(a) Mention the causative agent and means of spread of malaria. Also describe symptoms, diagnosis, treatment and preventive…

Causative agent and spread. Malaria is caused by Plasmodium species—P. falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi—spread mainly by infected female Anopheles mosquitoes, and also by blood transfusion, congenital transmission, shared needles and organ transplantation. In humans, sporozoites invade hepatocytes, then merozoites infect erythrocytes; asexual replication causes symptoms. Gametocytes taken by the mosquito form zygotes and ookinetes. Sporogony occurs in oocysts on the midgut wall, and sporozoites migrate to the salivary glands. In India, P. vivax and P. falciparum dominate; P. knowlesi is zoonotic in Southeast Asia.

Symptoms, diagnosis, treatment and prevention. Malaria presents with paroxysms of chills, rigors, fever and sweating, headache, anaemia and splenomegaly; fever is tertian in P. vivax/ovale, quartan in P. malariae, and may be severe/irregular in P. falciparum. Complications include cerebral malaria, severe anaemia, acute kidney injury, hypoglycaemia and blackwater fever from massive intravascular haemolysis. Diagnosis uses thick and thin peripheral blood smears; microscopy remains the reference method in endemic settings. Rapid diagnostic tests, PCR and serology are also used, serology showing past exposure rather than active infection. Treatment uses artemisinin-based combination therapies for uncomplicated falciparum malaria, parenteral artesunate for severe disease, and primaquine for hypnozoites and gametocytes after G6PD testing; supportive care manages severe anaemia, hypoglycaemia and organ failure. Chloroquine resistance limits its use. Prevention includes insecticide-treated nets, indoor residual spraying, larvivorous fish, environmental management, chemoprophylaxis and RTS,S/AS01 vaccine; India’s National Malaria Elimination Programme uses surveillance, case detection and vector control.

UV-Visible spectrophotometry. The instrument measures absorption of ultraviolet and visible light, roughly 190–800 nm, by chromophores undergoing electronic transitions. Its principle is the Beer–Lambert law, A = εcl: absorbance is proportional to analyte concentration and path length, while molar absorptivity ε is a constant for a given substance at a given wavelength. Light from a deuterium source for UV or tungsten source for visible light passes through a monochromator or filter, then through a cuvette containing the sample, and is measured by a detector such as a photodiode or photomultiplier tube; a blank corrects background, and data are recorded digitally. Double-beam instruments reduce drift. It is used qualitatively to identify chromophores and quantitatively to estimate proteins at 280 nm, nucleic acids at 260 nm, bilirubin, glucose and other clinical analytes, and to follow enzyme kinetics by measuring product or substrate changes. Calibration curves using standards give concentration. It also supports quality control in pharmaceuticals and clinical biochemistry.

Mechanical and olfactory perception. Animals detect mechanical stimuli through mechanoreceptors: hair sensilla and campaniform sensilla in arthropods, stretch receptors in muscles and skin, Pacinian corpuscles for deep pressure and vibration, and the lateral line system in fish for water movement. Mechanical deformation opens mechanosensitive ion channels, producing receptor potentials that are converted into nerve impulses. Auditory hair cells detect sound pressure, while vestibular receptors sense balance. Mechanoreception also includes tactile receptors in skin and joint proprioceptors. Olfaction differs by group. In insects, odorant binding proteins in antennae deliver odorants to ionotropic odorant and pheromone receptors on olfactory receptor neurons; signals are processed in the antennal lobe. Insects use pheromones for mate finding, colony recognition and alarm. Olfactory cues help locate hosts, food and mates. In vertebrates, odorants bind G-protein coupled receptors in the olfactory epithelium; G_olf activates adenylate cyclase, raising cAMP and opening cyclic nucleotide-gated channels. The olfactory bulb maps odor identity, while the vomeronasal organ detects social pheromones in many mammals. These systems guide feeding, mate choice through pheromone communication, danger avoidance and vector behaviour.

Together, malaria control, spectrophotometric diagnostics and sensory physiology show how biological mechanisms translate into public health action: interrupting transmission, measuring disease markers, and understanding how vectors and hosts detect environmental cues.