Karnataka School Examination and Assessment Board
II PUC Model Question Paper - 1 Solutions
Subject: 36 - Biology | Max Marks: 70 | Number of Questions: 44
General Instructions
- This question paper consists of four parts A, B, C, D and E.
- Part A consists of I and II and Part D consists of V and VI
- All the parts are compulsory.
- The answers for Part A written in the first two pages of the answer booklet are only considered for evaluation.
- Part E consists of questions for visually challenged students only.
I. Select the correct alternative from the choices given below:
1. Statement I: Pollination does not guarantee the transfer of right type of pollen. Statement II: Compatible pollen–pistil interaction guarantees double fertilization.
A) Both statements I and II are correct
B) Both statements I and II are incorrect
C) Statement I is correct but statement II is incorrect
D) Statement I is incorrect but statement II is correct
Pollination only brings pollen grains to the stigma and does not ensure that the pollen is compatible. A compatible pollen–pistil interaction permits pollen germination and pollen-tube growth, ultimately enabling double fertilization.
2. The secondary oocyte formation from primary oocyte occurs in which follicle?
A) Primary
B) Secondary
C) Tertiary
D) Graafian
The primary oocyte completes meiosis I shortly before ovulation in the mature Graafian follicle, producing the secondary oocyte and the first polar body.
3. Progenies with AB and O blood groups are not possible from which mating parents?
A) O × AB
B) AB × B
C) AB × AB
D) AB × A
AB × AB can produce offspring with A, B or AB blood groups, but group O is not possible because neither parent carries the recessive i allele.
4. Another chemical name for the nitrogenous base thymine is:
A) 2-Methyl uracil
B) 3-Methyl uracil
C) 4-Methyl uracil
D) 5-Methyl uracil
Thymine is chemically 5-methyluracil. It is a pyrimidine nitrogenous base present in DNA.
5. Select the correct match:
A) Spotted cuscus – Flying squirrel
B) Spotted cuscus – Bobcat
C) Spotted cuscus – Anteater
D) Spotted cuscus – Lemur
The spotted cuscus is an Australian marsupial, whereas the flying squirrel is a placental mammal.
6. Which of these ancient men protected their body with hide and buried their dead?
A) Homo habilis
B) Neanderthal
C) Dryopithecus
D) Homo erectus
Neanderthals used animal hides for protection against cold and are known for burying their dead.
7. Human Immunodeficiency Virus replicates in:
A) B-cells
B) NK-cells
C) Helper T-cells
D) PMNL
HIV primarily infects CD4+ helper T-lymphocytes and uses the cellular machinery of these cells for replication.
8. The drug which is depressant and slows down body function is:
A) Smack
B) Crack
C) Hashish
D) Charas
Smack is heroin, an opioid drug that acts as a central nervous system depressant and can slow body functions.
9. Saccharomyces cerevisiae, commonly called brewer's yeast, is used for fermenting malted:
A) Pulses
B) Cereals
C) Fruits
D) Vegetables
Brewer's yeast ferments sugars present in malted cereals to produce ethanol and carbon dioxide during brewing.
10. In 1963, the two enzymes responsible for restricting bacteriophage growth in E. coli were isolated. One cut DNA and the other added which group?
A) Methyl
B) Ethyl
C) Phosphate
D) Hydroxyl
The restriction-modification system includes restriction enzymes that cut DNA and methylases that protect DNA by adding methyl groups to specific sites.
11. Which of the following is the correct representation of primer annealing step in PCR?
During annealing, the temperature is lowered, generally to about 50–65°C depending on the primers. The short DNA primers bind by complementary base pairing to their respective single-stranded template DNA sequences.
PCR sequence: Denaturation → Annealing → Extension.
12. Given below are steps in gene therapy of a patient with ADA deficiency. What is the correct order?
I. Lymphocytes are grown in culture outside the human body.
II. Lymphocytes are altered with a functional ADA gene.
III. Lymphocytes are collected from the blood of the patient.
IV. Genetically modified lymphocytes are infused back into the patient.
First, lymphocytes are collected from the patient's blood. They are cultured, genetically modified with a functional ADA gene and finally returned to the patient.
