NEET Zoology - MCQ Practice Questions
Zoology in NEET is memory heavy but not memory only, because the diagram based and assertion reason questions need understanding. This set runs through human physiology, animal kingdom and classification, structural organisation, genetics and evolution, biotechnology, and ecology. Explanations point to the NCERT line the question came from, so revision stays anchored to the source text.
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Which of the following is the causative agent of Amoebiasis (Amoebic dysentery) in humans?
Understanding:
We need to identify the correct pathogen responsible for causing amoebiasis (amoebic dysentery) in humans.
Step 1: Identify each organism
Plasmodium vivax causes malaria, transmitted by female Anopheles mosquito.
Entamoeba histolytica is a protozoan parasite that lives in the large intestine and causes amoebiasis.
Trypanosoma brucei causes African sleeping sickness.
Giardia lamblia causes giardiasis, characterised by diarrhoea and malabsorption.
Step 2: Pathogenesis of Entamoeba histolytica
Entamoeba histolytica colonises the large intestine, produces flask-shaped ulcers in the intestinal mucosa, and causes symptoms like abdominal pain, cramps, and bloody mucous stools. It spreads via contaminated food and water (faeco-oral route).
Answer:
The causative agent of amoebiasis is Entamoeba histolytica.
Quick Tip:
Remember that the housefly (Musca domestica) acts as a mechanical carrier transmitting Entamoeba histolytica cysts from faeces to food — a common exam fact.
In the immune response, which type of immunity is provided by the secretion of antibodies by B lymphocytes against a pathogen?
Understanding:
We need to identify the type of immunity that involves antibody secretion by B lymphocytes.
Step 1: Classify types of adaptive immunity
Adaptive immunity has two major arms:
Step 2: Eliminate incorrect options
Innate non-specific immunity includes barriers like skin, mucus, and phagocytes — it does not involve B cells or antibodies.
Passive acquired immunity refers to receiving ready-made antibodies (e.g., from mother through placenta or colostrum), not the process of B cells secreting antibodies in response to a pathogen.
Step 3: Confirm correct answer
The secretion of antibodies by B lymphocytes in response to antigens constitutes humoral immunity, because antibodies circulate in body fluids (humor = fluid).
Answer:
The type of immunity involving antibody secretion by B lymphocytes is humoral immunity.
Quick Tip:
Humoral = antibody-mediated (B cells); Cell-mediated = T cell-mediated. This distinction is frequently tested in NEET.
Which of the following cancers is correctly matched with the type of tumour it represents?
Understanding:
We need to correctly match a cancer type with the tissue of origin and whether it is benign or malignant.
Step 1: Analyse each option
Melanoma — It is a malignant tumour of melanocytes, not benign. This makes option A incorrect.
Leukaemia — It is a cancer of blood-forming cells (bone marrow), not exclusively lymph nodes. Option B is incorrect.
Carcinoma — It is indeed a malignant tumour that arises from epithelial cells (skin, lining of organs). This is the standard classification used in oncology and NCERT.
Sarcoma — It arises from connective/muscular tissues (bone, cartilage, muscle), not blood-forming cells. Option D is incorrect.
Step 2: Confirm classification of carcinomas
Carcinomas form the largest group of cancers in humans. Examples include lung carcinoma, breast carcinoma, and colon carcinoma, all originating from epithelial cells.
Answer:
Carcinoma is correctly defined as a malignant tumour arising from epithelial cells.
Quick Tip:
Remember the classification: Carcinoma (epithelial) → Sarcoma (connective/muscle) → Leukaemia/Lymphoma (blood/lymphoid). Melanoma is always malignant — never benign.
In malaria caused by Plasmodium falciparum, the fever occurs every 48 hours. This periodicity is linked to which event in the parasite's life cycle?
Understanding:
We need to identify the specific event in the Plasmodium life cycle responsible for the periodic fever seen in malaria.
