These DAV Class 6 Science Notes and DAV Class 6 Science Chapter 9 Notes – Structure and Function of the Living Organisms: Animals act as excellent revision resources, particularly in preparation for board exams.
Structure and Function of the Living Organisms: Animals Class 6 DAV Notes
→ Cell: Cell is the smallest unit of life which can perform various life functions.
→ Tissue: A group of cells makes a tissue.
→ Organ: A group of tissues makes an organ.
→ Organ System: A group of organs makes an organ system. An organ system is responsible for a specialized set of functions.
→ Organism: Many organ systems group together to form an organism. An organism is an independent entity.
→ Digestive System: The digestive system in humans is responsible for digestion of food.
→ Digestion: The process of digestion involves four main steps, viz. ingestion, digestion, absorption and assimilation.
→ Mouth: The mouth is also called oral cavity. It contains tongue, teeth and salivary glands.
→ Teeth: Human beings get two sets of teeth in their lifetime. The first set of teeth is composed of milk teeth which appear when the child is about 6 months old. They are replaced by a set of permanent teeth which appear when the child is about 7 years old.
→ Structure of a tooth: A tooth is a hard structure which is composed of two parts, viz. crown and root. The visible part of the tooth is called crown. The root remains inside the gum and is attached to a socket in the jawbone. The outer layer of the crown is made up of enamel which is the hardest substance in the human body.
→ Function of tooth: Teeth help in breaking the food into smaller particles. They also crush and grind the food further.
→ Types of Teeth: There are four types of teeth, viz. incisors, canines, premolars and molars.
→ Tongue: The tongue is a muscular organ. The main functions of the tongue are as follows:
- It helps us to taste the food. The tongue is sensitive to four basic tastes, i.e. salt, bitter, sour and sweet.
- It helps in swallowing the food.
- Help in mixing the food with saliva produced by salivary glands.
- It helps in speech.
→ Salivary Glands: There are 3 pairs of salivary glands in the mouth. They produce a watery fluid called saliva. Saliva helps in moistening the food so that it can be easily swallowed. Saliva also contains a digestive enzyme which does some digestion of food.
→ Food Pipe: It is also called oesophagus. It is a tube-like structure which begins from the mouth and ends in the stomach. Food from mouth travels through the food pipe to reach the stomach.
→ Stomach: It is a bag-like organ which is composed of muscular walls. The food is mixed with gastric juice in the stomach. Gastric juice helps in digestion of food.
→ Liver and Pancreas: These are the glands which are associated with the digestive system. Liver is the largest gland in the human body. It secretes bile which is a brownish green fluid. Pancreas secretes pancreatic juice which contains various digestive enzymes.
→ Small Intestine: This is a tube-like structure which starts from the end of the stomach. It is the longest part in the human digestive system. Juices from bile and pancreas are secreted into the small intestine. The major part of digestion happens in the small intestine.
→ Large Intestine: The large intestine is thicker but shorter than small intestine. Absorption of water happens in the large intestine.
→ Anus: It is the last part of the digestive system where undigested food gets collected and expelled from time to time.
→ Respiratory System
→ Respiration: The process of breaking down of food to release energy is called respiration. For this, oxygen is taken in and carbon dioxide is released by the body.
→ The respiratory system consists of following parts:
→ Nasal Cavity: Nasal cavity is just behind the nostrils. Hairs present in the nostrils filter dust particles and germs from the air. The air warms up when it passes through the nasal cavity.
→ Pharynx: The nasal cavity opens into the pharynx. The pharynx opens into larynx. Larynx is also called the voice box.
→ Wind Pipe: It is a tube-like organ which has two branches; each entering into one of the lungs. The wind pipe is composed of cartilaginous rings.
→ Lungs: A lung is a balloon like structure. The bronchioles enter the lungs and divide into numerous branches. At the end of a branch; there is an air sac; called alveoli. When air reaches the alveoli oxygen enters the blood and carbon dioxide comes out of blood. The carbon dioxide rich air is finally expelled out through the nostrils.