13. The organisms that reproduce only once in their lifetime are:
A) Oysters
B) Pelagic fish
C) Salmon fish
D) Hippocampus
Salmon are examples of organisms that reproduce once during their lifetime and then generally die. This reproductive strategy is called semelparity.
14. The decomposers especially abundant at the bottom of the pond are:
A) Only fungi
B) Only bacteria
C) Only fungi and bacteria
D) Flagellates, fungi, bacteria
Decomposer communities in aquatic ecosystems include bacteria, fungi and various protists such as flagellates.
15. The IUCN Red List (2004) documented the extinction of species in the last 500 years to include:
A) 847
B) 784
C) 874
D) 478
II. Fill in the blanks by choosing the appropriate word/Words from those given below:
(Amoebiasis, richness, Nostoc, ovulation, colostrum, diversity)
16. The initial few days of milk produced after parturition is __________.
Colostrum is the yellowish first milk produced after childbirth and is rich in antibodies, especially IgA, and nutrients.
17. Oral pills as contraceptives effectively function by inhibiting __________.
18. Symptoms of constipation, abdominal pain and cramps are associated with disease __________.
19. Cyanobacteria can fix atmospheric nitrogen. An example is __________.
20. Alexander von Humboldt observed that within a region, species __________ increased with increasing explored area up to a certain limit.
This observation forms the basis of the species–area relationship.
Answer any FIVE. Each question carries 2 marks.
21. Draw a labelled diagram of a mature 2-celled pollen grain.
A mature two-celled pollen grain consists of a large vegetative cell and a smaller generative cell. The pollen grain is surrounded by an outer exine and inner intine.
22. Mention any four assisted reproductive techniques that can be advised to couples with infertility problems.
- In vitro fertilisation (IVF) followed by embryo transfer.
- Intracytoplasmic sperm injection (ICSI).
- Intrauterine insemination (IUI).
- Gamete intrafallopian transfer (GIFT).
23. Recombinants are obtained in both Mendelian and Morgan experiments. Yet, the processes involved are different. Comment.
In Mendel's dihybrid experiment, recombination results from the independent assortment of genes located on different chromosomes. In Morgan's experiment, recombination occurs because of crossing over between linked genes located on the same chromosome during meiosis.
24. Name the methodologies used in Human Genome Sequencing.
- Expressed Sequence Tags (ESTs).
- Sequence annotation based on sequencing the whole genome and then assigning functions to different regions.
25. Name the evolution of any two plant forms through geological periods from tracheophyte ancestors.
Two examples are:
- Tracheophyte ancestors → pteridophytes.
- Tracheophyte ancestors → gymnosperms → angiosperms.
26. Describe briefly the primary treatment of sewage.
Primary sewage treatment is a physical process. Large floating debris is removed by filtration through screens. The sewage is then passed through a grit chamber to remove sand, silt and small stones. In a settling tank, suspended solids settle as primary sludge while the supernatant forms primary effluent.
27. Differentiate between ex-situ and in-situ conservation.
| Ex-situ conservation | In-situ conservation |
|---|---|
| Species are conserved outside their natural habitats. | Species are conserved within their natural habitats. |
| Examples: botanical gardens, zoological parks and seed banks. | Examples: biosphere reserves, national parks and wildlife sanctuaries. |
Answer any FIVE. Each question carries 3 marks.
28. Draw a diagram of a monocot embryo and label three parts.
A typical monocot embryo has one cotyledon called the scutellum. The embryonal axis bears the plumule at its upper end and radicle at its lower end. The plumule is protected by the coleoptile and the radicle by the coleorhiza.
29. What is the menstrual cycle? Mention one pituitary and one ovarian hormone involved in it.
The menstrual cycle is the cyclic series of changes occurring in the female reproductive system approximately every 28 days from puberty to menopause. It includes menstrual, follicular, ovulatory and luteal phases.
