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UPMSP Intermediate Agricultural Zoology study materials
UPMSP Intermediate Agricultural Zoology study resources

UPMSP Intermediate Agricultural Zoology practice questions

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Question 1Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In the Linnaean hierarchy used in animal classification, which taxonomic rank lies directly between class and family?

  1. Genus
  2. Phylum
  3. Species
  4. Order Correct answer.

Explanation

In the standard Linnaean hierarchy the sequence is kingdom, phylum, class, order, family, genus and species. Order therefore lies directly below class and directly above family.

Question 2Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Under binomial nomenclature, the scientific name of an animal such as Panthera leo is made up of which two ranks?

  1. Phylum and class
  2. Family and genus
  3. Genus and species Correct answer.
  4. Species and subspecies

Explanation

Binomial nomenclature gives every species a two-part scientific name made of the genus name followed by the specific epithet. Panthera is the genus and leo is the species epithet.

Question 3Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which set of features is characteristic of the body plan of an adult sponge (phylum Porifera)?

  1. Radial symmetry with cnidoblasts
  2. Ostia, spongocoel and choanocytes Correct answer.
  3. Joint appendages and a chitinous exoskeleton
  4. Water vascular system with tube feet

Explanation

Sponges are sessile filter feeders with a porous body; water enters through ostia, passes into the spongocoel and is filtered by choanocytes. They lack jointed appendages, nematocysts and a water vascular system.

Question 4Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In cnidarians, the cells that contain nematocysts and are used for prey capture are called

  1. Collar cells
  2. Choanocytes
  3. Cnidocytes Correct answer.
  4. Flame cells

Explanation

Cnidocytes, also called cnidoblasts, are unique to cnidarians and contain nematocysts that discharge to capture prey or defend the animal. Choanocytes occur in sponges and flame cells in flatworms.

Question 5Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In the life cycle of Taenia solium, which host harbours the larval stage known as cysticercus?

  1. Mosquito
  2. Human
  3. Snail
  4. Pig Correct answer.

Explanation

The adult Taenia solium lives in the human intestine, and gravid proglottids release eggs. When a pig ingests the eggs, the oncosphere migrates to muscle and develops into the cysticercus larva, so the pig is the intermediate host.

Question 6Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Ascaris lumbricoides is a common roundworm of the human intestine. Which feature correctly distinguishes it as a nematode?

  1. Radial symmetry and ambulacral grooves
  2. Presence of a segmented true coelom and metanephridia
  3. Unsegmented cylindrical body with pseudocoelom Correct answer.
  4. Dorsal heart and a closed circulatory system

Explanation

Nematodes have an unsegmented, cylindrical body covered by a cuticle, and the body cavity is a pseudocoelom. They lack the segmented true coelom and metanephridia of annelids.

Question 7Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In Pheretima (earthworm), which structure is a thickened glandular band involved in cocoon formation and located in the clitellar region?

  1. Peristomium
  2. Nephridiopore
  3. Prostomium
  4. Clitellum Correct answer.

Explanation

The clitellum is a glandular swelling of the body wall in the clitellar region of earthworms. It secretes the cocoon in which eggs are deposited during reproduction.

Question 8Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Within Arthropoda, members of subphylum Chelicerata such as spiders and scorpions are separated from mandibulate arthropods mainly because chelicerates possess

  1. Chelicerae and pedipalps, with no antennae Correct answer.
  2. Mandibles and a distinct head with five pairs of appendages
  3. Two pairs of antennae and biramous appendages
  4. Three pairs of walking legs and one pair of antennae

Explanation

Chelicerates have a prosoma and opisthosoma, with six pairs of prosomal appendages: chelicerae, pedipalps and four pairs of walking legs. They lack antennae, whereas mandibulate arthropods have mandibles and antennae.

Question 9Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which feature is characteristic of the phylum Mollusca?

  1. A mantle and a muscular foot Correct answer.
  2. A water vascular system and pentaradial symmetry
  3. A pseudocoelom and a cuticle that is moulted
  4. A notochord and a dorsal hollow nerve cord

Explanation

Molluscs are characterized by a soft body with a mantle and a muscular foot. The mantle usually secretes the calcareous shell, although the shell is reduced or absent in some groups.

