Botany Solved Past Paper 2nd year 2012 Karachi Board


1. Choose the correct answer for each from the given options:

i) The capacity of a living system to lose water is:
• Osmotic pressure
Water potential
• Osmosis
• Plasmolysis

ii) Plants grow ing in saline marshlands are termed as:
• Hydrophytes
• Mesophytes
• Xerophytes

iii) Number of chromosomes in sugar cane is:
• 46
• 100
• 95

iv) The coldest desert is:
• Thar
• Thull
• Cholistan

v) The net movement of water molecules remains in equilibrium when a cell is placed in:
• Hypotonic solution
• Hypertonic solution
• Isotonic solution
none of these

vi) Phototropic curvature is due to light effect on distribution of this hormone:
• Gibberellin
• Cytokinin
• Ethene

vii) In grasses, intercalary meristem occurs:
at the base of internodes
• below the node
• at the tip of the shoot
• at the tip of the root

viii) At this meiotic prophase – I sub stage, termlnalizatlon takes place:
• Zygotene
• Diplotene
• Leptotene

ix) Plants growing In shade are known as:
• Heliophytes
• Mesophytes
• Halophytes

x) In this type of germination, the seed germinates inside the fruit while still attached to the parent plant and nourished by It:
• Hypogeal germination
• Epigeal germination
Viviparous germination
• Parthenocarpy

xi) Protein synthesis starts with this codon:

xii) The depth of oceanic zone where light reaches Is called:
• Aphotic
• Bathyal
• Abyssal

xiii) For their defense, infected plants produce a variety of chemical compounds:
• Phytohormone
• Phytoalexin
• Phytoplankton

xiv) This is a type of orderly or programmed cell death:
• Necrosis
• Synapsis
• Mitosis
• Apoptosis

xv) It is a defect in humans in which blood fails to clot after an external or internal injury:
• Sickle cell anaemia
• Phenylketonuria
• Haemophilia
• Colour blindness

xvi) It helps in determining the homozygosity or heterozygosity of the dominant parent:
• Epistasis
• Incomplete dominance
• Test Cross


2.i) Write a note on the role of Auxin.
See on Page # 458.

ii) Differentiate anyone of-the following:
a) Activities of Vascular cambium and Cork cambium

Activities of Vascular cambium and Cork cambium

Activities of Vascular cambium and Cork cambium

Heartwood and Sapwood

Heartwood and Sapwood

Heartwood and Sapwood

Heartwood and Sapwood

iii) Define Seed dormancy Q!: Vernalization.
Seed dormancy: See on Page # 465.
Vernalization: See on Page # 482.

iv) Write a note on the Phases of Growth in plants.
In lower plants (Bryophtes), growth occurs in diffused manner. While, In higher plants, growth involves the three phases or in three zones, which are as under.

1- Formative Phase: This phase is located at the tip of root and shoot of the plants. The cells of this phase are constantly divide, resulting in increase in their number.
2- Elongation Phase: This phase is located just behind the formation phase. The cells of this region are not divide, but increase in their size in terms of turgidity and elongate to attaintheir maximum size.
3- Maturation Phase: This phase is located behind the region of elongation. Here the enlarged and elongated cells are modified to permanent; so, this region is adapted to perform different functions. This phase is also so called differentiation phase.

v) Define Linkage and Crossing over.
linkage: The tendency of genes in a chromosome to remain together is called Linkage.
Crossing over: The exchange of chromosomal segments in synaptic pair is known as crossing over. It occurs between non-sister chromatids of homologous chromosomes. The crossing over occurs randomly along the length of the chromosome.

vi) Write a note on Down’s Syndrome.
Down’s Syndrome is a condition of aneuploid and also known as trisomy. Syndrome in human abnormality. It is an autosomal disorder and is commonly known as Mangolism. In this 21st chromosomal pair fails to separate resulting gamete with 24 chromosomes. When this gamete fertilized with normal gamete the new individual will have 47 (2n+1) chromosomes. It was observed one out of every 909 births (1/900) which is rela ed to age of mother

The chances for teenage mother having Down’s syndrom child is one in many thousands. (1/1000)

Forty year aged mother have chances of about one in hundred (1/100)

Forty-five years old mother have 3 times greater risk (3/100).

Abnormalities of Dawn’s Syndrome: The abnormalities of this disease includes.
Mental retardation and defective development of eNS with low IQ in 20-50 range.
Broad flat face
Eyes-with folds
Short stature
Short hands and large tongue.
Females may be fertile and may produce normal or trisomic progency but males never reproduce.
life span is about 17 years and only 8% can survive upto 40 or above.

vii) Define Point Mutation. Discuss Sickle Cell Anaemia or Phenytketonuria.

