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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...

· ‘T.H. Huxley’ made the first attempt to explain the origin of man on a scientific basis in his book ‘Man’s Place in the Nature’ (1863AD). · ‘Charles Darwin’ published his views on man’s ancestry in the book ‘Descent of Man’ (1871AD). · Linnaeus gave the scientific name Homo sapiens to man. · Lucretius called men ‘Babies born out of the womb of the earth’. · Mammals originated from Therapsid reptiles in the Triassic period of the Mesozoic era about 250 million years ago. Its teeth, limbs and other skeletal features resembled those of present mammals. · First primitive mammal was an egg-laying prototherian that originated from synapsid reptiles in the Cretaceous period of the Mesozoic era. · Lemurs were the first primates to evolve. Primates appeared in the Paleocene epoch of the tertiary period of the Cenozoic era about 65 million years ago from the small terrestrial shrew-like insectivores, a stock from which other types of existing mammals also arose. · Certain insectivores started ...

·   Many theories have been put forward by many scientists to explain the mechanism of evolution. ·   Some of the important theories are given below. 1.  Lamarckism  or Lamarck's theory or Theory of Inheritance of Acquired characters 2.  Darwinism  or Darwin’s theory or Theory of Natural selection 3.  Mutation theory  of Hugo de Vries 4.  Modern synthetic theory  or Neo-Darwinism or Modern Concept of Evolution 1. Lamarckism or Lamarck's theory or Theory of Inheritance of Acquired Characters (1744-1829 AD) · Lamarck, the great French biologist, put forward the theory of evolution for the first time. · His famous book  'Philosophie Zoologique'  (Zoological Philosophies) was published in 1809 AD (the same year Darwin was born.) in which he discussed his theory in detail. · He coined the terms invertebrates and Annelida. · The term  Biology   was given by Lamarck and Treviranus in 1802 AD. · Main theme of Lamarck's theory...