ISC Class 12 Biology Question Paper Solution 2019

The ISC Class 12 Biology – Paper I (Theory) was conducted on 14th March 2019. The exam started at 2 PM, and students were allotted 3 hours of time duration to finish the paper. Here, we have provided the ISC Class 12 Biology Question Paper Solution 2019. Solving the ISC Class 12 Biology Previous Year Question Papers will give the students an idea on types of questions asked in the exam and their difficulty level. They can download the ISC Class 12 Biology Question Paper pdf as well Solution pdf 2019 from the link below.

They can have a look at the ISC Class 12 Biology Question Paper Solution 2019 below.

Difficult Topics of ISC Class 12 Biology Paper 2019

Topics which students found difficult while writing the Biology 2019 exam are:

• Detritus
• Pedigree analysis
• Nucleosome
• Standing crops
• GEAC
• EFB full form
• Contribution of Scientists R. Mishra & Sanger
• Secondary succession
• Significance of SCP
• Golden rice
• Nomenclature of RE

Confusing ISC Class 12 Biology Questions 2019

Topics in which students got confused while answering the Biology questions during the exam.

• Biology concepts on which students got confused during the exam are listed below.
• Meiocytes and gametes.
• Back cross and test cross.
• Primary and secondary succession.
• Reproductive fitness and reproductive health.
• Primary and secondary lymphoid organs.
• Electrophoresis and electroporation.
• Lamarckism and Darwinism.
• Ovary and ovum/ovule.
• Stenothermal and cold-blooded organisms.

ISC Class 12 Biology Question Paper Solution 2019

Question 1:

(a) Answer the following questions briefly and to the point:

(i) Name the antibody which is most effective in allergies.

(ii) What is the function of GEAC ?

(iii) What is a clone?

(iv) What do detritus food chains begin with?

(v) Give the full form of EFB.

(vi) How many chromosomes are present in meiocytes of a fruit fly?

(vii) Name the common ancestor of apes and man.

(viii) Give the scientific term used for the preservation of germplasm at a very low temperature.

(b) Each of the following sub-parts, (i) to (iv) has four choices. Choose the best option in each case:

(i) Eyelids in human foetus separate in:

(1) 14 weeks

(2) 16 weeks

(3) 24 weeks

(4) 40 weeks

(ii) Study the given monohybrid cross:

(iii) Montreal Protocol aims at:

(1) Reduction of ozone depleting substances

(2) Biodiversity conservation

(3) Control of water pollution

(4) Control of CO2 emission.

(iv) In the given pedigree chart, the trait shown is:

(1) Autosomal dominant

(2) Autosomal recessive

(3) X-linked

(4) Y-linked

(c) Give one significant contribution of each of the following scientists:

(i) Wallace

(ii) R. Mishra

(iii) G. Gamow

(iv) Sanger

(d) Define the following:

(i) Carrying capacity

(ii) Homologous chromosomes

(e) Give a reason for each of the following:

(i) Bagging is essential in artificial hybridisation.

(ii) Climax stage is achieved quickly in secondary succession as compared to primary succession.

Answer: (a) (i) IgE

(ii) Monitors the safety standards of genetically modified organisms (products) released for public service.

Validate/regulates GM research and safety of introducing GM (Transgenic) organisms.

(iii) Morphologically and genetically similar individuals / Individuals produced by asexual reproduction /progeny exactly similar to parents.

(iv) Dead organic matter/dead plant or animal matter.

(v) European Federation of Biotechnology.

(vi) 4 pairs / 8.

(vii) Dryopithecus / Ramapithecus.

(viii) Cryopreservation.

(b) (i) (3) or 24 weeks

(ii) (2) or Tt × tt

(iii) (1) or Reduction of ozone depleting substances

(iv) (2) or Autosomal recessive

(c) (i) Wallace: Divided the earth into biogeographical regions / natural selection

(ii) R. Mishra: Father of Indian ecology

(iii) G. Gamow: Triplet nature of the codon

(iv) Sanger: DNA/ protein sequencing

(d) (i) The maximum number of individuals / people / animals/ organisms / crops which a given area of the environment can support without environmental degradation.

(ii) A pair of corresponding chromosomes of the same shape, size and sequence of genes, one from each parent.

(e) (i) To prevent contamination from foreign / self / unwanted pollen grains.

(ii) The rate of succession is much faster in secondary succession as the nutrient/

substratum (soil) is already present as compared to primary succession where the process starts from a bare area (rock) / OR Soil is rich in nutrients.

