Zoology Test - 4 (Medical Entrance)

The dopamine hypothesis of schizophrenia proposes that overactivity of dopamine transmission in certain brain regions is associated with schizophrenia symptoms. This is supported by the fact that antipsychotic drugs (which reduce dopamine activity) effectively treat schizophrenia, while drugs that increase dopamine can induce psychotic symptoms.

Sex-linked inheritance displays a characteristic 'criss-cross' pattern where X-linked traits appear in alternate generations, for example, a grandfather passes an X-linked trait to his grandson through a carrier daughter. This differs from atavism (return to ancestral type), reversion, or gene flow.

A single muscle twitch consists of a contraction phase followed by a relaxation phase. This is the fundamental unit of muscle activity in response to a single stimulus. 'Beat' refers to cardiac muscle, 'condition' is not a standard term, and 'stimulus' is the trigger, not the response.

When milk is left open, bacteria (especially Lactobacillus) ferment the lactose sugar into lactic acid through anaerobic respiration. The accumulation of lactic acid lowers the pH, giving milk its characteristic sour taste. Carbonic, citric, and malic acids are not produced in this process.

Earl Sutherland received the 1971 Nobel Prize in Physiology or Medicine for discovering how hormones act through second messengers, specifically cyclic AMP (cAMP). His work elucidated the mechanism of hormone action at the molecular level, revolutionizing understanding of cellular signaling.

Rh-positive blood type is an autosomal dominant trait; inheritance of one Rh+ allele results in Rh-positive phenotype. The other options are all recessive X-linked traits: color blindness, albinism (oculocutaneous), and hemophilia A/B require two X chromosomes with the recessive allele (or one in males) to be expressed.

Amphids are paired chemosensory organs located in the lips of nematodes like Ascaris. They function as the primary olfactory and chemoreceptive structures, detecting chemical cues in the environment. They do not secrete saliva, act as adhesive organs, or produce proteolytic enzymes.

Anaphylaxis is a severe, potentially life-threatening IgE-mediated allergic reaction. IgE antibodies bind to mast cells and basophils, triggering release of histamine and other mediators that cause widespread vasodilation, bronchoconstriction, and can lead to circulatory shock and asphyxia. Orthopnea is breathing difficulty when lying flat.

A maggot is the larval stage of a fly, specifically the housefly (Musca domestica) and related species. Houseflies lay eggs in decaying organic matter; the hatching larvae (maggots) feed before pupating into adult flies. Mosquitoes have aquatic 'wriggler' larvae, and frogs/fleas have completely different life cycles.

Choanocytes (or collar cells) are the feeding cells in sponges. Each choanocyte has a flagellum surrounded by a microvillar collar that creates water currents and traps food particles (bacteria, organic debris) which are then ingested by phagocytosis. Porocytes are pore cells, pinacocytes are covering cells, and trophocytes are nutritive cells in other animals.

Heparin is a glycosaminoglycan (sulfated polysaccharide) produced and stored in mast cells. It acts as a potent anticoagulant by enhancing antithrombin activity, inhibiting clotting factors. Hirudin is from leeches, fibrinogen is a clotting protein precursor, and serotonin is another mast cell mediator but not an anticoagulant.

The Ames test uses Salmonella typhimurium bacteria to detect mutagenic compounds, which correlates with carcinogenicity. It is a rapid bacterial assay, not performed on animals, making it different from animal testing methods.

Assimilation is the metabolic process where absorbed nutrients are converted into complex protoplasmic molecules for growth and repair. Digestion breaks down food, absorption moves nutrients into blood, and assimilation builds body tissues.

The medulla oblongata contains the cardiac center that regulates heart rate and force of contraction. The cerebrum controls higher cognitive functions, the cerebellum coordinates movement, and optic lobes (in non-mammals) process visual information.

New World monkeys (Platyrrhini) possess prehensile tails used for grasping branches, while Old World monkeys (Catarrhini) lack this adaptation. This anatomical feature is a key distinction between the two primate groups in the Americas versus Africa/Asia.

Eye color (brown, black, or blue) is determined by the concentration and distribution of melanin pigment in the iris. The iris contains melanocytes whose pigment production and scattering of light create different eye colors.

Java man (Homo erectus erectus) had a cranial capacity of approximately 900 cc, intermediate between earlier hominids and modern humans (1400 cc average). This measurement reflects evolutionary brain expansion in the human lineage.

Jonas Salk developed the first successful polio vaccine in 1955 using inactivated poliovirus. Edward Jenner developed the smallpox vaccine, and the other options are not associated with polio vaccine development.

Silk fibers are primarily composed of fibroin, a fibrous protein produced by silkworms. Fibrin is involved in blood clotting, casein is milk protein, making fibroin the correct silk protein.

Insects have a tracheal system, a network of tubes that delivers oxygen directly to body cells without using blood as the transport medium. Spiders and scorpions use different respiratory systems (book lungs/gills).

The Widal test detects Salmonella typhi antibodies in serum, diagnosing typhoid fever. It tests for agglutinating antibodies against O and H antigens, not for malaria, cholera, or dengue.

Birds and reptiles are uricotelic organisms, meaning they excrete nitrogenous waste primarily as uric acid. Uric acid is relatively non-toxic and can be concentrated to a white paste or solid, allowing these animals to conserve water - a critical adaptation for life in dry environments. Urea (mammals) and creatine are different nitrogenous compounds, while precipitated calcium is not involved in nitrogen excretion.

Epstein-Barr virus (EBV) is a herpesvirus that causes infectious mononucleosis, also known as glandular fever or 'kissing disease'. It is transmitted through saliva and does not cause the blood disorders listed in the other options.

Housefly, dragonfly, and butterfly are all insects belonging to the phylum Arthropoda and class Insecta. The other options mix different phyla or classes - 'worms' include annelids and platyhelminthes, 'fish' mix fish, molluscs, and echinoderms, and the sea creatures represent three different phyla.