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

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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
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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

for class XII biology students

Development of frog

Embryology is the science which deals with early developmental stages of organisms. Father of modern embryology is Von Baer. Embryogeny is the process of development of embryo. Embryo is a newly forming individual in early stages of development before hatching or birth.
Embryonic development in all sexually reproducing metazoans begins from a single cell called zygote and follows similar sequence. The sequence of evnts before and during the embryonic development of frog includes.
Gametogenesis – formation and differentiation of sex cells or gametes.
Fertilization – fusion of male and female gametes to form zygote.
Blastulation – formation of segmentation cavity called Blastula.
Gastrulation – movement and arrangement of embryonic cells to form primary layers.
Organogenesis or organ formation – differentiation and formation of organ system from primary germ layers.
Differentiation and morphogenesis – acquisition of characteristic morphological features of organism.
Growth – increase in size through development.
Gametogenesis takes place little before the commencement of breeding season. The gametogenesis in male frog is called spermatogenesis in which sperms are developed inside the testis. Similarly gametogenesis in female frog is called oogenesis in which eggs are developed in side the ovary. During the rainy season which is the breeding season, male frogs croak and large number of frogs accumulated near the shallow water. In the water, male frog mounts upon the female frog and copulation takes place. At the time of copulation, female frog discharges number of eggs and near eggs male also discharges even large number of sperms. Along with eggs, wall of ovisac secretes albuminous fluid. The albuminous fluid absorbs water and swells up. Then it becomes sticky. It binds large number about 40 to 50 eggs in a group. This group of eggs is called frog spawn. The jelly like substance is formed from the albuminous fluid. It is mainly protective in function.
Functions of jelly like substance
Bacteria and fungi spores can not grow on jelly. So eggs are protected from bacteria and fungi.
Jelly is distasteful. Birds also do not feed on distasteful eggs.
Due to swelling of jelly eggs are moved apart and eggs are protected from friction.
Algae can grow in the space which can provide oxygen by photosynthesis.
Jelly can act as peculiar condenser which can absorb heat from sunlight. The temperature is increased. Higher temperature is needed for development of egg.
Structure of egg
The egg of frog is about 1.8mm in diameter and oval in shape. It is covered by double layered vitelline membrane. The egg is half black(pigmented) and half white. The black half is known as animal pole and white half is known as vegetal pole. The animal pole or hemisphere contains cytoplasm and nucleus and vegetal pole or hemisphere contains yolk. Yolk is found only in the vegetal pole, so it is called telolecithal egg or polar egg. There is moderate amount of yolk, so the egg of frog is called mesolecithal egg. In the freshly laid egg, under the vitelline membrane there is presence of the first polar body.
Structure of sperm
Sperm of has head, middle piece and a long vibratile tail. In the head, there is large nucleus and at the tip, there is acrosome with sperm lysine. It swims in water to reach to the egg of its kind. It is always attracted toward the egg of frog.
Process of fertilization
Fertilization takes place in water out side the body of frog. It is called the external fertilization. Large number of sperms remain attached to one egg. All sperms break the tip of the sperm. They release the sperm lysine. The change in the sperm to release the sperm lysine is called capacitaton. These changes take place due to the activation of sperms. Sperm lysine contains the enzyme hyaluronidase. It dissolves the vitelline membrane of egg. The egg also produces a small outgrowth towards the animal pole. It is called the reception cone. With this change, the egg is also activated to take part in the fertilization.
Now, one of the sperms attached to the reception cone pierces the vitelline membrane of egg and enters into it. The tail is left behind. Through the puncture, water oozes out and fills the space in between vitelline membrane and plasma membrane. It becomes thick and hard. It is known as fertilization membrane. Its function is to prevent the entry of other sperms. As the sperm head moves, it carries the pigment granules. It is marked by dark streak and known as the penetration path. The route followed by make nucleus in side the egg is copulation path.
The sperm nucleus is now known as male pronucleus. The egg nucleus undergoes the second meiotic division. As a result of this, second polar body is extruded. The egg completes the meiotic division only after the entry of sperm. The egg nucleus moves toward the male pronucleus. Just behind the male pronucleus , there is the centrosome. Due to the approaching egg nucleus, the male pronucleus rotates so that the centrosome lies in the middle of male pronucleus and egg nucleus. The nuclear membrane of both nuclei disappear. The chromosomes are set free. Spindle fibres are formed between the chromosomes. One chromosome from the male pronucleus and one similar chromosome from egg nucleus come closer and make homologous pair. Similarly several pairs of homologous chromosomes are formed. This restoration of diploid number of chromosomes is called the fertilization. At the end of fertilization, single celled zygote is formed.
Effects of fertilization
o The fertilized egg can undergo further development. If there is no fertilization, the egg will be degenerated.
o When the vitelline membrane is punctured, some water oozes out and collects in the space between vitelline membrane and plasma membrane. Now the vitelline membrane is changed into perivitelline membrane or fertilization membrane. It is stiff and thick. This ensures the monospermy of egg by preventing entry of other sperms.
o The second polar body is formed which shows that the egg has completed the meiotic division.
o Diploid number of chromosomes is restored.
o Centrosome is introduced.
o Fertilized egg rotates so that the animal pole turns upward and vegetal pole down ward. The significance of this is that the black surface can absorb heat from the sun light and increase the temperature. Higher temperature is needed for the development.
o Grey crescent is formed opposite to the point of entry of sperm. This is due to the movement of pigment granules. This shows the bilateral symmetry in the future.
Cleavage
After about three hours of fertilization, the fertilized egg starts to divide. The rapid and repeated divisions of fertilized egg is called cleavage. All these divisions are mitotic. During the cleavage, all substances present in the egg are divided. There is complete division. So, the cleavage in frog is holoblastic.
First cleavage
It is vertical division from animal pole to vegetal pole. A small depression appears at the animal pole. It becomes deeper and deeper and goes toward vegetal. The fertilized egg is divided into two equal cells. So, the first cleavage is vertical and equal.
Second cleavage
This is also vertical and equal but at right angle to the first. Two cells are divided into four quarter cells. Each cell contains a small portion of animal pole and a small portion of vegetal pole. These cells can be called as blastomeres. Both of these divisions are along meridian also.
Third cleavage
This division is horizontal and unequal. It takes place little above the equator and toward the animal pole. The four cells are divided into eight cells. The upper four cells are smaller and also known as micromeres or epiblasts. The lower four cells are bigger and also known as macromeres or megameres or hypoblasts.

