for grade XII

digestive system
Human beings are heterotrophic. It means they can not manufacture their food and depend upon plants or other animals. They have holozoic type of nutrition. The nutrition is animal like. Human beings are omnivorous in nature.
The digestive system consists of alimentary canal and digestive glands. Alimentary canal is complete and has well defined regions. It is concerned with ingestion, digestion, absorption and egestion of waste material.

Alimentary canal
It is a long coiled tube of about 8 to 10 meters long. It is of various diameter at various parts. It starts from mouth and ends in anus.
Different parts are:
Mouth
Vestibule
Buccal cavity
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine
Anus


Mouth
It is a transverse slit like opening bounded by movable upper and lower lip. It opens into a small gap called vestibule. Vestibule is a space between lips and jaw. It opens not buccal cavity.

Buccal cavity
It is known as oral cavity or mouth cavity also. It is bounded by upper and lower jaws. The upper jaw is fixed and lower jaw is only movable up and down and sidewise. The jaws are provided with teeth in a row. At the floor, there is tongue. The roof of buccal cavity is made by palate.

Teeth
Human beings and most of other mammals are heterodont. They have different types of teeth with different functions.
1. incisors -- help to cut large piece into small pieces
2. canines -- help in tearing flesh
3. premolars – help in mastication
4. molars – help in mastication

They are diphyodont. They have two sets of teeth, milk teeth and permanent teeth.
Dental formula – it is expression of number and type of teeth on right or left side (one side) of jaw.
Dental formula of milk teeth i 2/2 c 1/1 pm 0/0 m2/2 5x2/5x2 = 20
Dental formula of permanent teeth i 2/2 c1/1 pm 2/2 m 3/3 8x2/8x2 = 32
i stands for incisor
c stands for canine
pm stands for premolar
m stands for molar
the numerator is for number of teeth in upper jaw
the denominator is for number of teeth in lower jaw

milk teeth start to drop out at about age of 5 or 6. the 3rd molar teeth are also known as wisdom teeth and appear at about the age of 17 to 21. teeth in females appear earlier than in males.
Structure of tooth
It has 3 regions
o Crown – part which project above gum
o Neck - part surrounded by gum
o Root - part embedded in bone, the incisor and canine and lower premolar have one root, upper premolar and lower molar have 2 roots and upper molar have 3 roots.

Tooth consists of enamel which is the hardest part of human body. It covers the dentine of crown. Dentine has many canaliculi that pass radially from the pulp cavity. Cement covers root of tooth. Periodontal membrane covers cement and fixes tooth in socket(thecodont).

Inside tooth, there is pulp cavity containing mass of cells, blood vessels and nerve constitute pulp. It is for growth of tooth. Dentine forming odontoblast and enamel forming ameloblast cells are also present.

Tongue
It is highly muscular organ attached at the floor of buccal cavity by a fold called frenulum. The upper surface is provided with numerous papillae containing taste buds. The taste buds are sensitive to taste of food.
Types of papillae
o Filliform- smallest, most numerous, conical, mostly found at center of tongue, white in color.
o Fungiform - less in no. red and rounded, found at tip and margin of tongue.
o Vallate papillae- large in size, about 5 to 12 in no. arranged in inverted v shape at the base of tongue.
o Foliate – leaf like, not developed in man, found at sides of tongue.

Tip of tongue – sweet
Sides of tongue – sour
Posterior end of tongue – bitter.

Functions of tongue
o Detects taste
o Helps in chewing, mix saliva
o Aids in swallowing
o Cleans teeth and gum
o Plays role in speech

Palate
The roof of buccal cavity is called palate. Anterior part is called hard palate. It bears transverse ridges called rugae. The posterior part is smooth and called as soft palate. The hinder part freely hangs down as a small flap called uvula.

Buccal cavity receives saliva from salivary gland.

Pharynx
It is wide opining at back of mouth cavity. It leads to two openings : gullet and glottis. There is a muscular flap called epiglottis which closes glottis when food is swallowed. There are 2 openings of internal nares above and two openings of Eustachian tubes at the sides.

It is the only part common to digestive and respiratory system.

Oesophagus
It is a long narrow muscular tube which connect mouth to stomach. It is about 25 cm long. It pierces diaphragm to open into stomach. It undergoes peristalsis to carry down food and water or fluid.

Stomach
It is a large muscular elastic bag situated below diaphragm on left side. It has four parts
o Cardiac – it is so called because it lies near heart. In between oesophagus and cardiac part of stomach there is cardiac sphincter.
o Fundus - it extends superiorly from the cardiac part. It is usually filled with air.
o Body - it is main part of stomach.
o Pyloric part - it is distal part of stomach. it opens into duodenum. It opens and closes several times. At the time of opening, a small amount of partially digested food(chime) is passed into duodenum.

Gastric gland secretes gastric juice.

Small intestine
It is divisible into 3 parts.
o Duodenum – it is c shaped and about 25 cm long. It receives bile juice and pancreatic juice through common bile duct.
o Jejunum - it is about 2.5 meter in length. It is coiled part.
o Ileum – it is about 3.5 meter long. It is highly coiled part. Both jejunum and ileum are suspended by mesenteries. The inner wall of ileum has number of folds called villi. It is mainly for digestion and absorption.

Large instestine
It is about 1.5 meter long and divisible into
o Caecum – it is pouch like structure about 6 cm long. There is ileocaecal valve preventing back flow. Attached to caecum is a slender vermiform appendix of about 10 cm long. It is vestigial in man but functional in herbivores. The inflammation of appendix is called appendicitis at the time of infection.
o Colon – it is inverted U shaped and divisible into

Ascending colon - it is the first part on right side. It moves upward from caecum.
Transverse colon - it is horizontal part.
Descending colon – it moves down at left side. It descends down
Pelvic colon – it is s shaped or sigmoid. Undigested material can remain in colon for about 36 hours.
Colon is for absorption of water mainly.
o Rectum - small muscular region, straight, about 15 cm long. It opens to the exterior through anus. Undigested material remains here for a short time. The anus is guarded by 2 sphincters

Through out the alimentary canal, mucous glands secrete mucus.

