PART - A
I. Select the correct alternative from the choices given below:
1. Which of the following organism exhibits oestrous cycle?
a) Monkey
b) Human
c) Rat
d) Apes
Ans: Rat
2. Triploid condition is observed in
a) Egg cell
b) Synergid
c) Antipodals
d) Primary endosperm nucleus
Ans: Primary endosperm nucleus
3. The first movements of the foetus are observed during which month of the pregnancy?
a) First month
b) Second month
c) Fifth month
d) Sixth month
Ans: Fifth month
4. An example for a non-medicated IUD is
a) Cu-T
b) Lippes loop
c) LNG-20
d) Multiload 375
Ans: Lippes loop
5. Appearance of autosomal recessive trait results in a condition called
a) Phenylketonuria
b) Turners’syndrome
c) Haemophila
d) Colour blindness
Ans: Phenylketonuria
6. Biopsy is useful in the detection of
a) Typhoid
b) Cancer
c) AIDS
d) Allergy
Ans: Cancer
7. Biofortified bitter gourd is enriched with
a) Vitamin A
b) Protein
c) Vitamin C
d) Iron
Ans: Vitamin C
8. A typical example for mycorrhiza forming fungus is
a) Penicillium
b) Aspergillus
c) Trichoderma
d) Glomus
Ans: Glomus
9. Select the correct sequence of steps in the polymerase chain reaction:
a) Annealing → Denaturation → Extension
b) Denaturation → Annealing → Extension
c) Annealing → Extension → Denaturation
d) Denaturation → Extension → Annealing
Ans: Denaturation → Annealing → Extension
10. In the equation GPP-R = NPP, the letter ‘R’ denotes
a) Respiratory quotient
b) Respiration loss
c) Intrinsic rate of natural increase
d) Regression coefficient
Ans: Respiration loss
11. Medical termination of pregnancies are considered relatively safe during
a) First trimester of pregnancy
b) Second trimester of pregnancy
c) Third trimester of pregnancy
d) Eighth month of pregnancy
Ans: First trimester of pregnancy.
12. A disorder characterized by trisomy of 21 is
a) Down’s syndrome
b) Haemophilia
c) Thalassemia
d) Cystic fibrosis
Ans: Down’s syndrome
13. The process of degradation of detritus into simpler inorganic substances by bacterial and
fungal enzymes is
a) Fragmentation
b) Leaching
c) Catabolism
d) Humification
Ans: Catabolism
14. Desert lizards bask in the sun when their body temperature drops below the comfort zone
and move into the shade when the ambient temperature starts increasing. This is an example for
a) Morphological adaptation
b) Behavioural adaptation
c) Physiological adaptation
d) Biochemical adaptation
Ans: Physiological adaptation
15. Each tropic level has a certain mass of living material at a particular time called as
a) Standing state
b) Standing crop
c) Biomass
d) Productivity
Ans: Physiological adaptation
II. Fill in the blanks by choosing the appropriate word/words from those given below:
(Saltation, Pioneer species, Tapetum, β-galactosidase, Retrovirus)
16. The commonly used vector for cloning genes in animals is Retrovirus
17. The species that invade bare areas are called Pioneer Species
18. The tissue that nourishes the developing pollen grains is Tapetum
19. In lac-operon, the ‘z’ gene codes for β-galactosidase
20. A single-step large mutation that causes speciation is Saltation
PART - B
III. Answer any FIVE of the following questions in 3-5 sentences each, wherever applicable:
21. What is parthenogenesis? Give an example.
Ans: The phenomenon in which the female gamete undergoes development to form new organisms without fertilization.
Examples: Rotifers, honeybees, and even some lizards and birds (turkey).
22. Define a) Emasculation b) Bagging
Ans:
a) Emasculation: The process of removal of anthers from the bisexual flower bud before the anther dehisces using a pair of forceps.
b) Bagging: To prevent pollination by unwanted pollen, the emasculated flower is enclosed in a bag. This is known as bagging.
23. List the criteria for a molecule that can act as genetic material.
Ans:
-
It should be able to generate its replica (Replication).
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It should chemically and structurally be stable.
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It should provide the scope for slow changes (mutation) that are required for evolution.
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It should be able to express itself in the form of 'Mendelian characters’.
24. What are homologous organs? Give an example.
Ans: The organs which are similar in their anatomical structure and origin [have common ancestry] but performs different functions are called homologous organs.
Examples: The forelimbs of some animals like whales, bats, cheetah,s and humans.
25. Differentiate between seasonal breeders and continuous breeders.
Ans:
Seasonal breeders: Organisms that breed only during specific times of the year are called seasonal breeders.
E.g., Frogs, Lizards.
Continuous breeders: Continuous breeders are organisms that can breed throughout the year.
E.g., Poultry, Rabbit, Cattle.
26. Distinguish between linkage and recombination.
Ans: Physical association of genes on a chromosome is called linkage.
The generation of non-parental gene combinations is called recombination.
27. Draw the pedigree symbols for
a) Affected male individual
b) Mating between relatives.
