Biology: CUET Mock Test - 4 - CUET MCQ

1. Vascular strand (A): correct

   • Contains vascular tissues (xylem & phloem) that supply nutrients and water to the anther.

   • Essential for the development and function of the anther.

• B: Parenchyma – While some parenchyma cells may be present, it is not the defining feature.

• C: Spongy cells – Found in leaf mesophyll, not in the connective.

• D: Corolla – Refers to the petals of a flower, unrelated to the connective.

Key Points

• Wings of a butterfly and wings of a bird are not an example of homology but rather an example of analogy. This is because, while both serve the same function of flight, they do not share a common evolutionary origin. The butterfly's wings are made of chitin and develop from the exoskeleton, whereas bird wings are made of feathers that develop from the skin.

Additional Information

• Forelimbs of a whale and forelimbs of a cheetah are examples of homology, indicating a common evolutionary ancestor, despite their different current functions.
• Forelimbs of humans and forelimbs of whales also share a common evolutionary origin, highlighting structural similarities despite different functions, making them homologous.
• The thorn of Bougainvillia and tendril of Cucurbita, despite serving different functions, are considered homologous structures as they both originate from the same part of the plant.

• (A) Correct : Invertebrates (e.g., sponges, jellyfish, worms) appeared around 600–500 million years ago (mya) during the Cambrian explosion (~541 mya), a period of rapid diversification. The statement’s timeline (~500 mya) is broadly accurate, though slightly late, as early invertebrates predate this.
• (B) Correct. Jawless fish (agnathans, e.g., lamprey-like organisms) evolved around 400–350 mya during the Devonian period, often called the “Age of Fishes.” The 350 mya estimate aligns with fossil records.
• (C) Incorrect or misleading. “Sea weeds” likely refers to multicellular algae or primitive aquatic plants. Algae (e.g., cyanobacteria, green algae) existed over 1 billion years ago, and multicellular algae were present by ~600 mya. Land plants evolved ~470 mya, so stating “sea weeds existed around 400 mya” is misleading, as they existed much earlier.
• (D) Incorrect. Dinosaurs went extinct ~66 mya (not 100 mya) due to a mass extinction event (likely an asteroid impact) at the Cretaceous-Paleogene boundary, as evidenced by the Chicxulub crater and fossil records.

The primary lymphoid organ is the Thymus.

Key Points

• The Thymus is a primary lymphoid organ where T lymphocytes (T cells) mature. T cells are essential for adaptive immunity.
• Primary lymphoid organs are where lymphocytes are formed and mature. This includes the bone marrow and the thymus.

Additional Information

• The Spleen is a secondary lymphoid organ, involved in filtering blood and responding to systemic infections.
• Tonsils are part of the mucosa-associated lymphoid tissue (MALT) and play a role in protecting the body from pathogens entering through the mouth or nose.
• The Appendix, like tonsils, is part of the gut-associated lymphoid tissue (GALT) and contributes to immunity.
• Secondary lymphoid organs, such as the spleen, tonsils, and appendix, are where mature lymphocytes interact with antigens and initiate adaptive immune responses.

Vaccination is not used as a direct treatment for cancer. While vaccines like the HPV vaccine can prevent certain types of cancer by targeting the viruses that cause them, vaccination itself is not a treatment method for existing cancer.

Key Points

• Radiation therapy uses high doses of radiation to kill cancer cells and shrink tumors. It's a common treatment for various types of cancer.
• Immunotherapy is a type of cancer treatment that helps your immune system fight cancer. It has become a crucial part of treating some types of cancer.
• Surgery is often used to remove cancerous tumors or tissues. It's one of the oldest forms of cancer treatment and can be effective in many cases.

Additional Information

While vaccines can play a role in preventing certain cancers, they are not used to treat cancer that has already developed. Instead, treatments like radiation therapy, immunotherapy, and surgery are utilized to directly target and treat cancer.

