Plus Two Biology (Bot + Zoo) | Practice Model Question Paper PDF with Answer key | SET 6

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PART A: BOTANY

I. Answer any 3 questions from 1 – 5. Each carries 1 score. (3 x 1 = 3)

1) A date palm seed discovered during archeological investigation retained viability even after 10000 years. The retention of viability is due to the state of inactivity of embryo called ……………….

✅ Seed Dormancy

2) Sequences of base pairs in DNA that reads the same on both the strands when the orientation of reading is kept the same are called ………………. sequences.

✅ Palindromic sequence

3) In a given habitat, the maximum number possible for a species is called ………………. of that species in that habitat.

✅ Carrying capacity.

4) Name a source of pest resistant gene.

✅ Bacillus thuringiensis

5) Observe the following food chain:

What is this type of food chain called?

✅ Grazing food chain (GFC)

II. Answer any 9 questions from 6 – 16. Each carries 2 scores. (9 x 2 = 18)

6) Using genetically modified crops, farmers can minimize use of insecticides and pesticides during cultivation.

a. Give name of one such genetically modified pest resistant crop.

b. Which gene is used for its production?

c. Write about its mode of action.

✅ Answer

(a) Bt cotton.

(b) Cry genes from Bacillus thuringiensis.

(c) When an insect ingests the Bt toxin, it becomes active due to alkaline pH of the gut which solubilise the crystals. Toxin binds to surface of mid-gut epithelial cells creating pores. It causes cell swelling and lysis and death of the insect.

7) In large number of plants, pollination is carried out by insects. List four characters of flowers that help insect pollination.

✅ Answer

Characters of insect pollinated flower:

a. Large, colourful, fragrant and rich in nectar. Nectar & pollen grains are the floral rewards for pollination.

b. Small flowers form inflorescence to make them visible.

c. The flowers pollinated by flies and beetles secrete foul odours to attract these animals.

d. The pollen grains are generally sticky.

8) EcoRI is a restriction endonuclease. What do E, Co, R, I represent?

✅ Answer

E = Escherichia (Genus name of bacteria)

Co = Coli (Species name of bacteria)

R = Strain

I = First extracted enzyme (Order of extraction).

9) The following graph shows two types of pollution growth curves.

a. Name the growth curves.

b. What does K stand for?

✅ Answer

(a) Exponential (Geometric) growth curve and Logistic (Sigmoid) growth curve.

(b) Carrying capacity.

10) Given number of individuals in a grass land ecosystem.

Grasshopper – 1500

Grass – 5,842,000

Wolf – 28

Birds – 215

a. Draw a pyramid of numbers showing various trophic levels.

b. Explain trophic level.

✅ Answer

(a)

(b) A specific place of organisms in the food chain is known as their trophic level.

11) Nita found that her grandma used to inject human insulin that is genetically engineered. She wants to know how such insulin can be produced. Give her an idea about structure of insulin and production of genetically engineered insulin.

✅ Answer

Insulin consists of two short polypeptide chains such as chain A and chain B. They are linked by disulphide bridges.

Two DNA sequences corresponding to A and B, chains of human insulin are prepared and inserted into E. coli plasmids to produce insulin chains. Chains A and B are extracted and combined by creating disulfide bonds to form human insulin.

12) In rice, the chromosome number present in the meiocyte is 24. Give the number of chromosomes present in the following. Justify your answer.

a. rice pollen        b. rice endosperm

✅ Answer

a. Rice Pollen: The rice pollen is a haploid cell, so it contains half the number of chromosomes as the meiocyte. Therefore, it has 12 chromosomes.

b. Rice Endosperm: The rice endosperm is a triploid cell, so it contains one and a half times the number of chromosomes as the meiocyte. Therefore, it has 36 chromosomes.

13) How can we make a host cell competent to receive a foreign gene or DNA?

✅ Answer

Treating the cells with specific concentration of a divalent cation such as calcium.

Incubating the cells with recombinant DNA on ice. Place them briefly at 42°C (heat shock). Again, place them back on ice.

14) Rate of biomass production is called productivity and it can be divided into GPP and NPP.

a. Define GPP and NPP.

b. How can we relate GPP and NPP?

✅ Answer

(a) Gross primary productivity (GPP): It is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is used by plants in respiration.

Net primary productivity (NPP): It is the available biomass for the consumption to heterotrophs (herbivores & decomposers).

(b) NPP is the Gross primary productivity minus respiration losses (R).

NPP = GPP – R

15) Humification leads to accumulation of a dark-coloured amorphous substance. Identity the substance and its peculiarities.