Question 2: Enumerate any four essential features of good and effective poultry farm management practices.

Answer: Essential features of good and effective poultry farm management practices:

– Selection of high yielding / disease resistant breeds/ proper (indigenous/ exotic) species of fowl.

– Shed must be clean, roofed with a sloping floor

– Safe enclosure / protection from predators / enemies

– Nutritious food and clean water must be provided

– Proper hygiene must be maintained

– Animals must be maintained disease free by vaccination

– Regular visit by the doctor / veterinarian

– Culling of diseased animals

– Regular inspection and record keeping

– Proper spacing to an individual fowl

– Proper lighting

– Proper ventilation

– Segregation according to age

Question 3: What is a single cell protein? How is it significant for human welfare?

Answer: Single cell protein: Proteins obtained from microbes/ algae, fungi, bacteria, yeast. Any microbial biomass / multicellular bacteria, yeast, fungi, algae which can be used as food.

Significance:

– Cost effective / cheap

– Rich in protein

– Low on fat

– Reduced pressure on agriculture

– Use of organic wastes and industrial effluents in raising SCP will reduce environmental pollution

– Absence of pathogenicity & toxicity

– Easy to digest

Question 4: (a) List four reasons for drug addiction.
OR
(b) List four effects of alcoholism on human health.

Answer: (a) Reasons for drug addiction:

– Peer pressure / Friends

– Curiosity

– Need of adventure / experiments / excitement / To remove boredom

– Avoid stress / Overcome hardships/relaxation

– Depression and frustration / low self-esteem / inferiority complex/emotional turbulence/sexual dysfunction/impotency.

– Avoid unsupportive family structure

– To enhance the performance in sports

– To relieve pain

– For weight loss

– Genetic history/ family history

OR

(b) Effects of alcoholism on human health:

– Lowering of blood sugar

– Damage to internal organs

– Loss of memory

– Socio-economic impact / lack of interest / low self-esteem

– Loss of reflexes /lack of muscles coordination.

– Sexual dysfunction / impotency

– Dependence / addiction

– Malnutrition

– Hallucination

– Cancer

– Hyperacidity

– Genetic defects

– Potentiates the effect of drugs

– Loss of sleep (amnesia)

– Lowers immunity

Question 5: State four features of flowers pollinated by insects.

Answer: Features of flowers pollinated by insects:

– Flowers are large in size

– Brightly coloured petals

– Flowers are usually scented / sweet smelling / fragrant

– Flowers contain nectar / Nectar guidelines on petals

– Sticky stigma

– Less wastage of pollen

– Stigmas are usually small, compact / do not protrude out of the flower / within the flower

– Flowers found in clusters

– Pollen grains are sticky and spiny

Question 6: What is reproductive fitness? Explain it with the help of an example.

Answer: Reproductive fitness is the individual’s reproductive success (equal to average contribution to gene pool).

OR

It is the relative production of fertile offspring by a genotype.

OR

Ability of an individual to add more number of progeny in the population.

OR

Individual’s contribution to next generation by reproduction.

OR

Individual’s contribution to phenotype and genotype of next generation.

OR

Ability to pass the genes to subsequent generations.

Examples: Ascaris lays 2 crore eggs, sea urchin / crabs / cod fish – millions of eggs, African driver ant – 3 to 4 million eggs OR any example where reproductive rate is high

Question 7: Give one significant difference between primary lymphoid organs and secondary lymphoid organs. Give one example of each.

Answer: Difference between primary and secondary lymphoid organs:

Question 8: (a) Explain the term biofortification. How is this technique useful for the production of golden rice?
OR
(b) Write a short note on Electrophoresis.

Answer: (a) Biofortification: Enrichment of crops with nutrients. OR

Golden rice:

– The grains are yellow as it contains β -carotene which is precursor of Vitamin A.

– Produced to control night blindness / overcome vitamin A deficiency.

OR

(b) Electrophoresis: It is a process of separation of biomolecules by placing them in mild

electric field.

1. Fragments of DNA are separated by agarose gel electrophoresis.

2. DNA fragments being negatively charged move towards positive electrode/anode.

3. Fragments separate according to size / charge.

4. Separated fragments are stained with ethidium bromide and exposed to UV rays.

5. They form orange coloured bands.

6. The bands are extracted by elution / blotting.

Question 9: Explain the evolution of long neck of giraffe according to Charles Darwin.

