Lesson 11 of 11 · 12 min
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Must-know facts
19 facts
- 01Only four basic tissue types build all complex animals: epithelial, connective, muscular and neural; the heart contains all four.
- 02Organ system = two or more organs doing a common function by physical and/or chemical interaction; the sharing of work is division of labour.
- 03Frog: class Amphibia, phylum Chordata; common Indian species Rana tigrina; poikilotherm.
- 04Aestivation = summer sleep, hibernation = winter sleep, both in deep burrows; gas exchange is then only through the skin.
- 05The frog never drinks water; it absorbs water through its moist, mucus-covered skin.
- 06Body = head + trunk; no neck, no tail.
- 07Fore limb 4 digits, hind limb 5 digits (larger, muscular, webbed).
- 08Male frog: vocal sacs, and a copulatory pad on the first digit of each fore limb.
- 09Short alimentary canal because the frog is carnivorous; tongue bilobed; bile and pancreatic juice reach the duodenum through a common bile duct.
- 10In water: cutaneous respiration only. On land: buccal cavity, skin and lungs.
- 11Heart: three chambers (two atria, one ventricle), pericardium, sinus venosus joining the right atrium, conus arteriosus on the ventral side.
- 12Hepatic portal system (liver–intestine) and renal portal system (kidney–lower body) are both present in the frog.
- 13Frog RBCs are nucleated; lymph lacks some proteins and RBCs; circulation is closed, with a three-chambered heart in which blood mixes in the one ventricle.
- 14Frog is ureotelic; kidneys are made of uriniferous tubules (nephrons).
- 15Male ureter = urinogenital duct; in the female, ureters and oviducts open separately into the cloaca.
- 16Ten pairs of cranial nerves; optic lobes in the mid-brain; medulla leaves through the foramen magnum.
- 17Eyes and internal ears are the only well-organised sense organs; no external ear, only a tympanum; the ear also balances.
- 1810–12 vasa efferentia → Bidder's canal → urinogenital duct → cloaca; testes held by the mesorchium.
- 19A female lays 2500–3000 ova at a time; fertilisation external in water; tadpole larva metamorphoses into the adult.
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Key terms
20 terms
- Tissue
- A group of similar cells, with their intercellular substance, doing a particular job.
- Organ system
- Two or more organs that work together, physically and/or chemically, for one common function.
- Division of labour
- The sharing of the body's work among cells, tissues, organs and organ systems.
- Morphology
- Study of the form of an organism; in animals, the external appearance of its organs and parts.
- Anatomy
- In animals, the study of the form of the internal organs.
- Poikilotherm
- A cold-blooded animal whose body temperature follows that of its surroundings.
- Aestivation
- Summer sleep in a burrow to escape extreme heat.
- Hibernation
- Winter sleep in a burrow to escape extreme cold.
- Nictitating membrane
- A membrane covering the frog's eye that protects it in water.
- Tympanum
- The membrane beside the frog's eye that receives sound; the only visible part of its ear.
- Cutaneous respiration
- Gas exchange through the moist skin by diffusion.
- Pulmonary respiration
- Breathing with the lungs.
- Sinus venosus
- Triangular chamber that receives blood from the vena cava and joins the right atrium.
- Conus arteriosus
- Sac-like structure on the ventral side of the heart into which the ventricle opens.
- Portal system
- A special venous link between two organs: hepatic portal (intestine–liver) and renal portal (lower body–kidney).
- Ureotelic
- Excreting nitrogenous waste mainly as urea.
- Urinogenital duct
- The male frog's ureter, which carries both urine and sperms to the cloaca.
- Mesorchium
- Double fold of peritoneum holding each testis to the kidney.
- Bidder's canal
- Canal in the kidney into which the vasa efferentia open, linking them to the urinogenital duct.
- Metamorphosis
- The change of the tadpole larva into the adult frog.