Question 10Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which statement about the notochord in chordates is correct?

  1. It remains throughout life in amphioxus but not in adult frogs Correct answer.
  2. It is always replaced by a vertebral column in adult tunicates
  3. It forms the main part of the chitinous exoskeleton in arthropods
  4. It is present only in the larval stage of all vertebrates

Explanation

In cephalochordates such as amphioxus the notochord persists throughout life and provides axial support. In adult frogs, as in most vertebrates, the notochord is replaced by the vertebral column during development.

Question 11Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Amoeba proteus moves and engulfs food particles by pushing out which temporary cytoplasmic structures?

  1. Cilia
  2. Pseudopodia Correct answer.
  3. Parapodia
  4. Flagella

Explanation

Amoeba forms pseudopodia, which are temporary projections of cytoplasm produced by the streaming of endoplasm. The same pseudopodia surround and engulf food particles by phagocytosis. Cilia and flagella are permanent locomotory organelles of other protozoans, while parapodia are fleshy outgrowths of polychaete annelids.

Question 12Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which class of vertebrates is characterised by pneumatic bones, air sacs connected with the lungs, and a syrinx?

  1. Amphibia
  2. Mammalia
  3. Aves Correct answer.
  4. Reptilia

Explanation

Birds (Aves) have hollow, air-filled pneumatic bones that reduce body weight and air sacs that ventilate the lungs in a one-way flow, both adaptations for flight. The syrinx is the voice-producing organ located at the base of the trachea in birds. Mammals, reptiles and amphibians do not possess this combination of features.

Question 13Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

The system of coelomic canals ending in tube feet, which helps a starfish in locomotion and feeding, is called the

  1. tracheal system
  2. hepatic portal system
  3. water vascular system Correct answer.
  4. lateral line system

Explanation

In echinoderms such as starfish, the water vascular system consists of the madreporite, stone canal, ring canal, radial canals and tube feet. Seawater enters through the madreporite and the hydraulic pressure extends the tube feet for slow crawling and for opening bivalve prey. The other systems listed belong to fishes, insects and vertebrates respectively.

Question 14Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In the life cycle of the liver fluke Fasciola hepatica, which larval stage encysts on aquatic vegetation and is infective to the definitive host?

  1. Metacercaria Correct answer.
  2. Redia
  3. Miracidium
  4. Sporocyst

Explanation

After leaving the snail, the cercaria swims to aquatic plants, loses its tail and secretes a cyst wall to become a metacercaria. The definitive host, usually a sheep or other herbivore, becomes infected by swallowing vegetation bearing these cysts. Miracidium, sporocyst and redia are earlier stages that develop inside the snail.

Question 15Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which statement correctly describes the division of labour between the two kinds of nuclei in Paramecium?

  1. Both nuclei fuse during binary fission to form a single nucleus.
  2. The micronucleus controls metabolic activities and the macronucleus takes part in reproduction.
  3. Both nuclei are concerned only with osmoregulation.
  4. The macronucleus controls metabolic activities and the micronucleus takes part in reproduction. Correct answer.

Explanation

Paramecium is heterokaryotic: the large kidney-shaped macronucleus is polyploid and governs vegetative or metabolic functions such as growth and protein synthesis. The small micronucleus is diploid and divides by mitosis or meiosis during reproduction. During conjugation the micronuclei exchange, while the macronucleus degenerates and is reorganised in the exconjugants.

Question 16Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which muscular structure, found only in mammals, separates the thoracic cavity from the abdominal cavity?

  1. Pericardium
  2. Pleura
  3. Peritoneum
  4. Diaphragm Correct answer.

Explanation

The diaphragm is a dome-shaped muscular sheet that divides the body cavity of mammals into an anterior thoracic cavity and a posterior abdominal cavity. Its contraction enlarges the thorax and drives inspiration, which is why mammals ventilate the lungs mainly by a diaphragm pump. The pleura, pericardium and peritoneum are serous membranes that cover organs rather than divide the cavities.

