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(2) LIFE PROCESSES
Life Processes:- The basic functions performed by living organisms to maintain their life on the earth is called life processes. Sequences:- Q- Which criteria do we use to decide whether something is alive? Ans- i) Molecular movement like O2, CO2, H2O, Food, etc. which is the main criteria. ii) Presence of Defining Characteristics/Processes like Nutrition, Cellular organization, Consciousness (Response to stimulus), Intrinsic growth, Only. Nutrition:- It is a process of intake (ingest) and utilization (digestion) of nutrients by an organism. (OR) The process by which an organism takes food and utilizes it to get energy, for growth, repair, maintenance, etc. is called nutrition. MODES OF NUTRITION: - There are mainly 2 types of Nutrition: - A) Autotrophic Nutrition B) Heterotrophic Nutrition Heterotrophic Nutrition is of 3 types: - i) Holozoic nutrition ii) Parasitic nutrition iii) Saprotrophic (Saprophytic) nutrition (A) Autotrophic Nutrition: - The nutrition in which an organism prepares(synthesis) its own food from organic sources like CO2 and water, etc is called autotrophic nutrition. Ex- i) All Green plants ii) Oxygenic Photosynthetic Bacteria Like Cyanobacteria (blue-green algae) iii) Anoxygenic Photosynthetic Bacteria Like Green sulphur bacteria, Purple sulphur bacteria
(B) Heterotrophic Nutrition:- The nutrition in which an organism cannot prepares its own food and depends on the other organisms for its food is called heterotrophic nutrition. Ex- Animals, Most of the bacteria, Fungi, etc. (NOTE:- Fungi are called the non-green heterotrophic plants of the plant kingdom. This includes Yeasts, Molds, Mushrooms, Smuts, Rusts, etc.) Heterotrophic Nutrition is of three types: - i) Holozoic nutrition – The nutrition in which an organism obtains complex substance and then breaks down into simpler form/ substance is called holozoic nutrition. Ex- Human being, Amoeba, cow, deer, etc. (NOTE:- Holozoic nutrition happens in five steps:- ingestion (intake), digestion, absorption, assimilation (utilization) and egestion.) ii) Parasitic nutrition – The nutrition in which an organism obtains its food from host organism without killing it is called parasitic nutrition. Ex- Lice, leeches, ticks, bed bugs, Tapeworm, Roundworm, mosquitoes, plasmodium, Cuscuta (Amarbel), etc. (NOTE:- A parasite is the organism which feeds on another living organism called its Host. A parasite gives the Host nothing in return and usually harms the Host.) iii) Saprotrophic/ Saprophytic nutrition – The nutrition in which an organism obtains its food from dead and decaying matter is called saprotrophic nutrition. OR The nutrition in which an organism breaks down the food material outside the body and then absorbs it is called saprotrophic nutrition. Ex- Fungi like bread moulds, mushrooms, yeast and many other bacteria.
Mesophyll cell:- The cell having Chloroplasts. Q- Why are stomata and guard cells are called turgor operated values? Ans- Stomata and guard cells are called turgor operated values. Because the opening and closing of stomata is regulated by turgidity of guard cells. Turgidity:- It is a state of being turgid or swollen due to uptake of water/ fluid. OR It is the point at which the cell membranes pushes against the cell wall. Q- Which surface of leaf has more stomata? Why? Ans- The lower epidermis has more stomata (especially in Dicotyledons ). Because it more often in the shade and cooler. So evaporation won’t takes place as much. [NOTE:- In Monocotyledons , usually have an equal number of stomata.] PHOTOSYNTHESIS in Desert Plants (CAM Photosynthesis) CAM- Crassulacean Acid Metabolism i) In desert plants, stomata is open during night. ii) During the daytime, stomata is closed to prevent loss of water by Transpiration.
iii) At night, CO2 is absorbed by the stomata and converted into Malic acid (Oxalo acetic acid) and store in the food vacuole. iv) During the daytime, the Malic acid is converted back into CO2 (Decarboxylation). v) Then CO2 is combine with H2O in the presence of light, starch is synthesized. ( NOTE: Chlorophyll is present in the stem of Cactus plant) Nutrition in Amoeba:- Amoeba is a unicellular organism which follows the holozoic mode of nutrition. i) Amoeba takes in (engulfs) food using temporary finger-like extensions called pseudopodia. [ NOTE- This process is called phagocytosis (a type of Endocytosis)] ii) When a food particle comes near amoeba, it forms pseudopodia around it. iii) When two pseudopodia fuse together forms a food vacuole. iv) Inside the food vacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm. v) The remaining undigested material is exit out to the surface of the cell and thrown out.
