Life Processes: Nutrition and Types

• Life processes are the series of actions that are required to maintain a living organism
• These processes occur at all levels of organization, from the molecular to the organismal level
• They include nutrition, respiration, transport, excretion, reproduction, growth, and movement

Nutrition

• Nutrition is the process of obtaining and utilizing nutrients
• Nutrients are substances that provide energy or are needed for growth and repair
• Autotrophs are organisms that can produce their own food from simple inorganic substances using light or chemical energy
• Photosynthesis is the process by which plants and other autotrophs use light energy to convert carbon dioxide and water into glucose and oxygen
• Heterotrophs are organisms that obtain their nutrients by consuming other organisms or organic matter
• Heterotrophic nutrition includes several types:
  • Saprophytic nutrition: deriving nutrients from dead and decaying organic matter
  • Parasitic nutrition: deriving nutrients from a living host organism
  • Holozoic nutrition: ingestion, digestion, absorption, assimilation, and egestion of food
• Ingestion is the process of taking food into the body
• Digestion is the breakdown of complex food substances into simpler, absorbable forms
• Absorption is the process by which digested nutrients are taken into the body fluids
• Assimilation is the utilization of absorbed nutrients for energy, growth, and repair
• Egestion is the elimination of undigested waste materials

Respiration

• Respiration is the process by which organisms obtain energy from food
• It involves the breakdown of glucose or other organic molecules in the presence or absence of oxygen
• Aerobic respiration is the process that uses oxygen to break down glucose, producing carbon dioxide, water, and a large amount of energy
• Anaerobic respiration is the process that breaks down glucose without oxygen, producing less energy and other byproducts like lactic acid or ethanol
• Glycolysis is the first step in both aerobic and anaerobic respiration, occurring in the cytoplasm and breaking down glucose into pyruvate
• In aerobic respiration, pyruvate is further oxidized in the mitochondria through the Krebs cycle and electron transport chain
• In anaerobic respiration, pyruvate is converted into other compounds through fermentation
• Breathing or ventilation is the process of moving air in and out of the lungs to facilitate gas exchange
• Gas exchange occurs in the alveoli of the lungs, where oxygen diffuses into the blood and carbon dioxide diffuses out
• In plants, gas exchange occurs through stomata in the leaves and lenticels in the stems

Transportation

• Transportation is the process of moving substances within an organism
• In animals, the circulatory system transports blood, nutrients, gases, hormones, and waste products
• The heart is the central organ of the circulatory system, pumping blood throughout the body
• Blood vessels include arteries, veins, and capillaries
  • Arteries carry blood away from the heart
  • Veins carry blood back to the heart
  • Capillaries are the site of exchange between blood and tissues
• Blood consists of plasma, red blood cells, white blood cells, and platelets
  • Plasma is the liquid matrix of blood
  • Red blood cells carry oxygen
  • White blood cells are involved in immune defense
  • Platelets are involved in blood clotting
• In plants, the vascular system transports water, minerals, and food
• Xylem transports water and minerals from the roots to the rest of the plant
• Phloem transports sugars produced during photosynthesis from the leaves to other parts of the plant
• Transpiration is the process by which water evaporates from the leaves, creating a pull that helps draw water up the xylem
• Translocation is the movement of sugars in the phloem from sources to sinks

Excretion

• Excretion is the process of removing metabolic waste products from the body
• In animals, excretory organs include:
  • Kidneys filter waste products from the blood and produce urine
  • Lungs excrete carbon dioxide
  • Skin excretes sweat
  • Liver detoxifies harmful substances
• Nephrons are the functional units of the kidneys, filtering blood and reabsorbing essential substances
• Urine consists of water, urea, salts, and other waste products
• In plants, excretion is less complex and may involve storing waste products in vacuoles or shedding leaves

Control and Coordination

• Control and coordination are the processes that regulate and integrate the various activities of an organism
• In animals, the nervous system and endocrine system work together for control and coordination
• The nervous system includes the brain, spinal cord, and nerves
• Neurons are the basic units of the nervous system, transmitting electrical and chemical signals
• The endocrine system consists of glands that secrete hormones
• Hormones are chemical messengers that regulate various physiological processes
• In plants, coordination is primarily achieved through plant hormones or phytohormones
• Auxins promote cell elongation and growth
• Gibberellins promote stem elongation, germination, and flowering
• Cytokinins promote cell division and delay aging
• Abscisic acid (ABA) inhibits growth and promotes dormancy
• Ethylene promotes fruit ripening and senescence
• Tropisms are growth responses to directional stimuli
• Phototropism is growth in response to light
• Geotropism is growth in response to gravity
• Chemotropism is growth in response to chemicals
• Nastic movements are non-directional responses to stimuli

Reproduction

• Reproduction is the process by which organisms produce new individuals of the same kind
• Asexual reproduction involves a single parent and produces offspring that are genetically identical to the parent
• Types of asexual reproduction include:
  • Binary fission: division of a single cell into two identical cells
  • Budding: outgrowth of a new individual from the parent organism
  • Fragmentation: breaking of an organism into fragments, each of which can develop into a new individual
  • Spore formation: formation of spores that can develop into new individuals
  • Vegetative propagation: development of new plants from vegetative parts such as roots, stems, or leaves
• Sexual reproduction involves two parents and produces offspring that are genetically different from the parents
• It involves the fusion of gametes (sex cells) to form a zygote
• Gametes are produced by meiosis, a type of cell division that reduces the chromosome number by half
• Fertilization is the fusion of male and female gametes to form a zygote
• In flowering plants, sexual reproduction involves pollination and fertilization
• Pollination is the transfer of pollen grains from the anther to the stigma
• Fertilization occurs when the pollen tube grows to the ovule, and the sperm fuses with the egg
• In humans, sexual reproduction involves the union of sperm and egg
• The male reproductive system produces sperm and delivers it to the female reproductive system
• The female reproductive system produces eggs and provides a site for fertilization and development

Growth

• Growth is the permanent increase in size or mass of an organism
• It involves cell division, cell enlargement, and cell differentiation
• In animals, growth is generally limited to a certain period of life
• In plants, growth can occur throughout the life of the plant
• Growth is influenced by genetic factors, nutrition, and environmental conditions

Movement

• Movement is the change in position of an organism or its parts
• It can be voluntary or involuntary
• In animals, movement is typically achieved through muscles and skeletal system
• Muscles contract to produce movement
• In plants, movement is generally slower and may involve growth or turgor pressure changes
• Turgor movements are changes in the turgor pressure of cells, causing movements such as the opening and closing of stomata