Step 1: Trace the erythrocytic cycle
After entering the liver (pre-erythrocytic stage), merozoites are released and invade red blood cells (RBCs). Inside RBCs, they feed on haemoglobin and multiply. At the end of each erythrocytic cycle, the RBCs rupture, releasing new merozoites along with toxic metabolic byproducts including haemozoin (malarial pigment) and other pyrogens.
Step 2: Link rupture to fever
The sudden release of merozoites, haemozoin, and cellular debris into the bloodstream triggers the immune system, causing a sharp rise in body temperature. In Plasmodium falciparum (malignant tertian malaria) and P. vivax (benign tertian malaria), the erythrocytic cycle is completed every 48 hours, giving a fever every 2nd day.
Step 3: Eliminate incorrect options
Sporozoite release from the mosquito initiates infection but does not cause fever.
Gametocytes form in RBCs (not liver cells) and are the sexual stage for the mosquito — not linked to fever periodicity.
Zygote formation occurs inside the mosquito's gut — irrelevant to fever in humans.
Answer:
The periodic fever in malaria is caused by the rupture of infected red blood cells, releasing merozoites and haemozoin into the bloodstream.
Quick Tip:
P. vivax and P. falciparum → 48-hour cycle (tertian fever); P. malariae → 72-hour cycle (quartan fever). This is a high-frequency NEET fact.
Widal test is used for the diagnosis of which of the following diseases?
Understanding:
We need to identify which disease is diagnosed using the Widal test.
Step 1: Identify the Widal test
The Widal test is a serological agglutination test that detects antibodies (agglutinins) in the patient's serum against Salmonella typhi antigens — specifically the O (somatic) and H (flagellar) antigens. A significant rise in titre confirms typhoid fever.
Step 2: Eliminate other options
Malaria is diagnosed by peripheral blood smear microscopy, rapid antigen (RDT) tests, or PCR.
Cholera is diagnosed by stool culture and dark-field microscopy for Vibrio cholerae.
Amoebiasis is diagnosed by stool examination for Entamoeba histolytica cysts or trophozoites.
Step 3: Confirm
The Widal test is exclusively used for diagnosing typhoid (enteric fever) caused by Salmonella typhi.
Answer:
The Widal test is used for the diagnosis of typhoid fever.
Quick Tip:
The Widal test is named after French physician Georges-Fernand Widal. An agglutination titre of 1:160 or above for O antigen is considered significant in most clinical settings — worth remembering for applied MCQs.
Which of the following drugs acts by binding to opioid receptors in the central nervous system, producing analgesia and euphoria, and is derived from the latex of Papaver somniferum?
Understanding:
We need to identify the drug that binds to opioid receptors, produces analgesia and euphoria, and is derived from Papaver somniferum (opium poppy).
Step 1: Identify the source plant and mechanism for each option
Cocaine — derived from Erythroxylum coca; it inhibits reuptake of dopamine, serotonin, and norepinephrine; classified as a stimulant, not an opioid.
Morphine — derived from the latex of Papaver somniferum; it directly binds to opioid receptors (mu, kappa, delta) in the CNS, producing powerful analgesia and euphoria; classified as an opioid narcotic analgesic.
Cannabis — derived from Cannabis sativa; acts on cannabinoid receptors (CB1, CB2), not opioid receptors.
LSD (Lysergic acid diethylamide) — a synthetic hallucinogen derived from ergot fungus; acts primarily on serotonin receptors.
Step 2: Confirm
Morphine satisfies all three criteria: opioid receptor binding, analgesia and euphoria, and derivation from Papaver somniferum latex.
Answer:
Morphine is the drug derived from Papaver somniferum latex that binds to opioid receptors to produce analgesia and euphoria.
Quick Tip:
All three — morphine, heroin (diacetylmorphine), and codeine — are opioids from Papaver somniferum. Heroin is synthesised by acetylation of morphine and is more potent due to faster CNS penetration.