Digestive glands
Glands associated with alimentary canal.

Salivary glands
There are three pairs of salivary glands. There is one pair of Parotid gland. It is the largest of the salivary glands. It is situated near the ears. Stenson’s duct of Parotid gland open near the upper 2nd molar. One pair of sublingual glands are small and situated beneath tongue. Ducts of Rivinus open into floor of oral cavity. One pair of submandibular(also submaxillary) glands are medium sized and situated at angle of lower jaw. Warton’s duct open near the lower central incisors.
Salivary glands secrete saliva into oral cavity. Saliva is slightly acidic pH 6.8. About 1 to 1.5 Liter of saliva is secreted daily. Saliva contains starch digesting enzyme salivary amylase also called ptyalin.


Liver
It is the largest gland. It lies in the upper right side of abdominal cavity just below diaphragm. It is reddish brown and weighs about 1.4 to 1.5 Kg. It has two lobes right and left separated by falciform ligament. The right lobe is further divisible into right lobe proper, quadrate lobe and caudate lobe.
Gall bladder is a pear shaped sac like structure. It stores bile juice. The right and left hepatic ducts join to form common hepatic duct. It joins the cystic duct which arises from GB. The cystic duct and other hepatic duct join to form bile duct. It runs down to join the pancreatic duct to form hepatopancreatic duct. It opens into duodenum. The liver lobes are made up of small lobules called hepatic lobules. Hepatic lobules are separated by Glission’s capsule. Liver cells are arranged radially and separated by hepatic sinusoids(wide capillaries). Attached to liver cells there are kupffer’s cells which are phagocytic in nature.
Functions of liver
o Liver is main organ of Bile production. Bile contains bile pigment and salts. Bile pigments are Bilirubin(yellow) and biliverdin(green) used in coloration of bile and faeces. Salts of Sodium and Potassium bicarbonate neutralize acids. Sodium glycocholate and taurocholate help in emulsification.
o Deamination - NH2 amino group is removed from aminoacid resulting in the production of ammonia. Ammonia is converted into urea.
o Glycogenesis - it is conversion of excess glucose into glycogen with the help of insulin.
o Glycogenolysis - conversion of glycogen into glucose by liver cells with the help of glucagon.
o Lipogenesis - conversion of excess glucose and aminoacid into fats.
o Gluconeogenesis - formation of glucose or glycogen from non carbohydrate sources( aminoacid, fatty acid and glycerol). It also occurs in kidney and muscle.
o Detoxification – converts toxic substance into harmless substance eg harmful prussic acid is neutralized and rendered harmless.
o Haemopoises - formation of blood corpuscles, produces RBC in embryo.
o Destruction of RBC - old and worn out RBC broken down in liver.
o Synthesis of Blood protein - Prothrombin and fibrinogen are synthesized.
o Secretion of Heparin ( anticoagulant)
o Synthesis of vitamin A – synthesis of vitamin A from Beta carotene (carrot).
o Phagocytosis – Kupffer’s cell engulf microorganisms and dead cells.
o Production of heat - high metabolic activities, enough heat produced, maintain optimum body temperature, maintain homoestasis.
o Osmoregulation - produce angiotensinogen(protein) helping maintain body fluid.
o Storage – glycogen, fat, vitamins A D E K, comps of Fe Cu K etc.
o Lymph formation – important seat for lymph formation.

Pancreas
It is soft, lobulated, greenish pink gland. It weighs about 60 grams, 2.5 cm wide and 12 to 15 cm long. It located posterior to stomach. It comprises head, body and tail. Head lies in the curve of duodenum, body behind the stomach and tail reaches the spleen near left kidney.
The main pancreatic duct is formed by smaller ducts within pancreas. The main pancreatic duct open into hepatopancreatic ampulla.
Internal structure
It has two parts, Exocrine part and Endocrine part.
Exocrine part consists of rounded lobules(acini) which secrete alkaline pancreatic juice pH 8.4 about 500 to 800 ml of pancreatic juice secreted every day. The pancreatic juice contains 3 proenzyme, trypsinogen, chymotrypsinogen and procarboxypeptidase and some enzymes like pancreatic amylase, DNase, RNase, Lipase etc
Endocrine part consists of islet of Langerhans. About one million islets are found mostly in tail.
Types of cells
o Alpha cells - constitute about 25% , found at periphery, produce glucagon
o Beta cells - constitute 60% , found at middle, produce insulin
o Delta cells- constitute 10% found at periphery, produce somatostatin(SS).


Physiology of digestion
Man is omnivorous. It means man depends on plant materials and animal products. The food contains carbohydrate, protein and fats. The food is digested at different parts of alimentary canal.

Digestion in mouth
In mouth, the food is mixed with the saliva from salivary gland. Saliva contains the enzyme called salivary amylase. Salivary amylase acts on carbohydrate and changes some of carbohydrate into maltose, isomaltose and limit dextrine. Food remains in mouth for a short time so digestion is not complete.

Enzyme substrate products
Salivary amylase + starch ------------- maltose + isomaltase+ limit dextrine

Digestion in stomach
In the stomach, the gastric juice is secreted by gastric gland. Gastric juice contains pepsiongen, HCl and water. Peptic cells or zymogenic cells secrete pepsinogen. Parietal cells secrete HCl. Prorenin is found in infants.