Answer: Evolution of long neck of giraffe according to Charles Darwin:

1. Two varieties initially / short necked and long necked

2. Ground vegetation disappeared

3. Short necked could not feed / perished

4. Long neck could feed easily / survived

5. Adaptation/ Natural selection

6. Characters passed to the offspring/inheritance

Question 10: (a) Draw a labelled diagram of the T.S. of a mature anther.
OR
(b) Draw a labelled diagram of the internal structure of the human ovary.

Answer: (a) T.S. of a mature anther (any six to be labelled):

OR

(b) Internal structure of human ovary:

Question 11: Describe the structure of a nucleosome with the help of a well-labelled diagram.

Answer: Structure of a nucleosome:

1. Core of 8 histones (octamer)

2. Core formed by two units each of H2A, H2B, H3 AND H4 molecules

3. DNA winds around the core (1¾ turn involving approximately 146 base pairs)

4. Two successive nucleosomes are joined together by Linker DNA (approximately 80 BP)

5. H1 histone holds the entire complex by connecting the linker DNA at the points of entry and exit

6. Repeating units in chromatin fibre

7. As beads on a string.

Question 12:

(a) Explain the Rivet Popper hypothesis.

OR

(b) Define:

(1) Standing crop

(2) Stenothermal organisms

(3) Niche

Answer: Rivet popper hypothesis:

– Paul Ehlrich proposed the rivet popper hypothesis

– Explains the effect of decrease in biodiversity / species richness on the ecosystem.

– An aeroplane has thousands of rivets that correspond to the ecosystem.

– Rivet corresponds to species

– Removal of rivets by passengers may not affect the safety of the flight initially.

– Removal of the rivet of a critical part like the wing (species performing major functions) will pose serious threat to the safety of the flight / ecosystem.

– In an ecosystem, the role of each species is important.

OR

(b) (1) Standing crop: amount of organic matter present at each trophic level at a given time or

Biomass per unit area at a given time.

(2) Stenothermal organisms: organisms which can tolerate a narrow range of temperature.

(3) Niche: Functional role of an organism in its ecosystem/habitat.

Question 13: Give the biological names of the following:

(i) The mould from which penicillin is obtained.

(ii) Baker’s yeast.

(iii) The microbe used to control insect larvae growing on cotton.

(iv) The microbe used to produce Swiss cheese.

(v) The fungus that is being developed as a bio-control agent.

(vi) A symbiotic nitrogen fixing bacterium found in root nodules.

Answer: (i) Penicillium notatum

(ii) Saccharomyces cerevisiae

(iii) Bacillus thuringiensis

(iv) Propionibacterium sharmanii

(v) Trichoderma polysporum / Aspergillus niger

(vi) Rhizobium leguminosarum

Question 14: Explain the different types of endosperms in angiosperms.

Answer: Different types of endosperms in angiosperms:

1. Free nuclear OR Nuclear type – Endosperm nucleus divides to give rise to a number of free nuclei which remain in the periphery. Finally, cell wall formation occurs. Examples: Coconut, maize, wheat, rice, sunflower/ common in polypetalous dicots.

2. Cellular type – Division of primary endosperm nucleus is immediately followed by wallformation so that the endosperm is cellular from beginning. Example: Impatiens, Datura, Petunia/ common in gamopetalous dicots.

3. Helobial Type – Endosperm development is intermediate between the free nuclear and cellular type. A partition wall develops between the two nuclei resulting in the first division of the endosperm. Examples:Asphodelus, Muscari (grape hyacinth), Saxifraga, Echium (borage).

Question 15: A homozygous pea plant with round seed coat and yellow cotyledons is crossed with another homozygous pea plant having wrinkled seed coat and green cotyledons.

(i) Give the types of gametes produced by plants of F1-generation.

(ii) Give the dihybrid phenotypic ratio with the corresponding phenotypes.

(iii) State the Mendel’s principle involved in this cross.

Answer: (i) RY, Ry, rY, ry

(ii) 9 : Round yellow

3: Round green

3: Wrinkled yellow

1: Wrinkled green

(iii) Law of Independent Assortment: Alleles of different characters assort independently of each other during gamete formation.

Question 16:

(a) Describe the physico-chemical events that take place during fertilization in humans.

OR

(b) (i) Define and give the role of amniocentesis.

(ii) Name the causative agent and give any one symptom of Gonorrhoea.

(iii) What is the significance of dispersal of seeds? Give any two points.

(iv) What are seasonal breeders? Give an example.

(v) How is the chromosome number maintained in sexually reproducing organisms?

Answer: (a) 1. Insemination.

