SECTION ‘A’ (MULTIPLE QUESTIONS ANSWER)
1. Choose the correct answer for each from the given options
i) Down’s syndrome is an example of this condition:
* none of these
ii) One complete turn of DNA contains:
* 2 nucleotides
* 5 nucleotides
* 10 nucleotides
* 20 nucleotides
iii) For synthesis of protein, cells use:
iv) The concentration of oxygen in an atmosphere is about:
v) Producers of a pond ecosystem are:
vi) These are capable of cell division:
* Mature cells
* Meristematic cells
* Permanent cells
vii) Increase in the diameter’ of a plant due to the activity of vascular and cork cambium is called:
* Primary growth
* Secondary growth
* Primary and Secondary growth
* none of these
viii) Plant hormone responsible for apical dominance is:
ix) Cells found at the stem and root apices are termed as:
* Apical meristem
* Intercalary meristem
* Lateral meristem
x) The study of living things in relation to its environment is called:
xi) The sea below 2000 meters having no light is called:
* Benthic zone
* Euphotic zone
* Neretic zone
xii) Water moves in or out of a living ‘cell by the-process of:
xiii) Growth movement of plants in response to touch stimulus is called:
xiv) In Bryophytes, growth takes place at:
* lateral region
* in the centre
* throughout the body
xv) Mendel performed his famous experiment of heredity on:
xvi) The total aggrE1gateof genes in a population at anyone time is
* Gene pool
* Crossing over
SECTION ‘B’ (SHORT QUESTIONS ANSWER)
Describe any two phases of Growth. or Draw L.S. of stem and
root apices showing -different growing zones.
Phases of Growth: In lower plants (Bryophytes), growth simply involves the enlargement of cells followed by cell-division. In higher plants like angiosperms, increase ~ length takes place only at the apices of the roots and shoots, which can be recognized as three regions exhibiting three phases of growth.
1. The Formative Phase
2. Elongation Phase
3. Maturation or DifferenUation Phase
1. The Formative Phase: This is restricted to the tips of roots and shots, where the cells constantly divide and thus increase in number. The cells in these formative regions are closely packed together. They have thin cellulose walls, dense cytoplasm and large nuclei.
2. Elongation Phase: This phase occurs immediately behind the formative region. The cells here do not divide, but on account of their turgid condition they enlarge and elongate until they reach their
maximum size. In the root, the region of elongation extends over a few millimeters and in the stem over a few centimeters
Differentiate between DNA and RNA.
v) Write a note on Biotic components of Pond Ecosystem.
Living components of an ecosystem are called biotic components. They may be classified into Autotroph and Heterotroph. Autotrophic Components: The organisms which prepare their own food, these includes green plants which are capable of preparing their own food by simple inorganic material that is C02 and H20 in presence of sunlight and chlorophyll. These producers are of two types.
Microphytes (Lower Plants):
Macrophytes (Higher Plants):
Heterotrophic Components: These are the individual that are unable to prepare their own food due to lack of chlorophyll and hence are dependent on other organisms to fullfill their nutritional requirements.
On the bases of mode of nutrition biotic compnents are classified
vi) Describe Coniferous or Temperate deciduous forests of Pakistan.
Coniferous Forests: The coniferous forest characterized by cold resistant, evergreen plants belonging to gymnosperm.
Coniferous Forest in Pakistan:
Occurance: Coniferous forests are found in Kaghan, Swat, Dir, Muree hills and Chilas etc.
Producers: The main plants of these area are Pinus Species, Cedrus, Deodara, Taxus, Buccata, etc.
The land covers mostly by Mosses, Lichens and numbers of family
Ericaceae and Rosaceae.
Primary Consumers: The herbivores animals of coniferous forest in Pakistan include deer, wild goat. sheep and variety of insects and birds.
Secondary and Tertiary Consumers: Most of the camivores of the
forest are wolves, leopard and lynx etc.
Temperate Deciduous Forest: The deciduous forests of temperate
regions are called temperate deciduous forests.
Temperate Deciduous Forests In Pakistan: Temperate deciduous
forest found in Shogran, Neelam valley of Azad Kashmir.
Characteristic Plants: These forests consist of broad leaved plants
like, Beech, Oak and Maple. Pinus and Taxus baccata are dominant Neelam valey and Shogran.-
The land covers with mosses and ferns. During spring colourful flowers are developed.