c) Pepsin digests Proteins and Renin digests milk proteins in infants. The mucus protects the inner lining of the stomach from the action of HCl. iii) Small intestine – a) From the stomach, the partial digested food enters the small intestine. The exit of food from the stomach is regulated by sphincter muscle. The small intestine is the site for complete digestion of carbohydrates, proteins and fats. It receives the secretions of the liver and pancreas. b) Liver and Pancreas- Liver secretes bile juice which stored in the gall bladder. Bile is alkaline (basic) and contains bile salts which helps to break down the fats (large globules) into smaller globules (emulsified fats). Bile makes the acidic food alkaline , so that pancreatic enzymes can act. The pancreatic juice contains inactive enzymes trypsinogen, Chymotrypsonogen, Amylase, Lipase, Nucleases, etc. Trypsin digests proteins and it also activates the other pancreatic enzymes. Lipase digests Emulsified fats. c) The walls of small intestine contain glands which secretes intestinal juice, that contains enzymes Maltase, Lipase, Dipeptidase, Nucleosidase, etc. This enzymes finally convert the proteins into amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol.
The digested food is absorbed to the blood through the walls of small intestine. Here, Villi (which has Brush border columnar epithelium) increases the surface area for absorption. ⁕ Maximum Digestion takes place in- Duodenum (Front Part) ⁕ Maximum Absorption takes place in- Jejunum (Middle Part) iv) Large intestine- Then the unabsorbed (undigested) food is entered to the large intestine. Caecum prevents backflow of faecal matter. Here, most of the water, some minerals and drugs are absorbed with the help of villi. v) Rectum and Anus- The waste material as faeces is removed from the body through rectum and anus. The exit of the waste material is regulated by the anal sphincter. DIAGRAM OF HUMAN ALIMENTARY CANAL
Important NOTE:- ►The digestion process begins/ starts at - Mouth. ►The complete digestion takes place at - Small intestine. ►The inner lining of the small intestine has numerous finger-like projections which increase the surface area for absorption of food - Villi (which has Brush border columnar epithelium) ► Protease enzymes are present in stomach (as pepsin), in small intestine (as peptidase) & in pancreas (as trypsin). ► Accessory glands: Salivary gland, liver and pancreas are the accessory glands which lie outside the alimentary canal. ►The lining of canal has sphincter muscles that contract rhythmically in order to push the food forward. Important Table:- Organs Enzymes present Types of food digested Mouth (Saliva secrets) Salivary amylase Carbohydrates Lysozyme Acts as an antibacterial agent that prevents infections. Stomach (Gastric juice) Pepsinogen (to Pepsin) Proteins Mucus Protects inner lining of stomach against action of HCl. Lipase (in small quantity) -------- Small intestine (Intestinal juice) Peptidases, Sucrase, Lactase, Maltase, Lipase, Nucleosidase, etc Carbohydrates, Proteins & Fats Glands Enzymes present Digested food by enzymes Pancreas (Pancreatic juice) Trypsin & Chymotrypsin Proteins Lipase Fats Amylase Carbohydrates Nuclease Nucleic acids Liver Bile & bile salts Bile salts- Large fats
Q- Why do the herbivores need a longer small intestine than carnivores? Ans - Herbivores eat grass which contain cellulose which is hard to digest. So they need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine. Dental caries/ Tooth decay:- The formation of small cavities (holes) in the teeth due to the action of acid-forming bacteria and improper dental care is called dental caries/ tooth decay. Dental plaque:- Masses of bacteria cells together with food particles (of sticky, yellowish layer) stick to the teeth to form dental plaque. ► Brushing teeth after eating food regularly removes the plaque before the bacteria produce acids. This prevents dental caries or tooth decay. Parts of Digestive System Substances absorbed Mouth Certain drugs ( in mucosa of mouth & lower side of tongue) Stomach Water, Simple sugar , Alcohol Small Intestine Nutrients Large Intestine Water, Some minerals, Drugs