Question 17Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

The lateral line system of a fish is primarily concerned with

  1. storing excess nitrogenous waste
  2. detecting water currents and vibrations Correct answer.
  3. maintaining neutral buoyancy
  4. exchanging respiratory gases

Explanation

The lateral line consists of a canal along each side of the body bearing receptor neuromasts in contact with the surrounding water. It is a mechanosensory system that detects low-frequency vibrations, water currents and pressure changes, helping the fish in schooling, prey detection and avoiding obstacles. It is not an excretory or respiratory organ.

Question 18Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Enterocoely, in which the coelom arises from outpocketings of the archenteron, is characteristic of which pair of phyla?

  1. Mollusca and Annelida
  2. Annelida and Arthropoda
  3. Echinodermata and Chordata Correct answer.
  4. Platyhelminthes and Nematoda

Explanation

In enterocoelous development the mesoderm and coelom form from pouches pinched off the embryonic archenteron, as seen in echinoderms and chordates, which are deuterostomes. Annelids, molluscs and arthropods are protostomes in which the coelom arises by schizocoely, through splitting of mesodermal bands. Flatworms are acoelomate and nematodes are pseudocoelomate, so neither forms a true coelom by either method.

Question 19Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which chordate group shows retrogressive metamorphosis, in which the free-swimming larva has a notochord and tail but the sessile adult loses these structures?

  1. Hemichordata
  2. Urochordata Correct answer.
  3. Cephalochordata
  4. Vertebrata

Explanation

In urochordates such as Ascidia, the tadpole-like larva has a notochord, dorsal hollow nerve cord and muscular tail, but after settling the adult loses its tail and most nervous system and becomes a sessile filter feeder. This degeneration from a complex larva to a simpler adult is called retrogressive metamorphosis. In cephalochordates the notochord persists throughout life, and in vertebrates it is replaced by vertebrae during development.

Question 20Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In Balanoglossus, the structure lying in the proboscis that is often compared with the notochord of chordates is the

  1. collarette
  2. stomochord Correct answer.
  3. pharyngeal bar
  4. proboscis gland

Explanation

The stomochord, also called the buccal diverticulum, is a short ciliated outgrowth of the buccal cavity extending into the proboscis of hemichordates. It was once considered a notochord, but it lacks the vacuolated chordate cells and is not homologous with it, which is why Balanoglossus is placed outside true Chordata. The pharyngeal bars support gill slits, and the collarette is merely a collar-like fold.

Question 21Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In the phylum Platyhelminthes, flame cells are primarily associated with which function?

  1. Digestion of host tissue
  2. Conduction of nerve impulses
  3. Production of gametes
  4. Excretion and osmoregulation Correct answer.

Explanation

Flame cells, also called protonephridia, collect excess water and nitrogenous wastes and expel them through excretory pores. Their ciliated tuft creates a current that drives fluid along the tubule. They are the excretory and osmoregulatory organs of flatworms.

Question 22Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which class of vertebrates is characterised by moist glandular skin, a three-chambered heart, and a life cycle that typically includes a tadpole larva?

  1. Mammalia
  2. Aves
  3. Reptilia
  4. Amphibia Correct answer.

Explanation

Amphibians have moist skin used for cutaneous respiration, a three-chambered heart, and metamorphosis from an aquatic larva to a terrestrial adult. Reptiles have dry scaly skin and amniotic eggs, while birds and mammals differ in skin, heart structure, and development.

Question 23Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In the life cycle of Plasmodium vivax, which stage is injected into the human bloodstream by the bite of an infected female Anopheles mosquito?

  1. Trophozoite
  2. Merozoite
  3. Gametocyte
  4. Sporozoite Correct answer.

Explanation

Sporozoites develop in the mosquito salivary glands and are inoculated into humans, where they first invade liver cells. Merozoites arise later in the human blood cycle, trophozoites are feeding stages, and gametocytes are taken up by a mosquito.

Question 24Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

A ciliated larval stage called the trochophore is characteristic of which pair of animal phyla, and its presence is used as evidence of a close relationship?