Differences between micromeres and megameres
micromeres
smaller
Contain cytoplasm and nucleus
Black in colour, pigmented
Upper cells
Divide rapidly
megamere
bigger
contain yolk
white in colour, non pigmented
lower cells
Divide slowly because of the presence of non living, inactive yolk

Fourth cleavage
It is again vertical. Two furrows appear at the same time dividing all eight cells into 16 cells.
Fifth cleavage
It is also horizontal. In this case also two furrows appear at the same time, one above and one below the previous division. All sixteen cells are divided into thirty two cells. The sixth division onward, all divisions are haphazard.
Morula stage
Now the embryo is mulberry shaped with number of smaller cells. The animal pole contains many smaller black cells and the vegetal pole contains many bigger white cells. This stage is very short

Blastulation
The macromeres due to the presence of inactive yolk, divide slowly where as micromeres divide rapidly. So, the lines of division do not coincide. A gap is appeared between these two types of cells. This gap is inside the embryo and in between the animal pole and vegetal pole. It is known as segmentation cavity or incipient blastocoel. Bastocoel increases in size and is filled fluid. This stage is known as blastula. The roof of blastocoel is made by smaller, black cells and floor is made by bigger white cells. It is comparable to one layered stage.
At the blastula stage, some potential differentiation of cells sets in. the smaller pigmented cells of animal pole represent the prospective ectoderm. It further divides into prospective epidermis and prospective neural plate. Near the vegetal pole, there is prospective notochord. On either side of which there are two lateral plates(mesoderm). The rest of the cells of vegetal pole represent the prospective endoderm.