• Variety of insects, birds and mammals feed upon plants.
• Predators include owls foxes, bears etc. These undergoes the h.bemation during cold wheather or moves to other places.
vii Draw a chart showing seven pairs of contrasting characters observed by Mendel. Also mention which of these characters are dominant or recessive.
viii) Write a note on Neritic region of ocean.
It is the shallow water found at the edge of continental shelf and upto the depth of 180 meters. It is further divided into .
Supratidal: It is the high tidal zone of neratic ocean .
Sub-tidal linter-tidal: It is the intermediate or intertidal zone at in between high and low tide of neratic zone .
Low tidal: It is below the low tide line region of the neratic ocean. Neratic ocean is the most productive zone of the sea and enough sunlight penetrates in it. Additionally, oxygen, carbondioxide and other nutreints are also helpful for the growth of plants.
Producers of this zone mainly include phytoplanktons, diatoms and
other algae like Caulerpa, Ectocarpus, Cladophora, Dictyota and Laminaria etc .
Producers of sub-tidal zones include phytoplankton, diatoms and animals are molluscs, star fish, sea cucumber, crustaceans, turtles, seals and whales .
Producers of inter tidal zones possess jelly like substances called plants that resist from desiccation. Animals of this zone possess shells and are burrowing type such as Snails, Shrimps, Clams, Bristle, Worm, Bugworms etc.
ix) What is a Test Cross? Explain with example.
See on Page # 460.
x) Write a note on Sickle cell anaemia or Vernalization.
Sickle Cell Anaemia: Sickle cell arfaemia is a heritable disorder in which the affected individuals are unable to transport..oxygen to their tissues properly because the molecules within red blood cells that carry oxygen, molecules of the protein hemoglobin, are defective. When oxygen js scarce, these effective hemoglobin molecules become insoluble and combine with one another, forming stiff, rod like structures. This results in the formation of sickle shaped red blood cells.
Vernalization: The phenomenon that shortens the vegetative period and initiate flowering is known as vernalization.
OR The low temperature treatment that result flowering in plants is
called vernalization. Garner in 1918 first time pointed out the relationsihp between temperature and early stages of seed qerrnination. The term vernalization was given by Lysenko (1928) for conversion of winter variety into the spring variety by low temperature or chilling treatment.
This winter variety is termed as vernalized.
Pine seeds will not germinate if not exposed to low temp.
Wheat and rice varieties exist in two races (the annual or spring and biennial or winter) ,
The biennial or winter variety is sown in fall and flowers in summer of the next year, while annual or spring variety is sown in spring and
flowers in summer of the same year.
Vernalization has found great application in Russia and other countries in the improvement of crop production.
xi) State four points of Chromosomal theory of heredity.
Chromosomal theory of heredity postulated by Walther Sutton in 1902. Their postulates are as follows.
Postulates of Chromosomal Theory:
1. The union of haploid sperm and eggs (that contains single set of chromosomes), re-stablish the double set of chromosome (Zygote) for the new organism as in parent organism.
The same fact proposed by Mendel that each parent contributes
equal number of genes.
2. During meiosis, the haploid number of chromosome segregate and received by the gamete in the same manner as Mendel. That is only single gene of each pair is present in gametes.
3. Each gamete have one copy of each pair of homologous chromosomes, but diploid individuals have two copies. According to Mendel, each gamete contain’s only one copy of gene while the resultant zygote have two copies of the same gene.
4. During meiosis, each pair of homologous chromosomes separate
individually and independently from the other. The same fact postulated by Mendel in his second Law i-e Law of Independent Assortment.
xii) Write a note on the significance of Secondary growth.
Vascular cambium that forms the secondary xylem and phloem is known as secondary growth. Successive secondary growth constitutes the formation of “annual rings”.
Number of vascular plant undergo secondary owth, increasing in
girth. The vascular cambium produces secondary xylem and secondary phloem, while the cork cambium produces tough and thick covering for
. stem by replacing epidermis. It takes place in all gymnosperms. In
angiosperms it takes place in most of the dicot species but rare in
When the secondary growth continues up to number of years,
secondary xylem accumulate in the form of wood. It mainly consists of
tracheids, vessel (in angiosperm) and fibers having thick lignified walls
which give hardness and strength. A fairly accurate estimate of age of a
tree can be made by counting the annual rings. Study of the rings of
large sample of very old tree can also give a clue to the climate of an
area. Tree-ring dating have been used in archeological studies.