  1. Mollusca and Annelida Correct answer.
  2. Echinodermata and Chordata
  3. Nematoda and Arthropoda
  4. Porifera and Cnidaria

Explanation

Trochophore larvae occur in many molluscs and annelids, and their similar ciliary bands and apical tuft support a close phylogenetic link. Porifera and Cnidaria have different larval plans, nematodes and arthropods moult a cuticle, and echinoderms and chordates are deuterostomes with different larvae.

Question 25Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

The main excretory organs of insects are which structures?

  1. Nephridia
  2. Malpighian tubules Correct answer.
  3. Green glands
  4. Flame cells

Explanation

Malpighian tubules are blind-ended tubes opening into the insect gut that remove nitrogenous wastes and regulate water balance. Green glands are crustacean excretory organs, nephridia occur in annelids, and flame cells are found in flatworms.

Question 26Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In the life cycle of the hookworm Ancylostoma duodenale, which larval stage normally penetrates the skin of a human host?

  1. Filariform larva Correct answer.
  2. Miracidium larva
  3. Rhabditiform larva
  4. Cysticercus larva

Explanation

The rhabditiform larva develops in soil into the infective filariform larva, which penetrates bare skin and migrates to the intestine. Cysticercus is a tapeworm stage and miracidium is a fluke stage; neither is the hookworm skin-penetrating stage.

Question 27Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

Which class of Mollusca is distinguished by a closed circulatory system and a well-developed brain and eyes?

  1. Cephalopoda Correct answer.
  2. Gastropoda
  3. Bivalvia
  4. Polyplacophora

Explanation

Cephalopods such as squid and octopus have a closed circulatory system with accessory hearts, plus large brains and image-forming eyes. Gastropods and bivalves have open circulatory systems, and chitons have a simpler nervous system and no such eyes.

Question 28Animal diversity and systematic zoology (classification, phyla, external features and life cycles of representative animals)

In the life cycle of the liver fluke Fasciola hepatica, which stage emerges from the egg and penetrates the snail intermediate host?

  1. Miracidium Correct answer.
  2. Redia
  3. Cercaria
  4. Metacercaria

Explanation

The ciliated miracidium hatches from the egg, swims to a suitable snail, and penetrates its tissues. Cercariae leave the snail later, metacercariae encyst on vegetation, and rediae are a multiplication stage inside the snail.

Question 29Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which organelle is the principal site of ATP synthesis in an animal cell?

  1. Mitochondrion Correct answer.
  2. Golgi apparatus
  3. Lysosome
  4. Ribosome

Explanation

Mitochondria contain the electron transport chain and ATP synthase, which carry out oxidative phosphorylation to produce most cellular ATP. Ribosomes synthesize proteins, the Golgi apparatus modifies and packages molecules, and lysosomes contain hydrolytic enzymes.

Question 30Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which tissue type forms the lining of body cavities and ducts and rests on a basement membrane?

  1. Connective tissue
  2. Epithelial tissue Correct answer.
  3. Nervous tissue
  4. Muscular tissue

Explanation

Epithelial tissue covers body surfaces and lines cavities and ducts, and it is anchored to a basement membrane. It is avascular and cells are closely packed, unlike connective, muscular, or nervous tissue.

Question 31Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Salivary amylase begins the chemical digestion of which dietary component in the mouth?

  1. Nucleic acids
  2. Proteins
  3. Fats
  4. Starch Correct answer.

Explanation

Salivary amylase hydrolyzes starch into maltose and other oligosaccharides in the mouth. Proteins are mainly digested by pepsin in the stomach, fats by lipases, and nucleic acids by nucleases.

Question 32Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

In the mammalian lung, gas exchange between air and blood occurs across the walls of which structures?

  1. Bronchi
  2. Trachea
  3. Alveoli Correct answer.
  4. Pleura

Explanation

Alveoli are tiny air sacs with thin walls surrounded by capillaries, providing a large surface area for diffusion of oxygen and carbon dioxide. Bronchi and trachea conduct air, while pleura is a protective membrane.

Question 33Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which blood vessel carries oxygenated blood from the lungs to the left atrium of the heart?