Gastrulation
It is the process of rearrangement prospective areas so that these different areas occupy definite position and proportion. Gastrulation in frog is completed in three steps.
Epiboly
The micromeres can divide rapidly. These cells migrate and spread over those of vegetal pole. The migration of these cells may be termed as formative movement. These cells cover the megamere leaving a small opening known as blastopore. At this time also these cells are dividing rapidly. These cell now move in between outer smaller cells and inner bigger cells. These cell make the chordamesoderm . this process of moving in between outer and inner cells is involution.
Intucking (invagination) or imboly
This is in pushing of bigger cells from blastopore. A groove is formed by this invagination. This groove is the beginning of second cavity archenteron. The margin above blastopore is dorsal lip. On the sides of blastopore there are lateral lips. As there is more invagination, the lips of blastopore becomes wide. The archenteron increases in size and blastocoels becomes reduced and crescentic in shape due to more in pushing some other yolk laden cells protrude out through the blastopore.
Contraction of lips of blastopore
As yolk laden cells protrude out through the blastopore, the blastopore becomes narrow. This is known as contraction of lips of blastopore. These cells make yolk plug.
The second cavity archenteron is formed. So the center of gravity is shifted. Due to this shifting, the embryo rotates now. The epidermis comes to anterior the neural plate to dorsal and he endoderm to posterior.
The gastrula stage is comparable to two layered stage. The outer layer is ectoderm and inner layer is chrodamesoderm + endoderm. The chordamesoderm and endoderm are not distinguishable. The roof of the archenteron is made by chorda mesoderm and floor by endodermal cells. These three steps occur simultaneously.
Significance of gastrulation
o Formation of different layers like ectoderm, chordamssoderm and endoderm
o Formation of different structures and organ these layers.
Neurulation

Due to rotation of embryo, the neural plate comes to lie at the dorsal surface. The neural plate becomes stiff and hard a little bit. It sinks down in the middle. The edges of neural plate come up. These edges are now known as neural folds. The depression in the middle forms the neural groove. These neural folds increase in height. They come closer to each other. These folds meet and fuse in the middle. The fusion proceeds anteriorly and posteriorly. Anteriorly it remains open by neuropore. Posteriorly it communicates with archenteron by neurenteric canal. Later on both of thwse are closed. A completely closed neural tube is formed having a swollen portion anteriorly. This stage is now known as neurula. It is little bit elongated and oval in shape.

During neurulation, some important changes occur at the roof of archenteron. Just below the place where neural tube is being formed, some cells of chordamesoderm separate,. He become vacuolated and become hard and stiff. These cells make a rod like structure. It is known as notochord.
The process of notochord formation form chord mesoderm is known notogenesis. The main function of notochord is to support the neural tube. Later on the swollen part of neural tube forms the different parts of brain. And tubular part forms the spinal cord. The notochord is replaced by backbone or vertebral column.

Coelom formation

The rest of cells of chordamesoderm forms two lateral plates. Both of these lateral plates split into outer somatic or parietal layer and inner visceral or splanchnic layer. In between outer and inner layer, these develop a gap called splanchnocoel. Later splanchnocoel is filled with fluid and gives rise to the formation of coelom. The fluid inside is called coelomic fluid. The coelom this formed is said to be schizoclelic coelom.
By this time, the chordamesoderm has been separated from the endoderm. The roof of archenteron is formed by endoderm. Now the embryo has three primary germinal layers namely ectoderm mesoderm and endoderm.



Fate of three primary germinal layers
All three layers are primary means they are equally important. They are germinal because they can be changed from one form to another form. The process of formation of different organs from either ectoderm, mesoderm or endoderm is called organogenesis.

