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Biology Mock Test - 9
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Biology Mock Test - 9
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  • Question 1/50
    5 / -1

    Internal fertilisation occurs in
    Solutions

    Concept:

    • The first step in the process of reproduction is the fusion of a sperm and an ovum.
    • When sperms come in contact with an egg, one of the sperms may fuse with the egg. Such fusion of the egg and the sperm is called fertilization.
    • During fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a fertilized egg or zygote

    Key Points 

    • Fertilization is of two types - Internal fertilization & External fertilization.
    1. Internal Fertilization - The fertilization which takes place inside the female body is called internal fertilization. Internal fertilization occurs in many animals including humans, cows, dogs and hens.
    2. External Fertilization - The fertilization which takes place outside the body of the female is called external fertilisation. It is very common in aquatic animals such as fish, starfish, frogs etc.

                                             Fertilization

  • Question 2/50
    5 / -1

    Consider the following statements regarding sexual reproduction in plants:

    1. Reproduction in plants takes place only through asexual methods.

    2. Reproduction in spirogyra takes place through the process of fragmentation.

    3. Vegetative propagation in plants can be achieved only by natural method.

    Which of the statements from above is/are correct?
    Solutions
    • There are two methods by which reproduction occurs in plants by Sexual and Asexual methods. Hence statement 1 is incorrect.
    • The reproduction in which only one parent plays a role, and in which cohesion (combination) of two nuclei do not take place is known as ‘Asexual Reproduction’.
    • The reproduction in which one new cell is formed by the fusion of two-parent cells from two different parents is known to be ‘Sexual Reproduction.
    • It is a process in which a parent organism breaks into fragments, each capable of growing independently into a new organism. This type of reproduction is seen in the Spirogyra. Hence statement 2 is Correct.
    • Vegetative propagation is a type of asexual reproduction in which new plants are produced from roots, stems, leaves, and buds.
    • Since reproduction is through the vegetative parts of the plant, it is known as ‘vegetative propagation.
    • Vegetative propagation in plants can occur both naturally or also can be artificially induced by horticulturists. Hence statement 3 is incorrect.
  • Question 3/50
    5 / -1

    Minimum number of meiotic divisions required to obtain 100 pollen grains of wheat -
    Solutions

    The correct answer is 25.

    Key Points

    • In one meiotic division, one microspore mother cell in the anther forms 4 microspores, each of which develops as a pollen grain.
    • When there are 100 pollen grains, the meiotic divisions which will be required are 100/4= 25.
    • Therefore, the number of meiotic divisions required to obtain 100 pollen grains of wheat is 25. 

  • Question 4/50
    5 / -1

    With reference to Tapetum found in flowering plants, consider the following statements:

    i. It is a specialised layer of nutritive cells found within the anther.

    ii. It is important for the nutrition and development of pollen grains.

    Select the correct answer using the code given below:

    Solutions

    The correct answer is Both i and ii.

    • The tapetum is a specialized layer of nutritive cells found inside the anther of the flowering plants.

    Key Points

    • It is located between the sporogenous tissue and the anther wall.
    • Tapetum is important for the nutrition and development of pollen grains.
    • It nourishes the developing pollen grains.
    • Apart from this, it also serves various other functions such as pollen wall formation, transportation of nutrients to the inner side of the anther, synthesis of callase enzyme for separating microspore tetrads.
  • Question 5/50
    5 / -1

    Double fertilization is a rule of which plants?
    Solutions

    The correct answer is Angiosperms.

    Key Points

    • Double fertilization
      • It is a complex fertilization mechanism in Angiosperms. Hence, Option 3 is correct.
      • This process involves the joining of a female gametophyte (ovary) with two male gametes (sperm).
      • Double fertilization or triple fusion is common in angiosperms.

    Additional Information

    • A pteridophyte
      • It is a vascular plant that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as cryptogams, meaning that their means of reproduction are hidden.
      • Ferns, horsetails, and lycophytes are all pteridophytes.
    • Gymnosperms are flowerless plants that produce cones and seeds. 
      • Cycas, pinus, Cedrus are a few examples of Gymnosperms.
    • Flowering plants whose embryos have a single cotyledon are called monocots, or monocotyledonous plants. 
    • Bryophytes are small, non-vascular plants.
      • The reproduction of Bryophytes is via spores.
      • Bryophytes are live in the soil, even though they need water for sexual reproduction this is the reason why the Bryophytes are often referred to as the amphibians of the plant kingdom.
      • Bryophytes are generally classified into three coordinate phyla namely the liverworts, hornworts, and mosses.
  • Question 6/50
    5 / -1

    After fertilization, the seed coats develop from the
    Solutions

    The correct answer is integuments.

    Explanation:

    • The fertilised ovule, which is the end product of sexual reproduction, is known as seed.
    • Integument is the protective covering of the ovule (nucellus). It is thin and living.
    • The megasporangium and the embryo sac are protected by a double-layered integument. 
    • After fertilisation, one or two protective integuments transform into the seed coat, which protects the entire seed.
    • In seed, seed coats are 1 or 2 in number, having an opening called micropyle.
    • Outer integument forms outer seed coat (testa) and inner integuments form inner seed coat (tegmen).
    • The hard seed coats (testa and tegmen) provide protection against injury.

    Thus, After fertilization, the seed coats develop from the integuments.

    Additional Information

    • The micropyle remains a small pore in the seed coat.
    • It helps in the entry of water and oxygen into the seed for germination.
    • Seeds may germinate immediately or may undergo dormancy for a period before germinating.
  • Question 7/50
    5 / -1

    Spermatogenesis in mammalian testes controlled by
    Solutions

    Concept:

    • The process of the formation of sperms is called spermatogenesis. It involves 3 phases:
    1. In the multiplication phase, male germ cells also called spermatogonia, which undergo mitotic divisions to form a large number of spermatogonia.
    2. In the growth phase, spermatogonia prepare for meiotic division by increasing their size and called primary spermatocytes (46 chromosomes).
    3. In the maturation phase, the primary spermatocyte undergoes the first meiotic division and produces 4 haploid cells called secondary spermatocytes (23 chromosomes), which after the second meiotic division produces four equal, haploid spermatids.

    Explanation:

    • Spermatogenesis in mammalian testes controlled by ''Follicle-stimulating hormone''
    • Pituitary-derived FSH provides indirect structural and metabolic support for the development of spermatogonia into mature spermatids via its membrane-bound receptor in Sertoli cells.
    • FSH also plays a crucial role in the determination of the number of Sertoli cells and thus their capacity to maintain spermatogenesis. 

    Additional Information 

    • Estrogen, or oestrogen: It is a sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. 
    • Luteinizing Hormone is found in both males and females. In males, it stimulates the growth and function of Leydig (interstitial) cells, while in females, it stimulates ovulation, development of the corpus luteum, and secretion of progesterone by the corpus luteum.
  • Question 8/50
    5 / -1

    What is the age of menopause in women?
    Solutions
    • Menarche: It is the first menstrual flow beginning at puberty.
    • Menopause: At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is known as menopause.
    • From the age of puberty up the menopause (from 10 – 17 years of age up to 45 – 50 years), an ovum is released every month from the ovary. i.e. out of 2 – 4 million ova, approximately only 400 oocytes are released up to the age of menopause. Remaining oocytes undergo degeneration.
  • Question 9/50
    5 / -1

    The egg is carried from the ovary to the uterus by
    Solutions

    The correct answer is a Fallopian tube.

    Key Points

    • The egg is carried from the ovary to the uterus by the fallopian tube
      • The ovaries produce the egg cells, called the ova or oocytes.
      • The oocytes are then transported to the fallopian tube where fertilization by a sperm may occur.
      • The fertilized egg then moves to the uterus, where the uterine lining has thickened in response to the normal hormones of the reproductive cycle.