2. Coagulation of semen.

3. Transfer/Movement of coagulated semen into uterus by peristalsis.

4. Liquefaction of coagulated semen.

5. Capacitation of the sperm.

6. Acrosome reaction: Hyaluronidase digests the cement holding cells of corona radiata so that they are dispersed.

7. Acrosin digests zona pellucida. Calcium ions are needed for this.

8.The egg cytoplasm extends around the head of sperm to form a fertilization cone that engulfs the sperm so that the head and mid piece enter the ovum.

9. Cortical reaction: Formation of fertilization membrane around the egg which prevents polyspermy / allows single sperm to enter.

10. Completion of 2ndmeiotic division of the ovum causing release of second polar body.

11. Amphimixis or Karyogamy: The sperm nucleus travels through the ovum to its nucleusThe intermingling of paternal and maternal chromosomes is called amphimixis. The Fertilized egg is now called the zygote.

(b) (i) Definition: Technique of withdrawing amniotic fluid from the amniotic sac

Role: Prenatal diagnosis of genetic defects.

(ii) Causative agent: Neisseria gonorrhoeae.

Symptom of Gonorrhoea:

– Itching in genital region

– Fluid discharge

– Pain and swelling

– Sterility

(iii) Significance of dispersal of seeds:

– Avoids intraspecific competition

– Avoids overcrowding

– Helps in rapid evolution

– To provide suitable conditions for germination

(iv) Seasonal breeders become reproductively active only during favourable seasons. Examples: Tiger, cat, dog, sheep, goat, horse, cattle, pig.

(v) During gametogenesis the chromosome number is reduced to half by meiosis.

During fertilization, the diploid number is restored in the zygote.

Question 17:

(a) (i) What are restriction endonucleases? Give the rules of their nomenclature.

(ii) Explain the mechanism of action of restriction endonucleases that makes them suitable for genetic engineering.

OR

(b) (i) Explain what are the desirable characteristics of an ideal cloning vector used in rDNA technology.

(ii) Describe two vectorless methods of gene transfer used in rDNA technology.

Answer:

(a) (i) Restriction endonucleases are enzymes that target the interior of the DNA molecule and cleave the molecule at palindromic sequence. OR

The enzymes which cut DNA at specific sequences. OR

The rules of their nomenclature:

1. First alphabet = the genus from which these enzymes are isolated

2. Next two alphabets = the species from which these enzymes are isolated

3. Fourth alphabet = name of the strain from which they are isolated

4. The roman number = the order in which the enzyme was isolated. Eg: Eco RI.

(ii) Mechanism of Action:

1.Each RE recognises a specific palindromic base sequence in the DNA.

2.Cuts sugar-phosphate backbone of both strands of the double helix at specific pointsin the palindromic sequence.

3.The foreign DNA and vector DNA are cut by same RE.

4.It produces a complementary sticky end / staggered cut in both the DNA molecules.

5.So that both can be joined by enzyme ligase.

OR

(b) (i)

– Origin of replication (ori) This is the sequence from which replication starts and theforeign gene linked to it will clone itself and it also controls the copy number of the linked DNA

– Cloning sites: The ligation of alien DNA is carried out at this recognition site.

– Selectable marker: These will help in identifying and eliminating non-transformants and selectively permitting the growth of transformants.

– Small in size/ less than 10 kB

(ii) Describe two vector-less method of gene transfer used in rDNA technology

– Gene gun / Biolistic: Gold or tungsten beads coated with DNA are bombarded with high velocity on the host tissue. The foreign gene gets incorporated in host DNA.

– Microinjection: Using a micropipette/ microneedle DNA is injected into the nucleus.

– Transformation /Transfection: Bacteria are made competent to take up foreign genes by placing them in cold calcium chloride /by heat shock.

– Electroporation: This is the introduction of r DNA into bacterial cells by exposing them toa high electric pulse.

– Liposome mediated transfer – lipid droplets

Question 18: (a) Give a graphic representation of carbon cycle in nature.
OR
(b) Give a graphic representation of phosphorus cycle in nature.

Answer: (a) Give a graphic representation of carbon cycle in nature.

OR

(b) Give a graphic representation of phosphorus cycle in nature.

The ISC Class 12 Biology Question Paper Solution 2019 must have helped students with their exam preparation. Apart from the 2019 paper solution, students can also find the answers to other papers of ISC Class 12 Previous Years Questions by clicking here. Happy Learning and stay tuned to BYJU’S for the latest update on ICSE/CBSE/State Boards/Competitive exams. Also, don’t forget to download the BYJU’S App.