CBSE Class 12 Biology 2024 question paper (57/4)

Maximum marks 70 · Time 3 hours · 3 sets

Try each question first, then open its model answer. Where the paper offers a choice, both questions are shown with OR between them.

Section A

1 mark each

Q.11 mark $In a fertilized ovule of an angiosperm, the cells in which n, 2n and 3n conditions respectively occur are :$
Tap an option to check your answer.
Q.21 mark $Select the option that gives the correct identification of ovum, morula and blastocyst in a human female reproduction system as shown in the following diagram :$
Tap an option to check your answer.
Q.31 mark $Study the table given below : Contraceptive / Contraceptive Method Mode of Action A. The pill I. Prevent sperm reaching cervix B. Condom II. Prevent implantation C. Vasectomy III. Inhibits ovulation D. Copper-T IV. Semen contains no sperm Select the option where contraceptive/contraceptive method are correctly matched with their mode of action.$
Tap an option to check your answer.
Q.41 mark $Identify the category of genetic disorder depicted in the pedigree chart given below :$
Tap an option to check your answer.
Q.51 mark $Which was the last of the 24 human chromosome to be completely sequenced ?$
Tap an option to check your answer.
Q.61 mark $Study the following diagram of Transverse Section of a young anther of an angiosperm : Select the option where parts 'A', 'B' and 'C' are correctly identified.$
Tap an option to check your answer.
Q.71 mark $Turner's syndrome in humans occurs due to$
Tap an option to check your answer.
Q.81 mark $Which of the options has correct identification of 'P', 'Q' and 'R' in the illustration of 'Central Dogma' given below ?$
Tap an option to check your answer.
Q.91 mark $Who proposed the mutation theory in favour of organic evolution ?$
Tap an option to check your answer.
Q.101 mark $Study the following list of bioactive substances and their action : Bioactive Substance Role A. Statin I. Removal of oil stains B. Cyclosporin A II. Removal of clots from blood vessels C. Streptokinase III. Lowering of blood cholesterol D. Lipase IV. Immuno-suppressive agent Select the option in which the bioactive substances are correctly matched with their action.$
Tap an option to check your answer.
Q.111 mark $The 'molecular scissors' fall in the category of :$
Tap an option to check your answer.
Q.121 mark $ELISA technique is based on the principle of$
Tap an option to check your answer.
Question Nos. 13 to 16 consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :
Q.131 mark $Assertion (A) : A given fig species can be pollinated only by its partner' wasp. Reason (R) : The wasp pollinates the fig inflorescence while searching for suitable egg laying sites.$
Tap an option to check your answer.
Q.141 mark $Assertion (A) : Plasmids are autonomously replicating circular extra-chromosomal DNA. Reason (R) : Plasmids are usually present in Eukaryotic cells.$
Tap an option to check your answer.
Q.151 mark $Assertion (A) : Patents are granted by government to an inventor. Reason (R) : Patents prevents others from commercial use of an invention.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Some aquatic ecosystems have inverted biomass pyramids. Reason (R) : More energy is required by the organisms occupying higher trophic levels.$
Tap an option to check your answer.

Contraceptive / Contraceptive Method	Mode of Action
A. The pill	I. Prevent sperm reaching cervix
B. Condom	II. Prevent implantation
C. Vasectomy	III. Inhibits ovulation
D. Copper-T	IV. Semen contains no sperm

Bioactive Substance	Role
A. Statin	I. Removal of oil stains
B. Cyclosporin A	II. Removal of clots from blood vessels
C. Streptokinase	III. Lowering of blood cholesterol
D. Lipase	IV. Immuno-suppressive agent

Section B

2 marks each

Q.172 marks $Study the graph given below that represents the changes in the thickening of the uterine wall in women 'X' and women 'Y' over a period of one month : What does the graph with respect to woman 'X' and woman 'Y' indicate ? Give suitable reason.$
Q.182 marks $(a) Intensely lactating mothers generally do not conceive. Why ? (b) Our government has intentionally imposed strict conditions for MTP. Why ?$
Q.192 marks $(a) Name the source from which insulin was extracted in earlier times. Why is this insulin no more in use by the diabetic patients ? (b) Why does the insulin synthesised in the human body undergo processing whereas the insulin produced by Eli Lilly company does not need to undergo any processing ? Explain.$
Q.20 (a)2 marks $Differentiate between grazing food chain and detritus food chain.$
OR
Q.20 (b)2 marks $Explain Brood parasitism with the help of a suitable example.$
Q.212 marks $(a) Biodiversity hotspots cover less than 2% of Earth's land area. Strict protection of these areas can reduce the rate of ongoing extinctions. Explain. (b) Name any two hotspots in India.$