    Additional Information

    • The ureter is a tube that carries urine from the kidney to the urinary bladder.
      • There are two ureters, one attached to each kidney.
      • The upper half of the ureter is located in the abdomen and the lower half is located in the pelvic area.
    • The spermatic cord is the cord-like structure in males formed by the vas deferens (ductus deferens) and surrounding tissue that runs from the deep inguinal ring down to each testicle.
      • It is serosal covering, the tunica vaginalis, is an extension of the peritoneum that passes through the transversalis fascia. 
    • The cervix is the lower end of the womb (uterus).
      • It is at the top of the vagina.
        • It is about 2.5 to 3.5 centimeters (1 to 1.3 inches) long.
        • The cervical canal passes through the cervix. It allows blood from a menstrual period and a baby (fetus) to pass from the womb into the vagina.
  • Question 10/50
    5 / -1

    Consider the following statements regarding Respiration in Plants:

    1. Estrogen plays a major stimulatory role in the process of spermatogenesis.

    2. Androgens regulate female sexual behaviour.

    Which of the statements given above is/are not correct?
    Solutions

    Both statements are not correct.

    Key Points

    • A pair of the testis is present in the scrotal sac (outside abdomen) of male individuals.
    • Testis performs dual functions as a primary sex organ as well as an endocrine gland.
    • Testis produces a group of hormones called androgens, mainly testosterone.
    • Androgens play a major stimulatory role in the process of spermatogenesis (formation of spermatozoa). Hence statement 1 is not correct.
    • Females have a pair of ovaries located in the abdomen.
    • Ovary is the primary female sex organ which produces one ovum during each menstrual cycle.
    • Ovary also produces two groups of steroid hormones called estrogen and progesterone.
    • The estrogen is synthesised and secreted mainly by the growing ovarian follicles.
    • Ruptured follicle is converted to a structure called corpus luteum, which secretes mainly progesterone.
    • Estrogen- produce wide-ranging actions such as stimulation of growth and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g., high pitch of voice, etc.), mammary gland development.
    • Estrogens also regulate female sexual behaviour. Hence statement 2 is not correct.
    • Progesterone - supports pregnancy also acts on the mammary glands and stimulates the formation of alveoli.
  • Question 11/50
    5 / -1

    The main objective of family welfare programme is
    Solutions

    Explanation:

    • The International Conference on Population and Development held in 1994 established an international consensus on a new approach to policies to achieve population stabilization.
    • In 1951 India became the first country in the world to launch a family planning programme to reduce population growth in the country.
    • The department of Family welfare undertook many pilot activities for the implementation of the family welfare program to meet the needs of women who are at risk of unwanted births and has assisted the country to accelerate fertility decline.

    Family Welfare Programmes Mainly include:

    • Family planning information, counselling and services to women for healthy reproduction.
    • Education about safe delivery and post-delivery of the mother and the baby and the treatment of women before pregnancy.
    • Health care for infants immunization against preventable diseases.
    • Prevention and treatment of sexually and Reproductive Tract infection.

    The basic and fundamental objective of the family welfare programme is population control.

  • Question 12/50
    5 / -1

    Which of the following disease is transmitted sexually?
    Solutions

    The correct answer is Syphilis.

    Key Points

    • Sexual transmission disease
      • More than 30 different bacteria, viruses, and parasites are known to be transmitted through sexual contact.
      • Eight of these pathogens are linked to the greatest incidence of sexually transmitted disease. Of these 8 infections, 4 are currently curable: syphilis, gonorrhea, chlamydia, and trichomoniasis. Hence, Option 4 is correct.
      • The other 4 are incurable viral infections: hepatitis B, herpes simplex virus (HSV or herpes), HIV, and human papillomavirus (HPV). Symptoms or diseases due to incurable viral infections can be reduced or modified through treatment.
      • STIs are spread predominantly by sexual contact, including vaginal, anal, and oral sex.
      • Some STIs can also be spread through non-sexual means such as via blood or blood products.
      • Many STIs—including syphilis, hepatitis B, HIV, chlamydia, gonorrhea, herpes, and HPV—can also be transmitted from mother to child during pregnancy and childbirth.
      • A person can have an STI without having obvious symptoms of the disease. Common symptoms of STIs include vaginal discharge, urethral discharge or burning in men, genital ulcers, and abdominal pain.

    Additional Information

    • Kala-azar
      • It is also known as visceral leishmaniasis.
      • It is the second-largest parasitic killer in the world—only malaria is more deadly.
      • Along with Chagas disease and sleeping sickness, kala-azar is one of the most dangerous neglected tropical diseases (NTDs).
    • Jaundice
      • It is a condition in which the skin, whites of the eyes, and mucous membranes turn yellow because of a high level of bilirubin, a yellow-orange bile pigment. Jaundice has many causes, including hepatitis, gallstones, and tumors. In adults, jaundice usually doesn't need to be treated.
    • Cholera
      • It is an infectious disease that causes severe watery diarrhea, which can lead to dehydration and even death if untreated.
      • It is caused by eating food or drinking water contaminated with a bacterium called Vibrio cholera.
  • Question 13/50
    5 / -1

    Child with blood group ‘O’ has ‘B' group father and ‘A’ group mother. The father and mother have a genotype of :
    Solutions

    Concept-

    • The blood of human beings differs in certain aspects though it appears to be similar.
    • Various types of grouping of blood have been done.
    • Two such groupings - the ABO and Rh - are widely used all over the world. 
    • ABO grouping is based on the presence or absence of two surface antigens (chemicals that can induce an immune response) on the RBCs namely A and B.
    • Similarly, the plasma of different individuals contains two natural antibodies (proteins produced in response to antigens).
    • The distribution of antigens and antibodies in the four groups of blood, A, B, AB, and O. 

    Explanation-

    • ii - The blood group is O(child).
    • To have a child with an O blood group, both parents should have at least one copy of i allele.
    • So the parents are heterozygous.
    • IBi - The blood group of the father.
    • IAi - The blood group of the mother.

    Therefore the father and mother have a genotype of IAi × IBi.

    Additional Information

    • ABO blood groups are determined by three alleles - IA, IB, IO.
    • I = Dominant
    • IB = Dominant
    • IO = Recessive
    Allele from Parent 1Allele from Parent 2Genotype of offspring Blood types of offspring
    IAIAIA IAA
    IAIOIA IOA
    IAIBIA IBAB
    IBIBIB IBB
    IBIOIB IOB
    IOIOI IOO
  • Question 14/50
    5 / -1

    Mendel's work of genetics was based upon which of the following?
    Solutions

    The correct answer is Pisum sativum.

    Key Points

    • Johann Gregor Mendel is considered as the Father of Genetics.
    • He conducted hybridization experiments on garden peas for seven years (1856-1863) and proposed the laws of inheritance in living organisms.
    • The factors, now known as genes, are responsible for transfer of characteristics from one generation to another.
    • Genetics is the science which deals with the inheritance, as well as the variation of characters from parents to offspring.
    • Inheritance is the process by which characters are passed on from parent to progeny; it is the basis of heredity.
    • This simply means that due to inheritance, the members of the same family possess similar characteristics.
    • Variation is the degree by which progeny differ from their parents or to put in simple words, it refers to the differences among individuals of the same species.