Functions of HCl 1. converts inactive pepsinogen into active pepsin
2. provides acidic medium
3. stops growth of Bacteria
Pepsin changes inactive prorenin into active rennin. Pepsin acts on protein and changes it into peptones and proteoses. Rennin acts on milk casein. Milk casein is changed into paracasein. Paracasein combines with Calcium ion to form Calcium paracaseinate. It is then acted by pepsin and changed into peptones and proteoses. In the stomach, gastric lipase is also secreted. It acts on fats to change into fatty acids and glycerol.

Enzyme substrate products
Pepsin + protein --------- peptones + proteoses
Rennin + milk casein ------- paracasein
Paracasein + Ca ++ -- --- Calcium paracaseinate
Pepsin + Calcium paracaseinate --- peptones + proteoses
Lipase + fats -------------------- fatty acids and glycerol


Digestion in duodenum

The partially digested food called chime is passed on to the duodenum slowly. It is mixed with bile juice and pancreatic juice. The bile juice contains bile pigments and bile salts. The pancreatic juice contains enzymes like trypsinogen, amylase and lipase etc. The inactive trypsinogen is converted into active trypsin by enterokinase. Trypsin then acts on protein, peptones and proteoses and change into polypeptides. Amylase acts on starch and changes into maltose. Lipase acts on emulsified fat and change into fatty acids and glycerol.

The functions of bile 1. it neutralizes acids
2. it provides alkaline medium
3. it emulsifies fats
Enzyme substrate products
Trypsin + protein, proteoses, peptones ------ polypeptides
Amylase + starch ----------------------------- maltose
Lipase + emulsified fat ---------------------- fatty acids, glycerol

Digestion in jejunum and ileum

Here, intestinal juice is produced by crypts of Lieberkuhn. The intestinal juice contains aminopeptidase, dipeptidase, maltase, lactase, sucrase etc. the aminopeptidase acts on polypeptides and changes into smaller peptides. Dipeptidase acts on dipeptides and changes into aminoacids. Maltase acts on maltose. It is changed into glucose. Lactase acts on lactose to change that into galactose and glucose. Sucrase acts on sucrose and changed into fructose and glucose.

Enzyme substrate products
Aminopeptidase + polypeptides -------------------- smaller peptides
Dipeptidase + smaller peptides --------------- aminoacid
Maltase + maltose ------------------------- glucose
Lactose + lactose --------------------------- glucose and galactose
Sucrase + sucrose -------------------------- glucose and fructose

Absorption
Absorption takes place in the ileum mainly. For this, the internal lining of ileum is provided with large no. of finger like projections called villi. The villi increase the absorptive surface. These are provided with blood vessels and lymph. Glucose, aminoacid etc are absorbed into the blood vessel. Blood takes them to liver for storage of glucose. The fatty acids and glycerol come into the lymph which is taken into adipose tissue for storage.
Assimilation
Glucose, fatty acids and glycerol are used for the liberation of energy in the body. Aminoacids are used to produce protoplasm in the body for growth and repair of damaged tissue.

Egestion
Undigested materials are passed into large intestine. Water is absorbed here. Then these are carried down. Lastly undigested materials are discharged out from anus. It is called egestion.

for Grade XI and XII

Unit wise weightage for Zoology grade XI
1. Introduction to Biology - very short questions 2, short questions x, long questions x.
2. evolution of life – very short questions 2 or 1 opt, short questions 0 or 1 opt, long question 1( 8 marks)
3. biodiversity – very short questions 1 or 1 opt, short questions 3 or 1 opt, long questions 1 or 1 opt (7.5 marks)
4. biota and their environment – very short questions 2 or 1 opt, short questions 2, long questions x

one full question of 8 marks will be asked either from the unit Evolution of life or Biota and environment.


Unit wise weightage for Zoology grade XII
1. Anatomy and physiology of organisms – very short question 1, short questions 1, long questions x.
2. Developmental biology – very short questions x or 1 opt, short questions 1, long questions x
3. Human biology and health- very short questions 3 or 2 opt, short questions 2 or 1 opt , long questions 1(8 marks) and 1( 7.5 marks) or 1 opt
4. Application of biology – short questions 3, short questions 1, long questions x

Long question from Developmental biology can be asked by reducing the marks from the unit of Human Biology and Health.

for BLAS

1. Principle of independent assortment.

the law states that the agaenes of different characters located in different pairs of chromosomes are independent of one anotrher in theeir segregation during gamete formation ( meiosis) . the principle of independent assortment can also be defined as “ if we consider the inheritance of tow or more genes at a time their distribution in the gametes and in progeny of subsequent generations in independent of each other.

in the experiment of dihybrid cross between the round yellow and wrinkled green seed plants, we can get the emergence of new characters like round green and wrinkled yellow seed plants. these new characters in combination were not present in the parents.we have the ratio of the dihybrid cross as follows. The round yellow:round green:wrinkled yellow:wrinkled green is 9:3:3:1 in the F2 generation. this showed that the factors responsible characters are separated during the segregation and they are free to combine with any other of the factors. they combine haphazardly. there is no any hard and fast rule for their combination. this is known as principle of independent assortment.

Wildlife conservation

In fact, it refers to any living organisms(animals and plants), micro organisms living in its natural habitat. These are free from human check and interference. So it excludes the cultivated plants and domesticated animals. It is renewable natural resource.

Necessity for wild life conservation

• Helps in maintaining the balance of nature.
• Use commercially to earn foreign exchange if linked with tourism- ecotourism.
• Study by naturalists, biologists, help in conservation
• Provides means of sports and recreation.
• Cultural asset – deep rooted effect on art, sculpture, literature and religion.

Reasons for depletion of wildlife

• Absence of cover or shelter
• Deforestation for cultivation, urbanization etc, reduction in area for free movement, retard reproduction capacity
• Destruction of wild plants for timber, charcoal, firewood; deprive wild animals from most palatable food, affects survival.
• Pollution – noise, pesticides
• Natural calamities – flood, drought, volcanic eruption etc.
• Poaching – food, hide, fur, plumage musk, tusk and horn etc.
• Hunting – recreation.