Section C

3 marks each

Q.223 marks $Draw a well labelled diagram of sectional view of male gametophyte/microspore of an angiosperm and write the functions of any two parts labelled. (Any four labels).$
Q.233 marks $(a) A man with blood group 'A' marries a woman with blood group 'AB'. The first child born to them has blood group 'B'. Work out a cross to find the genotype of the father. Give the possible blood groups and their genotypes of the children that could be born to this couple. (Use a Punnet square). (b) State the basis of 'ABO' blood grouping in humans.$
Q.243 marks $(a) Whose skulls 'A', 'B', and 'C' are shown below ? Which of the two are more similar to each other ? (b) Name the (i) ape like (ii) man like primates that existed 1.5 million years ago.$
Q.25 (a)3 marks $(i) Name the group of drugs whose skeletal molecule is shown below : (ii) How are such drugs consumed ? (iii) Name the human body organ affected by the consumption of these drugs.$
OR
Q.25 (b)3 marks $Draw a schematic diagram of an antibody molecule and label any 4 parts. Mention their chemical nature. Name the cells which produce them.$
Q.263 marks $Explain the role of the following during the sewage treatment : (a) flocs (b) anaerobic sludge digester$
Q.273 marks $Study the steps shown below, that are carried during a specific technique : (a) Identify the steps 'A' and 'D' in the diagram. (b) What does 'B' represent ? (c) Write what is 'C' ? Name its source organism. (d) Mention the use of this technique in molecular diagnostics.$
Q.283 marks $Explain the role of transgenic animals in : (a) Production of Biological products (b) Studying diseases (c) Chemical safety testing$

Section D

Populations evolve to maximise their reproductive fitness in the habitat in which they live. Ecologists suggest, the life history of organisms have evolved in relations to the constraints imposed by the biotic and abiotic components of the habitat in which they live. This gets reflected in the population growth pattern of all organisms including humans. Study the population growth curves shown in the given graph and answer the questions that follow :
Q.29 (a)1 mark $Identify the growth curves 'A' and 'B'.$
Q.29 (b)1 mark $Mention what does the dotted line in the graph indicate and state its importance also.$
OR
Q.29 (b) OR1 mark $Growth curve 'B' shows a different pattern from that of growth curve 'A'. Justify giving one reason.$
Q.29 (c)2 marks $(i) Which one of the two curves is more "realistic" and why ? (ii) Which one of the two curves is relevant in present days with respect to human population in our country and why ?$
Generally, in eukaryotic cells the average length of a transcription unit along a DNA molecule is about 8,000 nucleotides, so the RNA product of the transcription is also that long. But it only takes about 1200 nucleotides from the above RNA product to translate average sized polypeptide of 400 Amino acids.
Q.30 (a)1 mark $Name this RNA product transcribed from the DNA that subsequently translates into a polypeptide of 400 amino acids. Mention the enzyme responsible for transcribing this type of RNA from the DNA.$
Q.30 (b)2 marks $Name and explain the process the RNA molecule transcribed from 8000 nucleotide long DNA undergoes to be able to translate a polypeptide of 400 amino acids.$
Q.30 (c)1 mark $Write the number of RNA polymerases involved in the transcription of DNA in a prokaryote and eukaryotes.$
OR
Q.30 (c) OR1 mark $Mention the difference in the site of transcription in a prokaryote and eukaryote cell.$

Section E

5 marks each

Q.31 (a)5 marks $The given diagram shows the sectional view of a seminiferous tubule of Human testis : (i) Name and describe the process depicted in the diagram which results in the development of spermatozoa. (ii) Identify the cell where you are seeing a cluster of spermatozoa attached in the diagram. Write the function of the cell.$
OR
Q.31 (b)5 marks $Observe the picture of Commelina plant bearing two types of flowers given above. (i) Identify the two types of flowers labelled 'A' and 'B' in the picture. (ii) Compare the two types of flowers with reference to : (1) Characteristic feature (2) modes of pollination (iii) List any two 'out breeding devices' in flowering plants. Explain why do plants develop such devices.$
Q.32 (a)5 marks $\overline{\text{X}}$
OR
Q.32 (b)5 marks $(i) Why is sickle-cell anaemia, a human blood disorder so named ? (ii) Explain the genetic basis that results in the expression of this disorder. (iii) Work out a cross to explain how normal parents may have a sickle-cell anaemic child.$
Q.33 (a)5 marks $Describe the life cycle of HIV from the time of its entry into the human body till full blown AIDS sets in.$
OR
Q.33 (b)5 marks $(i) Write the symptoms of malaria in human and explain what causes these symptoms. (ii) Describe the different steps in the sexual mode of reproduction in the life cycle of a malarial parasite from the time of its initiation till where it is completed and ready to start a fresh cycle.$