In the context of AIDS, the virus HIV preferentially infects which type of cells, leading to progressive immunodeficiency?
Understanding:
We need to identify the primary target cell of HIV that leads to progressive collapse of the immune system in AIDS.
Step 1: Mechanism of HIV infection
HIV (Human Immunodeficiency Virus) is a retrovirus. Its surface glycoprotein gp120 binds specifically to the CD4 receptor present on the surface of helper T lymphocytes (T-helper cells / CD4+ T cells). The co-receptors CCR5 or CXCR4 also facilitate entry.
Step 2: Consequence of CD4+ T cell depletion
Helper T cells are the master regulators of adaptive immunity. They stimulate B cells to produce antibodies (humoral arm) and activate cytotoxic T cells (cell-mediated arm). Progressive destruction of CD4+ T cells by HIV reduces their count from the normal range of 500–1500 cells/µL. When the count falls below 200 cells/µL, the patient is diagnosed with AIDS and becomes susceptible to opportunistic infections.
Step 3: Eliminate incorrect options
CD8+ T cells (cytotoxic) and NK cells are not the primary targets of HIV.
B lymphocytes lack CD4 receptors and are not directly infected.
Answer:
HIV preferentially infects helper T cells (CD4+ T cells), destroying them and leading to progressive immunodeficiency (AIDS).
Quick Tip:
The CD4+ T cell count is the key diagnostic and prognostic marker in HIV/AIDS. A count below 200 cells/µL defines AIDS irrespective of symptoms.
Which of the following statements correctly describes the role of memory cells in secondary immune response?
Understanding:
We need to identify the correct description of the role of memory cells in the secondary immune response.
Step 1: Formation of memory cells
During the primary immune response (first exposure to an antigen), some activated B and T lymphocytes differentiate into long-lived memory cells instead of effector cells. These memory cells persist in the body for years or even a lifetime.
Step 2: Role in secondary immune response
On second exposure to the same antigen, memory cells are rapidly activated and proliferate quickly (clonal expansion). This results in:
This is called an anamnestic (secondary) response and forms the immunological basis of vaccination.
Step 3: Eliminate incorrect options
Memory cells are produced during the primary immune response, not only the secondary one.
Memory B cells lead to antibody production; they do not directly kill cells (that is the role of cytotoxic T cells).
Memory cells are long-lived — they can persist for decades, not just a few days.
Answer:
Memory cells respond rapidly to a second antigenic exposure, producing a faster and stronger antibody response than the primary immune response.
Quick Tip:
The secondary immune response is the scientific basis of booster doses in vaccination — the booster rapidly reactivates memory cells to produce high antibody titres.
Ascaris lumbricoides, the causative agent of ascariasis, infects humans primarily through which of the following routes?
Understanding:
We need to identify the correct mode of transmission of Ascaris lumbricoides, the roundworm causing ascariasis.
Step 1: Life cycle of Ascaris lumbricoides
Adult worms live in the small intestine of humans and produce eggs excreted in faeces. In soil, these eggs develop into infective embryonated eggs (containing the second-stage larva) over 2–3 weeks under warm, moist conditions. Infection occurs when a human ingests these embryonated eggs through contaminated food or water.
Step 2: After ingestion
Once swallowed, larvae hatch in the small intestine, penetrate the intestinal wall, travel through the liver via portal blood, then to the lungs via pulmonary circulation (causing Löffler's syndrome), ascend the trachea, are swallowed, and finally mature into adult worms in the small intestine.
Step 3: Eliminate other options
Anopheles mosquito bite transmits Plasmodium (malaria).
Direct skin penetration is characteristic of Hookworm (Ancylostoma duodenale / Necator americanus), not Ascaris.
Ascaris is not sexually transmitted.
Answer:
Ascaris lumbricoides infects humans through ingestion of embryonated eggs from contaminated food and water.
Quick Tip:
Ascaris has the largest egg output among intestinal parasites — a single female can lay up to 200,000 eggs per day. This explains the widespread prevalence of ascariasis in areas with poor sanitation.
