LIFE PROCESS

• Visible movement is a common evidence for being alive
• Some sort of movement, either growth-related or not, is considered as common evidence for being alive
• Plants that are not visibly growing are still alive
• 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
• Living creatures must keep repairing and maintaining their structures to stay alive
• All living structures are made up of molecules, so molecules must be moved around all the time
• Life processes are the processes that perform maintenance job in living organisms
• Maintenance functions of living organisms must go on even when they are not doing anything particular
• Energy is needed for maintenance processes, which comes from outside the body of the organism
• Life processes include nutrition, respiration, transportation, and excretion
• Nutrition is the process of transferring a source of energy from outside the body of the organism to the inside
• Different organisms use different kinds of nutritional processes depending on the complexity of carbon sources
• Autotrophs use simple food material obtained from inorganic sources like carbon dioxide and water
• Heterotrophs use complex substances that need to be broken down into simpler ones using enzymes
• Autotrophic organisms fulfil their carbon and energy requirements through photosynthesis
• Photosynthesis is the process by which autotrophs convert carbon dioxide and water into carbohydrates in the presence of sunlight and chlorophyll
• Carbohydrates produced in photosynthesis are used to provide energy to the plant and are stored in the form of starch
• Heterotrophic organisms depend directly or indirectly on autotrophs for survival
• Heterotrophic nutrition involves obtaining energy and materials from outside sources
• Water used in photosynthesis is taken up from the soil by the roots in terrestrial plants
• Other materials like nitrogen, phosphorus, iron, and magnesium are also taken up from the soil
• Nitrogen is an essential element used in the synthesis of proteins and other compounds
• Organic compounds prepared by bacteria from atmospheric nitrogen
• Heterotrophic Nutrition:

  • Each organism is adapted to its environment
  • Form of nutrition depends on type and availability of food material and how it is obtained
  • Differences in accessing food based on whether the food source is stationary or mobile
  • Range of strategies for taking in and using food material
  • Some organisms break down food material outside the body and then absorb it (e.g. fungi like bread moulds, yeast, mushrooms)
  • Others take in whole material and break it down inside their bodies
• • Some organisms derive nutrition from plants or animals without killing them (parasitic nutritive strategy used by organisms like cuscuta, ticks, lice, leeches, tape-worms)
• How do Organisms obtain their Nutrition:

  • Digestive system differs in various organisms based on food and how it is obtained
  • Single-celled organisms may take in food by entire surface
  • Complexity of organism leads to different parts specialized for different functions
  • Examples: Amoeba takes in food using temporary finger-like extensions of cell surface, Paramoecium takes in food at specific spot using cilia
• Nutrition in Human Beings:

  • Alimentary canal is a long tube from mouth to anus
  • Different parts of tube specialized for different functions
  • Food is processed by crushing with teeth and wetted by saliva for smooth passage
  • Saliva contains enzyme salivary amylase that breaks down starch into sugar
  • Food mixed with saliva and moved around mouth while chewing by muscular tongue
  • Peristaltic movements in lining of canal push food forward
  • Stomach expands when food enters, mixing food with digestive juices released by gastric glands
• • Intestinal juice converts proteins to amino acids, complex carbohydrates to glucose, fats to fatty acids and glycerol
  • Villi in small intestine increase surface area for absorption
  • Absorbed food taken to cells via blood vessels, utilized for energy, building new tissues, repairing old tissues
  • Unabsorbed food sent to large intestine, water absorbed, waste removed via anus
• • Gastric glands release hydrochloric acid, pepsin (protein digesting enzyme), and mucus
  • Acid in stomach creates acidic medium to facilitate pepsin action, mucus protects stomach lining
  • Food regulated by sphincter muscle into small intestine
  • Small intestine site of complete digestion of carbohydrates, proteins, fats
  • Receives secretions of liver and pancreas
  • Bile juice from liver makes food alkaline, acts on fats
  • Pancreatic juice contains enzymes like trypsin for proteins, lipase for emulsified fats
• Respiration:

  • Break-down of glucose into pyruvate in cytoplasm
  • Pyruvate converted into ethanol and carbon dioxide in yeast during fermentation (anaerobic respiration)
  • Break-down of pyruvate into carbon dioxide and water in mitochondria (aerobic respiration)
  • Aerobic respiration releases more energy than anaerobic
  • Build-up of lactic acid in muscles during lack of oxygen causes cramps
  • Energy released during cellular respiration used to synthesize ATP, energy currency for cellular processes
  • ATP broken down to provide energy for various cellular activities
• During the day, CO2 generated during respiration is used up for photosynthesis, hence there is no CO2 release
• Instead, oxygen release is the major event at this time
• Animals have evolved different organs for the uptake of oxygen from the environment and for getting rid of the carbon dioxide produced
• Terrestrial animals can breathe the oxygen in the atmosphere, but animals that live in water need to use the oxygen dissolved in water
• Fishes take in water through their mouths and force it past the gills where the dissolved oxygen is taken up by blood
• In human beings, air is taken into the body through the nostrils, filtered by fine hairs and mucus, then passes through the throat and into the lungs
• Rings of cartilage in the throat ensure the air-passage does not collapse
• The passage divides into smaller tubes which terminate in balloon-like structures called alveoli, where the exchange of gases takes place