Section A

1 mark each

Q.11 mark $In a fertilized ovule of an angiosperm, the cells in which n, 2n and 3n conditions respectively occur are :$
Tap an option to check your answer.
Q.21 mark $Turner's syndrome in humans occurs due to$
Tap an option to check your answer.
Q.31 mark $Which of the options has correct identification of 'P', 'Q' and 'R' in the illustration of 'Central Dogma' given below ?$
Tap an option to check your answer.
Q.41 mark $Study the following diagram of Transverse Section of a young anther of an angiosperm : Select the option where parts 'A', 'B' and 'C' are correctly identified.$
Tap an option to check your answer.
Q.51 mark $Select the option that gives the correct identification of ovum, morula and blastocyst in a human female reproduction system as shown in the following diagram :$
Tap an option to check your answer.
Q.61 mark $Study the table given below : Contraceptive / Contraceptive Method Mode of Action A. The pill I. Prevent sperm reaching cervix B. Condom II. Prevent implantation C. Vasectomy III. Inhibits ovulation D. Copper-T IV. Semen contains no sperm Select the option where contraceptive/contraceptive method are correctly matched with their mode of action.$
Tap an option to check your answer.
Q.71 mark $Identify the category of genetic disorder depicted in the pedigree chart given below :$
Tap an option to check your answer.
Q.81 mark $ELISA technique is based on the principle of$
Tap an option to check your answer.
Q.91 mark $Homologous organs indicate$
Tap an option to check your answer.
Q.101 mark $The 'molecular scissors' fall in the category of :$
Tap an option to check your answer.
Q.111 mark $Which of the chromosome in a human possesses the least number of genes ?$
Tap an option to check your answer.

Contraceptive / Contraceptive Method	Mode of Action
A. The pill	I. Prevent sperm reaching cervix
B. Condom	II. Prevent implantation
C. Vasectomy	III. Inhibits ovulation
D. Copper-T	IV. Semen contains no sperm

Q.121 mark

Given below is a list of some commercially important products in column A, whereas in column B are names of source organisms : Column - A Column - B Bioactive Products Source Organisms A. Cyclosporin - A (i) Streptococcus B. Statins (ii) Trichoderma polysporum C. Streptokinase (iii) Penicillium notatum D. Penicillin (iv) Monascus purpureus Select the option where the product and their source organisms are correctly matched.

Column – A	Column – B
Bioactive Products	Source Organisms
A. Cyclosporin – A	(i) Streptococcus
B. Statins	(ii) Trichoderma polysporum
C. Streptokinase	(iii) Penicillium notatum
D. Penicillin	(iv) Monascus purpureus

Tap an option to check your answer.

Question Nos. 13 to 16 consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :
Q.131 mark $Assertion (A) : Plasmids are autonomously replicating circular extra-chromosomal DNA. Reason (R) : Plasmids are usually present in Eukaryotic cells.$
Tap an option to check your answer.
Q.141 mark $Assertion (A) : Patents are granted by government to an inventor. Reason (R) : Patents prevents others from commercial use of an invention.$
Tap an option to check your answer.
Q.151 mark $Assertion (A) : A given fig species can be pollinated only by its partner' wasp. Reason (R) : The wasp pollinates the fig inflorescence while searching for suitable egg laying sites.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Some aquatic ecosystems have inverted biomass pyramids. Reason (R) : More energy is required by the organisms occupying higher trophic levels.$
Tap an option to check your answer.