Pituitary hormone: Follicle-stimulating hormone (FSH).
Ovarian hormone: Oestrogen.
30. Write any three principles to be followed by people to remain free from sexually transmitted infections.
- Avoid sex with unknown or multiple partners.
- Use condoms properly during sexual intercourse.
- Maintain personal and genital hygiene and seek early medical diagnosis and treatment if symptoms occur.
31. List the three connotations of the theory of special creation.
The theory of special creation proposes that:
- Life was created by a supernatural power.
- The earth and organisms have remained unchanged since their creation.
- All species were created separately and independently.
32. Name the disease caused by the following pathogens:
a) Wuchereria
b) Microsporum
c) Plasmodium
- Wuchereria: Filariasis (elephantiasis).
- Microsporum: Ringworm.
- Plasmodium: Malaria.
33. Mention the uses of the following bioactive agents:
a) Streptokinase
b) Cyclosporin-A
c) Statins
- Streptokinase: Used as a clot-buster to dissolve blood clots in patients with myocardial infarction.
- Cyclosporin-A: Used as an immunosuppressive agent in organ transplantation.
- Statins: Used to reduce blood cholesterol levels by inhibiting cholesterol synthesis.
34. Describe the steps of decomposition that operate simultaneously on detritus.
Decomposition involves several processes that may operate simultaneously:
- Fragmentation: Detritivores break detritus into smaller particles.
- Leaching: Water-soluble inorganic nutrients move into the soil.
- Catabolism: Bacterial and fungal enzymes break down complex organic matter.
- Humification: A dark amorphous substance called humus is formed.
- Mineralisation: Microbial activity releases inorganic nutrients from organic matter.
V. Answer any FOUR
35. Draw a diagrammatic sectional view of the human male reproductive system and label five parts.
The male reproductive system consists of a pair of testes, accessory ducts, accessory glands and external genitalia.
Five important labels: Testis, vas deferens, seminal vesicle, urethra and penis.
36. Represent schematically the results of two gene interaction by taking seed shape and seed colour in pea plant.
Two gene interactions can be demonstrated using seed shape and seed colour. Consider:
R = Round, r = Wrinkled
Y = Yellow, y = Green
A typical dihybrid cross is:
RRYY × rryy
F1: RrYy – all round and yellow.
Selfing of F1:
RrYy × RrYy
| Phenotype | Expected ratio |
|---|---|
| Round yellow | 9 |
| Round green | 3 |
| Wrinkled yellow | 3 |
| Wrinkled green | 1 |
Thus, the classical phenotypic ratio is 9 : 3 : 3 : 1.
37. DNA is genetic material in both prokaryotes and eukaryotes, yet the packaging process is not the same. Explain.
In prokaryotes, DNA is generally a circular double-stranded molecule present in the nucleoid. It is not enclosed by a nuclear membrane. The DNA is compacted mainly through supercoiling and association with nucleoid-associated proteins.
In eukaryotes, DNA is linear and is present inside the nucleus. It is associated with positively charged histone proteins. DNA wraps around a histone octamer to form nucleosomes, giving the appearance of a beads-on-string structure. Further coiling and folding produce chromatin and ultimately highly condensed chromosomes.
Therefore, although DNA acts as genetic material in both types of cells, its organisation and packaging differ because of differences in cellular organisation and chromosome structure.
38. a) Differentiate innate immunity and acquired immunity.
b) Mention the cells involved in acquired immunity.
c) Refer to the below given diagram and answer the questions;
i) Name the molecules trapped in the lymph nodes responsible for the activation of lymphocytes that bind to the ‘A’ and ‘B’ site
ii) What does H2 L2, in an antibody represent?
| Innate immunity | Acquired immunity |
|---|---|
| Present from birth. | Develops after exposure to particular antigens. |
| Non-specific. | Antigen-specific. |
| Does not produce strong immunological memory. | Produces immunological memory. |
b) Cells involved: B-lymphocytes and T-lymphocytes.
c)(i) Molecules trapped in lymph nodes responsible for activation of lymphocytes: Antigens.
c)(ii) H2L2 in an antibody represents: Two heavy chains (H2) and two light chains (L2) of an antibody molecule.