    Mendel's experiment in short

    • Mendel conducted artificial pollination/cross-pollination experiments using several true-breeding pea lines.
    • He selected 14 true-breeding pea plant varieties, as pairs which were similar except for one character with contrasting traits like - smooth or wrinkled seeds, yellow or green seeds, inflated (full) or constricted green or yellow pods and tall or dwarf plants.
    • The genetic makeup of the plant is known as the genotype. On the contrary, the physical appearance of the plant is known as phenotype.
    • The genes are transferred from one generation (parent) to the another (offspring) in pairs known as allele (variant form of genes).

    Explanation:

    • Pisum sativum was selected by Mendel because:
      • It is an annual plant, therefore, many generations can be studied within a short period of time.
      • The pea plant can be easily grown and maintained.
      • It is a naturally self-pollinating but can also be cross-pollinated.
      • It has several contrasting characters.

    Additional Information

    1. Gallus gallus domesticus (Andulusian Fowl) 
      • It is one of the breeds of domestic chicken, also known as the Blue Andalusian.
      • They are either black, blue, or white-feathered.
      • The Andalusian fowl reveals the heritage of mixing.
      • The cross is made between the black and white feathers of the fowls in this breed of the Andalusian fowl. The blue feathered fowl is the product obtained from the cross.
    2. Oenothera lamarkiana (Evening primerose)
      • This plant is originally native to Brazil, but has become naturalized in many countries and planted as an ornamental plant in gardens.
      • De Vries conducted experiment on Oenothera lamarckiana or Evening Primrose plant.
      • It is a self-pollinated plant and its seeds were allowed to grow, the majority of F1 plants were similar to the parents, but a few were different plants.
      • The same results were found in the F2 generation.
      • Later on, it was revealed that most of the variants isolated from Oenothera lamarckiana were due to its anomalous chromosome behaviour.
      • The chromosomes form multiple rings at meiosis and chromosomal end segments only involves in recombination (low-level crossing over) and plant shows complex heterozygosity i.e., during meiosis maternal and paternal chromosomes are arranged in alternate order.
    3. Drosophila melanogaster (Fruit fly) 
      • The phenomenon of linkage was studied by the scientist T.H. Morgan using the common fruit fly or Drosophila melanogaster.
      • Linkage and recombination are phenomena that describe the inheritance of genes.
      • A linkage is a phenomenon where two or more linked genes are always inherited together in the same combination for more than two generations.
      • Morgan performed a cross between a heterozygous red-eyed female with a white-eyed male. This gave a ratio of 1:1:1:1 in the progeny (1 white eyed female, 1 red eyed female, 1 white eyed male and 1 red eyed male).
      • He performed many such crosses and came to the determination that the gene responsible for the eye color was situated on the X chromosome (one of the two sex chromosomes).
  • Question 15/50
    5 / -1

    Haemophilia is
    Solutions
    Key Points
    • Haemophilia is a genetic disorder that can be inherited from one generation to the next.
    • It is classified as a Mendelian disorder which is caused by a mutation in a single gene.
    • It is a sex-linked recessive disorder i.e., the inheritance of this disorder is associated with the sex chromosomes.
    • In a recessive disorder, the disease is expressed only in homozygous recessive state i.e., when 2 recessive alleles for the trait are present in an individual.
    • In a sex-linked recessive disorder:
      • Normal - Woman with XX; Man with XY.
      • Affected - Woman with XhXh; Man with XhY. [Xh is the affected allele]
      • Carrier - Woman with XhX chromosomes.
    • If a woman has heterozygous condition, she becomes a carrier for the disease.
    • A carrier does not express the disease but can transfer the disease to the next generation.

    Explanation:

    • Queen Victoria was a carrier of haemophilia and therefore, passed on the disease to several descendants.
    • This is why haemophilia is also known as 'the royal disease'.
      • Hence, option (2) is correct.
    • The mutation affects a single protein involved in the blood clotting process.
    • This results in non-stop bleeding even in case of a small cut or wound.
      • Hence, option (3) is correct.

    Additional Information

    Features of sex-linked (X-linked) recessive disorder:

    • Males can pass on the disease only to a daughter.
    • Females can pass the disease to son and daughter both.
  • Question 16/50
    5 / -1

    Which of the following represents the pair of sex chromosomes in men?
    Solutions

    The correct answer is XY.

    Key Points

    • Sex chromosomes in humans are responsible for sex determination.
    • In human beings, in each cell, there are 46 (23 pairs) chromosomes.
    • Twenty-two of these pairs are autosomes and the 23rd pair, the sex chromosome differs in males and females.
    • Females have 2 copies of the X chromosome while males have one X and one Y chromosome.
    • Each parent donates his or her offspring a set of 23 chromosomes, out of which one pair is of sex chromosomes, which are X and Y. 
    • A combination of X and Y produces a male, whereas a combination of XX produces a female. 

    Important Points

    • Mendel’s laws of inheritance, suggesting the transmission of single-gene characters in the families, along with more complex types of inheritance such as multi-factorial or polygenic inheritance.
    • Gregor Johann Mendel was born on July 22, 1822, to peasant parents in a small agrarian town in Czechoslovakia.
    • He is considered the father of genetics.
    • The laws of inheritance were proposed by Gregor Mendel in 1865 and 1866. 
  • Question 17/50
    5 / -1

    ______ is a chromosomal disorder that causes undeveloped feminine character and sterility 
    Solutions

    The correct answer is Turner's Syndrome.

    • Turner's syndrome is a chromosomal disorder that causes undeveloped feminine character and sterile female.

    Key Points

    • This disorder is caused due to the absence of one X chromosome and the number of chromosomes becomes 45.
    • Symptoms-
      • Sterile female with rudimentary ovaries.
      • Shield-shaped thorax.
      • Webbed neck
      • Poor development of breasts
      • Short stature, small uterus, and puffy fingers.
    • A Female with this syndrome is sterile and her ovaries are vestigial due to undeveloped feminine characters.

    Additional Information

    • Whereas Klinefelter Syndrome is the presence of one extra X- chromosome due to which feminine characters develop in the male.
  • Question 18/50
    5 / -1

    In DNA, thymine always pairs with ______.
    Solutions

    The correct answer Adenine.

    Key Points

    • There are four nitrogen bases in a DNA-
      • Adenine
      • Guanine
      • Thymine
      • Cytosine
    • Adenine pairs with up Thymine
    • Guanine pairs up with Cytosine.

    Additional Information

    • DNA stands for Deoxyribose Nucleic Acid.
    • It contains genetic information.
    • It is made up of
      • sugar group - deoxyribose sugar
      • phosphate group
      • nitrogen base - (Adenine, Guanine, Thymine, Cytosine)
    • Genetic information in DNA is wrapped up around a protein called Histones.

    Important Points

    • RNA (Ribose Nucleic Acid) also has 4 nitrogenous base.
      • Adenine
      • Guanine
      • Cytosine
      • Uracil (instead of Thymine which is present in DNA)
    • RNA is single-stranded biopolymer
    • It is of 3 types-
      • mRNA (messenger)
      • tRNA (transfer)
      • rRNA (ribosomal)
  • Question 19/50
    5 / -1

    Consider the following statements:

    1. DNA Polymerase uses a DNA template to catalyse the polymerisation of deoxynucleotides. 

    2. Adenosine triphosphate (ATP) are an energy-carrying molecule found in the cells of all living things that captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes.

    Which of the following statements given above is/are correct?

    Solutions

    The correct answer is Both 1 and 2.