Which of the following correctly describes the mechanism by which heroin (diacetylmorphine) acts as an addictive drug in the nervous system?
Understanding:
We need to identify the correct mechanism by which heroin produces its addictive effects in the nervous system.
Step 1: Chemical nature of heroin
Heroin (diacetylmorphine) is synthesised by acetylating two hydroxyl groups of morphine. This chemical modification makes heroin more lipid-soluble than morphine, allowing it to cross the blood-brain barrier much faster.
Step 2: Mechanism of action
Once inside the CNS, heroin is rapidly de-acetylated (hydrolysed) back to morphine. Morphine then binds to endogenous opioid receptors (mu, kappa, delta receptors) in the brain and spinal cord. This mimics the action of endogenous opioids (endorphins, enkephalins), causing:
Step 3: Basis of addiction
Repeat activation of the dopaminergic reward pathway by opioid receptor stimulation leads to neuroadaptation, tolerance, and physical dependence — the hallmarks of addiction.
Step 4: Eliminate incorrect options
Adrenergic receptor stimulation is the mechanism of cocaine and amphetamines, not heroin.
Blocking ACh at the neuromuscular junction is the mechanism of neurotoxins like botulinum or curare.
Serotonin antagonism and hallucinations describe LSD, not heroin.
Answer:
Heroin is rapidly converted to morphine in the body, which then binds to opioid receptors in the CNS, producing euphoria, analgesia, and CNS depression leading to addiction.
Quick Tip:
Heroin's higher lipid solubility compared to morphine explains its faster onset and greater abuse potential — it enters the brain quicker, causing a more intense initial rush.
Which of the following pathogens is responsible for causing Kala-azar (Visceral Leishmaniasis) in humans, and what is its primary vector?
Understanding:
We need to identify the causative agent of Kala-azar (Visceral Leishmaniasis) and its vector.
Step 1: Identify the pathogen
Kala-azar is caused by Leishmania donovani, a protozoan parasite. It is an intracellular parasite that resides within macrophages of the liver, spleen, and bone marrow, leading to enlargement of these organs (hepatosplenomegaly).
Step 2: Identify the vector
The vector for Leishmania donovani is the female Phlebotomus sandfly. The sandfly injects the promastigote form of the parasite during a blood meal. Inside the human host, the parasite transforms into the amastigote form.
Step 3: Eliminate incorrect options
Trypanosoma cruzi causes Chagas disease and is transmitted by the Reduviid (kissing) bug, not the Tsetse fly (which transmits African sleeping sickness). Plasmodium vivax causes malaria, transmitted by the female Anopheles mosquito. Anopheles is not the vector for Leishmaniasis.
Answer:
Kala-azar is caused by Leishmania donovani, transmitted by the female Phlebotomus sandfly.
Quick Tip:
Remember the triad: Kala-azar → Leishmania donovani → Phlebotomus sandfly. "Kala-azar" means "black fever" in Hindi, reflecting the darkening of skin seen in affected individuals.
In active immunisation, which of the following best describes the basis of its long-term protective effect?
Understanding:
We need to understand why active immunisation provides long-term protection.
Step 1: Define active immunisation
Active immunisation involves introducing an antigen (via a vaccine — attenuated, killed pathogen, or subunit) into the body. The immune system mounts a primary immune response, producing effector cells and antibodies.
Step 2: Role of memory cells
Crucially, this primary response also generates long-lived memory B cells and memory T cells. These cells persist in the body for years or decades. Upon re-exposure to the same pathogen, these memory cells rapidly proliferate and differentiate, producing a faster, stronger, and more sustained secondary immune response — often eliminating the pathogen before disease develops.
Step 3: Eliminate incorrect options
Pre-formed antibody injection describes passive immunisation (e.g., antivenom, antitoxin), which provides immediate but short-lived protection. Transfer of antibodies from donor to recipient is also passive immunisation. Innate immune cells do not provide the antigen-specific memory that underlies long-term protection.