Some terms

Extinct – the species not definitely reported during past 50 years in wild condⁿ example pink headed duck – suspected to be extinct.

Endangered - if trend of loss of wildlife species contineus at the same rate, species would be in immediate danger of extinction mainly due to habitat loss. Example Panthera tigris, Elephus maximus, Bengal florican etc

Vulnerable - number decreasing due to over exploitation, destruction of habitat, likely to be endangered in near future. Example Asiatic wild dog, Himalayan Black bear etc

Rare - the popⁿ of wild life at risk but not endangered or vulnerable, popⁿ localized within extensive area, example Imperial eagle, Rufous necked Hornbill etc.

Threatened – general term to denote species that are endangered, rare or vulnerable, insufficiently known

IUCN – International Union for conservation of Nature and Resources 1948, head quarter in Switzerland. Red data book – compiled by IUCN , list of endangered spp

WWF world wildlife fund 1961

CITES Convention of International Trade of Endangered species of fauna and flora 1973

Wildlife management

• Habitat management, establishment of National Parks, Reserves, Sanctuaries etc
• Breeding in captivity – ginko and metasequiria survival in captivity only
• Reintroduction- rhinoceros reintroduced in Berdia
• Mass education
• Promulgation of laws

Protected areas in Nepal

ü Until 1950, rich in flora and fauna

ü Adverse effect on wildlife due to increase in human popn, used forest for cultivation and housing

ü Destroyed forest for economic benefit, rhinoceros killed for horn, tiger for skin, deer for meat

In 1970, Royal Chitwan National Park and Langtang National Park established.

In 1973, law passed to set up more National Parks and wildlife reserves.

National Park –

o It is the reserved area set aside for conservation, management and utilization of animals and vegetation.

o In this area, soil, principal geographic areas, landscapes are also managed properly. Entry into NP is restricted without permit and guarded by army

o Animal hunting, cutting of plants etc are strictly prohibited. Grazing of domestic animals and construction of houses are also not allowed.

o All NP are managed by Dept of National Parks and wildlife conservation (DNPWC)

Khaptad NP

Area 225 Km², established in 2042 BS

Location mid mountain region of far western Nepal

Common trees – chirpine, spruce, fir, maple birch, rhododendron

Common fauna – leopard, himlayan black bear, musk deer, ghoral, Himalayan tahr

Lake Rara NP

Area 106 Km², established in 2032 BS

Location North west Nepal

Common tree coniferous forest dominated by blue pine ideal habitat for Musk deer

Common fauna musk deer, Himalayan black bear, leopard. Ghoral, himalayn tahr, wild boar, impeyan pheasant, kaliz

Royal Berdia NP

Area 968 Km² established 2045 BS

Location Far western Terai

Common tree – nearly 70% dominated by sal forest, excellent habitat for endangered animal like rhinoceros

Common fauna wild elephant, tiger, swamp deer, black buck, gharial, Dolphin

Shey Phoksundo NP

Area 3555 Km² largest established 2040 BS

Location mountain region of western Nepal

Common tree blue pine spruce, poplar, deodar quercus provide habitat for snow leopard

Common fauna blue sheep, ghoral leopard, wolf jackal Himalayan mouse hare langur

Royal Chitwan NP

Area 932Km² established 2030 BS

Location sub tropical inner Terai lowland, world heritage site in 1984

Common tree- sal

Common fauna - Park renowned for one horned Rhino, tiger, gharial crocodile gaur, wild

elephant four horned antelope striped hyena, pangolin, sambar deer, chital etc

Langtang NP

Area 1710 Km² established 2032

Location central Himalayan region

Common fauna wild dog, red panda, musk deer rhesus monkey, langur etc

Sagarmatha NP

Area 1148 Km² established 2032 BS

Location North eastern part , includes the highest peak Mt. Everest

World heritage site in 1979

Common tree pine hemlock forest, fir, juniper

Common fauna Himalayan tahr, ghoral musk deer

Makalu Barun NP

Area 1500 Km² established 2047 BS

Location Eastern part

Some unique pocket of plant and animals 47 varieties of orchid, 67 spp of medicinal plants, rhododendron

Red panda, musk deer, clouded leopard, snow leopard, barking deer, more than 400 spp of birds

Shivpuri NP

Previously Shivpuri watershed management and wildlife reserve

Area 144 Km²

North of Ktm habitat for Himalayan plants and many birds

Wildlife reserves

Royal Suklaphanta WR

Area 155 Km² established 2031

Southeastern part

Habitat for swamp deer, wild elephant, tiger, leopard, chital etc

Persa WR

Area 499 Km² established 2040 BS

Provide habitat for wild elephant, tiger leopard, wild dog etc

Koshitappu WR

Area 175 Km² established 2039 BS

Location eastern flood plain of Saptakoshi river

Habitat for last surviving popn of wild buffalo Arna, wild boar, spotted deer, ghoral

Dhorpatan Hunting reserve

Area 1375 Km² established 2041 BS

For purpose of spot hunting guarded by army

Habitat for blue sheep, leopard, ghoral, black bear

Annapurna conservation area

Area 7000 Km² established 2043 BS

Managed under King Mahendra Trust for Nature conservation

Blue sheep, snow leopard

Makalu Barun conservation Area

Area 830 Km² established 2047 BS

Birds, medicinal plants

Kanchanjunga conservation area

for BLAS

Origin of new characters

Heredity is the presence of characters in the off springs which are present in the parents. These characters are directly transmitted to children from parents. The children thus get some characters from father and some other characters from mother. Some children get more of the characters from father and less from mother and vice versa. So, any child is not the photocopy of the father or mother. The child is little bit different from the father as well from the mother.