    Key Points

    • In living cells, such as E. coli, the process of replication requires a set of catalysts (enzymes). 
      • The main enzyme is referred to as DNA-dependent DNA polymerase since it uses a DNA template to catalyze the polymerization of deoxynucleotides.  Hence statement 1 is correct.
      • These enzymes are highly efficient as they have to catalyze the polymerization of a large number of nucleotides in a very short time. 
      • E. coli that has only 4.6×106 bp (compare it with a human whose diploid content is 6.6 × 109 bp), completes the process of replication within 18 minutes; that means the average rate of polymerization has to be approximately 2000 bp per second.
    • Not only do these polymerases have to be fast, but they also have to catalyze the reaction with a high degree of accuracy. 
    • Any mistake during replication would result in mutations. 
    • Deoxyribonucleoside triphosphates serve dual purposes.
      • In addition to acting as substrates, they provide energy for polymerization reaction (the two terminal phosphates in deoxynucleoside triphosphates are high-energy phosphates, same as in the case of ATP).
      • Adenosine triphosphate (ATP) is an energy-carrying molecule found in the cells of all living things that captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes. Hence statement 2 is correct.
      • In addition to DNA-dependent DNA polymerases, many additional enzymes are required to complete the process of replication with a high degree of accuracy. 
      • For long DNA molecules, since the two strands of DNA cannot be separated in their entire length (due to very high energy requirement), the replication occurs within a small opening of the DNA helix, referred to as replication fork.
      • The DNA-dependent DNA polymerases catalyze polymerization only in one direction, that is 5'à3'.
      • This creates some additional complications at the replicating fork.
      • Consequently, on one strand (the template with polarity 3'à5'), the replication is continuous, while on the other (the template with polarity 5'à3'), it is discontinuous.
      • The discontinuously synthesized fragments are later joined by the enzyme DNA ligase.
  • Question 20/50
    5 / -1

    The two complementary strands of DNA are held together by
    Solutions

    Key Points

    • According to Watson and Crick (1953), DNA is a double helical structure with the following features:
      • DNA is a double-stranded helical molecule.
      • The two strands are complementary and anti-parallel.
      • The hydrogen bonds between the paired bases (A-T and G-C), repeated along the length of the DNA double helix, hold the two strands together in the double helix.
      • There are two hydrogen bonds between Adenine and Thymine base pair, whereas, there are three hydrogen bonds between Guanine and Cytosine base pair.

    Additional Information

    Phosphodiester Bond:

    • In a polynucleotide chain, consecutive nucleotides are linked to one another through phosphodiester bonds formed between the phosphate of one nucleotide and the sugar of the next nucleotide.
    • It helps in the formation of dinucleotide or polynucleotide.

    Glycosidic Bond:

    • A glycosidic bond is present between pentose sugar and a nitrogen base of a nucleotide.
    • It helps in formation of a nucleoside.

    Peptide Bond:

    • The peptide bond is a link formed between the –NH2 group of one amino acid and the –COOH group of the second amino acid.
    • It helps in the formation of peptide chains or polypeptides.

  • Question 21/50
    5 / -1

    Peptide synthesis in a cell occurs in
    Solutions

    Concept:

    • Translation refers to the process of polymerization of amino acids to form polypeptides.
      • Activation of Amino acids
      • Charging of tRNA
      • Activation of Ribosomes
      • Assembly of Amino acids (Polypeptide Formation)
      • Modification of the released polypeptide

    Explanation-

    • The amino acids are joined by a bond which is known as a peptide bond. 
      • The formation of a peptide bond requires energy.
      • Therefore, in the first phase itself, amino acids are activated in the presence of ATP  and form the Amino acyl AMP enzyme complex that is also known as activation of amino acid.
      • Activated amino acid linked to their cognate tRNA – a process commonly called as charging of tRNA or aminoacylation of tRNA to be more specific. 
      • If two such charged tRNAs are brought close enough, the formation of a peptide bond between them would be favoured energetically.
      • The presence of a catalyst would enhance the rate of peptide bond formation.

    Since Protein synthesis takes place in ribosomes so peptide formation also occurs in ribosomes.

    Additional Information

    • Polypeptide chain synthesis is signaled by two initiation codon AUG or GUG.
    • Out of 64 codons, 3- codons are nonsense codons.
    • Ribosomes are also called “Organelle within an organelle” and “Protein factory of the cell”
    • Ribosomes are the smallest cell organelles.
  • Question 22/50
    5 / -1

    Consider the following statements about DNA Sequencing:

    1. DNA Sequencing is used to detect the presence of a complementary sequence by hybridization with a nucleic acid sample.

    2. DNA sequencing is the process of determining the nucleic acid sequence - the order of nucleotides in DNA.

    Which of the above statements is/are incorrect?
    Solutions

    DNA sequencing is the process of determining the nucleic acid sequence - the order of nucleotides in DNA.

    • It includes any method or technology that is used to determine the order of the four bases: Adenine, Guanine, Cytosine, and Thymine.
    • The DNA base sequence carries the information a cell needs to assemble protein and RNA molecules.
    • DNA sequence information is important to scientists investigating the functions of genes.
    • DNA sequencing may be used to determine the sequence of individual genes, larger genetic regions (clusters of genes or operons), full chromosomes, or entire genomes of any organism.
    • DNA sequencing is also the most efficient way to indirectly sequence RNA or proteins (via their open reading frames). In fact, DNA sequencing has become a key technology in many areas of biology and other sciences such as medicine, forensics, and anthropology.
    • A DNA sequence that is used to detect the presence of a complementary sequence by hybridization with a nucleic acid sample is called Nucleic acid probes.
  • Question 23/50
    5 / -1

    Evolution is best defined as
    Solutions

    Key Points

    • The theory of evolution was described by Charles Darwin as descent with modification by natural selection.
    • 'Descent with modification' explains how existing life forms can have a common ancestor as well as show variations.
    • These variations were inheritable in nature i.e., they can be passed on from one generation to another.
    • Some of these inheritable variations would enhance the survivability of some, enabling them to leave more progeny.
    • These progenies would also survive better and hence give rise to new life forms.

    Additional Information

    • Inheritance of acquired characters was proposed by Lamarck, which states that physical characteristics of an organism acquired by use and disuse in a lifetime can be passed on to the next generation.
    • The concept of struggle for existence refers to the competition for the available resources that are required for survival. Darwin suggested that there is a continuous struggle for existence in which only the fittest would survive.
    • 'Like begets like' is a phrase that refers to the similarity of offspring with the parents due to inheritable characters.
  • Question 24/50
    5 / -1

    (i)_______ tells us how life evolved from simple to more complex forms and (ii)________ give us the mechanism for the inheritance of traits from one generation to the next.
    Solutions

    The correct answer is (i) Darwin's theory of evolution, (ii) Mendel's experiments.

    Explanation:
    Darwin's theory of evolution:

    • Evolution is the process of development from a simple form to a complex form.
    • Darwin's theory of evolution tells us how life evolved from simple to more complex forms 
    • Darwin proposed that evolution occurred through natural selection. The rate of emergence of new forms is related to the life cycle over a lifetime.
    • Some organisms are better adapted to survive in a hostile environment than others.

    Mendel's experiments:

    • Gregor Johann Mendel (1822-1884) is known as the 'Father of Genetics'.
    • Mendel's experiments give us the mechanism for the inheritance of traits from one generation to the next.
    • Mendel combined his scientific and mathematical knowledge and was the first to keep track of individuals who exhibited a particular trait in each generation.
  • Question 25/50
    5 / -1

    The tendency of population to remain in genetic equilibrium may be disturbed by
    Solutions

    The correct answer is ​lack of random mating.

    Key Points

    • G.H. Hardy and Wilhelm Weinberg independently described the basic principle of population genetics that is known as the Hardy-Weinberg principle.
    • According to the Hardy-Weinberg principle, allele frequencies in a population are stable and constant from generation to generation.
    • The gene pool remains constant and is referred to as genetic equilibrium or Hardy-Weinberg equilibrium.
    • Gene pool - It is the total of all genes and alleles in a population.
    • Allele frequencies in a population will remain constant over generations only if the following conditions are met:
      • Lack of mutation
      • Lack of gene flow and gene migration
      • Random mating
      • Lack of natural selection, i.e., all genotypes reproduce equally.