Ectoderm
Epidermis of skin,
Epithelia lining of olfactory and auditory organs,
Lining of stomodaeum and proctodaeum,
Brain and spinal cord (CNS),
PNS and ANS,
Pituitary gland,
Sclera and retina of eye,
Enamel of tooth etc

Mesoderm
Dermis of skin,
Bones and cartilage,
Muscles ,
Circulatory system, heart, vessels, blood, lymph,
Spleen,
Excretory system, kidney,
Reproductive system, testis, ovary ,
Choroid of eye etc


Endoderm
Alimentary canal, associated glands liver and pancreas,
Respiratory tract, larynx, trachea, bronchioles, alveoli,
Lungs,
thyroid and parathyroid glands,
urinary bladder etc

for BLAS students

this article is published in the seto pana magazine of HWHIC.
Pls go through this article


Nature’s balance

Raghubar Shrestha
Dept of Biology

In the early childhood, not many differences can be seen between male and female baby. In the society, it is realized that the female baby learns fast to speak. The female baby is slightly talkative in comparison to male baby.

Major differences set as they grow. As early as 8 or 9 years of age, in female child, the hormones come into play. The Follicle Stimulating Hormone FSH from the pituitary gland starts the developing of the female reproductive organ like the ovaries. The eggs develop inside the ovaries. The development of the eggs in the ovary is expressed by the onset of menstrual cycle. The developing egg also produces the hormone - Estrogen. This hormone has various effects on the body of girls. There is deposition of fat at different parts of body like thigh and hip. The mammary gland starts being developed. With these, they also develop little shyness. As they grow, they give attention towards the things which can make them pretty.

In case of male child, it is slightly late. Only at about the age of 12 or onward, the Follicle Stimulating Hormone from the pituitary gland starts developing the testis. The Leydig cells inside the testis produce the hormone called Testosterone. The testis starts the production of sperms. The hormone brings the changes like the different pattern of hair distribution in the body, the low pitched voice, and the muscular body. As boys enter puberty, they tend to exhibit more aggressive behaviour, and there is little doubt that the dramatic rise in male sex hormones surging through their blood is responsible for this change. For any hormone to influence behaviour, it must first reach the brain and affect it. Both male and female sex hormones (Testosterone and Estrogen) concentrate selectively in certain regions that play an important role in courtship, sex and mating behaviour and aggressive– behaviour in which the sexes differ most.

In 1973, it was demonstrated for the first time that male and female brains differ structurally in many ways. Castration of male monkeys shortly after birth produced the female hypothalamic pattern while injection of testosterone into female triggered the development of the male pattern. This was the first evidence that there were structural brain differences in the sexes that the sex hormones circulating before, at, or after birth could change the brain. Based on these and later observation, scientists concluded that the basic plan of the mammalian brain in female and stays that way unless “told to do other way” by masculinizing hormone. Females tend to have a longer left temporal lobe and the posterior portion of the corpus callosum is bulbous and wide, while in males the corpus callosum is generally cylindrical and fairly uniform in diameter. This may indicate that there are more communicating fibers between the hemispheres in females.

Both male and female children come up into adolescent with these changes. All these changes are developed to suit the reproduction later on. The effect of the hormones is that, unknowingly, they are being attracted towards the opposite sex. Puberty is the period of life, generally between ages of 10 and 15 years, when the reproductive organs grow to their adult size and become functional. These changes occur in response to rising levels of Gonadial hormones (Testosterone in male and Estrogen in female). It is important that puberty represent the earliest time that reproduction is possible. The eggs are developed earlier in the girls, but the whole body system is fully made ready for the reproduction at about the age of 20 only. Most women reach the peak of their reproductive abilities in their late 20s. After that ovarian function declines gradually, presumably because the ovaries become less and less responsive to gonadotropin signals. Estrogen production declines. Eventually the ovulation and menstruation cease. This normally occurs between the age of 46 and 54 years. This event is called menopause. This signifies that the female is no more capable of reproduction. But there is no equivalent of menopause in males. The male’s reproductive capability seems unending. Healthy men are able to become father of children well into their 80s. However there is noticeable difference in sperm motility with aging.