In the sexually reproducing animals including human beings, at the time of gamete formation, there is meiosis. During this cell division meiosis, the chromosomes number is reduced to half. For example, in case of human beings, there are 23 pairs of chromosomes. It is said to be Diploid number of chromosomes, denoted as 2n. In the sperm and ova(eggs), there are only 23 chromosomes. This number of chromosomes is said to be Haploid number of chromosomes and denoted as n. At the time of fertilization, the chromosomes of sperm and egg together make Homologous pairs of chromosomes and thus make Diploid number of chromosomes. During the process of formation of Homologous pair of chromosomes, there is crossing over to make the new set of chromosomes. This new set of chromosomes are little bit different from the those of parents. This new set of chromosomes are responsible for the origin of new characters in the off spring or children.

The new set of chromosomes are formed because of meiosis. The pattern of transmission of characters depend on the way the new set of chromosomes are formed. The pattern of transmission of characters in the off spring is studied in Genetics. This term Genetics was first used by W Bateson in 1905. The foundation of Genetics was laid in 1865 by Gregor Johann Mendel. For his overriding contribution in Genetics he is called as Father of Genetics.

Biography of Gregor Mendel

Gregor Mendel was born on 22 July 1822 at Heinzendorf of Silesian village in Austria. He joined Augustinian monastery at Brunn in Austria in 1843. He was sent to University of Vienna to study Natural Science and Mathematics. He returned to Monastery in 1853. He conducted research on common garden pea plant (Sativum pisum) for eight years from 1956 to 1864. Mendel presented data and conclusion derived from his experiments in a paper entitled “ Experiments in plant hybridization” which was read before Brunn Natural History Society in 1865 and was published in Annual proceedings of Natural history Society in 1866. His work was not recognized in his life. Unrecognized and bitterly disappointed , he died in 1884. Mendel’s observations went unnoticed on account of

• He published his work in an obscure journal.
• Failure of he scientists to notice his work because scientific world was at that time busy in the controversy arisen by the Darwin’s theory of origin of species.
• His ideas were ahead of his time as the ignorance was prevalent in that period about cytological basis of heredity.

In 1900, three eminent biologists Hugo de Vries of Holland, Karl Correns of Germany and Eric Von Tshermak of Australia working independently on heredity discovered the same phenomena originally uncovered by Mendel. Thus the genius of Mendel came to be discovered after 16 years of his death. Mendel for his great contribution is now famous as “Gather of Genetics”.

Mendel’s experiment

Mendel selected garden pea (Pisum sativum) as plant material for his experiment since it had following advantages.

• Possess many varieties with well defined characters.
• Flowers are bisexual and can pollinated easily.
• Easily be grown and readily be crossed.
• Very short life span, many generations formed.
• Hybrid pea plants are fertile.
• Flowers completely closed by petal, so plants predominantly self pollinating and self fertilizing.

Reasons for Mendel’s success

• Studied the inheritance of one character at a time.
• Carried out experiments to F2 and F3 generations only.
• Maintained statistical records, analyzed carefully.
• Selected pure line parent plants.
• All possible precautions taken to prevent self pollination.
• Even reciprocal crosses conducted but no change in the expected ratio of off springs.

Seven pairs of contrasting characters of pea plant used by Mendel

Trait dominant recessive

1. Seed color yellow green
2. Seed shape round wrinkled
3. Pod color green yellow
4. Pod shape inflated constricted
5. Flower color purple white
6. Flower shape axial terminal
7. Plant height tall dwarf

These seven pairs of contrasting characters of pea plant mean that if one character is expressed the other is not expressed. If the character tallness is expressed the other character dwarfness cannot be expressed. In the same way, if dwarfness is expressed, the other character tallness is not expressed.

Some basic terms used in inheritance studies

Gene or Factor

Mendel called it factor which carry the character from the parent to offspring. In the modern sense an inherited factor that determines a biological character of an organism is called gene. This is the function unit of hereditary material. It is a segment of DNA. Gene is equivalent to the factor of mendel.

Allelomorphs or allele

Allele is abbreviated form of allelomorphs, which means one form or the other. It indicates the alternative forms of the same gene. Each character has two determiners called factor. In pure tall or pure dwarf plant, same allele is duplicated like TT or tt. But in the hybrid tall plant both alleles are present like Tt. An organism having same allele or two identical alleles is known homozygous and an individual with different alleles is called the heterozygous. For example an organism with both TT or tt is called homozygous and an organism with Tt is called heterozygous.

Homozygous plants are genetically pure or that character. They give rise to offspring having same character on self breeding. The heterozygous hybrid plants do not breed true on self fertilization. The heterozygous plants on self fertilization produce both tall and dwarf plant.

Homozygous organism bear either dominant or recessive alleles and never both. Where as heterozygous organism bear both dominant(T) and recessive(t) alleles. The homozygous organism(plant) produces one types of gametes either T or t only. But heterozygous organism produces two types of gametes nearly half with T and another nearly half with t. The homozygous plants do not show vigor but the hybrid or heterozygous plants show extra vigor.

Genotype and phenotype

It is the genetic composition of an organism. It can be like TT, Tt or tt for a particular character. The genotype can be ascertained from ancestry or progeny of individual. On the other hand, phenotype is character which can be observed from the outside like the tall plant or dwarf plant. Phenotype is expressed like form, sex, color, behaviour etc. phenotypes of organism is expression or observable structural traits or characters produced due to interaction of genes and environment. In some cases, the phenotype is not visible from outside. For example, the blood groups like Blood group A, B, O and AB and Rhesus Factor like Rh +ve or –ve is not expressed outside.

Monohybrid and dihybrid cross

In the monohybrid cross, Mendel considered only one pair of contrasting characters like tallness and dwarfness of plant. Similarly, the other characters like round or wrinkled seed or yellow or green seed etc. can be considered but only one pair of the contrasting characters. The other characters are not taken into consideration. In case of dihybrid cross, two pairs of contrasting characters are taken into consideration at the same time like the yellow or green and round or wrinkled seeds.