✅ Answer

The substance is Humus.

Peculiarities:

It is highly resistant to microbial action and decomposition.

Serves as a reservoir of nutrients.

Release inorganic nutrients.

16) Differentiate natality and mortality. Write the alphabets used to indicate natality and mortality.

✅ Answer

Natality: It is the number of births in a population during a given period.

Mortality: It is the number of deaths in a population during a given period.

Natality is indicated by the letter B.

Mortality is indicated by the letter D.

III. Answer any 3 questions from 17 – 20. Each carries 3 scores. (3 x 3 = 9)

17) Students involved in nature club activity found some inter-specific interactions between organisms in a garden area. They made a table of interaction giving ‘+’ for beneficial interaction, ‘-‘ for detrimental and ‘0’ for neutral interaction.

a. Give name of interaction in each case.

b. Explain how parasitism differs from predation.

c. Give the significance of species interaction.

✅ Answer

(a) i. Mutualism

ii. Competition

iii. Commensalism

iv. Amensalism

(b) Predation: A predator kills and consumes its prey.

Parasitism: A parasite lives off a host, causing harm but not immediate death.

(c) It is essential to form a biological community, for energy flow and nutrient cycling.

18) (a) Match the Column A with Column B.

(b) What is the principle of ELISA?

✅ Answer

(a)

(b) It is based on the antigen – antibody interaction

19) Identify the following figure and label A to E.

✅ Answer

It is a diagrammatic representation of the mature embryo sac.

A= Antipodals

B= Polar nuclei

C= Egg

D= Synergids

E= Filiform apparatus

20) While studying nucleotide sequence, Raj found that following sequence which can be recognized by some enzymes:

5’ – GAATTC – 3’

3’ – CTTAAG – 5’

a. Give salient features of this sequence.

b. Write name of enzymes which recognize such sequences.

c. Elaborate importance of this enzyme in Genetic engineering.

✅ Answer

(a) Palindromic sequence

(b) EcoRI Restriction endonuclease

(c) This enzyme cuts at specific nucleotide sequence to get sticky ends. The same restriction enzyme is used to cut both foreign DNA and cloning vector. This helps to create recombinant DNA.

PART B: ZOOLOGY

I. Answer any 3 questions from 1 – 5. Each carries 1 score. (3 x 1 = 3)

1) The implanted stage during embryonic development is

a. Gastrula        b. Morula

c. Zygote        d. Blastocyst

✅ d. Blastocyst

2) Select the initiation codon from the triplet codons given below:

a. AAA        b. AUG

c. GUA        d. UGA

✅ b. AUG

3) Pick out the odd one giving reason.

a. HIV        b. Haemophilia

c. Genital warts        d. Hepatitis B

✅ Haemophilia. It is a genetic disorder. Others are STIs.

4) Scientist who proposed Rivet Popper Hypothesis is ………………….

✅ Paul Ehrlich.

5) Expand the following terms:

a. MALT        b. NACO

✅ a. Mucosa Associated Lymphoid Tissues.

b. National AIDS Control Organisation.

II. Answer any 9 questions from 6 – 16. Each carries 2 scores. (9 x 2 = 18)

6) When the urine sample of a lady was tested, presence of HCG was found.

a) Expand HCG.

b) What does the presence of HCG indicate?

c) Which is the source of HCG?

✅ Answer

a) Human Chorionic Gonadotropin

b) She is pregnant.

c) Placenta.

7) CuT is a contraceptive device.

a. Suggest the contraceptive action of CuT.

b. Name the hormone releasing IUDs.

✅ Answer

a) Cu ions suppress motility and fertilising capacity of sperms.

b) Progestasert, LNG-20.

8) As part of a dispute of parentage, the Court put an order to conduct a test for proving the father of the child.

a. Name the test used.

b. Procedure of the test is given below. Complete it.

i. Isolation of DNA

ii. DNA is cut using restriction endonuclease

iii. …………………

iv. …………………

v. Hybridisation using VNTR probe

vi. ………………….

✅ Answer

a) DNA fingerprinting.

b) iii. Separation of DNA fragments by gel electrophoresis.

iv. Transfer of separated DNA fragments into nitrocellulose or nylon membrane.

vi. Detection of DNA using autoradiography.

9) Observe the figure given below:

a. Identify the figure.

b. How many histone molecules are present in the histone core?

c. Distinguish Euchromatin and Heterochromatin.

✅ Answer

a) Nucleosome.

b) 8

c) Euchromatin: Loosely packed, light stained and transcriptionally active chromatin.