Secondary growth meet the need of more water, minerals and food
conduction for growing plant. It also provides the firm support to it by
producing new conducting and mechanical tissues, in addition to these
the cambium forms callus on or around the wound. The I
parenchymatous tissues are rapidly formed below the damaged surface of stem and root. Callus also develop during grafting to unite the graft with the plant.
xiii) Write a note on the role of Growth hormones in plant movement.
Plants do not move from one place to another like other animals, so termed as sessile orgainsm. But shows growtlun(}vement. There are certain chemical substances which eentron me growth ef-ptants called nPhytohormo1’leS \ArlXins-; ~'”ryereliins, Cytokinin, Abscisic Acid etc)
Example: Auxins (1M), play important role in cruvature movement of phototropism. It was found that oat (“‘Ileoptile possess only c-r% auxins in illuminated side, whereas uni! rminated side possessed 57% auxin. The region in which auxin is in higr’ concentration shows rapid growth, which result in growth curvature towards the light.
Auxins also play an imports : role in geotropism. It is responsible for positive geotropic movement .of roots and negative geotropism in shoots.
Patlo between Auxin and Abscisic acid play role in nastic movement.
Epinasty in plants found due to IAA .
Senescence is caused by ABA. •
Gibberelline causes hypo nasty.
xiv) Write a note on anyone of the following:
(a) Cymose inflorescence
In cymose infiorenscene. main axis soon stops growing. The flowers develop in basipetal succession <1M opening of flower is centrifugal. Kinds of Cymose: The followin~,1are the types of cymose infloresence.
Uniparous (Monochaslal) C~’ME: Main axis soon en,.•s into a- rC'”‘6r and produces only one lateral branch at a time endmg in a flower. The succeeding lateral branches ag;,un follow the same mode of producing flowers. .,
a) Scorpoid Cyme: If the succ llediflg branches are produce on the
alternate sides, it is called Scorpo’d cyme
Example: Cotton, forget-me-not.
b) Helicoid Cyme: If the succeeding branches are produced on same side, it is called helicoid cyme.
2- Biparous (Dichasial) CYME: Main axis soon terminate into a flower and produces two flowers. This mode is followed by each succeeding flowers.
Example: Pink night jasmine.
(b) Tissue Culture
It is” a test tube technique to create a clone of a cell. Tissue culturing is a popular method to grow whole plant from a single cell or a piece of plant plant cells are consider as totipotent (means with full ..” F “geneticpotenliarof an organism).
In 1950, Frederick Steward produced a carrot from a single phloem
cell, that was grown on nutritional medium containing sugar, minerals and vitamins with coconut milk (having harmones cytokinins) Cultered plants among certain plants give rise to embryo like structures that are smaller and simplest than plantlets, These embryo are called somatic embryos as they derived from somatic cells.
Example: Tomato, celery, asparagus, lilies, I)egonia etc).
Anther culture is another type of culture in which anthers are cultured-in all artificial medium.
xv) Explain why interpnaseJs-not a resting phase of cell cycle
:See on Pag #463.
SECTION ‘C’ (DETAILED QUESTIONS ANSWER)
(i) Slate the Law of Independent Assortment. Explain it with “fhe help of checker board method.
MENDEL’S SECOND LAW
LAW OF INDEPENDENT ASSORTMENT: According to this law when two pairs of contrasting characters are brought together in hybrid union, each pair of different character will segregate independently at the time of gametes formation, and then assort alleles in each pair independent to each other.
In this walj along with the parental combination, new combinations of genes also formed..
MENDEL’S STATEMENT: “Members of one pair of factors segregate (assort) independently of members of another pair of factors. Therefore, all possible combinatlons of factor’s can occur in the gametes.”
Example: Mendel selected pea plants with two contrasting characters i.e colour of seeds and shape of seeds. As it is cross between differing in two characters so called Dihybrid Cross and the ratio is I$,nownas Dihybrid Ratio.
Yellow and Wrinkled -3/16
Green and Round -3/16
Green and Wrinkled -1/16
This pattem onnnefita~~i” also observed in animals.
(ii) What is Ecological succession? Describe Hydrosere or Xerosere. or How do male and female gametophytes of argiospermic plants develop from anthers and ovaries respectively?
Ecological Succession: The process that change community orderly or in a sequential way is called “Ecological Succession”. The succession leads to formation of stable community in a particular area after certain period of time.