Reciprocal cross

The reciprocal crosses involve tow crosses concerning the same characteristics but with reversed sex. For example, if in first cross, A is as the female and B is as male, then in the second cross A is as male and B is as female.

The interpretation of Mendel’s results

The principles of inheritance as given by Mendel are as follows.

1. Principle of Dominance

Out of two contrasting characters only one is expressed itself in an individual. The factor which is expressed is called dominant while the other which has not shown its effect is termed as recessive. In monohybrid cross, when homozygous (true breed) tall pea plant is crossed with homozygous dwarf plant, all the plants appeared in F1 generation are tall although they receive both factors (Tt) T from tall plant and t from dwarf plant. In the F1 generation, the character of t is not expressed. The character which is expressed in the F1 generation is called the dominant character and the character which is not expressed in F1 generation is called the recessive. The factors responsible for certain character is always found in the pair like TT or Tt or tt. To these Mendel’s factors, Danish botanist Johansson introduced the term gene in 1909.

Importance of principle of dominance - the phenomenon of dominance is of practical importance as the harmful recessive characters remain hidden by normal dominant character in hybrids. In human beings, a form of idiocy, diabetes and hemophilia are recessive characters.

2. Principle of segregation ( purity of gametes)

The law of segregation states that when a pair of contrasting factors or allelomorphs or genes are brought together in a hybrid(heterozygote) these factors do not blend or mix up but simply associate themselves and remain together and separate at the time of gamete formation.

3. Principle of independent assortment.

for BLAS

Flood

It is overflow of water from river, stream etc into nearby land. It occurs when vegetation and soil can absorb all of the rain water.

Causes

o Heavy rain fall during monsoon.

o Snow melt

o Glacier lake outburst (GLOF) common in mountainous country

o Urbanization , ground surface becomes impermeable to water.

o Earthquake tidal moves generated by quake cause flood , tsunami.

Types

 Periodic flood which occur naturally in many river during the monsoon.

 Flash flood which occur rapidly flood rises and falls without warning. It is resulted from heavy rain over a small area or GLOF or dam failure.

Effects

 Destruction of agricultural crops like rice , potato etc

 Destruction of property, disease like cholera typhoid dysentery etc.

 Death loss of life of man and animals

 Loss to government, damage to roads, buildings, telephone electrical infrastructure.

Land slide

Down ward and upward movement of slope forming materials like rock soil etc. It is caused by falling sliding flowing at faster rate. It occurs in steep slopes where hard and heavy rock overlies softer ones.

Causes

o Natural factor, steep slopes, development of weak rocks, high weathering of rock, heavy rain fall seismic activity.

o Anthropogenic factors, deforestation, over grazing, agricultural activity on steep slope, construction of roads, building canals etc are artificial factors which cause landslides.

Effects

 High amount of fertile soil washes down leaving unproductive land or area.

 Destroy ecosystem of area.

 Destroy road and building.

 Blocks stream, river etc cause huge flood.

 Landslides in public settlement take life and property.

 Terrestrial animals are highly affected.

 Streams or river may dry out or appear in improper places.

Earth quake

Sudden temporary vibrations set up on earth’s surface ranging from a faint tremor to a wild motion. The motion is due to sudden release of energy stored inside the earth surface. It lasts from a few seconds to a minute. Sometimes the vibrations are so feeble that we cannot feel them.

Terms

 Focus/hypocenter - it is the point under the earth from where the earth waves originate the earth quake.

 Epicenter – it is the point on the surface of earth directly above the focus of a earth quake. This is the most affected area during the earth quake.

Causes

o Natural cause

 Tectonic cause - about 95% if the earth quake are due to crack or fracture developed on a rock by accumulation of more stress, dislocation of rock and waves of energy are sent out through earth.

 Non tectonic – explosion of volcano etc.

o Anthropogenic - some earth quakes are caused due to human activity like underground explosion of bombs, passage of trains and tank, heavy machinery in indusrial area, extraction of mines, minerals and fossil fuels from earth’s crust, fracture of dam and collapsing of large buildings etc.

Effects

 Due to vibrations of ground, the infrastructure got heavily damaged. It can take life of people.

 Earth quake also changes geological structures of an area and destroys road, water and gas pipes.

 Responsible for fire due to fallen wires and broken gas pipes.

 Earth quake below sea generates seismic waves causes tsunami.

 Causes landslides and flood.

Fore shock- minor shock which occur before major earth quake.

After shock- minor but destructive earth quake which occur after major earth quake.

Seismograph – it is the graphic representation of measurement of origin and frequency(the magnitude of earth quake).

The largest earth quake so far measured is 8.6 in Richter scale.

Prof. Charles Richter of California proposed a scale of earth quake magnitude in 1935 AD to measure the quantity of energy released during earth quake.

Role of forest

1. Timber and wood collection for building and industries.

2. Firewood consumption, rural people about 80% depend upon fire wood.

3. Industrial raw material like paper industry lokta plywood dyes resins gum turpentine etc.

4. Ecological balance.

5. Maintenance of global climate, absorb CO2.

6. Check soil erosion, landslide, land degradation.

7. Sources of medicinal plants, essential oil, used in soap cosmetics and pharmaceuticals etc.

8. Habitat for wild animals

9. Beauty, natural beauty tourism industry, visit forest for peace and recreation.

10. Fodder

11. Ornamental and religious

12. Fruits

Role of river

Water is the most important component for life. Cells and tissue of animals and plant body contain 60 to 90 % of water. Plants use water as raw material for photosynthesis, water essential for cooking and washing, bathing etc.

1. Sources for water supply in urban area.

2. For irrigation (agriculture)

3. Power industry (boiler)

4. Habitat for fresh water and marine water animals.

5. Beauty

6. Hindu rituals cremation in the bank of river.

7. Generate electricity

8. Water mill

9. Control pollution

10. Civilization, settlement eg Nile river.

for Grade XI students

following is the marking scheme prepared by HSEB for checking answer book of board exam 2066 zoology and botany separately.

