bioresources for a brief understanding. You can Download this HS 2nd Year Biology Notes in PDF 2025.