Heterochromatin: Densely packed, dark stained and transcriptionally inactive chromatin.

10) Distinguish Darwinian variation and Mutational variation. (Any 4 differences).

✅ Answer

Darwinian variations: These are minor, slow and directional. It results in gradual evolution.

Mutational variations: These are sudden, random and directional. Speciation is by saltation.

11) State whether the following statements are true or false. If false, rewrite them by changing the word underlined.

a. Double helical model of DNA was proposed by Jacob and Monod.

b. Sugar present in RNA is Ribose.

c. Introns are the coding sequences of a eukaryotic gene.

d. DNA replication occurs by semi-conservative method.

✅ Answer

a) False. Double helical model of DNA was proposed by Watson and Crick.

b) True.

c) False. Exons are the coding sequences of a eukaryotic gene.

d) True.

12) During a monohybrid cross involving a tall pea plant, the offspring population were tall and dwarf in equal ratios. Work out a cross to show it is possible.

✅ Answer

Hence monohybrid test cross ratio= 1:1

13) Stanley Miller set up an experimental apparatus as shown below.

a. Which theory was proven by this experiment?

b. State that theory and name the scientists who proposed it.

✅ Answer

a) Theory of Chemical Evolution.

b) It states that the first form of life was originated from non-living inorganic & organic molecules.

This theory was proposed by Oparin and Haldane.

14) Read the principle and answer the questions:

“Allele frequencies in a population are stable and is constant from generation to generation.”

a. Name the principle mentioned here.

b. Mention any three factors that affect the equilibrium.

✅ Answer

a) Hardy-Weinberg Principle.

b) Gene migration, genetic drift, Mutation, Natural selection etc.

15) In an E. coli culture, lactose is used as food instead of glucose.

a. How do the bacteria respond to the above situation at genetic level?

b. If lactose is removed from the medium, what will happen?

✅ Answer

a) In E. coli, lac operon will be switched on. Lactose (inducer) binds with repressor protein. So repressor protein cannot bind to operator region. It induces the RNA polymerase to bind with promoter. Then transcription starts.

b) If lactose is removed, lac operon remains switched off. The regulator gene synthesizes mRNA to produce repressor protein. This protein binds to the operator region and blocks RNA polymerase movement. So the structural genes are not expressed.

16) (a) Expand STDs.

(b) A person has earlier symptoms of STDs. What will happen if he/she does not consult a doctor? (Mention any two consequences).

✅ Answer

a) Sexually Transmitted Diseases.

b) Pelvic Inflammatory Diseases (PID), Infertility, Ectopic Pregnancy, abortions, still births, cancer of the reproductive tract etc.

III. Answer any 3 questions from 17 – 20. Each carries 3 scores. (3 x 3 = 9)

17) Blood of a man is tested positive for cannabinoid.

a. What are these?

b. Mention any 4 ill-effects of alcoholism.

✅ Answer

a) Cannabinoids are a group of drugs obtained from Cannabis sativa. E.g., marijuana, hashish, ganja.

b) • Reckless behaviour, vandalism and violence.

• Coma and death.

• Damage of nervous system and liver cirrhosis.

• Mental and social distress to family and friends.

18) The diagrammatic representation of a process in bacteria is given below:

a. Identify the process.

b. Name the enzyme involved in this process.

c. Explain the three major steps in this process.

✅ Answer

a) Transcription.

b) RNA polymerase.

c) Initiation, Elongation, Termination.

• Initiation: Here, RNA polymerase binds at the promoter site of DNA. An initiation factor (σ factor) present in RNA polymerase initiates the RNA synthesis.

• Elongation: RNA chain is synthesized in 5’-3’ direction. Ribonucleoside triphosphates are added.

• Termination: A termination factor (ρ factor) binds to the RNA polymerase and terminates the transcription.

19) Mention and explain three arguments of the reasons for biodiversity conservation.

✅ Answer

Three arguments of the reasons for biodiversity conservation:

a. Narrowly utilitarian arguments: Human derive economic benefits from nature.

b. Broadly utilitarian arguments: Biodiversity has ecosystem services. E.g. production of O2, Pollination, Aesthetic pleasures.

c. Ethical arguments: Every species has an intrinsic value. We have to care them.

20) (a) Mention any two properties of an ideal contraceptive.

(b) Categorise the given birth control methods into two groups under proper headings.

Cervical caps, vasectomy, diaphragms, condoms, tubectomy

✅ Answer

a) User-friendly, easily available, effective and reversible, no or least side-effects etc.

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