In the society, the marriage is a legal process to undergo reproduction. In the reproduction, the male partner has very short role. The husband donates the sperms for fertilization. Once the egg/s is/are fertilized, the fertilized egg/eggs are implanted in the uterus of the female or the wife. The fetus develops within the womb in about nine months. This gestation period is much challenging in the life of woman. After nearly nine months period, she gives birth to baby/babies either female or male. After nine month long period of very difficult situation, she can now breathe with peace. The act of giving birth to baby (parturition) is even more challenging and difficult. Parturition is the culmination of pregnancy. The series of events that expel the infant from the uterus are referred to collectively as labor. During this period, the mother may sacrifice herself. This act is much painful to the female but male partner is free from all these troublesome jobs.

After the birth of child, both partners look after the child, but it is mainly the responsibility of the mother to rear the young one/s. The Nature has given the main responsibility to the female counter part.

All these are due to the fact that the females have a pair of X chromosomes in the nucleus of the cells together with 22 pairs of Autosomes. Unlike, in the males, there is only one X chromosomes and one Y chromosome in addition to 22 pairs of chromosomes. The very thing here to notice is that the females are much safer as they have a pair of X chromosomes. It is a boon for the females as they do not generally develop the different types of genetic diseases like hemophilia, color blindness etc. In human beings, about fifty X chromosome linked defects have been reported up to now. The most important and common defects in man are :

1. Color or red - green blindness 2. Haemophilia
3. Anhidrotic ectoderma ( non functional sweet gland) 4. Night blindness
5. Myopia ( short sightedness) 6. Juvenile glaucoma
7. White fore lock etc.
Hemophilia is most serious and notorious disease which is more common in man than in woman. It is also known as Bleeder’s disease. The person which contains recessive gene for hemophilia lacks in normal clotting substance in blood. So, normal and minor injuries cause continuous bleeding and ultimate death due to the hemorrhages. This hereditary disease was first reported by John Cotto of Philadelphia in 1803 in man. This disease has been most common in Royal families of Russia and England. Queen Victoria and her further generation were having hemophilic disease. The males are easily victimized to these diseases because of only one X chromosome. The defects in the X chromosome are frequently expressed in males. When one of the X chromosomes is defective, the women are not affected by any deadly disease as it is dominated by another X chromosome. The women in this condition is said to be carrier of the defective X chromosome. They can transmit the defective X chromosome to daughters and sons. However the sons are easily affected by it. Knowing the fact that the daughters transmit the recessive genes to their sons, the Royal families in those days got their daughters married in other countries.

The daughters are affected by such deadly diseases only when both of the X chromosomes are defective. It is possible only when there is marriage between the diseased man and woman or diseased man and carrier woman. Generally diseased men and women do not get married easily. In case of the marriage between diseased man and carrier woman, only half of the daughters will get both defective X chromosomes and other half will get one defective X chromosome. When there is only one defective X chromosome, these daughters are not affected, they will just become carrier of defective X chromosome and transmit it to sons.

There are certain other cases which are linked to the Y chromosome. The Y chromosome is only present in males. So these Y chromosome linked defects are directly transmitted from father to son. One of the simple examples of this can be taken as ichthyosis hystrix gravis hypertrichosis (excessive development of hairs on pinna or ear). Still others are both X-Y linked. In human beings, several diseases are X-Y linked such as total colour blindness, skin diseases (Xeroderma pigmentosum and Epipermolysis bullosa), Retinitis pigmentosa, Spastic paraplegia etc. From all these, it is now clear that the females are much safer from all these notorious and deadly inheritable genetic diseases.

At the end, it can be said that the Nature is looking both the males and females equally without any discrimination. Any one of the males and females is not important for the Nature. Both are needed and both can contribute to the continuity of the race. Both should go together for the betterment of the race.

BLAS questions

Natural Science VI semester

Questions for the Pre board exam 2065

Time 3 hours

Long question (attempt any two) 2X20=40

Describe the Oparin Haldane theory of origin of life.
Describe the theory of Natural selection with its limitation.
Discuss the strategies in the management of wildlife in Nepal.

Short questions (attempt any five) 5X8= 40
How is Chemistry related with Biology?
Describe Miller Urey experiment about origin of life.
Illustrate the use and disuse of organ in Lamarckism.
Give the meaning of a) Punnet Square b) Genotype
Why did Mendel select pea plant for his experiment.
Write down the role of forest.
Why are mountains important to us?
Write consequences of deforestation.




