Life processes

• Life processes are essential for all living organisms, including plants and animals
• Life processes maintain homeostasis and proper functioning of the body
• In unicellular organisms, all life processes are carried out by a single cell
• In multicellular organisms, well-developed systems are present to carry out life processes
• Nutrition is the process of acquiring food needed for nourishment and sustenance of the organism
• There are two main modes of nutrition: autotrophic and heterotrophic
• Autotrophic nutrition is present in plants, algae, and some bacteria, where organisms produce their own food using light energy or chemical energy
• Heterotrophic nutrition is present in bacteria, fungi, and animals, where they derive energy from organic compounds
• Heterotrophic nutrition has subtypes such as holozoic, saprophytic, and parasitic nutrition
• Autotrophic nutrition is when an organism can make its own food using sunlight or chemicals
• Plants photosynthesize using light energy and are called photoautotrophs
• Few bacteria use chemicals to derive energy and are called chemoautotrophs
• Photosynthesis is the process by which plants make food using sunlight and water
• Chlorophyll absorbs light energy, splitting water into hydrogen and oxygen
• Hydrogen is used to reduce carbon dioxide into carbohydrates, typically glucose
• Stomata are pores on leaves that help in the exchange of gases
• Stomata are mostly found on the underside of the leaf and are guarded by guard cells
• Guard cells control the opening and closing of the pore based on water content
• Saprophytic nutrition is when organisms feed on dead and decaying organic matter
• Food is partially digested outside the body and then absorbed
• Fungi are examples of saprophytes
• Parasitic nutrition is when organisms feed at the expense of another organism
• Parasites live on or in the body of a host organism, deriving nutrients directly from the host
• Examples include leeches, Ascaris, and Cuscuta
• Amoeba feeds by holozoic mode of nutrition
• It engulfs food particles using pseudopodia in a process called phagocytosis
• Food vacuoles form for digestion, absorption, and assimilation, with undigested food egested
• Humans are omnivores, capable of eating plant-based and animal-based food
• The digestive system consists of an alimentary canal and associated digestive glands
• There are five stages in human nutrition: Ingestion, Digestion, Absorption, Assimilation, and Egestion
• Digestive system starts with the mouth and ends with the anus, including the oesophagus, stomach, small intestine, and large intestine
• Teeth help in cutting, shearing, and masticating food
• Teeth have four layers: enamel, dentine, cement, and dental pulp
• Different types of teeth (incisors, canines, molars, premolars) have specific functions in food processing
• The oesophagus transports food from the mouth to the stomach through peristaltic movements
• The stomach churns food into chyme using gastric juices and enzymes
• The small intestine is where most chemical digestion and absorption occur, with villi for increased surface area
• The large intestine absorbs water and salts, with the colon and rectum responsible for digestion and temporary storage of undigested food
• The colon has ascending, transverse, and descending regions, with the appendix housing useful bacteria
• Peristalsis is the wave-like movement of the alimentary canal for food propulsion