Tamil Nadu HSE First Year Zoology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Binomial nomenclature

A two-part scientific naming system in which the genus name is capitalised, the species epithet is lowercase, and both are italicised in print or underlined in handwriting.

Notochord

A flexible rod of cells along the dorsal side of chordate embryos that provides skeletal support; in vertebrates it is replaced largely by the vertebral column during development.

Water vascular system

The unique echinoderm canal system of madreporite, ring canal, radial canals and tube feet, used for locomotion, feeding and gas exchange.

Clitellum

A thickened glandular band of segments 14 to 16 in the earthworm that secretes the cocoon in which fertilised eggs are deposited.

Typhlosole

A longitudinal fold of the earthworm intestinal wall that projects into the lumen and increases the surface area available for absorption of digested food.

Malpighian tubules

Slender excretory tubules of insects such as the cockroach that remove nitrogenous wastes from the haemolymph and empty into the gut.

Cardiac muscle

Striated involuntary muscle of the heart wall whose cells branch and join at intercalated discs, allowing rapid coordinated conduction of impulses.

Myelin sheath

A fatty insulating covering formed by Schwann cells around some axons that speeds impulse conduction by allowing saltatory jumping between nodes.

Gastrin

A hormone released by the stomach lining when food arrives that stimulates secretion of gastric acid and pepsinogen for protein digestion.

Chylomicrons

Small fat droplets formed in intestinal cells from absorbed fatty acids and glycerol, transported through lacteals into the lymphatic system rather than blood capillaries.

Vital capacity

The maximum volume of air a person can expel after a deepest possible inspiration, roughly equal to tidal volume plus inspiratory and expiratory reserve volumes.

SA node

The sinoatrial node in the right atrial wall that generates impulses setting the heart rhythm and is therefore called the natural pacemaker.

Counter-current mechanism

The opposing flow of filtrate in the loop of Henle and blood in its vessels that builds a medullary salt gradient and permits concentrated urine formation.

Uricotelic excretion

Excretion of nitrogenous waste mainly as uric acid, a water-saving strategy typical of birds, reptiles and insects, released as a semi-solid paste.

Sarcomere

The repeating contractile unit of a muscle fibre between two Z lines, containing actin and myosin filaments whose sliding shortens the muscle.

Acetylcholine

A neurotransmitter released at the neuromuscular junction that depolarises the muscle membrane and initiates contraction of skeletal muscle fibres.

Reflex arc

The neural pathway of a reflex, running from receptor through a sensory neuron to the spinal cord, then a motor neuron to an effector.

Saltatory conduction

Rapid impulse conduction in myelinated axons in which the action potential jumps from one node of Ranvier to the next rather than travelling continuously.

Negative feedback

A control mechanism in which rising levels of a hormone or product inhibit its own further secretion, keeping concentrations within a narrow range.

Parathyroid hormone

A hormone that raises blood calcium by stimulating bone resorption, increasing kidney reabsorption of calcium and activating vitamin D.

Corpus luteum

The glandular body formed from the ruptured ovarian follicle after ovulation that secretes progesterone to maintain the uterine lining.

Placenta

The temporary organ formed from fetal chorion and maternal uterine tissue that exchanges nutrients, gases and wastes and secretes hormones such as hCG.

Law of segregation

Mendel's principle that the two alleles of a gene separate during gamete formation, so each gamete receives only one allele of each pair.

Homologous organs

Structures in different species that share a common evolutionary origin and basic plan but may differ in function, such as the forelimbs of vertebrates.

Coelom

A true body cavity lined completely by mesoderm, present in annelids and all higher animals, distinguishing them from acoelomates and pseudocoelomates.

Compound eye

An eye made of many optical units called ommatidia, found in insects such as the cockroach, giving a mosaic image and wide field of view.

Areolar tissue

The most widespread loose connective tissue, with scattered cells in a gel matrix, binding skin to muscle and supporting small blood vessels and nerves.

Bile

A liver secretion stored in the gall bladder that contains bile salts and pigments but no enzymes; it emulsifies fats and neutralises acidic chyme.

Bohr effect

The shift in the oxygen dissociation curve to the right when carbon dioxide or hydrogen ion concentration rises, causing haemoglobin to release oxygen more readily.

Glomerular filtration

Pressure-driven ultrafiltration of blood in the Bowman's capsule, retaining cells and large proteins while passing water and small solutes into the tubule.

Antagonistic muscles

A pair of muscles that produce opposite movements at a joint, such as biceps flexing and triceps extending the elbow.

Action potential

A rapid reversal of membrane potential from negative to positive and back, caused by sodium entry followed by potassium exit, which propagates along an axon.