Section B

2 marks each

Q.172 marks $What is artificial insemination in ART ? Under what conditions is the person medically advised to go for it ?$
Q.182 marks $Why does a patient of ADA - deficiency require repeated infusions of genetically engineered lymphocytes ? Suggest a possible permanent remedy.$
Q.192 marks $Study the graph given below that represents the changes in the thickening of the uterine wall in women 'X' and women 'Y' over a period of one month : What does the graph with respect to woman 'X' and woman 'Y' indicate ? Give suitable reason.$
Q.202 marks $(a) Biodiversity hotspots cover less than 2% of Earth's land area. Strict protection of these areas can reduce the rate of ongoing extinctions. Explain. (b) Name any two hotspots in India.$
Q.21 (a)2 marks $Differentiate between grazing food chain and detritus food chain.$
OR
Q.21 (b)2 marks $Explain Brood parasitism with the help of a suitable example.$

Section C

3 marks each

Q.223 marks $\text{F}_1$
Q.233 marks $Draw a well labelled diagram of sectional view of male gametophyte/microspore of an angiosperm and write the functions of any two parts labelled. (Any four labels).$
Q.24 (a)3 marks $(i) Name the group of drugs whose skeletal molecule is shown below : (ii) How are such drugs consumed ? (iii) Name the human body organ affected by the consumption of these drugs.$
OR
Q.24 (b)3 marks $Draw a schematic diagram of an antibody molecule and label any 4 parts. Mention their chemical nature. Name the cells which produce them.$
Q.253 marks $Explain the role of transgenic animals in : (a) Production of Biological products (b) Studying diseases (c) Chemical safety testing$
Q.263 marks $The schematic representation as above is showing the linking of two DNA fragments. (a) Name 'A' and 'B' fragments. (b) Write the 'palindrom' recognised by EcoRI. (c) Where does EcoRI cut the palindrome ? Write the events followed thereafter to form a recombinant DNA.$
Q.273 marks $How do the following organisms act as bio-fertilisers ? Explain. (a) Mycorrhiza (b) Anabaena (c) Rhizobium$
Q.283 marks $(a) Whose skulls 'A', 'B', and 'C' are shown below ? Which of the two are more similar to each other ? (b) Name the (i) ape like (ii) man like primates that existed 1.5 million years ago.$

Section D

Generally, in eukaryotic cells the average length of a transcription unit along a DNA molecule is about 8,000 nucleotides, so the RNA product of the transcription is also that long. But it only takes about 1200 nucleotides from the above RNA product to translate average sized polypeptide of 400 Amino acids.
Q.29 (a)1 mark $Name this RNA product transcribed from the DNA that subsequently translates into a polypeptide of 400 amino acids. Mention the enzyme responsible for transcribing this type of RNA from the DNA.$
Q.29 (b)2 marks $Name and explain the process the RNA molecule transcribed from 8000 nucleotide long DNA undergoes to be able to translate a polypeptide of 400 amino acids.$
Q.29 (c)1 mark $Write the number of RNA polymerases involved in the transcription of DNA in a prokaryote and eukaryotes.$
OR
Q.29 (c) OR1 mark $Mention the difference in the site of transcription in a prokaryote and eukaryote cell.$
Populations evolve to maximise their reproductive fitness in the habitat in which they live. Ecologists suggest, the life history of organisms have evolved in relations to the constraints imposed by the biotic and abiotic components of the habitat in which they live. This gets reflected in the population growth pattern of all organisms including humans. Study the population growth curves shown in the given graph and answer the questions that follow :
Q.30 (a)1 mark $Identify the growth curves 'A' and 'B'.$
Q.30 (b)1 mark $Mention what does the dotted line in the graph indicate and state its importance also.$
OR
Q.30 (b) OR1 mark $Growth curve 'B' shows a different pattern from that of growth curve 'A'. Justify giving one reason.$
Q.30 (c)2 marks $(i) Which one of the two curves is more "realistic" and why ? (ii) Which one of the two curves is relevant in present days with respect to human population in our country and why ?$

Section E

5 marks each

Q.31 (a)5 marks $(i) Explain the following phases in the menstrual cycle of a human female : (1) Menstruation (2) Follicular phase (3) Luteal phase (ii) 'A proper understanding of the menstrual cycle can help immensely in family planning.' Do you agree with the statement ? Provide reasons for your answer.$
OR
Q.31 (b)5 marks $(i) Why does endosperm development precede embryo development in angiosperm seeds ? State the role of endosperm in mature albuminous seeds. (ii) Draw a labelled diagram showing the different embryonic stages of a dicot plant, upto a fully mature embryo.$
Q.32 (a)5 marks $Describe the life cycle of HIV from the time of its entry into the human body till full blown AIDS sets in.$
OR
Q.32 (b)5 marks $(i) Write the symptoms of malaria in human and explain what causes these symptoms. (ii) Describe the different steps in the sexual mode of reproduction in the life cycle of a malarial parasite from the time of its initiation till where it is completed and ready to start a fresh cycle.$
Q.33 (a)5 marks $\overline{\text{X}}$
OR
Q.33 (b)5 marks $(i) Why is sickle-cell anaemia, a human blood disorder so named ? (ii) Explain the genetic basis that results in the expression of this disorder. (iii) Work out a cross to explain how normal parents may have a sickle-cell anaemic child.$