Key Points

• The 'cry' gene produces the cry protein, which is also known as the Bt-toxin.
• It is present in the bacterium Bacillus thuringiensis.
• This toxin is effective in killing insects like -
  • Lepidopterans - Tobacco budworm, armyworm.
  • Coleopterans - Beetles.
  • Dipterans - Flies, mosquitoes

Mechanism of Action of Cry protein -

• The bacteria produce crystals containing insecticidal Cry proteins during a particular growth phase.
• The protein exists in the inactive protoxin form in the bacteria.
• It gets activated in the alkaline gut of insects, where the crystals get solubilized.
• This releases the active toxin, which binds to the midgut epithelial cells of insects.
• This creates pores causing cell swelling and lysis, that leads to the death of the insect.

Explanation:

• The cry genes produce insect-group specific toxins and thus can be introduced into crop plant genomes to make them pest-resistant.
• There are different forms of cry genes that are effective only against a specific insect pest.
• Example -
  • cryIAb - effective against corn borers.
  • cryIAc, cryIIAb - effective against cotton bollworms.

Hence, the correct answer is option 1.

Concept:

• 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.

Important PointsExponential Growth -

• Growth of a population depends on the resources available.
• Therefore, ideally if the resources in a habitat are unlimited, the growth in also unlimited.
• Such cases where the population keeps growing exponentially is known as exponential growth.
• As observed by Darwin, with unlimited resources the species are able to realize their full growth potential.
• This results in an increased reproductive ability leading to exponential growth of the population.

It can be denoted by the equation:

where, N = Population Density,

= Rate of change of population density.

• Here, 'r' represents the intrinsic rate of natural increase, which is the difference between the per capita birth and death (b-d).
• The 'r' value varies from population to population:
  • Norway rat - 0.015
  • Flour beetle - 0.12
  • Human population in India (1981) - 0.0205
• When the population density (N) is plotted against time (t), it produces a J-shaped curve for exponential or geometric growth.

Additional InformationThe integral form of the above equation is:
N_t = N₀e^rt  
where, N_t = Population density after time 't'
N₀ = Population density at time 0 (zero)
e = Base of natural log (2.71828)
r = Intrinsic rate of natural increase

The correct answer is Mast cells

• The cells that release histamine and other vasoactive substances in response to allergens are mast cells.
• Mast cells are a type of white blood cell that is found in connective tissue and mucous membranes.
• When allergens bind to IgE antibodies attached to the surface of mast cells, it triggers the release of histamine, leukotrienes, prostaglandins, and other vasoactive substances.
• These substances cause inflammation, vasodilation, bronchoconstriction, and other symptoms associated with allergic reactions.

Additional Information

• Neutrophils: Neutrophils are a type of white blood cell that plays a key role in the body's immune response to infections. They are primarily involved in phagocytosis, which is the process of engulfing and destroying pathogens like bacteria and fungi. While neutrophils are important in fighting infections, they are not typically involved in allergic reactions or the release of histamine.
• Macrophages: Macrophages are another type of white blood cell that is involved in the immune response. They function by engulfing and digesting cellular debris, pathogens, and other foreign substances. Macrophages also play a role in presenting antigens to other immune cells to initiate an immune response.
• NK cells: NK cells, or natural killer cells, are a type of lymphocyte that plays a role in the innate immune response against infected or abnormal cells, such as cancer cells. NK cells recognize and destroy these abnormal cells through a process called cytotoxicity.

Conclusion:
Cells that release histamine and other vasoactive substances in response to allergens are Mast cells.

Key Points

• DNA was discovered by Friedrich Meischer (1869) as an acidic substance present in the nucleus.
• By 1926, the search for genetic material was already narrowed down to the chromosomes present in the nucleus.
• But the molecule acting as the genetic material was yet to be determined.
• Frederick Griffith (1928) conducted a series of experiments with Streptococcus pneumoniae in search for the genetic material.
• He found that S. pneumoniae produced 2 types of strains when grown in culture medium:
  • S strain- produced smooth shiny colonies because of a mucous polysaccharide coating.
  • R strain- produced rough colonies that lacked the mucous coating.