Point Mutation: It is a type of mutation in which a change in genetic sequence occurs by producing an alteration by only one or few nucleotide. It is also called “Gene Mutation”.
Sickle Cell Anaemia: Sickle cell anaemia 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 is 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.
Phenytketonuria: Phenylketonuria (PKU), a hereditary condition in.
which the affected individuals are unable to break down the amino acid phenylalanine. In such individuals, phenylalanine is instead converted to other chemicals that accumulate in the bloodstream. Although not harmful to an adult, these abnormal derivatives of phenylalanine are harmful to infants because they interfere with the development of brain cells: An infant with this disorder suffers severe mental retardation

viii) Write a note on various Ecological Levels of Organization.
The scientific study of various relationships of living organisms to each other and wi1htheir enviroment is called “Ecology”. In ecosystem, ecological studies begin from individual organism then
the group of the organisms and ends on an ecosystem.

1. Individual organism (species).
2. Population (Group of similar organisms)
3. Community (Group of different populations).
4. Ecosystem
a. Aquatic
i. Fresh water
ii. Marine water
b. Terristrtal (Biome)
5. Biosphere

ix) Define R” factor. Describe how children are In danger of betng born with the disease ‘Erythroblastosis foetalls’.
Rh antigen first discovered by landsteiner in 1930 in Rhesus monkey. The blood is -of two types according to antigen known as Rh factor, which is c0ntr0lied by a gene called Rhesus factor that named according to genes discovered in Rhesus monkeys_About 85% of a population of human beings is R”+ve (positive). Its knowledge is very important in transfusion of blood and pregnancies. If a peISOfllacks this R” antigen then it is called Rhnegative.
Rn+ve RnRn,Rnr Rnpresent
Rn_ve Rnabsent
Erythroblastosis foetaIls: If Rh negative woman marries with R~
positive man, her child are likely to be positive, because antibody
production in ~ blood.
This R”+ve child will be in danger of being born with erythroblaStosis foetalis. In this condition the R” antibodies of mother invade the foetus and attack its red blood cells, causing the child to be born severely anaemic.
Now a days, this condition can be easily prevented by injections of a
substance that prevents formation of R” antibodies by the pregnant

x) Write a note on Test Cross?
See on Page # 460.

xi) Write. n_ on Excretion in Plants.
Ans: See an Page # 462.

xii) How do plants cope with Cold and Heat stress?
Ans: See on Page # 461. –

xiii) Explain either Positive or Negative Inte~s.
Positive Interactions: In this type of interaction in which living organisms interact with each other for mutual benefit to get food or shelter or for support etc. In this benefit may be for both organisms or one can get benefit aOd other neither get benefit nor harm.
Example: Mutualism, commensalisms Negative Interactions: This is a· type of interaction in which living organisms interact with each ather and cause harm to one of them for getting food, shelter or support or may compete for other resource.
Example: Predation, Grazing

xiv) Write a note-on Flow of Energy In an Ecosystem.
All the-living organisms require energy to do work. They obtain energy directly from non-living things or by other living organisms. The autotrophs of the ecosystem are the living organism that capture solar energy and then convert it into the chemical energy by photosynthesis. A part of this energy store in them and can be available for other heterotrophic organisms of the ecosystem

The energy finally release back into atm~sphere by decomposing of
these living organisms or either by loss of heat at various trophic levels.

About 1% of the total enery from the sun is trapped by the producers in an ecosystem. The remaining 99% of solar energy is used to evaporate water, heat up soil and then lost to the outer space. As energy transferred from one trophicallevel to the next, from ~ to primary consumer, between 80 to 90% of the orginal energy is lost as heat as a bybroduct of respiration. HoWever, a continuous flux of energy from the sun prevents ecosystem from ruMing down. A pyramid of energy can be constructed Showing energy transfer in a community of organisms

xv) Explain the significance of Secondary growth.
See on Page # 482.


3.i) Define Mitosis. Describe vanous stages of Mitosis with the help of diagrams.
See on Page # 411.

3.ii) Define Ecosystem. Describe Desert ~r any type of Fon=it Ecosystem wHh special reference to Pakistan.
Ecosystem: Ecosystem was first defined by Tansely in 1935 as WAnecosystem is a structural and functional·unit of a-community, whidt shows relationship between flow of energy and eyeing of maaer in be~ Biotic and Abiotic component- OR “The biotic community and abiotic component together is caIed Ecosystem

An ecosystem is self supporting unit in which exchange of malelial between living organism and non living components takes place in cyclic manner.

Desert Ecosystem: A desert is defined as the reginr. where rainfall is less than 25 an per year, although desert can develop in certain hot regions where there may be more rainta’ but an uneven dislnbution of animal cycle.

Occurance: Desert covers about 17% of land surface and ate found
commonly in, Africa, North Mexico, Western USA The desert of Pakistan and IrKia are Thar, Thai; Cholistan.

Forest Ecosystem: H is alsO a type of terrisbial ecosystem. H incbJes large and small trees. It roughly occupies about J5.4O% of the land surface and in Pakistan, it is of about 6% of the total land area.

Forest roughly occupies about 35-40% of the land surface and in Pakistan it is of about 6% of the total land area.