Model Questions for the Practice during Dashain vacation


Long question 20 Marks each

Describe the Oparin Haldane theory of origin of life.
Describe the Mendel’s Laws of Inheritance.
Describe the theory of Natural selection with its limitation.
Discuss the various scopes of Natural science.
Discuss the strategies in the management of wildlife in Nepal.
What is Law of Independent Assortment? Describe it with dihybrid cross of Mendel’s experiment.

Short questions (attempt any five) 8 marks each
How is Chemistry related with Biology?
Write short notes on spontaneous generation.
Describe Miller Urey experiment about origin of life.
Illustrate the use and disuse of organ in Lamarckism
Write a short note on survival of the fittest.
Describe Redi’s experiment. How does it prove Biogenesis?
Give the meaning of a) Punnet Square b) Genotype
Describe the monohybrid cross of Mendel’s experiment.
Describe the dihybrid cross of Mendel’s experiment.
Why did Mendel select pea plant for his experiment.
Write down the role of forest.
Write down the role of the river.
Write short account of any one National Park of Nepal.
What are the causes of Flood.
What are the strategies in the management of landslides
What are the protective measures to be carried out at the time of earth quake?
Why are mountains important to us?
How are the Himalayas different from mountains?
Write short note on mountain ecosystem
Write consequences of deforestation
Write short notes on special creation regarding origin of life.
The giraffe has long neck and long fore limb. What do this prove.?
Why have snakes lost legs?
Give name of four endangered animals of Nepal.

BLAs notes

Kingdom Monera

Characters
Unicellular, microscopic, prokaryotic and found greatest in number on earth
Lack of well organized nucleus, not surrounded by nuclear membrane, nucleus consists of double stranded DNA, nuclear contents lie any where scattered in protoplasm.
Most of them rigid cell wall
Various mode of nutrition, autotrophic, parasitic, symbiotic or saprophytic known as decomposers which convert complex organic matter into simple and soluble forms.
Can tolerate extreme environmental conditions like temperature pH absence of O2.
Bacteria were first discovered by Dutch naturalist Anton Van Leeuwenhoek (1632-1723). He discovered the first microscope in the 17th C. He observed Bacteria in June 10, 1675. The term bacteria was given by Ehrenberg in 1838. The study of Bacteria is called Bacteriology. Bacteria can withstand temp up to 78 oC and -190 oC. There are two types of Bacteria Gram +ve and Gram –ve based on stain.

Kingdom Protista
Characters
Unicellular microscopic eukaryotic organism with well organized nucleus. Besides nucleus, mitochondria , endoplasmic reticulum, golgi bodies plastids etc present.
Both autotrophic and heterotrophic mode of nutrition.
Photosynthetic protists are chief prodders of ocean, fresh water bodies and known as phytoplankton .
The non photosynthetic protists are called zooplankton which are primary consumers.
Some act as decomposers
Reproduce both sexually and asexually. Some like Euglena exhibit flexible life style. In absence of light ingest food and in he presence of light show autotrophic mode of nutrition.

Kingdom Animalia
Characters
Includes multi cellular, eukaryotic animals.
Heterotrophic mode of nutrition.
They are called consumers as they depend on others
Great variety ranging from invertebrates to vertebrates.
Lack of green pigment chlorophyll, cell wall.
Holozoic, parasitic
Reserve food in the form of glycogen
Have locomotory organ and sense organ.

Kingdom plantae
Characters
Includes multi cellular eukaryotic plants found on land, sea water or freshwater. They can be alga, bryophytes, pterydophytes, gymnospersm and angiosperm. All are photosynthetic hence called autotrophs and producers of ecosystem.
Cell wall is made up of cellulose
Some are parasitc(Cuscuta). Some insectivorous like Pitcher plant and others symbiotic( leguminous plants.
Fixed on land and no locomotory organ.
Have chlorophyll and can synthesize food.