39. a) Explain preparation of competent host for transformation with recombinant DNA.
b) Refer to the given diagram of pBR322 and answer the question that follows
Bacterial cells are treated with divalent cations such as calcium ions. The cells are kept on ice and are then subjected to a brief heat shock, commonly at about 42°C. This treatment increases the ability of the bacterial cells to take up recombinant DNA.
b)(i) Restriction enzymes used for insertional inactivation of antibiotic-resistance genes:
Examples include BamHI and SalI, depending on the restriction sites represented in the pBR322 map.
b)(ii) Number of cloning sites:
The pBR322 map contains several unique restriction sites; the exact number expected for this question depends on the labelled diagram supplied with the paper.
40. Genetically modified plants have been developed through core techniques of biotechnology. How are these plants useful to humans?
Genetically modified plants are useful in several ways:
- They can be made resistant to insect pests, reducing crop damage.
- They can be made resistant to certain plant diseases.
- They can tolerate environmental stresses such as drought and salinity.
- They can have improved nutritional quality.
- They can have improved shelf life and reduced post-harvest losses.
- They can provide products of commercial and pharmaceutical importance.
41. a) Write an equation to calculate population density at time t. b) Mention and define four basic processes responsible for population-density fluctuations.
A general expression is:
Nt+1 = Nt + [(B + I) − (D + E)]
where:
- Nt = population density at time t
- B = births
- I = immigration
- D = deaths
- E = emigration
- Birth: Addition of new individuals through reproduction.
- Death: Removal of individuals from the population through mortality.
- Immigration: Entry of individuals into a population from another area.
- Emigration: Movement of individuals out of a population.
VI. Answer any ONE
42. a) Complete the table comparing mature male and female gametophytes of angiosperms. b) Mention one advantage offered by seeds.
| Character | Mature Male Gametophyte | Mature Female Gametophyte |
|---|---|---|
| i) Number of cells present | 3 cells at the time of fertilisation in the usual 3-celled stage | 7 cells |
| ii) Number of gametes present | 2 male gametes | 1 egg cell |
| iii) Type of cell division involved in development | Mitosis | Mitosis |
| iv) Ploidy of the cells | Haploid (n) | Haploid (n) |
b) Advantage of seeds:
Seeds provide protection to the developing embryo and can remain dormant during unfavourable environmental conditions, helping angiosperms survive and disperse under changing conditions.
43. Mendelian disorders may be autosomal or sex-linked, dominant or recessive, homozygous or heterozygous. Pedigree symbols are used to analyze these disorders in human population. Mention the genotypes for the following pedigree symbols.
a) Autosomal dominant – ∎
b) Autosomal recessive- 〇
c) Sex – linked dominant – □
d) Sex – linked recessive – ∎ ⬮
| Type of inheritance | Representative genotypes |
|---|---|
| Autosomal dominant | AA or Aa |
| Autosomal recessive | aa |
| Sex-linked dominant | XAXA, XAXa or XAY |
| Sex-linked recessive | XaXa or XaY |
44. Justify the following statements.
a) “RNA polymerase cannot transcribe a gene by itself.”
RNA polymerase requires several additional factors for accurate initiation of transcription. In prokaryotes, the sigma factor helps RNA polymerase recognise the promoter. In eukaryotes, general transcription factors assist RNA polymerase in promoter recognition and initiation. Therefore, RNA polymerase cannot initiate transcription of a gene independently.
b) “Transcription and translation are separated by site and not coupled in eukaryotes.”
In eukaryotic cells, transcription occurs inside the nucleus, whereas translation occurs mainly in the cytoplasm on ribosomes. The primary RNA transcript is processed inside the nucleus before mature mRNA is transported to the cytoplasm. Therefore, transcription and translation are spatially separated and are not coupled.
c) Which RNA polymerase is involved in transcription of 5S rRNA?
Answer: RNA polymerase III.
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