Section A

1 mark each

Q.11 mark $In a fertilized ovule of an angiosperm, the cells in which n, 2n and 3n conditions respectively occur are :$
Tap an option to check your answer.
Q.21 mark $Study the following diagram of Transverse Section of a young anther of an angiosperm : Select the option where parts 'A', 'B' and 'C' are correctly identified.$
Tap an option to check your answer.
Q.31 mark $Identify the category of genetic disorder depicted in the pedigree chart given below :$
Tap an option to check your answer.
Q.41 mark $Which of the options has correct identification of 'P', 'Q' and 'R' in the illustration of 'Central Dogma' given below ?$
Tap an option to check your answer.
Q.51 mark $Hugo de Vries proposed the mutation theory of organic evolution after his experiments on$
Tap an option to check your answer.
Q.61 mark $A list of organisms is given in column 'R', whereas in column 'S' a list of products produced by them : Column 'R' (Organisms) Column 'S' (Products) (A) Lactobacillus (i) Cheese (B) Saccharomyces cerevisiae (ii) Curd (C) Aspergillus niger (iii) Citric acid (D) Acetobacter aceti (iv) Bread (v) Acetic acid Select the option where the organisms are correctly matched with the product.$
Tap an option to check your answer.
Q.71 mark $Study the table given below : Contraceptive / Contraceptive Method Mode of Action A. The pill I. Prevent sperm reaching cervix B. Condom II. Prevent implantation C. Vasectomy III. Inhibits ovulation D. Copper-T IV. Semen contains no sperm Select the option where contraceptive/contraceptive method are correctly matched with their mode of action.$
Tap an option to check your answer.
Q.81 mark $Select the option that gives the correct identification of ovum, morula and blastocyst in a human female reproduction system as shown in the following diagram :$
Tap an option to check your answer.
Q.91 mark $The commonly used vector for human genome sequencing was/were :$
Tap an option to check your answer.
Q.101 mark $Turner's syndrome in humans occurs due to$
Tap an option to check your answer.
Q.111 mark $ELISA technique is based on the principle of$
Tap an option to check your answer.
Q.121 mark $The 'molecular scissors' fall in the category of :$
Tap an option to check your answer.
Question Nos. 13 to 16 consist of two statements – Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :
Q.131 mark $Assertion (A) : Plasmids are autonomously replicating circular extra-chromosomal DNA. Reason (R) : Plasmids are usually present in Eukaryotic cells.$
Tap an option to check your answer.
Q.141 mark $Assertion (A) : A given fig species can be pollinated only by its partner' wasp. Reason (R) : The wasp pollinates the fig inflorescence while searching for suitable egg laying sites.$
Tap an option to check your answer.
Q.151 mark $Assertion (A) : Some aquatic ecosystems have inverted biomass pyramids. Reason (R) : More energy is required by the organisms occupying higher trophic levels.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Patents are granted by government to an inventor. Reason (R) : Patents prevents others from commercial use of an invention.$
Tap an option to check your answer.

Column 'R' (Organisms)	Column 'S' (Products)
(A) Lactobacillus	(i) Cheese
(B) Saccharomyces cerevisiae	(ii) Curd
(C) Aspergillus niger	(iii) Citric acid
(D) Acetobacter aceti	(iv) Bread
	(v) Acetic acid

Contraceptive / Contraceptive Method	Mode of Action
A. The pill	I. Prevent sperm reaching cervix
B. Condom	II. Prevent implantation
C. Vasectomy	III. Inhibits ovulation
D. Copper-T	IV. Semen contains no sperm

Section B

2 marks each

Q.172 marks $(a) Name the first developed transgenic cow. (b) Explain the improvement in the quality of the milk produced by it.$
Q.182 marks $Study the graph given below that represents the changes in the thickening of the uterine wall in women 'X' and women 'Y' over a period of one month : What does the graph with respect to woman 'X' and woman 'Y' indicate ? Give suitable reason.$
Q.192 marks $(a) Mention any two ways by which HIV and Hepatitis-B can be transmitted to a healthy person. (b) Why is an early detection of these diseases essential ?$
Q.202 marks $(a) Biodiversity hotspots cover less than 2% of Earth's land area. Strict protection of these areas can reduce the rate of ongoing extinctions. Explain. (b) Name any two hotspots in India.$
Q.21 (a)2 marks $Differentiate between grazing food chain and detritus food chain.$
OR
Q.21 (b)2 marks $Explain Brood parasitism with the help of a suitable example.$