    Therefore, the tendency of population to remain in genetic equilibrium may be disturbed by lack of random mating.

    Additional Information

    • Random mating refers to mating in a population that occur in proportion to their genotypic frequencies.
    • The equilibrium is also expressed as a mathematical equation: Sum of all allelic frequencies = 1
    • Therefore, p2 + q2 + 2pq = 1 where, 
      • p2 = frequency of homozygous dominant alleles
      • q2 = frequency of homozygous recessive alleles
      • 2pq = frequency of heterozygous alleles
  • Question 26/50
    5 / -1

    Which of the following primates were found 15 mya and was more man-like?

    1. Dryopithecus

    2. Ramapithecus

    Choose the correct code-

    Solutions

    The correct answer is Only 2.

    Explanation:

    • Ramapithecus are prehistoric primates that lived 15 million years ago.
    • Edward Lewis (1932) discovered a Ramapithecus fossil in the Shivalik Hills of India.
    • About 15 million years ago, Ramapithecus had some features like man, so it was more man-like.
    • There are a large number of hairs on Ramapithecus's body.
    • Ramapithecus is similar to chimpanzees and gorillas.
    • Their teeth are like modern men's.

    Additional InformationDryopithecus-

    • Dryopithecus lived 25 million years ago.
    • Dryopithecus has more features in common with apes than with humans, so it was more ape-like.
    • Dryopithecus had a large brain and ate soft fruits and leaves.
    • Their arms and legs are the same length.
  • Question 27/50
    5 / -1

    Which of the following is not the causal organism for ringworm
    Solutions

    Key Points

    Ringworm disease - 

    • Fungi belonging to the genera Microsporum, Trichophyton and Epidermophyton are responsible for ringworms.
    • Symptoms:
      • Dry, scaly lesions on various parts of the body such as skin, nails and scalp
      • Intense itching
    • Heat and moisture help the fungi grow within the lesion.
    • They usually infect the skin folds of the groin or between the toes.
    • Transmission - Ringworms are generally acquired from soil or by using towels, clothes or comb of infected individuals.

    Therefore, from the given options only Macrosporum is not the causal organism for ringworm.

    Additional InformationSome common diseases in man

    DiseaseCausal Organism
    TyphoidSalmonella typhi
    Pneumonia

    Streptococcus pneumoniae

    Haemophilus influenzae

    Common coldRhino virus
    Malaria

    Plasmodium vivax

    P. falciparum

    P. malariae

    AmoebiasisEntamoeba histolytica
    AscariasisAscaris
    Filariasis/ Elephantiasis

    Wuchereria bancrofti

    W. malayi

    Ringworms

    Microsporum

    Trichophyton

    Epidermophyton

     

  • Question 28/50
    5 / -1

    HIV cause reduction in ______ in AIDS patients
    Solutions

    Key Points

    • AIDS stands for Acquired Immuno Deficiency Syndrome
    • It is caused by the Human Immunodeficiency Virus (HIV), a member of a group of viruses called retrovirus.
    • It is an RNA virus and carries reverse transcriptase.
    • Virus enters macrophages through T4 receptor site and causes infection.
    • ​This attack on T-lymphocytes destroys them and reduces their number.
    • This cycle continues and leads to a decrease in T-lymphocytes in infected persons.
    • These events lead to a decrease in the immunity of the infected person.

    Steps in HIV infection and establishment of AIDS - 

  • Question 29/50
    5 / -1

    Transplantation of tissues/organs to certain patients often fail due to rejection of such tissues/organs by the patient. Which type of immune response is responsible for such rejections?
    Solutions

    Concept:

    • A graft is a tissue or organ of foreign origin.
    • A graft is received from another individual usually who is called a donor.
    • The body can recognize self and non-self cells (foreign cells).
    • That is why it is very important to look for a proper match before organ donation.
    • Donor cells can be recognized by the and the graft can be attacked by the immune system.
    • So, tissue matching and blood group matching are essential before undertaking any graft/transplant.
    • The patient has to take immunosuppressants throughout their life.
    • This type of immunity is conferred by cell-mediated immunity.
    • T-lymphocyte cells mediate this immunity.

    Key Points

    • Cell-mediated immunity does not produce antibodies.
    • The T-lymphocytes can recognize antigens of a foreign cell.
    • T-lymphocytes themselves latch onto foreign cells.
    • This initiates the destruction of non-self cells.

    Additional Information

    1.  Auto-immune response
      • Sometimes due to malfunction of the immune system T-cells misidentify self cells as non-self or foreign.
      • They lead to the destruction of self-cells called auto-immune responses.
    2. Humoral Immune response
      • The humoral immune response produces antibodies against antigens.
      • B-lymphocytes do not latch onto the foreign cells but produce antibodies against them.
      • Antibodies produced by them have a variable region that can recognize and attach to the foreign cell.
      • This initiates the destruction of foreign cells.
    3. Physiological Immune Response
      • Physiological responses to infection are inflammation and increase in body temperature.
      • They also include the production of more mucus, saliva, stomach acid, etc., to eliminate the infectious agent.
  • Question 30/50
    5 / -1

    The antibodies produced during allergy are
    Solutions

    Key Points

    Antibodies

    • Antibodies are a specific types of proteins produced by B-cells against antigens.
    • Each antibody is made up of four peptide chains.
    • Two small chains are called light chains and two longer chains are called heavy chains.
    • Both chains are joined by disulfide bond. 
    • They also have specific antigen-binding sites at the N-terminal of the peptide chains.
    • The antibodies have the ability to recognize the antigens and eliminate them.
    • They also recognize the cancerous cells, pathogen-infected cells, cells from grafts, etc.
    • IgA, IgM, IgE, IgG are the different types of antibodies produced in our body.

    Allergy -

    • The exaggerated response of our immune system to certain allergens is called allergy.
    • Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.
    • The antibodies produced by the immune system against allergens are IgE type.

    Important Points

    • Different individuals have allergies to different substances making it an unusual type of reaction.
    • Causes - Allergies may be caused by dust mites, pollens, and even some food.
    • Symptoms -
      • Sneezing
      • Watery eyes
      • Runny nose
      • Difficulty in breathing
    • Treatment - Anti-histamine drugs, adrenaline and steroids help in reducing the symptoms.
  • Question 31/50
    5 / -1

    Hybridization for the process of crop improvement can be ____________
    Solutions

    The correct answer is All the above.
    Explanation-

    • Crop improvement can give a good yield
    • Varieties or strains of crops can be selected by breeding for various useful characteristics such as disease resistance, response to fertilizers, product quality, and high yields. 
    • Hybridization is one of the ways of obtaining desirable characters into crop varieties.
    • The hybridization process in plants is Hybridization between the parents is done to produce hybrids that are genetically combined to give desired characters in one plant. 
    • In simple words, Hybridization refers to crossing between genetically dissimilar plants.

    This Hybridization crossing is are of three types-

    • Intervarietal Hybridization-
      • When the crossing occurs between different varieties of plants, it is known as intervarietal hybridization.
    • Interspecific Hybridization-
      • When the crossing occurs between two different species of the same genus of plants, it is known as interspecific Hybridization.
    • Intergeneric Hybridization-
      • When the crossing occurs between different genera of plants, it is known as Intergeneric Hybridization.

    Another way of improving the crop is by introducing a gene that would provide the desired characteristic. This results in genetically modified crops.