Sub code 114


HSEB- Grade XI
2066(2009)
Biology
Marking Scheme
Full Marks: 75
Time: 3hrs Pass Marks: 27

Group ‘A’
(Zoology)
Q. No. 1.
(a) Taxonomy is the scientific study of classification of organisms and its principles. The organisms are classified into various levels such as species, genus, order, class, phylum etc. 1
(b) Biology is inter related with other sciences for example
(i) relation of biology with chemistry
Metabolism is the purely chemical phenomenon. Genetic material are formed by chemical compounds. The enzymes, hormones ant other body fluids found within the plants and animals are exclusively the chemical substances etc.
(ii) relation of biology with physics-
Some biological processes like evaporation conduction, transpiration of water and absorptions of minerals shows physical phenomenon. Photosynthesis is concerned with light which is physical factor.
(iii) relation of biology with sociology and anthropology-
(iv) relation of biology with technology as biotechnology biomedical engineering, bio engineering etc any point above. 1
(c) Zoological name of –
Jelly fish – Aurelia, Rhizostoma etc
Pigeon – Columba livia 1
(d) Von Baer proposed recapitulation theory 1
(e) there are two valves in auriculo ventricular aperture that’s why it is also known as bicuspid valve 1
(f) pellicle is a colorless, thin, firm, elastic and cuticular membrane secreted ectoplasm which gives body shape. 1
(g) the boring organ of earthworm is pointed anterior end called prostomium 1
(h) any modification is a part of body or the whole animal that makes it better for its existence in its present environment so that it can secure food, protect itself and rear its young one is called adaptation. Simply adaptation is the adjustment of animals or plants with their habitat. 1
(i) the full form of IUCN is International Union for Conservation of Nature and natural resources 1
(j) a taxis is a movement of he whole organism is response to an external directional stimulus. 1
2.
(a) Draw backs of Lamarckism are-
(i) the first proposition Tendency to increase in size.
(ii) the second statement- new organs result from new needs.
(iii) the third principle- organ will develop due to use and degenerate due to disuse.
(iv) the forth final proposition- inheritance of acquired characters.
Students should give critical analysis of any three of these above points of Lamarckian theory. 1+1+1=3
(b) students should give any three of the following points of significance of conjugation in paramecium in elaborative form. The points are
(i) Rejuvenation
(ii) hereditary variations
(iii) nuclear reorganization
(iv) formation of new strains 1+1+1=3
(c) description of pre-erythrocytic cycle of Plasmodium vivax with diagram 2.5+ 0.5=3
(d) students have to give the difference between flat worm and round worm in their body cavity, digestive tract and excretory organ 1+1+1=3
(e) a neat & well labeled diagram of T.S. through typhlosolar region of earthworm. Diagram and labeling. 1.5+1.5=3
(f) At least six pints for control measures of water pollution each point - 0.5x6 = 3
( g) different types of fish migration, advantages of fish migration 2.5+ 0.5=3
3. Evolution of man from Dryopithecus- - Ramapithecus – Australopithecus – Homo habilis – Homo erectus – Homo sapiens neanderthalensis – Homo sapiens fossilis – Homo sapiens sapiens with their prominent characters 8
4. different types of nephridia -- 0.5, structure of septal nephridia with labeled diagram – 5.5, physiology of excretion – 1.5, chlorogogen cells – 0.5 = 7.5
Or
Description of structure with diagram (labeled) including T.S. of L.S. - 3.5, working mechanism with diagram – 4 = 7 .5

- 0 -







HSEB- Grade XI
2066(2009)
Biology
Marking Scheme
Full Marks: 75
Time: 3hrs Pass Marks: 27

Group ‘A’
(Botany)

Q. No. 1 Answer in short (any seven) 1x7=7
(a) adventitious roots are those roots that develop from any part of the plant other than the radical of the seed.
(b) division of the cytoplasm after the division of the nucleus during cell division is cytokinesis.
(c) scientific name of any organism consist of two parts , the first generic name and second specific name. such system of naming is called binomial nomenclature.
(d) an incipient nucleus lacks nuclear membrane, nucleolus and nucleoplasm. Its genetic material is represented by a circular strand of naked DNA.
(e) sporangium is the spore producing organ of plants. In higher plants two types of sporangia ie. Microspore producing microsporangia and megaspore producing megasporangia are found.
(f) abiotic factors are non-living or physical factors. They are of following types
(i) Climatic factors : light, temperature, precipitation, wind, atmospheric Humidity etc
(ii) edaphic (soil) factors: soil temperature etc
(iii) topographic factors: Altitude slope aspect etc.
(g) lichens are composite organisms produced by a permanent symbiotic association of alga and fungus.
(h) the transfer of food energy from the producers through a series of organisms ie herbivore to carnivore to decomposer with repeated eating and being eaten is a food chain.
(i) micronutrients are essential elements required in relatively small quantities for the proper growth and development of plants e.g. Fe, Mn, B, Cu, Zn, Mo, Cl.
(j) the mode of arrangement of floral leaves(calyx and corolla) in relation to other members of the same whorl in the bud condition is called aestivation.
Q. No. 2 describe in brief (any five) 5x3=15
(a) difference between saturated and unsaturated fats. ( 0.75 marks for each point)
Saturated fat
It has single bond between the carbon atoms chain.
Have higher melting point .
Usually solid at ordinary temperature .
Mostly found in animal fat eg palmitic acid, stearic acid.
unsaturated fat
It has one or more double bonds between the carbon atoms.
Have lower melting point.
Usually liquid at ordinary temperature.
Mostly found in plant fat e.g. oleic acid, linoleic acid.

