CUET UG Biology: Mock Test - 4 Free Online Test 2026

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.

Correct answer: (B)

• (A) Incorrect. The theory of inheritance of acquired characteristics is associated with Lamarck, not with Darwin.

• (B) Correct. Natural selection causes differential survival and reproduction of individuals with heritable traits that increase fitness in a given environment; those best adapted tend to leave more offspring.

• (C) Incorrect. New variation can arise by mutations, but evolutionary change can also occur via genetic recombination, genetic drift, and gene flow, not only mutations.

• (D) Correct. Adaptive radiation describes divergence of a lineage into multiple forms that occupy different ecological niches, producing distinct traits suited to those niches.

• (E) Correct. Genetic recombination during gametogenesis creates new combinations of alleles, increasing genetic variation among offspring and providing material on which evolutionary processes can act.

(B), (D) and (E) are the correct statements; choose option (B).

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