Experiment:

Observations:

• Mice injected with S-strain died of pneumonia infection, while mice injected with R-strain did not.
• Therefore, S-strain was the virulent (infectious) form.
• Heat-killed S-strain bacteria did not cause any infection, so the mice lived.
• When heat-killed S-strain bacteria were injected along with R-strain, the mice died and live S-strain bacteria were recovered from the dead mice.

Conclusions:

• From the above observations, Griffith concluded that R-strain had somehow been "transformed" by the heat-killed S-strain to become virulent.
• Some substance was transferred from the heat-killed S-strain to the R-strain that enabled the R-strain bacteria to produce the mucous coating and become virulent.
• This substance was named as the 'transforming principle'.

Drawback:

• The biochemical nature of the genetic material could not be defined.

According to WHO, reproductive health includes not just physical well-being but also emotional and social aspects related to reproduction.

The RCH program focuses on increasing awareness, providing medical facilities, and improving reproductive well-being in society.

Sex education in schools helps young individuals understand reproductive health, dispel myths, and adopt safe reproductive practices.

Reproductive health programs improve medical care, leading to better maternal and infant health outcomes.

(A) Correct: The Hershey-Chase experiment demonstrated that DNA, not protein, is the genetic material.
(B) Correct: The RNA world hypothesis suggests that RNA was the first genetic material in the early stages of life.
(C) Incorrect: The lac operon is regulated by both positive and negative regulation.
(D) Correct: Translation begins at the start codon (AUG) in eukaryotes.
(E) Incorrect: In eukaryotes, transcription occurs in the nucleus, and translation occurs in the cytoplasm, so they do not happen simultaneously.

(A) Correct: Charles Darwin proposed the theory of natural selection as the mechanism of evolution.
(B) Incorrect: Evolution can occur through gradual changes or sudden large mutations (saltation).
(C) Correct: Fossils are crucial evidence of past life forms and their changes over time, supporting evolution.
(D) Correct: Adaptive radiation occurs when new species evolve from a common ancestor to occupy different ecological niches.
(E) Incorrect: Genetic drift is random changes in allele frequency due to chance events, not natural selection.

(A) Incorrect: The theory of inheritance of acquired characteristics is part of Lamarck's theory of evolution.
(B) Correct: Natural selection favours the survival and reproduction of individuals with advantageous traits.
(C) Incorrect: Evolution can also occur through genetic recombination, genetic drift, and gene flow, not just mutations.
(D) Correct: Adaptive radiation occurs when organisms adapt to different ecological niches, often from a single ancestor.
(E) Correct: Genetic recombination creates genetic variation, which plays a critical role in evolutionary processes.

In the given figure, A is cervix, B is vagina, C is Uterus, D is urinary bladder, E is clitoris and F is vaginal orifice

Line in NCERT: "The female reproductive system consists of a pair of ovaries alongwith a pair of oviducts, uterus, cervix, vagina and the external genitalia located in pelvic region (Figure 2.3a)."

The incorrect option in the given table is:

Option (b) – "It changes a haploid structure into another haploid structure." (for Spermatogenesis)

Corrections:

• Spermatogenesis involves the conversion of a diploid spermatogonium into haploid spermatids via mitosis and meiosis. Thus, it is not a haploid-to-haploid process.

• Spermiogenesis (correct in the table) transforms a haploid spermatid into a haploid spermatozoon (mature sperm), which is accurate.

Why Other Options Are Correct:

• (a) Correctly defines spermatogenesis (formation of spermatozoa) and spermiogenesis (maturation of spermatid to spermatozoon).

• (c) Correctly states that spermatogenesis involves growth & divisions (mitosis/meiosis), while spermiogenesis involves only differentiation (no divisions).

• (d) Correctly notes that one spermatogonium yields four spermatozoa, while one spermatid forms one spermatozoon.