  1. Aorta
  2. Pulmonary vein Correct answer.
  3. Vena cava
  4. Pulmonary artery

Explanation

Pulmonary veins return oxygenated blood from the lungs to the left atrium. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs, while aorta and vena cava are systemic vessels.

Question 34Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

What is the structural and functional unit of the mammalian kidney?

  1. Alveolus
  2. Neuron
  3. Hepatocyte
  4. Nephron Correct answer.

Explanation

The nephron is the kidney's structural and functional unit, consisting of a renal corpuscle and tubule that filter blood and reabsorb useful substances. Neurons, alveoli, and hepatocytes belong to nervous, respiratory, and liver tissues respectively.

Question 35Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which neurotransmitter is released at the neuromuscular junction to stimulate skeletal muscle contraction?

  1. Acetylcholine Correct answer.
  2. Norepinephrine
  3. Serotonin
  4. Dopamine

Explanation

Acetylcholine is released from the motor neuron terminal and binds to nicotinic receptors on the motor end plate, triggering muscle contraction. Dopamine and serotonin are mainly central neurotransmitters, and norepinephrine is primarily autonomic.

Question 36Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which hormone is secreted by the beta cells of the islets of Langerhans and lowers blood glucose?

  1. Cortisol
  2. Insulin Correct answer.
  3. Thyroxine
  4. Glucagon

Explanation

Insulin from pancreatic beta cells lowers blood glucose by promoting cellular uptake and glycogen synthesis. Glucagon from alpha cells raises glucose, while thyroxine and cortisol have broader metabolic roles.

Question 37Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

During fertilization in mammals, the acrosome reaction is necessary because it releases enzymes that perform which function?

  1. Cause the oocyte to complete meiosis II
  2. Digest the zona pellucida surrounding the oocyte Correct answer.
  3. Trigger the cortical reaction in the oocyte
  4. Increase the number of sperm reaching the oviduct

Explanation

The acrosome reaction releases hydrolytic enzymes such as hyaluronidase and acrosin that digest the zona pellucida, allowing the sperm to reach the oocyte membrane. The cortical reaction occurs after sperm fusion and blocks polyspermy.

Question 38Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which statement correctly explains saltatory conduction in a myelinated axon?

  1. Impulses jump between nodes of Ranvier, speeding conduction Correct answer.
  2. Saltatory conduction relies on chemical synapses along the axon
  3. Myelin raises membrane capacitance and slows conduction
  4. Impulses propagate continuously along the entire axon

Explanation

In myelinated axons, myelin insulates the internodes and ion exchange occurs mainly at the nodes of Ranvier. The action potential therefore jumps node to node, a process called saltatory conduction, which is faster than continuous propagation.

Question 39Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which membrane-bound organelle of an animal cell contains hydrolytic enzymes and carries out intracellular digestion?

  1. Smooth endoplasmic reticulum
  2. Lysosome Correct answer.
  3. Ribosome
  4. Golgi apparatus

Explanation

The lysosome is a membrane-bound vesicle containing acid hydrolases that digest macromolecules and worn-out organelles. Its interior is kept acidic, which activates these enzymes and protects the cytoplasm.

Question 40Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which muscle tissue is striated, involuntary, and restricted to the heart wall?

  1. Skeletal muscle
  2. Cardiac muscle Correct answer.
  3. Dense regular connective tissue
  4. Smooth muscle

Explanation

Cardiac muscle cells are striated because of organized sarcomeres, but they contract involuntarily through intrinsic pacemaker activity and autonomic modulation. Intercalated discs couple the cells electrically and mechanically.

Question 41Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which part of the mammalian digestive tract is the main site for absorption of water and mineral salts from undigested material?

  1. Large intestine Correct answer.
  2. Oesophagus
  3. Oral cavity
  4. Stomach

Explanation

The large intestine absorbs most remaining water and electrolytes from the chyme, converting it into faeces. Its epithelium also secretes mucus that lubricates the passage of waste.

Question 42Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which flap-like structure closes over the opening of the larynx to prevent food from entering the trachea during swallowing?