Following are the main types of forest biomes.
1. Tropical Rain forest
2. Coniferous forest
3. Temperate decidous forest
Coniff#fOUs Forest The coniferous forest characterized by cold resistant, evergreen plants belonging to gymnospenn.

Occurance: This kind of forest covers predominanUy northern hemisphere that include from Alaska to central America which is heavily glaciated. While few in southern hemisphere

There is heavy snow fan during winter.
Plants show xerophytic features, like needle leaves..
Plants grow slowly.
low decomposition of dead plants and aninals.
Rainfall is fairly heavy.

Producers: The main plants of the forest are pine, fir and spruce, Dicot pIanIs include Bisch willwo and Populus found in this area. Consumers: Black bears and flying squirrals are common anmats in the forest..

coniferous Forest in Pakistan

Occurance: Coniferous forests are found in Kaghan, Swat. Dir, MJ1ree hils 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 m.mbers 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 carnivores of the forest are wolves, leopard and lynx etc.

3.iii) Why did Mendel choose Garden pea for his experiments? State the Law of Segregation. Prove it with the help of Monohybrid cross.

Mendel Father of Genetics and his laws were known as Mendelism..

Choise of material and methadology are the two main objectives of Menders study.

Chaise of Material: Mendel selected experimental plant i.e., Pisum sativum (Garden Pea) because of following useful characters.

6. These plants are cultivated easily, as their generation time is very short.
7. These are seIt-poIinating ‘plant’s but cross poIination can only take place artificially.
8. Artifical breeding is easy as flowers are comparatively large with numerous varities are available with sharply define contrasting characters. That may include.

a. Height of plant (taU or dwarf)
b. Shape of the seed (round or wrinkled)
c. Colour of seed (Green or Yellow)
d. Shape of the pod (Smooth or consIicted)
e. Colour of pod (Yellow or Green)
f. Colour of flower (Red or White) etc.

9. These plants produce fertile hybrid
10. This plant do not show complexities that had troUbled.earfier worker.

Law of Segregation: According to this law when a pair of contrasting characters are brought together in an individual, they neither mix up nor affect each other, but at the time of gamete formation genes are segregated and pass into different gametes. In this way each gamete contains only some allele of a gene for particular character and is pure. So, this law is also called “Law of Purity of Gametes
Mendel’s Statements: -Each organism contains two factors for each trait and these factors segregate during the formation of gametes. So, the each gamete contains only one factor for each trait. When fertilization occurs, the new organism receives 2 factors for each trait, one from each parent
Example: When a pure (homozygous) tall pea plant TT crossed with a pure dwarf pea plant tt. The F1 had al hybrid (heterozygous) -tall pea plants Tt.

When the F1 individual self pollinated, the F2 had tal and dwarf plants in a ratio of 3:1 (phenotypic ratio). AInOrIg these plants one was pure tall n. two were hybrid tal Tt and one- was pure dwarf tL SO, the genotypic ratio is 1:2:1. It is known as monohybrid cross. The result obtained from monohybrid cross is known as Single. TraiI’lrlheritance



Tall plants = 3
Dwarf plants = 1
Homozygous Tall = 1 (TT)
Heterozygous Tall = 2 (Tt)
Homozygous Dwarf = 1 (tt)

Mendel’s laws of inheritance also applicable in animals as well.
Like in Guinea pig. Black (88) hair colour is clOminantover brown hair (bb)

What is Osmoregulation? Classify various types of plants on the basis of Osmoregulation.

Osmoregulation involves in maintaining balance between water and solute concentrations of cells. It is one of the important aspects of homeostasis

Flowering plants in the natural habitat classify into tow groups on
the basis of water availability.
1. Hydrophytes
2 Halophytes
3. Mesophytes .
4. Xerophytes-

1. Hydrophytes: Those plants which are found partially or compIeteJy sub-merged in fresh water habitat tenned. as Hydrophytas. They  excess water and donot face any difficulty in.obtaining water.
Examples: Hydrilla, Typha, Water lily.etc· .
2- Halophytes: Those plants which grow in sail rnarsIIes-fteiKtnsea or coastal areas are termed as Halophytes. They absorb waIer.from such soil that contain higher salt concentration and lower waIer JX*ntiaI for high osmotic pressure).
Examples: Glassworts, Cord-GrasS,Limonium ete:
3- Mesophytes: Most of the land plants of temperale zones are known as mesophytes. They grow in well watered soil. They can, easily compensate loss of water (transpiration) through absorbing water from soil. ;.
Example: Brassica, Rose, Mango etc.
4- Xerophytes: Those plants which grow·in.dry places such as, desert, steep hills etc are termed as xerophytes. They face scarcity of water. . Under such conditions water potential.of air and soil are very low.So, the Xerphytes have developed following adaptations to conserve  water for their survival.
Examples: Accacia, Cactus, Prosopis Casuarina etc

Posted on December 30, 2015 in 2nd Year 2012 Karachi Board Past Papers

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