Answer:
Active immunisation works by generating immunological memory through memory B and T cells, which ensure rapid and robust protection upon future exposure to the pathogen.
Quick Tip:
Active immunisation = the host actively produces its own antibodies and memory cells. Passive immunisation = antibodies are given externally — fast but temporary.
The drug cocaine exerts its stimulant effect primarily by which of the following mechanisms?
Understanding:
We need to identify the mechanism of action of cocaine as a stimulant drug.
Step 1: Cocaine's pharmacological action
Cocaine is a powerful central nervous system stimulant. It blocks the reuptake transporters for dopamine, norepinephrine, and serotonin at presynaptic nerve terminals. Normally, after neurotransmitter release, these molecules are transported back into the presynaptic neuron (reuptake). Cocaine prevents this process.
Step 2: Consequence of reuptake blockade
With reuptake blocked, dopamine (and other monoamines) accumulate in the synaptic cleft, overstimulating postsynaptic receptors. The flood of dopamine in the reward pathway (nucleus accumbens) produces intense euphoria and is responsible for cocaine's addictive properties.
Step 3: Eliminate incorrect options
Opioid receptor stimulation is the mechanism of morphine and heroin, not cocaine. GABA enhancement is the mechanism of benzodiazepines and alcohol — GABA is inhibitory, producing sedation rather than stimulation. Nicotinic acetylcholine receptor binding describes nicotine's mechanism.
Answer:
Cocaine acts by blocking the reuptake of dopamine, norepinephrine, and serotonin, causing their accumulation in the synapse and producing stimulant and euphoric effects.
Quick Tip:
Cocaine is a reuptake inhibitor — it does NOT directly stimulate receptors. This distinction is commonly tested in NEET.
Rheumatoid arthritis is an example of which of the following types of disease?
Understanding:
We need to classify rheumatoid arthritis correctly in terms of its immunological basis.
Step 1: Define autoimmune disease
Autoimmune diseases arise when the immune system fails to distinguish self from non-self and mounts an immune response against the body's own tissues. This loss of self-tolerance leads to chronic inflammation and tissue damage.
Step 2: Rheumatoid arthritis as an autoimmune disease
In rheumatoid arthritis, the immune system (particularly T cells and autoantibodies called rheumatoid factor) attacks the synovial membranes lining the joints. This causes chronic inflammation, pain, swelling, and progressive joint destruction.
Step 3: Eliminate incorrect options
IgE-mediated allergic diseases include asthma, hay fever, and anaphylaxis — not rheumatoid arthritis. Streptococcus pyogenes causes pharyngitis and can lead to acute rheumatic fever, which is different from rheumatoid arthritis. Immunodeficiency involves loss of immune function, whereas in autoimmune disease, immunity is misdirected, not absent.
Answer:
Rheumatoid arthritis is a classic autoimmune disease in which the immune system attacks the body's own joint tissues, causing chronic inflammatory damage.
Quick Tip:
Other autoimmune diseases to remember for NEET: Type 1 diabetes mellitus (attack on beta cells), multiple sclerosis (attack on myelin), and systemic lupus erythematosus (SLE).
During the life cycle of Plasmodium, which stage of the parasite is injected into the human bloodstream by the infected female Anopheles mosquito?
Understanding:
We need to identify the correct infective stage of Plasmodium that enters the human body via a mosquito bite.
Step 1: Plasmodium life cycle overview
The life cycle of Plasmodium involves two hosts — the female Anopheles mosquito (definitive host, where sexual reproduction occurs) and humans (intermediate host, where asexual reproduction occurs).
Step 2: Stage injected into humans
When an infected female Anopheles mosquito bites a human, it injects sporozoites from its salivary glands into the bloodstream. Sporozoites are the infective stage for humans. They travel to the liver and invade hepatocytes, where they undergo schizogony to form merozoites.