(b) Plastids ( 1 marks for each type) 3
(i) chloroplast with example and function
(ii) leucoplast with examples and function
(iii) chromoplast with example and function
(c) Process of crossing over in meiosis 3
Diagram =1, description – 2 marks
(d) structure of Yeast 3
Diagram = 1.5 & description 1.5 marks
(e) scalariform conjugation in Spirogyra 3
Diagram =1.5, description =1.5
(f) male cone of Pinus 3
Diagram = 1 , & description =2
(g) difference between Prokaryotic and Eukaryotic cell 3
( 0.5 marks for each point)

Prokaryotic cell
Nucleus unorganized with naked DNA.
All membrane bound structures i.e. chloroplast, mitochondria , endoplasmic reticulum, Golgi complex, lysosome are absent.
Photosynthesis pigment occur in flattened sacs called chromatophores.
Mesosomes are the site of respiration.
Cytoplasm has 70S types of ribosomes
Found only in lower organism such Bacteria & Blue green algae.

Eukaryotic cell
Nucleus organized DNA covered with histone
All present
Photosynthesis pigments organized into chloroplast.
Mitochondria are the sites of respiration.
Cytoplasm has 80S types of ribosomes, 70S ribosomes are present in cell organelles
It is found in all higher organim.

Q. No. 3 life cycle of Dryopteris = 4
Diagram and cyclic representation = 3.5
Description
Or
Family Cruciferae = 1.5
Floral Diagram = 1.0
Floral formula = 1.0
Examples, description = 4
Q. No. 4 Ecosystem
Definition =2
Components
Abiotic = 3
Biotic =3
- O -

for Grade XI students

Sub code 114
HSEB- Grade XI
2066(2009)
Biology
Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicates full marks.
Full marks 75
Time 3hrs Pass marks 27
Note: this question paper contains Zoology portions in Group ‘A’ and Botany portions in Group ‘B’. So use separate answer books for Group ‘A’ and Group ‘B’

(New course)
Group ‘A’
Zoology
Attempt all questions
Answer in very short (any seven) 7x1=7
(a) What do you understand by taxonomy?
(b) How is biology inter related with other sciences?
(c) Give the zoological name of (i) Jelly fish and (ii) Pigeon
(d) Who [proposed recapitulation theory?
(e) Mention the number of valves in auriculo-ventricular aperture.
(f) What is pellicle?
(g) Name the boring organ of earthworm.
(h) Define adaptation.
(i) Write the full form of IUCN.
(j) What is taxis?

Describe in brief: (any five) 5x3=15
(a) Point out the drawbacks of “Lamarckism”.
(b) List the significances of conjugation in Paramecium.
(c) Describe pre-erythrocytic schizogony of malarial parasites.
(d) How do flatworms and roundworms differ in body cavity, digestive tract and excretory organs?
(e) Draw a well labeled diagram of T.S. of earthworm passing through typhlosole.
(f) Discuss the control measures of water pollution.
(g) Write short notes on fish migration.

Write an essay on “evolution of man”. 8

Five an illustrated account of the excretory system of earthworm. 7.5
Or
Describe the structure of lung of frog. Discuss its working mechanism.

Group ‘B’
Attempt all questions
Answer in short (any seven) 7x1=7
(a) Define adventitious root.
(b) What do you mean by cytokinesis?
(c) What do you understand by binomial nomenclature/
(d) What is incipient nucleus?
(e) What is sporangium?
(f) Mention abiotic factors.
(g) What is lichen?
(h) What is food chain?
(i) What do you mean by micronutirents?
(j) Define aestivation.

Describe in brief (any five) 5x3=15
(a) Differentiate between saturated and unsaturated fatty acids.
(b) Describe the plastids.
(c) Describe the process of crossing over in meiosis.
(d) Describe the structure of Yeast.
(e) Describe the scalariform conjugation in Spirogyra.
(f) Describe the male cone of Pinus.
(g) Differentiate between a prokaryotic and eukaryotic cell.

Describe the life cycle of Dryopteris with alternation of generation. 7.5
Or
Describe the family Cruciferae with necessary diagrams and five the two examples of economic value of this family.

Define ecosystem and discuss the main components of ecosystem. 8







(Old course)
Group ‘A’
Zoology
Attempt all questions
Answer in short: 7x1=7
(a) Define helminthology.
(b) What so you understand by convergent evolution.
(c) Define biogenesis.
(d) What is connecting link?
(e) What is protandrous?
(f) Give an example of a migratory bird.
(g) What do you mean by endangered species?

Describe in brief: 5x3=15
(a) Give the classification of phylum Platyhelminthes with example.
(b) Drew a neatly labeled diagram of Bucco-pharyngeal cavity of male frog. ( no description is required).
(c) Write a note on the economic importance of earthworm.
(d) Mention the effects of water pollution.
(e) Discuss the causes of depletion of wildlife.

Describe the life cycle pf plasmodium in mosquito. 7.5
Or
What is portal system? Describe the hepatic portal system of frog.

Discuss the evolution of man from hominids. 8

Group ‘B’
Botany
Attempt all questions.
Answer in short: 7x1=7
(a) What is the prothallus of fern?
(b) How do the bacteria get their nutrition?
(c) Give two examples of cyanobacteria.
(d) Define alternation of generation.
(e) What is the genetic material of viruses?
(f) What do you understand by primary productivity?
(g) Define trophic level.

Describe in brief: 5x3=15
(a) Different types of RNA and their functions.
(b) Vegetative structure of Spirogyra.
(c) Female cone of Pinus.
(d) Impact of Green house effect on environment.
(e) Meaning and causes of ecological succession.

Describe the characteristic features of family cruciferae with its floral diagram and formula. Give scientific names of any two edible plants of this family. 7.5
Or
Describe the life cycle of Mucor.

Sketch a well labeled diagram of a typical plant cell and describe the structure and function of mitochondria and Nucleus. 8