Ans:
28. Sketch and label a scrubber used in controlling air pollution.
Ans:
PART - C
IV. Answer any FIVE of the following questions in about 40-80 words each, wherever applicable:
29. What is the placenta? Name the hormones secreted by it.
Ans: The placenta is a structural and functional unit present between the developing embryo and the maternal body forms in the uterus during pregnancy.
The main hormones produced by the placenta are;
-
Human chorionic gonadotropin (hCG),
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Human placental lactogen (hPL),
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Estrogens,
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Progesterone.
30. Explain natural methods for birth control.
Ans:
a. Periodic abstinence: is a method in which a couple avoids or abstains from coitus from day 10-17 of the menstrual cycle when ovulation is expected to occur.
b. Coitus interruptus: or withdrawal is a method in which the male partner withdraws his penis from the vagina just before ejaculation so as to avoid insemination.
c. Lactational amenorrhea: (Absence of menstruation) is based on the principle that during the period of lactation after parturition, ovulation does not occur.
31. Mention the different steps involved in DNA fingerprinting.
Ans: The following are the steps involved in DNA fingerprinting:
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Isolating the DNA.
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Digesting the DNA with the help of restriction endonuclease enzymes.
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Separating the digested fragments as per the fragment size by the process of electrophoresis.
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Blotting the separated fragments onto synthetic membranes like nylon.
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Hybridizing the fragments using labeled VNTR probes.
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Analyzing the hybrid fragments using autoradiography.
32. Draw a labeled diagram of Stanley Miller’s apparatus.
33. Describe any three barriers of innate immunity with examples.
Ans:
a. Physical barriers: These barriers do not allow pathogens and foreign agents to enter the body, such as skin, mucous membranes of digestive, respiratory, and urinogenital tracts trapping microorganisms.
b. Physiological barriers: Sweat, tears, the acid in the stomach and saliva prevent microbial growth.
c. Cellular barriers: Certain types of leucocytes (WBCs) of our body like polymorpho-nuclear leukocytes [PMNL-neutrophils] and monocytes, natural killers (type of lymphocytes), and macrophages, phagocytose and destroy microbes.
d. Cytokine barriers: Interferons produced by virus-infected cells protect non-infected cells from further viral infection.
34.
a) Why meristerm is preferred in tissue culture as an explant?
b) Mention the objectives of plant breeding.
Ans:
a) Meristem (apical and axillary) is the only virus-free part of a virus-infected plant. Hence it is used as an explant in tissue culture.
b) objectives of plant breeding;
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To increase tolerance to environmental stress (salinity, extreme temperature, drought).
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Resistance to pathogens (viruses, fungi, and bacteria).
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To increase tolerance against insect pests.
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To get the high-yielding and improved quality of crop plants.
35.
a) Define endemism.
b) “Over-exploitation of natural resources by humans resulted in the extinction of many species in the last 500 years”. List any two examples for this.
Ans:
a) Endemism is the state of a species being found in a single defined geographic location,
b) When the biological system is over-exploited by man for natural resources, it results in the degradation and extinction of the resources.
For example, Stellar's sea cow, passenger pigeon, and many marine fishes.
36. Schematically represent phosphorous cycling in a terrestrial ecosystem.
Ans:
PART - D
V. Answer any THREE of the following questions in about 200-250 words each, wherever applicable:
37. Describe the structure of a mature female gametophyte in angiosperms.
Ans:
-
The embryo sac is referred to as a female gametophyte.
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The formation of a female gametophyte (embryo sac) is called megagametogenesis.
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The megaspore increases in size and its nucleus divide mitotically into two nuclei which move apart to opposite poles. Thus, a 2-nucleate embryo sac is formed.
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The two daughter nuclei undergo another mitotic division giving rise to the 4-nucleate stage.
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The third mitotic division gives rise to an 8-nucleate 7-celled embryo sac.
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The central cell contains 2 nuclei known as polar nuclei.
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The three nuclei at the micropylar region form the egg apparatus.
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In the egg apparatus, the middle cell is the largest and is called oosphere/egg/ovum, while the other two naked cells adjoining the egg cell are called synergids.
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The three nuclei at the chalazal end are surrounded by cytoplasm and cellular wall. These are called antipodal cells.
38. Explain any five features of the genetic code.
Ans:
-
The codons are triplets. Out of 64 codons, 61 code for 20 amino acids and 3 codons (UAA, UGA, UAG) do not code for any amino acid, hence function as stop or terminating codons. The codons are triplets. Out of 64 codons, 61 code for 20 amino acids and 3 codons (UAA,
-
specific. One codon codes for only one particular amino acid, hence the code is unambiguous and
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Some amino acids are coded by more than one codon, hence the code is degenerate.
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code is commaless. The codon is read on mRNA in a continuous fashion, i.e., without punctuations, and thus the
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organisms except in mitochondria and few protozoa. Genetic code is nearly universal,i.e., a particular codon codes for the same amino acid in all
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AUG is a dual-function codon, it codes for methionine (met) and it also acts as an initiator codon.
39. Explain the different steps involved in the development of a new genetic variety of crop plant.
Ans: The main steps in breeding a new genetic variety of a crop are:
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Collection of variability: The entire collection of plants/seeds having all the alleles for all genes in a given crop is called the germplasm collection.