Section C

3 marks each

Q.223 marks $Draw a schematic diagram of the E.coli vector pBR 322 and mark the following in it : (a) ori (b) rop (c) ampicillin resistant gene (d) tetracycline-resistant gene (e) restriction site Bam HI (f) restriction site EcoRI$
Q.233 marks $How has the use of Agrobacterium as vector helped in controlling Meloidogyne incognita infestation in tobacco plants ? Explain in correct sequence.$
Q.243 marks $Explain the role of the following during the sewage treatment : (a) flocs (b) anaerobic sludge digester$
Q.253 marks $(a) Whose skulls 'A', 'B', and 'C' are shown below ? Which of the two are more similar to each other ? (b) Name the (i) ape like (ii) man like primates that existed 1.5 million years ago.$
Q.26 (a)3 marks $(i) Name the group of drugs whose skeletal molecule is shown below : (ii) How are such drugs consumed ? (iii) Name the human body organ affected by the consumption of these drugs.$
OR
Q.26 (b)3 marks $Draw a schematic diagram of an antibody molecule and label any 4 parts. Mention their chemical nature. Name the cells which produce them.$
Q.273 marks $A pea plant with purple flowers, when crossed with a plant with white, produced 50 plants with only purple flowers. On selfing these plants produced 482 plants with purple flower and 162 with white flowers. Explain the pattern of inheritance with the help of Punnet square.$
Q.283 marks $Draw a well labelled diagram of sectional view of male gametophyte/microspore of an angiosperm and write the functions of any two parts labelled. (Any four labels).$

Section D

Generally, in eukaryotic cells the average length of a transcription unit along a DNA molecule is about 8,000 nucleotides, so the RNA product of the transcription is also that long. But it only takes about 1200 nucleotides from the above RNA product to translate average sized polypeptide of 400 Amino acids.
Q.29 (a)1 mark $Name this RNA product transcribed from the DNA that subsequently translates into a polypeptide of 400 amino acids. Mention the enzyme responsible for transcribing this type of RNA from the DNA.$
Q.29 (b)2 marks $Name and explain the process the RNA molecule transcribed from 8000 nucleotide long DNA undergoes to be able to translate a polypeptide of 400 amino acids.$
Q.29 (c)1 mark $Write the number of RNA polymerases involved in the transcription of DNA in a prokaryote and eukaryotes.$
OR
Q.29 (c) OR1 mark $Mention the difference in the site of transcription in a prokaryote and eukaryote cell.$
Populations evolve to maximise their reproductive fitness in the habitat in which they live. Ecologists suggest, the life history of organisms have evolved in relations to the constraints imposed by the biotic and abiotic components of the habitat in which they live. This gets reflected in the population growth pattern of all organisms including humans. Study the population growth curves shown in the given graph and answer the questions that follow :
Q.30 (a)1 mark $Identify the growth curves 'A' and 'B'.$
Q.30 (b)1 mark $Mention what does the dotted line in the graph indicate and state its importance also.$
OR
Q.30 (b) OR1 mark $Growth curve 'B' shows a different pattern from that of growth curve 'A'. Justify giving one reason.$
Q.30 (c)2 marks $(i) Which one of the two curves is more "realistic" and why ? (ii) Which one of the two curves is relevant in present days with respect to human population in our country and why ?$

Section E

5 marks each

Q.31 (a)5 marks $\overline{\text{X}}$
OR
Q.31 (b)5 marks $(i) Why is sickle-cell anaemia, a human blood disorder so named ? (ii) Explain the genetic basis that results in the expression of this disorder. (iii) Work out a cross to explain how normal parents may have a sickle-cell anaemic child.$
Q.32 (a)5 marks $Describe the life cycle of HIV from the time of its entry into the human body till full blown AIDS sets in.$
OR
Q.32 (b)5 marks $(i) Write the symptoms of malaria in human and explain what causes these symptoms. (ii) Describe the different steps in the sexual mode of reproduction in the life cycle of a malarial parasite from the time of its initiation till where it is completed and ready to start a fresh cycle.$
Q.33 (a)5 marks $(i) State the objective of adopting artificial hybridisation programme in plants. (ii) Describe the steps followed in this technique.$
OR
Q.33 (b)5 marks $(i) Describe the development of placenta during pregnancy in a human female. (ii) Explain its role.$