  1. Soft palate
  2. Epiglottis Correct answer.
  3. Uvula
  4. Glottis

Explanation

The epiglottis is a cartilaginous flap that folds down over the glottis during the pharyngeal phase of swallowing. This diverts the bolus into the oesophagus and protects the airway.

Question 43Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which plasma protein is most important for maintaining the colloid osmotic pressure of blood?

  1. Albumin Correct answer.
  2. Lipoprotein
  3. Globulin
  4. Fibrinogen

Explanation

Albumin is the most abundant plasma protein and, because it is retained in capillaries, draws water back into the vascular compartment by osmosis. This helps preserve blood volume and tissue fluid balance.

Question 44Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Along which nephron segment are glucose and amino acids most actively reabsorbed from the filtrate?

  1. Proximal convoluted tubule Correct answer.
  2. Collecting duct
  3. Distal convoluted tubule
  4. Descending limb of the loop of Henle

Explanation

The proximal convoluted tubule has abundant microvilli and mitochondria that support near-complete active reabsorption of glucose and amino acids. These nutrients are normally absent from urine when their plasma levels are within the renal threshold.

Question 45Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which region of the brain integrates information to regulate body temperature, hunger, and thirst?

  1. Cerebellum
  2. Hypothalamus Correct answer.
  3. Thalamus
  4. Medulla oblongata

Explanation

The hypothalamus contains homeostatic centres that sense and adjust temperature, osmolarity, and energy status. It links the nervous system to the endocrine system through the pituitary gland.

Question 46Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which hormone, released from the posterior pituitary, increases water reabsorption by the collecting ducts of the kidney?

  1. Antidiuretic hormone Correct answer.
  2. Thyroid-stimulating hormone
  3. Adrenocorticotropic hormone
  4. Oxytocin

Explanation

Antidiuretic hormone, or vasopressin, makes the collecting duct epithelium more permeable to water by inserting aquaporin channels. This concentrates urine and conserves body water.

Question 47Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

During mammalian spermatogenesis, which cell is the first haploid cell formed after meiosis I?

  1. Secondary spermatocyte Correct answer.
  2. Spermatogonium
  3. Spermatid
  4. Primary spermatocyte

Explanation

Primary spermatocytes are diploid and divide by meiosis I to produce two secondary spermatocytes, each with a haploid chromosome number. Spermatids become haploid later, after meiosis II, so they are not the first haploid cells.

Question 48Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

In skeletal muscle contraction, which event directly exposes the myosin-binding sites on actin?

  1. Binding of ATP to the myosin head
  2. Acetylcholinesterase breaking down acetylcholine
  3. Calcium ions binding to troponin Correct answer.
  4. Acetylcholine binding to the sarcolemma

Explanation

Calcium released from the sarcoplasmic reticulum binds troponin, shifting tropomyosin away from the actin active sites. This allows cross-bridge formation between actin and myosin and enables contraction.

Question 49Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

In an epithelial sheet, which junction forms a continuous belt that seals the space between adjacent cells and limits paracellular diffusion?

  1. Desmosome
  2. Gap junction
  3. Hemidesmosome
  4. Tight junction Correct answer.

Explanation

Tight junctions, or zonula occludens, form continuous strands of claudin and occludin that fuse adjacent epithelial membranes and block paracellular leakage. Desmosomes anchor intermediate filaments to adhesion plaques, gap junctions permit small-molecule exchange, and hemidesmosomes attach the basal cell surface to the basement membrane.

Question 50Cell biology, histology and animal physiology (cell structure, tissues, digestion, respiration, circulation, excretion, nervous and endocrine coordination, reproduction)

Which resident cell of connective tissue is chiefly responsible for synthesizing collagen fibres and the amorphous ground substance?

  1. Plasma cell
  2. Adipocyte
  3. Mast cell
  4. Fibroblast Correct answer.

Explanation

Fibroblasts are the principal cells that synthesize procollagen, elastin, and glycosaminoglycan-rich ground substance in connective tissue. Mast cells store histamine and heparin, adipocytes store lipid, and plasma cells produce antibodies rather than matrix.