  • Question 32/50
    5 / -1

    The process of selecting parents for obtaining special characters in their offspring is called:
    Solutions

    The correct answer is Selective Breeding.

    Key Points

    • Selective Breeding:
      • The process of selecting parents for obtaining special characters in their offspring is called selective breeding.
      • In this animals or plants with commercially useful traits are selected, the others are rejected.
      • It is the first step in any genetic hybridization technique.

    Additional Information

    • Hybridisation:
      • Hybridization means mixing.
      • In genetic terms, hybridization means the mixing of parents to produce superior offspring.
      • The parents used, get selected by selective breeding.
    • Mutation:
      • A Mutation is a phenomenon that results in the alteration of DNA sequences.
      • It consequently results in changes in the genotype and the phenotype of an organism.
    • Cloning:
      • Cloning is the process of producing genetically as well as morphologically similar offspring.
      • The offspring produced are called clones.
  • Question 33/50
    5 / -1

    Which one of the following impurities is easiest to remove from wastewater
    Solutions

    Key Points

    • Before disposal, sewage is treated in sewage treatment plants (STPs) to make it less polluting.
    • First, there is a physical treatment to remove small and large particles.
    • Then the BOD of the sewage is decreased by microbial treatment.
    • A mere 0.1 percent impurities make domestic sewage unfit for human use.
    • There are three components of waste - 
      • Suspended solids e.g., sand, silt, and clay 
      • Colloidal wastee.g., fecal matter, bacteria, cloth, and paper fibers
      • Dissolved materialse.g., nitrates, phosphates, and other nutrients, and toxic metal ions
    • Suspended solids which are removed by physical treatment are relatively easy to remove.
    • These particles can be removed by sequential filtration and sedimentation processes.
    • Dissolved salts such as nitrates, phosphates, and other nutrients, and toxic metal ions and organic compounds are most difficult to remove.

    Therefore, suspended solids are the impurities that are easiest to remove from wastewater.

    Additional Information

    • The organic matter in sewage can only be removed by secondary treatment, which is a biological treatment.
    • It utilizes aerobic and anaerobic microbes which can use up the organic matter for their energy production.
    • This reduces the BOD of the sewage, making it suitable to be discharged into water bodies.
  • Question 34/50
    5 / -1

    Which of the following biofertilizer is added in rice fields?
    Solutions

    The correct answer is Blue green algae.

    Key Points

    • Bio-Fertilizers and Their Use in Agriculture:-
      • For a sustainable agriculture system, it is essential to use renewable inputs (fertilizer, pesticides, water etc.) which can benefit the plant and cause no or minimal damage to the environment.
      • One of the energy-efficient and pollution-free methods is to exploit the ability of certain microorganisms like bacteria, algae, and fungi to fix atmospheric nitrogen, solubilize phosphorus, decompose organic material or oxidize sulphur in the soil.
      • When they are applied to the soil, they enhance the growth and yield of crops, improve soil fertility and reduce pollution. They are known as “biofertilizers”.
    • Blue-green algae:-
      • Blue-green algae (BGA or cyanobacteria) like Nostoc and Anabaena are free-living photosynthetic organisms also capable of fixing atmospheric nitrogen.
      • In the flooded rice fields blue-green algae serve as a nitrogen biofertilizer.
  • Question 35/50
    5 / -1

    Which one of the following is not required for DNA-cloning?
    Solutions

    The correct answer is Methylases.

    • Methylases are not required for DNA-cloning.

    Key Points  

    • Methylases add methyl groups (—CH3) to adenine or cytosine bases within the recognition sequence, which is thus modified and protected from the endonuclease.
    • DNA ligase is an enzyme that can connect two strands of DNA together by forming a bond between the phosphate group of one strand and the deoxyribose group on another. It is used in cells to join together the Okazaki fragments which are formed on the lagging strand during DNA replication.
    • A cloning vector is a piece of DNA that can be stably maintained in an organism, and into which a foreign DNA fragment can be inserted for cloning purposes.
  • Question 36/50
    5 / -1

    Small circular DNA molecules that are capable of self-replication are called
    Solutions

    The correct answer is Plasmid.

    • Plasmids are small circular DNA molecules that are capable of self-replication.
    • These are extrachromosomal DNA molecules within a cell that is physically separated from chromosomal DNA.
    • They are most commonly found as small circular, double-stranded DNA molecules in bacteria.
    • Sometimes, they are also found in archaea and eukaryotic organisms.

  • Question 37/50
    5 / -1

    ‘RNA interference (RNAi)’ technology has gained popularity in the last few years. Why?

    1. It is used in developing gene silencing therapies.

    2. It can be used in developing therapies for the treatment of cancer.

    3. It can be used to develop hormone replacement therapies.

    4. It can be used to produce crop plants that are resistant to viral pathogens.

    Select the correct answer using the code given below.

    Solutions

    The correct answer 1, 2 and 4.

    Key Points

    • Statement 3 is absurd. Rest of them are correct.
    • RNA interference (RNAi) is a biological process in which
      RNA molecules inhibit gene expression or translation. Hence, Statement 1 is correct.
    • Since the discovery of RNAi and its regulatory potentials, it has become evident that RNAi has immense potential in
      suppression of desired genes (gene silencing). Hence, Statement 2 is correct.
    • Numerous studies have demonstrated that RNAi can provide a
      more specific approach to inhibit tumor growth by targeting
      cancer-related genes (i.e., oncogene).
    • RNAi has resulted in the invention of novel crops such as
      nicotine-free tobacco, decaffeinated coffee, nutrient fortified
      vegetation, and hypoallergenic crops. Hence, Statement 4 is correct.
    • The genetically-engineered Arctic apples received FDA approval in 2015.
  • Question 38/50
    5 / -1

    Genetically modified (GM) crops contain modified genetic material due to:

    1. Introduction of new DNA

    2. Removal of existing DNA

    3. Introduction of RNA

    4. Introduction of new traits

    Select the correct answer using the code given below:
    Solutions

    The correct answer is Option 4, i.e 1, 2 and 4.

    • When the DNA of a plant had been modified using genetic engineering methods, it is called Genetically modified crops.
    • It is widely used to make crops resistant to certain pests and disease.
    • It is also used to improve nutrition value in a crop.
    • Insect-resistant crops contain genes from the soil bacterium Bacillus thuringiensis.
    • GM crops are sometimes discouraged to consume due to the following potential threats: an allergic reaction (allergenicity), gene transfer and outcrossing.
    • Genetically modified (GM) crops contain modified genetic material due to introduction of DNA by removing the existing DNA, resulting in the change in traits.
  • Question 39/50
    5 / -1

    Consider the following statements regarding Genetically modified hormones

    1. This technique enabled us to isolate any genes from any source in a pure form, and to move them from one cell to another.

    2. We can produce viral and bacterial antigens of various types of cells by this method.

    Select the correct answer using the code given below:
    Solutions

    Genetic engineering (recombinant DNA technology) revolution in molecular biology has enabled us to isolate any genes from any source in a pure form, and to move them from one cell to another.