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Evaluation and selection of parents: The germplasm is evaluated so as to identify plants with desirable combinations of characters.
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Cross hybridization among the selected parents: Two parents with desirable characteristics are crossed to produce hybrids that have desired characteristics of both parents.
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Selection and testing of superior recombinants: The progeny having desired characteristics are selected and self-pollinated for several generations till they become homozygous.
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Testing, release, and commercialization of new cultivars: The crops are grown in research fields followed by testing in farmers’ fields, for at least three growing seasons at different locations in the country, representing all the agroclimatic zones where the crop is usually grown.
40. Mention the roles played by microbes in household products.
Ans:
-
Micro-organisms such as Lactobacillus and others commonly called lactic acid bacteria grow in milk and convert it into curd. During growth, the LAB produces acids that coagulate and partially digest the milk proteins. The starter or inoculum contains millions of LAB, which at suitable temperatures multiply, thus converting milk to curd.
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Different varieties of cheese are known by their characteristic texture, flavour, and taste, the specificity is determined by the microbes used. For example, large-holed Swiss cheese is ripened with the help of a bacterium called propionibacterium shermanii. Roquefort cheese are ripened by fungi Penicillium roqueforti.
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Toddy- A traditional drink of some parts of southern India, is made by fermenting sap from a palm known as Caryota urens.
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Other foods- Microbes are also used to ferment fist, soybean, and bamboo-shoots to make foods.
41. Explain the process of separation and isolation of DNA fragments using gelelectrophoresis.
Ans:
-
Gel electrophoresis is a technique for separating DNA fragments based on their size and net electric charges.
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Firstly, the sample DNA is cut into fragments by restriction endonucleases.
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The DNA fragments being negatively charged can be separated by forcing them to move towards the anode under an electric field through a medium/matrix.
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The commonly used matrix is agarose, which is a natural linear polymer of D-galactose and 3, 6-anhydro- L -galactose which is extracted from seaweeds.
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The DNA fragments separate out according to their size because of the sieving property of agarose gel. Hence, the smaller the fragment size, the farther (faster) it will move.
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The separated DNA fragments are visualized after staining the DNA with ethidium bromide followed by exposure to UV radiation.
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The DNA fragments are seen as orange-colored bands.
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The separated bands of DNA are cut out and extracted from the gel piece. This step is called elution.
42. Define the following:
a) Biochemical oxygen demand
b) Eutrophication
c) Biomagnification
d) Algal bloom
e) Ecological sanitation
Ans:
a) Biochemical oxygen demand: The amount of oxygen required for the microbial breakdown of biodegradable organic matter called BOD.
b) Eutrophication: It is defined as the natural aging of a lake by the biological enrichment of its water.
c) Biomagnification: The process in which an increase in the concentration of toxicants at successive trophic levels.
d) Algal bloom: Domestic sewage contains nutrients like nitrogen and phosphorus which favour the excessive growth of planktonic (free-floating) algae called an algal bloom.
e) Ecological sanitation: Ecological sanitation is a sustainable system for handling human excreta using dry composting toilets. Such “eco save” toilets are working in many areas of Kerala and Sri Lanka.
VI. Answer any TWO of the following questions in about 200-250 words each, wherever applicable:
43. Draw a sectional view of the human male reproductive system.
44. Explain the benefits of transgenic animals for humans.
Ans:
-
Transgenic animals are useful to study gene regulation, their effect on the normal functions of the body, and their development.
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To study of genes that are responsible for diseases in human and their treatment.
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Useful biological products can be produced by introducing, into transgenic animals, the portion of DNA (or genes) that codes for a particular product. For example, human protein (α-1-antitrypsin) is used to treat emphysema.
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Transgenic mice are developed to test the safety of vaccines, before being used on humans.
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Transgenic animals are made to carry genes, which makes them more sensitive to toxic substances than non-transgenic animals.
45. In Mendel’s experiment, when two pairs of traits are combined in a hybrid, the segregation of one pair of characters is independent of the other pair of characters. Justify this by representing schematically the two gene inheritance.
Ans: Law of Segregation states “A pair of alleles segregate from each other during gamete formation, such that a gamete receives only one of the two factors”.
Inheritance of genes is explained by the law of Independent Assortment as follows;
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46.
a) Differentiate between euryhaline animals and stenohaline animals.
b) Describe sexual deceit in Ophrys.
Ans:
a) The organisms tolerating a wide range of salinities are called euryhaline and
the organisms that tolerate only a narrow range of salinities are called stenohaline.
b) Sexual deceit is the process in which the petal of an orchid flower bears an uncanny resemblance to the female of the bee in size, colour, and markings to attract the male bee for pollination.
47. List out the measures used for the prevention and control of alcohol and drug abuse among adolescents.
Ans:
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Avoid undue peer pressure.
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Educating and counseling the problems and stresses to avoid disappointments and failures in life.
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Seeking help from parents and peers.
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Looking for danger signs to take appropriate measures on time.
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Seeking professional and medical help whenever required.