Life processes

• Visible movement is a common evidence for being alive
• Plants are considered alive because they grow over time
• Some animals can breathe without visible movement
• Invisible molecular movement is necessary for life
• Living organisms are well-organised structures with tissues, cells, and smaller components
• Organised, ordered nature of living structures is likely to break down over time due to environmental effects
• Living creatures must keep repairing and maintaining their structures to remain alive
• Living structures are made up of molecules that must be moved around all the time
• Maintenance processes in living organisms are called life processes
• Energy is needed for maintenance processes, which comes from outside the organism's body
• Energy transfer from outside the body to the inside is called nutrition
• Most food sources for organisms are carbon-based
• Different organisms use different nutritional processes based on the complexity of carbon sources
• Chemical reactions in the body, like oxidising-reducing reactions, break down molecules for energy generation
• Oxygen is commonly used in the process of breaking down food sources for cellular needs, known as respiration
• Multi-cellular organisms require specialised tissues for functions like food uptake, gas exchange, and waste removal
• Transportation systems are needed to carry food and oxygen to different parts of the body
• Waste by-products created during chemical reactions need to be removed from the body through excretion
• Organic compounds prepared by bacteria from atmospheric nitrogen are called nitrogenous compounds
• Heterotrophic nutrition varies depending on the type and availability of food material and how it is obtained by the organism
• Organisms are adapted to their environment
• Form of nutrition differs based on the type and availability of food material
• Food source being stationary or mobile affects how the food is accessed
• Nutritive apparatus used by different organisms varies
• Some organisms break down food material outside the body and then absorb it
• Examples of organisms that break down food material outside the body: fungi like bread moulds, yeast, and mushrooms
• Other organisms take in whole material and break it down inside their bodies
• Parasitic nutritive strategy used by organisms like cuscuta, ticks, lice, leeches, and tape-worms
• In single-celled organisms, food may be taken in by the entire surface
• Complexity of the organism leads to different parts being specialized for different functions
• Examples of single-celled organisms with different methods of taking in food: Amoeba and Paramoecium
• Alimentary canal in human beings is a long tube extending from the mouth to the anus
• Various regions of the alimentary canal are specialized to perform different functions
• Food is processed in the alimentary canal to generate small, uniform particles for absorption
• Food is crushed with teeth to aid in digestion
• Saliva contains an enzyme called salivary amylase that breaks down starch into sugar
• Muscles in the lining of the canal contract rhythmically to push food forward (peristaltic movements)
• Stomach expands when food enters and mixes food with digestive juices released by gastric glands
• Gastric glands release hydrochloric acid, pepsin (protein digesting enzyme), and mucus in the stomach
• Bile juice from the liver helps in making the food alkaline and acts on fats in the small intestine