The community that become stable after successional changes is called “Climax Community”.
The term succession was first time use by Hult in 1885. There are two main kinds of succession which are as under.
1- Primary 2- Secondary
Hydrosere: Primary succession in open water like, ponds, pools or
lakes which converted to land cornrrumlty constitute “hydrosere”. The successional changes found in both animals and plants. But is more clear in plants. The seral stages in a pond are as follows.
1- Phytoplankton Stage: The colonial planktons are first invaders of pond. Algal spores may brought by wind along with soil particles are deposited in water. The phy!oplanktons are pioneer species and so form pioneer community. These include blue-green algae (cyanobacteria) green algae (spirogyra, oedogonium, ulothrix etc), bacteria and diatoms. Protozoanes like Amoeba, Paramecuim and Euglena are the pioneer species of pond.
11-Submerged Stage: In this stage soil become soft and suitable for growth of rooted hydrophy!es due to decay of phy!oplanktons and zooplanktons.
Plants: Hydrilla, Vallisnaria, Potamageton, Elodea etc.
Animals: Blue fish Sunfish, Daphnia etc. Due to decomposing of these organisms, soil become rich in nutrients and silting reduce the depth of water.
Floating Stage; Decaying of hydrophy!es of submerged stage resulting the water depth upto few feet. So, plant developed in this stage are rooted’ in soil and their leaves float on the surface of water. These plants reduce water level by transpiration.
a) Rooted-Nymphea, Eichomia, Trapa, Nelumbium.
b) Free floating plants include Azolla, Lemma, Pistia, Solvinia etc.
Animals: Hydra, Snails, frog diving beetles. etc.
Reed Swamp Stage: It is also known as amphibious stage. In this stage water table reduces and pond become more shallow due to decay of plants and animals of the floating stage. The plants of this stage although rooted in soil but most of their parts found above water table. These plants have well developed rhizome and thick vegetation.
Plants: Typha, Polygonum, Phragmites, Sagittaria. etc.
Animals: Lymnea, Physae, Insects like water Scorpion and giant Bugs.
Sedge Meadow Stage: The soil in this stage become more suitable for plant growth due to continuous decomposing of organisms of reed swamp stage and reduce water table. The plants of this stage have much branched rhizome system and dense growth of plants increase the rate of transpiration. The nutriants in the soil converted into oxides of nitrate and sulphates due to action of oxygen.
Plants: Juneus, Cyperus, Carex.
Animals: Snails, like Anodonta and Psidium.
Wood Land Stage: In this stage marshy soil become drier and available for terrestrial plants. ‘
Plants: Salix (shrub), Populs (trees)
Animals: Terrestrial animals like zebra, deer etc.
Climax Stage: Finally, wood land’ community of trees invade on the terrestrial environment. Now the vegetation of these trees are dependent on environmental conditions .
If there is heavy rainfall, then it develops the tropical rain forest.
If there is moderate rainfall as in temperate region then the mixed forest is developed.
Xerosere: It occurs in the area where water and organic matter are not available. Additionally, it has some minerals. Xerosere stages are assigned on the basis of dominant plants types of the stage.
These seral stages are as under.
Crustose Lichen Stage: It is the first seral stage of xerosere. In this stage bare rock or land do not contains moisture and organic matter, So, lichens are the pioneer species of this area. Lichens can also survive in extreme temperature. They produce acids, which help in chemical weathering of rocks and produce substratum for other species.
Example: Rhizo-carpon.Rinodine, Lecanora etc.
Foliose and Fructiose Lichen Stages: The lichens of this stage are more stable and have ability to absorb moisture and retain it. In this stage a layer of soil is developed on the rock surface. This soil surface provide rich substratum.
Examples of Lichens: Pasmelia, Dermatocarpon etc.
Animals: Mites, ants and spiders present in rock cracks.
Moss Stage: In this seral stage of xerosere soil is more suitable for the growth of mossess due to decay of lichen. Mosses requires little water, (mainly for reproduction).
Plants: Polytrichum, Grimmia, Selaginella etc.
Animals: Mites and spiders increase their number.
Herbs Stage: In this stage, soil accumulation results the xeric conditions which later changed into shallow rooted plants. In this seral stage initial stages showed growth of annual herbs and later perennial herbs. This stage also favours the
Plants: Aristida, Poa etc.
Animals: Nematodes, larval insects, mites, ants etc.
