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Symbols and Formulae Some typical symbols derived from Latin names: English name Latin name Symbol Sodium Natrium Na Potassium Kalium K Iron Ferrum Fe Copper Cuprum Cu Silver Argentum Ag Gold Aurum Au Tin Stannum Sn Mercury Hydrargyrum Hg Lead Plumbum Pb Antimony Stibium Sb → German name of Tungsten is Wolfram & its symbol is W. → The term Atom was first used by Dalton in his atomic theory. → The term Molecule was first used by Avogadro in his ‘Avogadro’s hypothesis. → Dalton used the term compound atom instead of molecule. → Atom is the smallest particle that takes part in a chemical reaction. Elements and Compounds → There are 92 natural elements and more than 31 artificial elements. → The compound is composed of elements in a fixed proportion. → A substance composed of two or more non-reacting compounds is a mixture. ...

The development of frog is divided into two phases: 1. Pre-natal or Embryonic development ·   It is the development that takes place inside the egg or inside the womb of the mother up to the gastrula stage from the zygote. 2. Post-natal or Organogenesis ·   In this period, development from the birth of an organism to death is studied or the formation of organs from three germinal layers. a. Breeding: ·  Breeding takes place during the rainy season, in water. ·  Male frog croaks (mating call) by staying at shallow water region at night time to attract females.  ·   Many female frogs attract towards a male frog and male frog mounts over a female frog. ·  This Sexual embracing condition is called  amplexus or pseudocopulation . ·   Then the females lay the eggs in water and the male also releases the sperms. b. Ovulation: ·  It is a process of release of secondary oocytes from the ovary to the body cavity. c. Spawning: ·  When the...

Nervous System · The nervous system of earthworm is not well developed and is divided into the Central nervous system (CNS), Peripheral nervous system (PNS) and Sympathetic nervous system (SNS). a. Central nervous system (CNS) · Central nervous system passes through the centre of the body and consists of a brain ring that is present around the pharynx in segments 3 and 4.  · It is made up of: (a) two fused cerebral (Supra-pharyngeal) ganglia lying mid-dorsally and  (b) two fused sub-pharyngeal ganglia lying mid-ventrally. · The cerebral and sub-pharyngeal ganglia are connected by a ring-like circum-pharyngeal connective . Nervous system of Earthworm (a) Ventral nerve cord: It is paired, solid and show segmental ganglion from the 5th to the last segment. Each segmental ganglion is made up of two fused ganglia as evidenced by two segmental nerves that emanate from it. The nerve cord is made up of neurons and fibres and is covered by the visceral peritoneum and epineurium. Bipola...

Circulatory System and Circulation · Circulatory system of earthworms is of closed type as the blood flows in the closed blood vessels. · It consists of various types of blood vessels, heart, capillaries and  Plexi  which facilitate collection of the  deoxygenated  and the distribution of oxygenated blood to all organs and tissues of the body. · The blood contains the respiratory  pigment  called  haemoglobin  which is dissolved in the plasma. · Only one type of blood corpuscle, the  leukocytes  are present in the blood which kill the harmful germs. · No Red Blood Corpuscles (RBC) Present.  [BPKIHS 2005; IOM 2007; MOE] · Circulatory system  consists of three types of blood vessels- longitudinal, lateral or transverse blood vessels and intestinal plexus. I. Longitudinal blood vessels These function both as collecting and distributing blood vessels. These are  five  in number. a. Dorsal blood vessel · It is the...

Digestive System and Digestion · The digestive system of earthworm consists of the tubular alimentary canal and digestive glands associated with it. · Alimentary canal is a long straight tube with a variable diameter extending from mouth to anus. It consists of the following parts. a.  Mouth and Buccal cavity (1st to 3rd segments) b.  Pharynx (4th segment) c.  Oesophagus (5th to 7th segments) d. Gizzard (8th segment) e.  Stomach (9th to 14th segments) f.  Intestine (15th to the last segment except for anus) g.  Anus (last segment) · Digestion is the process of breaking down complex organic food by a biochemical process to change into a simple and soluble form to be utilized in the body. 1. Mouth and Buccal cavity The mouth is a  crescentic  aperture lying below the  fleshy lobe, the prostomium,  in  the peristomium . It leads into a short, narrow and thin-walled buccal cavity, extending up to the middle of the 3rd segment. The bucca...