Final Answer:

Incorrect option: (b) 

• Parturition starts with the signal released by the fetus and the placenta.
• These act on the pituitary to release oxytocin.
• Oxytocin acts as a stimulant leading to contractions of the uterine muscles.
• The uterine contractions feedbacks to release more oxytocin from the pituitary.
• This results in more powerful contractions of the uterus until the baby is delivered in the process of parturition.

Antibiotics are chemical substances secreted by certain microbes which inhibit the growth and development of other microbes. Most of them produced by actinomycetes and filamentous fungi. Some inportant antibiotics are tetracycline, chloramphenicol, steptomycin etc.

• Methanogens produce methane.
• Fermentors are large vessels for growing microbes.
• Organic waste in water increase BOD.
• Biogas is methane rich fuel gas.

pBR322 was the first artificial cloning vector constructed in 1977 by Boliver and Rodriguez. It is widely used in gene cloning experiments. In pBR322 plasmid vector, p - denotes that it is a plasmid; BR - stands for Boliver and Rodriguez who constructed this plasmid; 322 - Is a number given to distinguish this plasmid from others developed in the same laboratory. E coli cloning vector pBR 322 has restriction sites {Hind III, Eco R I, Bam H l, SaI I, PvuI I, Pst I, Cla I), ori(origin of replication) and antibiotic resistance genes (amp^R and tet^R). rop codes for the proteins involved in the replication of the plasmid.

The sequence of the 5’ and 3’ primers for the given DNA sequence will be 5’ AATGC 3’, 5’ GACTC 3’. In primer design, the forward primer is derived directly from the start of the DNA sequence, which is 5’ AATGC 3’. The reverse primer is complementary to the end of the sequence, considering the antiparallel nature of DNA, resulting in 5’ GACTC 3’. This follows the standard method for designing primers, as discussed in PCR techniques and DNA replication processes.

Meloidogyne incognita infects the roots of tobacco plants and causes great reduction in yield. Fire and Mello (1998) invented a novel strategyt to prevent this infestation. It was based on the process of RNA interference.

Total number of plants (in the beginning ) = 30
New plants added by reproduction = 25
Birth rate (of a population)
= New plants / Total number of plants = 25/30
=0.83 individuals per lotus per year
Number of plants died =8
Death rate (of a population) = number of deaths /Total number of plants
= 8/30 = 0.26 individuals per lotus per year.

Solution:

The logistic growth curve is considered more realistic because it accounts for the limitations imposed by the environment, such as limited resources and carrying capacity. In contrast, the exponential growth curve assumes unlimited resources, which rarely occurs in nature. Therefore, Option B is the correct answer as it reflects more realistic conditions for population growth.

Topic in NCERT: Logistic Growth Model

Line in NCERT: "the logistic growth model is considered a more realistic one."

• Decomposition is the process by which decomposers breakdown complex organic matter into inorganic substances.
• The rate of decomposition is controlled by chemical composition of detritus and climatic factors. Decomposition is slower if detritus is rich in lignin and chitin and quicker, if detritus is rich in nitrogen and water soluble substances like sugars.

Topic in NCERT: Decomposition

Line in NCERT: "decomposition is largely an oxygen-requiring process. the rate of decomposition is controlled by chemical composition of detritus and climatic factors. in a particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars."

• A-II: Lion, a tertiary consumer.
• B-III: Wolf, as a secondary consumer.
• C-IV: Goat, a primary consumer.
• D-I: Grass, a primary producer.

To determine the correct statements, let's analyze each one:

- Statement i: Correct. India's share of global species diversity is indeed 8.1% while covering only 2.4% of the land area.

- Statement ii: Correct. The text states that nearly 45,000 species of plants and twice as many animals have been recorded; this means there are about 90,000 animal species documented.

- Statement iii: Correct. The text supports this claim by mentioning that only 22% of total species have been recorded globally.

- Statement iv: Incorrect. The text estimates that there are probably more than 100,000 plant species yet to be discovered, not less.