→ Diaphragm: Diaphragm is a membrane which separates the chest and abdominal cavity. The movement of diaphragm facilitates the expansion and contraction of lungs.
→ Circulatory System
→ The circulatory system is composed of blood vessels, heart and blood.
→ Heart: Heart is a muscular organ, which pumps the blood. There are four chambers in the human heart, viz. right auricle, right ventricle, left auricle and left ventricle. Deoxygenated blood comes to the right side of the heart and oxygenated blood comes to the left part of heart.
→ Blood Vessels: Arteries and veins are the two main types of blood vessels which branch out in blood capillaries. Arteries are thick-walled blood vessels and carry blood from heart to different organs. Veins are thin-walled blood vessels and carry blood from different organs to the heart.
→ Blood: Blood is a fluid tissue which is composed of blood plasma, blood cells and platelets. Red Blood Cells and White Blood Cells are the blood cells. Platelets help in blood clotting. Blood is responsible for carrying various substances in the body.
→ Nervous System
→ Nervous system is responsible for controlling and coordinating various activities in the body. It is composed of the brain, spinal cord and peripheral nerves.
→ Brain: Brain is the main control centre of the body. The human brain is divided into three main parts, viz. cerebrum, cerebellum and medulla.
→ Spinal Cord: Spinal cord emerges from the brain and goes through the vertebral column.
→ Neuron: Neuron is the functional and structural unit of the nervous system. Neurons are specialized cells which are responsible for transmission of nerve impulses.
→ Sense Organs: There are five sense organs in the human body, viz. eyes, nose, ear, tongue and skin. The nose detects the sense of smell, eyes give sense of vision, ears give sense of hearing, tongue gives sense of taste and the skin gives sense of touch. Sense organs help us in gathering information about the external environment so that the body can react accordingly.
→ Excretory System
→ Removal of waste substances from the body is called excretion. Excretory system is composes of a pair of kidneys, ureters, urinary bladder and urethra.
→ Kidney: A kidney is a bean-shaped organ. Kidney filters the impurities and excess water from blood. Urine formation takes place in the kidneys.
→ Male Reproductive System: The male reproductive system is composed of a pair of testis; which produce sperms.
→ Female Reproductive System: The female reproductive system is composed a pair of ovaries and a uterus.
→ Skeletal System: The skeletal system is composed of skull, backbone, ribs, hip bones and bones of arms and legs.
→ Functions of skeletal system:
- It provides shape and form to the body.
- It helps in movements (with the help of muscles).
- It protects the delicate internal organs.
→ Ligaments: Strands which join two bones together are called ligaments.
→ Tendons: Strands which join a bone to a muscle are called tendons.
→ Muscles contract and relax to facilitate movements.
→ Reproductive System: The system responsible for reproduction is called reproductive system. The male reproductive system consists of a pair of testes and the female reproductive system consists of a pah’ of ovaries. Testis produces sperms, while ovary produces eggs.
→ Fertilization: The union of sperm and egg is called fertilization. Fertilized egg develops into an embryo. The embryo grows and forms a human baby inside the body of the female.
→ Cell: It is the structural and functional unit of life.
→ Tissue: A group of cells is called tissue.
→ Organ: A group of tissues is called an organ.
→ Organ system: Various organs group together to form an organ system.
→ Digestion: The process of taking and breaking the food into simple substances is called digestion.
→ Respiration: The process of utilizing the food to release energy is called respiration.
→ Excretion: The process of removal of waste substances is called excretion.
→ Gastric: Anything associated with stomach is given a prefix ‘gastric’; such as gastric enzymes.
→ Reproduction: The process of producing offspring by living beings is called reproduction.
→ Ligament: The stretch which joins a bone to another bone.
→ Tendon: The stretch which joins a bone to a muscle.
→ Fertilization: Union of sperm and egg.