Step 3: Other stages and their roles
Merozoites are released from liver cells and infect red blood cells (RBCs) — they are NOT the stage injected by the mosquito. Gametocytes are the sexual stage found in human blood — they are taken up by the mosquito during a blood meal. Trophozoites are the feeding stage inside RBCs.
Answer:
The sporozoite is the stage injected into the human bloodstream by the infected female Anopheles mosquito.
Quick Tip:
Memory aid: Sporozoites → Liver (Schizogony) → Merozoites → RBCs → Gametocytes → Mosquito. The mosquito injects sporozoites; the mosquito ingests gametocytes.
Which of the following correctly describes the difference between benign and malignant tumours?
Understanding:
We need to distinguish between benign and malignant tumours based on their biological behaviour.
Step 1: Characteristics of benign tumours
Benign tumours are masses of cells that proliferate abnormally but remain confined to the tissue of origin. They are encapsulated, do not invade adjacent tissues, do not metastasise (spread to distant sites), and are generally not life-threatening, though they can cause problems by pressing on nearby structures.
Step 2: Characteristics of malignant tumours
Malignant tumours (cancers) are characterised by uncontrolled proliferation, loss of contact inhibition, invasion of surrounding normal tissues, and metastasis — the ability to spread to distant organs via the bloodstream or lymphatic system. Metastasis is the key property that makes cancer potentially fatal.
Step 3: Eliminate incorrect options
Neither tumour type is exclusively caused by viruses. Benign tumours are generally slow-growing and less dangerous. There is no organ restriction for where benign tumours form.
Answer:
Benign tumours are localised and non-invasive, while malignant tumours invade surrounding tissues and can metastasise to distant organs through blood or lymph.
Quick Tip:
The word malignant comes from Latin meaning "evil-born" — the hallmark property that distinguishes it from benign tumours is metastasis. Contact inhibition is lost in cancer cells.
Which of the following statements correctly describes the role of interferons in the body's defence against viral infections?
Understanding:
We need to understand the mechanism of action of interferons in viral defence.
Step 1: What are interferons?
Interferons (IFNs) are a family of signalling proteins (cytokines) that form a key part of the innate immune response to viral infections. They are not antibodies and are not specific to a single virus.
Step 2: How do interferons work?
When a cell is infected by a virus, it synthesises and secretes interferons. These interferons bind to receptors on neighbouring uninfected cells and trigger the expression of antiviral genes (such as those encoding protein kinases and endonucleases). This creates an "antiviral state" in the neighbouring cells, limiting the spread of the virus. Interferons also enhance natural killer (NK) cell activity and promote adaptive immune responses.
Step 3: Eliminate incorrect options
Interferons are not antibodies — antibodies are produced by plasma cells (differentiated B cells) and are antigen-specific. Interferons are not enzymes that directly lyse viruses. While NK cells respond to interferon signals, interferons themselves are produced by infected cells (including fibroblasts, leukocytes, and T cells) and act before or alongside adaptive immunity.
Answer:
Interferons are antiviral cytokines secreted by infected cells that warn and protect neighbouring cells by inducing an antiviral state, limiting viral spread.
Quick Tip:
Interferons do not directly kill viruses — they "interfere" with viral replication by making neighbouring cells inhospitable to viral multiplication. This is why they are part of the non-specific (innate) immune response.
A patient presents with high fever, chills, headache, and jaundice. Blood examination reveals parasitised red blood cells. The patient reports visiting a forest area. Which of the following is the most likely causative species of Plasmodium, and why is it considered the most dangerous?
Understanding:
We need to identify the most dangerous species of Plasmodium and explain why, in the context of a patient with severe malaria symptoms.
Step 1: Species of Plasmodium infecting humans
Four species of Plasmodium infect humans: P. vivax, P. falciparum, P. malariae, and P. ovale. Among these, P. falciparum causes malignant tertian malaria and is the most lethal.