    • It has become possible to program bacterial or yeast cells with foreign genes and force the new host to produce commercially valuable proteins (e.g. hormones, enzymes, diagnostic reagents).
    • It is now also possible to produce viral and bacterial antigens in various types of cells. We hope that this will soon enable us to manufacture vaccines cheaply.
    • The production of a foot-and-mouth-disease virus vaccine, the first promising example of a genetically engineered effective vaccine--has recently been reported.
    • Expression of hepatitis B surface antigen, influenza virus haemagglutinin and polio-virus proteins from the cloned genes have also been reported, and many more viral genes have been cloned although not yet expressed in bacteria.
    • Despite the extremely rapid development, there are a number of problems, both technical and immunological, which have to be extensively studied and eventually solved, before we can hope to obtain effective and safe genetically engineered viral vaccines for clinical use
    • All vaccines are genetically modified in a way. A gene may be programmed to produce an antiviral protein in a bacterial cell.
    • Once sealed into the DNA, the bacteria is now effectively re-programmed to replicate this new antiviral protein.
    • Recombinant engineered vaccines are being extensively explored, especially to eradicate infectious diseases, allergies, and cancers.
    • Protocols for genetically engineered vaccines raise issues on their efficacy and overall benefit
    • In medicine, genetic engineering has been used to mass-produce insulin, human growth hormones, follistim (for treating infertility), human albumin, monoclonal antibodies, antihemophilic factors, vaccines,and many other drugs.
    • Vaccination generally involves injecting weak live, killed, or inactivated forms of viruses or their toxins into the person being immunized.
    Genetically engineered viruses are being developed that can still confer immunity, but lack the infectious sequences. Mouse hybridomas, cells fused together to create monoclonal antibodies have been humanised through genetic engineering to create human monoclonal antibodies.
  • Question 40/50
    5 / -1

    The drug produced through biotechnology for cancer treatment is
    Solutions

    The correct answer is Interferon.

    Key Points

    • Interferon drugs produced through biotechnology for cancer treatment.
    • Interferons are a group of signaling proteins made and released by host cells in response to the presence of several viruses.
    • In a typical scenario,  it is a virus-infected cell that releases interferons which causes nearby cells to heighten their anti-viral defenses.

    Important Points

    • Interferons are categorized as cytokines, small proteins that are involved in intercellular signaling.
    • They are secreted by cells in response to stimulation by a virus or other foreign substance, but it does not directly inhibit the virus’s multiplication
    • They were discovered in 1957 by British bacteriologist Alick Isaacs and Swiss microbiologist Jean Lindenmann.
    • In the 1980s alpha-interferon came into use, in low doses, to treat hairy-cell leukemia (a rare form of blood cancer) and, in higher doses, to combat Kaposi sarcoma, which frequently appears in AIDS patients.

    Additional Information

     

    DrugsDescription
    H.G.H.Growth hormone (GH) or somatotropin, also known as human growth hormones (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals.
    T.S.H.TSH stands for thyroid-stimulating hormone. A TSH test is a blood test that measures this hormone. The thyroid is a small, butterfly-shaped gland located near your throat.
    InsulinInsulin is a hormone created by your pancreas that controls the amount of glucose in your bloodstream at any given moment. It also helps store glucose in your liver, fat, and muscles.
  • Question 41/50
    5 / -1

    Carrying capacity of a population is determined by
    Solutions

    Concept:

    • Growth of a population depends on the resources available.
    • Population growth can be explained by various growth models.
    • Growth models help us understand if the growth of any population over time follows a particular pattern or not.
    • This also helps us to understand several other attributes of the population.
    • Growth models explain 2 types of growth curves:
      • Exponential - This takes place when the resources are unlimited and the population keeps growing.
      • Logistic - This is a growth model that takes the limitations of resources into account.

    Key Points

    • Ideally if the resources in a habitat are unlimited, the population shows exponential growth pattern.
    • But resources are not available to any species population in unlimited amount.
    • Thus, the species compete for the available resources to survive.
    • This competition for the limited resources restricts the exponential or unlimited growth of any population.
    • Any given habitat can only provide resources to support a maximum possible number, beyond which it further growth of population is not possible.
    • This is known as the carrying capacity (K) for a particular species in a habitat.
    • The maximum number of individuals or the carrying capacity that can be sustained by a habitat depends on the available resources.

    Therefore, the carrying capacity of a population is determined by its limiting resource.

    Additional Information

    • Carrying capacity is an important factor in logistic growth patterns of populations.

    Logistic growth is represented as:

    dNdt=rN(KNK)

    where, N = Population Density,

    K = Carrying Capacity,

    r = Intrinsic rate of natural increase

    dNdt = Rate of change of population density.

    • 'r' value denotes the difference between the per capita birth and death (b-d).
    • The environmental resistance is represented in the equation as (KNK).

  • Question 42/50
    5 / -1

    The geographic limit within which a population exists is called
    Solutions

    Concept:

    • Habitat is the natural home or environment where an organism lives.
    • It is the selection of resources, biotic and abiotic factors present in an area suitable for organisms who live there.
    • For a particular animal, its habitat will be where it can find everything it needs to locate and gather food, select a mate, and successfully reproduce.
    • habitat is the geographical limit within which a population is found.

    Important Points

    • Any organism is only suited to survive in their own particular habitat.
    • Outside their habitat they cannot find food, the temperature may be unsuitable, can face competition, will not be able to find mating partnersetc.
    • For example, a polar bear is only found in the extremely cold temperature of the poles and are carnivores who usually feed on fish.
    • If you put them in the desert, their fur will make them feel extremely hot, and will not be able to find any food and eventually die.
    • So a polar bear is limited to the cold icy regions, that is its geographical limit.
    • Hence a population of polar bears is limited to the polar region, which is its habitat and can not survive elsewhere.

    Key Points

    • Niche - 
      • Many organisms live together in the same habitat which can cause competition among them.
      • So, each species develops its own niche to avoid competition.
      • Niche is the function of a species, the role it plays in a habitat.
      • Niche is a defined physical condition, particular kind of resources, and distinct functional role in the habitat for each organism.
      • Physical conditions like time of foraging, optimum temperature, water required, etc., and resources needed are different from any other organism in the same habitat.
    • Ecosystem - 
      • An ecosystem consists of all the organisms and the physical environment with which they interact.
      • E.g. - lake ecosystem, forest ecosystem.
    • Biome -
      • It​ comprises a variety of habitats and consist of many communities.
      • They are formed in response to a shared climatee.g., tropical biome, desert.
  • Question 43/50
    5 / -1

    In a grassland ecosystem, the population of
    Solutions
    Key Points
    • Trophic system refers to the system in which energy flows from one trophic level to another.
    • Trophic level is the specific place in the food chain that is occupied by an organism based on their source of food.
    • In an ecosystem, the trophic level starts with a producer and is succeeded by different levels of consumers.
    • The organisms may be classified into different categories according to their feeding order:
      • Producers - synthesize food from solar energy. This covers all photosynthesizing plants and algae.
      • Primary consumers - come immediately after producers and comprise herbivores that feed on the producers directly.
      • Secondary consumers - feed on primary consumers and hence comprise of carnivores.
      • Tertiary consumers - feed on secondary consumers and are also carnivores.
      • Decomposers - break down dead, decaying organisms into simpler inorganic substances. E.g. - Fungi.

    Explanation:

    • In a grassland ecosystem, a typical food chain can be represented as: Grass → Deer → Lion
    • Here:
      • Grass - Producer
      • Deer - Primary consumer
      • Lion - Secondary consumer
    • The graphical representation of the trophic levels can be done by ecological pyramids.
    • These pyramids can be upright (base broader than top), inverted (top broader than base) or variable in shape.
    • The number of individuals or population of each trophic level is represented as the pyramid of number.
    • For a grassland ecosystem, the pyramid of number is always upright.
    • Therefore, we can say that the population of primary producers is more than that of primary consumers.

  • Question 44/50
    5 / -1

    Which of the following is a source of energy to an ecosystem
    Solutions

    Concept:

    • Producers are organisms that have the ability to capture energy from the environment and convert it into biomass and ATP.
    • The primary producer in all terrestrial systems are plants.
    • They capture the energy from the sun to produce their own food.
    • The roots uptake inorganic nutrients.
    • Energy from the sun is utilized to form biomass and other energy-storing compounds from the inorganic nutrients.