Kingdom Fungi( Mycota)
Characters
Includes multi cellular eukaryotic plants with heterotrophic mode of nutrition. Size vary from microscopic to bracket fungi, toadstools. Puffballs which are seen
with unaided eye.
Mostly saprophytes feeding on dead and decaying organic matter also known as decomposers.
Cell wall is made up of chitin or cellulose or both
Exists as a mycelium made of network of branching multi cellular threads called hyphae
Some are parasitic eg. Puccinia
Body is thallus( not differentiated into root, stem and leaf.
Lack chlorophyll, cannot manufacture food
Non vascular
Reproduce by spore forming, asexual and sexual method
Reserve food in the form of glycogen and oil globules.
Some harmful, causes diseases
Some beneficial, used in industry like alcohol, enzymes. Vitamins, bread and antibiotics, some as food.
Found in almost all habitat where organic material is available.

BLAS notes

Classification
Grouping of living organisms according to their similarities and dissimilarities is known as classification. It is the important part of modern taxonomy. There are millions of living organisms on earth. No systematic study can be done without classifying them.
The classification is not only for identification but also to know the evolutionary trend. Different systems of classification
Artificial classification
It is the classical type of classification. Ancient people tried to classify plants and animals according to use to mankind. This type of classification is based on one or few characters. It is not based on natural characters and phylogenetic relationship. Artificial classification is put forwarded by different workers in pre Darwinian era.
Natural system of classification
Natural system is based on truly natural characters such as characters of resemblance or correlation, affinities among them etc. this system considers all aspects by which closely related plants and animals come together. The best and highly recognized natural system of natural classification was proposed by George Bentham (1800 to 1894) and Joseph Dalton Hooker (1817-19110). They made the thorough observation of the plants and presented classification.
Phylogenetic system of classification
The study of history of development of a race or simply evolutionary history is called phylogeny. It includes he knowledge of ancestor, place and time of origin. This is the most advanced type of classification. This system classifies the plants and animals according to their evolutionary sequence and genetic relationship. This system was put forwarded by A Engler(1844-1893) this system enables the taxonomists to trace out ancestor and evolutionary trend.

Hierarchic system in classification

Hierarchy is a system of arrangement where taxonomic categories are placed in major units of classification
Kingdom
This is the highest caterory. There are kingdoms like Monera, Protista, Fungi or Mycota, Plantae and Animalia etc.
Division or Phylum
The division or phylum includes classes of different organisms having common characters.
Class
It is the group of orders.
Order
Group of related Families
Family
Group of related genera
Genus
Aggregation of two or more species
Species
This is the basic unit of classification. The closely resembling individuals of same kind constitute species. They can freely interbreed and produce fertile offspring. Among the member of species, there may be presence of minor differences in color, form and size etc
Two Kingdom classification
Carolus Linnaeus (1707-1778) divided all living things into two Kingdoms for the first time.
Kingdom Plantae or Plant kingdom
Some characters
Autotrophic mode of nutrition
Immobility
Rigid cellulosic wall
Less sensitive
Includes all plants
Kingdom Animalia or Animal kingdom
Some characters
Heterotrophic mode of nutrition
Mobility
Made up of cells without rigid cellulosic wall.
More sensitive because of presence of nerve cell
Includes all animals
The two kingdom classification is appreciable effort. However it could not address a great variety of animals and plants. So, it is inadequate and unsatisfactory in modern age.

Five kingdom classification
RH Whittaker of USA (1969) gave five kingdom system of classification (Science,163:150-160)
This system focuses on
Complexities of cell structure and body organization
Mode of nutrition
Phylogenetic relationship
Features of five kingdom classification
Advancement over the two kingdom classification
Based on phylogenetic relationship
Solves many problems of two kingdom classification.
Characters of five kingdom classification
Separated prokaryotes from eukaryotes
Removed anomaly of positions of many transitional and intermediate forms
All multi cellular, photosynthetic, eukaryotic with cellulosic wall included in kingdom Plantae
All multi cellular, non photosynthetic, eukaryotic with cellulosic wall included in Animal kingdom
All multi cellular, non photosynthetic plants separated from photosynthetic plants and kept in kingdom Fungi.
Brought out phylogenetic relationship amongst the primitive forms