Step 2: Why P. falciparum is the most dangerous
Unlike other species, P. falciparum infects RBCs of ALL ages (not just young or old RBCs), leading to a massive parasitaemia and severe haemolytic anaemia. Infected RBCs become sticky and form rosettes, clogging capillaries in vital organs. When this occlusion occurs in cerebral blood vessels, it causes cerebral malaria — a medical emergency with high mortality. P. falciparum also causes blackwater fever (haemoglobinuria due to massive haemolysis).
Step 3: Eliminate incorrect options
P. vivax causes relapse through hypnozoites but is rarely fatal. P. malariae causes quartan fever (72-hour cycle) and is milder. P. ovale is the rarest and is not resistant to all antimalarials.
Answer:
Plasmodium falciparum is the most dangerous species because it infects RBCs of all ages, causes severe anaemia, and can lead to cerebral malaria through capillary occlusion.
Quick Tip:
Remember the fever patterns: P. vivax/ovale = tertian (48 hours, benign); P. falciparum = malignant tertian (48 hours, dangerous); P. malariae = quartan (72 hours).
Which of the following statements regarding the ELISA (Enzyme-Linked Immunosorbent Assay) test is correct in the context of HIV/AIDS diagnosis?
Understanding:
We need to understand what ELISA detects in HIV diagnosis and how a positive result is confirmed.
Step 1: Principle of ELISA in HIV diagnosis
ELISA (Enzyme-Linked Immunosorbent Assay) is a serological test that detects the presence of antibodies against HIV antigens in the patient's serum or plasma. HIV antigens are coated on a plate; if the patient's serum contains anti-HIV antibodies, they bind to these antigens. An enzyme-linked secondary antibody is then added, and a colour change (upon substrate addition) indicates a positive result.
Step 2: Confirmatory test
Because ELISA can occasionally give false positives, a reactive (positive) ELISA result must be confirmed by the Western Blot test, which is more specific and identifies antibodies against individual HIV proteins (e.g., gp120, gp41, p24).
Step 3: Eliminate incorrect options
DNA amplification from blood cells describes PCR (Polymerase Chain Reaction), not ELISA. CD4+ T cell count is measured by flow cytometry (CD4 count), not ELISA. ELISA is widely used for both blood screening and clinical diagnosis of HIV.
Answer:
ELISA detects anti-HIV antibodies in the patient's serum, and a reactive result is confirmed by the more specific Western Blot test.
Quick Tip:
ELISA = screening test (sensitive); Western Blot = confirmatory test (specific). For NEET, remember this hierarchy: ELISA first, then Western Blot to confirm HIV infection.
Which of the following pairs correctly matches a disease with its causative agent AND the correct category of that agent?
Understanding:
We need to match a disease with its correct causative agent and the correct biological category of that agent.
Step 1: Evaluate each option
Option A: Typhoid is caused by Salmonella typhi — this pathogen is a bacterium, NOT a virus. So the category is wrong.
Step 2:
Option B: Pneumonia can be caused by Streptococcus pneumoniae, which is indeed a bacterium (Gram-positive diplococcus). This match is completely correct — the disease, causative agent, and category all align.
Step 3:
Option C: Ringworm is caused by fungi (dermatophytes such as Trichophyton and Microsporum), NOT by Taenia solium. Taenia solium is a tapeworm (helminth) that causes taeniasis/cysticercosis. So both the agent and category are wrong.
Step 4:
Option D: Common cold is caused by Rhinovirus (a virus), NOT by Plasmodium vivax. Plasmodium vivax is a protozoan causing malaria. Both the agent and category are wrong.
Answer:
Pneumonia caused by Streptococcus pneumoniae is correctly categorised as a bacterial disease.
Quick Tip:
Ringworm is a common NEET trap — despite the name, it is NOT caused by a worm. It is a fungal skin infection caused by dermatophytes. Always remember: Ringworm = Fungi.