    Key Points

    • Solar energy is the source of energy for all ecosystems except the ones on the sea floor.
    • This solar energy is used by plants to produce ATP. 
    • ATP is produced and used for other metabolic processes such as respiration and translocation.
    • Some of the energy from the sun is also stored as sugar and other carbohydrates.
    • At night or in absence of long sunny days, plants can use the energy stored in the chemical bonds of sugar molecules.
    • The sugar is broken down via respiration and ATP is produced.
    • The process of respiration is exothermic.
    • Energy is released in the form of heat during the production of ATP by the breakdown of sugar molecules during respiration.
    • ATP and sugar molecules can also provide energy but they are made only if solar energy is present.
    • In absence of solar energy, sugar and ATP cannot be produced and as a result, respiration cannot happen.

    Hence solar energy is the source of energy for an ecosystem.

  • Question 45/50
    5 / -1

    In which of the following cycle does the reservoir of the nutrient exist in the Earth's crust?
    Solutions

    Concept:

    • Organisms need a constant supply of nutrients for various metabolic activities.
    • The nutrient amount varies in different ecosystems and also due to seasonal variations.
    • The amount of nutrients present in the soil at any given point of time is known as the standing state.
    • Though variable, but nutrients are never lost from the ecosystem.
    • This is due to the process of nutrient cycling, which refers to the movement of nutrient elements through the different components of the ecosystem.
    • They are also known as biogeochemical cycles.
    • The rate of release of nutrients into the atmosphere is controlled by environmental factors like soil, moisture, pH and temperature.

    Important Points

    Phosphorus Cycle -

    • It is a sedimentary type of biogeochemical cycle.
    • Phosphates in the rocks are the main reservoir for this biogeochemical cycle.
    • The function of these reservoirs is to meet the deficit that might be caused due to imbalance in the rate of influx and efflux.
    • Here gaseous exchange of phosphorus between organisms and the environment is negligible.

    Additional Information

    Types of biogeochemical cycles - 

    • Gaseous -
      • These include the nitrogen and carbon cycles.
      • The main reservoir for these cycles is in the atmosphere.
    • Sedimentary -
      • These include the sulphur and phosphorus cycles.
      • Their reservoir is in the Earth's crust.
  • Question 46/50
    5 / -1

    Which of the following statement is correct
    Solutions
    Key Points
    • Parthenium is an endemic species of our country - INCORRECT
      • ​Parthenium is an invasive or exotic species for our country.
      • Invasive species are those species that have been introduced into a habitat where it was not naturally found.
      • Endemic species refers to a species that is confined to a particular area and is not found elsewhere in the world.
      • Parthenium is a shrub that grows aggressively in our country as an invasive species.
    • African catfish is not a threat to indigenous catfishes - INCORRECT
      • ​African catfish (Clarias gariepinus) is also an invasive species that has been illegally introduced in our country for aquaculture.
      • This species is a threat to the indigenous catfishes in our rivers.
    • ​Steller's sea cow is an extinct animal - CORRECT
      • ​Stellar's sea cow is an extinct animal species from Russia.
      • It got extinct due to overexploitation by humans.
    • ​Lantana is popularly known as carrot grass - INCORRECT
      • Parthenium is popularly known as carrot grass.
      • Lantana is another invasive species in our country.

    Additional Information

    Major causes for loss of biodiversity:

    • Habitat loss and fragmentation - Loss of habitat of several species have occurred due to deforestation and pollution.
    • Overexploitation - Overuse and overharvesting of species has led to extinctions of many species.
    • Invasive species - Exotic species become invasive as they survive better in the absence of their natural competitors/predators.
    • Coextinctions - The species that live in obligatory associations face the same threats of extinction.
  • Question 47/50
    5 / -1

    Wildlife conservation means the protection and preservation of
    Solutions

    Key Points

    • Wildlife conservation is the strategy to protect wild plant and animal species and their habitats. 
    • It aims to maintain healthy wildlife species or populations and to restore, protect or enhance natural ecosystems.
    • Wildlife consists of any animal living in wild.
    • Wild consists of non domesticated plants and animals like lion, tiger, bear, etc.

    Hence option 4) is correct.

    Important Points

    Any conservation effort for a species can be in-situ or ex-situ:

    1. In-situ - conserving the species in its own habitat, e.g., biodiversity hotspots, national parks, animal reserves.
    2. Ex-situ - conserving the species outside its habitat, e.g., zoos, germplasm banks.
    • Wildlife conservation methods are generally in-situ and are protected in national parks, biosphere reserves, wildlife sanctuaries, etc.
    • They are also maintained in zoos, for education purposes and for those animals who are not strong enough to survive in the wild.
  • Question 48/50
    5 / -1

    The high amount of E. coli in water is the indicator of
    Solutions

    Concept:

    • Escherichia coli is a microorganism that is found in the animal's intestine.
    • After digestion, some of it is passed into feces.
    • One of the major components of sewage waste is animal excreta.
    • Therefore, presence of E. coli in water indicates that presence of fecal matter in that water.
    • Thus, it shows water pollution due to human feces and sewage pollution.

    So, a high amount of E. coli presence indicates sewage pollution in the water.

    Additional Information

    • Hardness of water is indicated by the mineral ions concentration, mostly calcium and magnesium ions.
    • Industrial pollution is indicated by the presence of heavy , toxins, petrochemicals, cyanotoxinsetc.
    • Chlorine in the form of bleaching powder is added for the treatment or purification of water.
  • Question 49/50
    5 / -1

    Which one of the following is not an air pollutant
    Solutions

    Key Points

    • Air pollutants are any gas, solid, or liquid suspended in the air that reduce the quality of air.
    • They make the air harmful to humans, animals, and plants.
    • The major air pollutants include
      • suspended particles
      • ground-level ozone
      • carbon monoxide
      • sulfur dioxide
      • nitrogen dioxide
      • lead

    Important Points

    PollutantCharacters
    Pollen from plants
    • Are very small particles that suspend in the air
    • cause allergies
    • can be considered pollutants if the quantity is large
    • not major pollutants
    Phosphates
    • Not listed as air pollutants
    • Usually released by industries engaged in phosphate fertilizer production
    • Majorly cause water pollution, algal bloom, and eutrophication
    Carbon monoxide
    • from emissions by fossil fuel burning and vehicles
    • harmful when breathed in because it displaces oxygen in the blood
    Hydrocarbons
    • Produced due to incomplete combustion of fuels 
    • released by vehicles

     

  • Question 50/50
    5 / -1

    This is a non biodegradable pollutant
    Solutions

    Key Points

    • Non-biodegradable pollutants
      • Non-biodegradable pollutants CANNOT be broken down into simpler, harmless substances in nature.
      • The bacteria and other microorganisms do not have any enzyme to degrade them.
      • They stay in the environment for a very long time and do not degrade and cause pollution.
      • Example - plastics, insecticides, pesticides, mercury, lead, arsenic, synthetic fibers, glass objects.
    • Lead vapor is one such non-biodegradable pollutant.
    • Lead vapors enter the environment through smelters, mining operations, waste incinerators, battery recycling, etc.
    • It was a very big problem in the past when lead was added to fuel used by vehicles and caused a lot of damage to the environment and human health.

    Additional Information

    • Biodegradable pollutants
      • Biodegradable pollutants which CAN be broken down into simpler, harmless, substances in nature.
      • This is done by the action of  micro-organisms like certain bacteria and some fungi called decomposers.
      • Example - domestic wastes (garbage), sewage, agriculture waste, cattle dung.
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