Shrub Stage: In this stage soii become more suitable for the growth of shrubs and is more rich with moisture and Minerals. This stage promote the growth of flora as well as fauna
Plants: Rhus, Phytocarpus.
Animals: Slugs, snails, millipedes, Centipedes: Salamanders, frog, reptiles, birds, mammals like shrew, squirrels and foxes.
Climax Stage: In this seral stage, soil accumulation and humus formation results more fertile soil, which favours the growth of some xerophytic trees. This lead to the formation of mesophytic form of plants and thus final population is developed and the community is called climax community. This vary from place to place.
In angiosperms, gametophyte phase is very reduce and short. The male and female gemetophyte develop from anther and ovary respectively.
1. Microspore mother cell in anther (pollen sac) under goes reduction division (meiosis) to form 4 haploid cells.
2. Each microspore termed as pollen grain which consisting of two cells, generative cell and tube cell.
3. As the pollen tube develops incontacted with stigma, the generative cell divide and give rise to formation of two haploid male gametes ‘called sperm.
1. Ovule in ovary contains megaspore mother cens which undergoes reduction division to form four haploid megaspore.
2. Each megaspore after successive mitotic division develops into seven-cell (eight nucleated) structure called female gemetophyte or embryosac.
3. In Whicht hree antipodal cells found towards chalaza, three cells found towards micropyle, two of which termed as synergid cells and one comparatively large, cell; is egg cell and two central cells called secondary nuclei or definitive nuclei.
3. (iii) Draw and describe Prophase 1 of Meiotic division. or
Describe the process of Gene expression.
Meiotic Division: The process of cell division leading to the production of daughter nuclei with half of the genetic material to the parent cell is called Meosis.
The cell that formed by meiosis give rise to the formation of haploid gametes. The fusion of gametes result the fertilization and hence become diploid.
Prophase I: The first phase is divided into following substages.
Chromatin network separated into diploid number of chromosomes. The chromosomes appear granulated or beaded longitudinally.
The parental chromosomes come close together and become associated with each other to form a bivalent
The pairing of homologous chromosomes is known as synapsis .
Chromosomes are attached at the region of centromere.
The homologous chromosomes become thick and each member is now visible to consist of two chromosomes .
Each chromosome of bivalent gets replicated and tetrads are formed.
At this stage, bivalent consist of four chromotids which are uncoiled and separated .
This separation is not completed because at certain points they are in contact which is known as chiasmata .
Here exchange of genetic material that is exchange of non] – sister part of cheomotids take place between the paired chromosomes by thebreaking and rejoining of weaker chromotids at the point of chiasmata. This process is called as crossing over.
The bivalent separated due to. repulsive force between homotoqous chromosomes. This is known as terminalization .
The chromotids become shorter and thicker .
Nucleolus and nuclear membrane are both disappear .
Spindle formation occurs .
The bivalent with their exchange parts get separated and move towards the equatorial plane. This is the end of prophase I .
DNA which carries information as. a message translate to form proteins due to expression of genes. Gene expression comprises into two steps, i.e., transcription and translation
Transcription: The synthesis of RNA from DNA is called “Transcription”. This process involves following steps.
i) Transcription is initiated when RNA polymerase enzyme binds a particular nucleotide sequence on one of the DNA strand.
ii) RNA polymerase proceed to assemble a single strand of RNA with a complimentary nucleotides.
iii) When enzymes arrive at special points, the stop signal at edge of
the gene results the termination of transcription
iv) Later on synthesized RNA modified to form either type of RNA i.e. mRNA, tRNA and rRNA.
Translation: It is a second stage of gene expression in which polypeptide chain is formed. This process of mRNA directed polypep.tide synthesis by ribosome is called “translation” as nucleotide sequence translated into aminoacid. This process involve following steps.
i) As the ribosomes moves along the strand of mRNA from first triplet codon to second triplet codon.
ii) tRNA molecules move towards the amino acid pool (cytoplasm) to form tRNA- aminoacyl complex.
iii) This tRNA-aminoacyl complex moves toward the mRNA where it decode the codes present on mRNA and release aminoacid.
iv) Now this empty tRNA again moves toward amino acid pool.
v) Another aminoacid along with tRNA comes to decode another code and translate this code as amino acid.
vi) Now, both of these amino acids join together by peptide bond as ribosome move on mRNA resulting the formation of polypeptide