excretion

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• Edexcel IGCSE Biology: Double Science
• Characteristics of Living Organisms


  • 1.1 Characteristics of Living Organisms
  • 1.2 Common Features: Eukaryotic Organisms
  • 1.3 Common Features: Prokaryotic Organisms
  • 1.4 Pathogens
• The Unifying Characteristics of Living Organisms


  In order for something to be considered 'living', it must fulfil specific criteria that are true of all living organisms
• Criteria for living organisms (MRS C GREN)


  • Movement
  • Respiration
  • Sensitivity
  • Control
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• If something does not carry out all of these life processes, it is either dead or non-living
• Viruses are a good example of non-living particles/agents
• Nutrition


  Organisms must obtain food to provide energy
• Nutrition in plants


  Plants use sunlight, carbon dioxide and water to produce oxygen and glucose in the process of photosynthesis

  
• Nutrition in animals


  Animals consume other living organisms in order to obtain the energy they require
• Autotrophs


  Make their own food
• Heterotrophs


  Obtain food from a range of food sources
• Respiration


  A chemical reaction carried out in all living organisms to release energy from glucose

  
• Aerobic respiration


  Glucose + Oxygen → Carbon dioxide + Water + Energy

  
• Energy is transferred in the form of ATP
• Excretion


  The removal of toxic materials and substances from organisms
• Waste products excreted by animals

  • Carbon dioxide from respiration
  • Water from respiration and other chemical reactions
  • Urea which contains nitrogen resulting from the breakdown of proteins
• Waste products excreted by plants


  • Oxygen from photosynthesis
  • Carbon dioxide from respiration
  • Water from respiration and other chemical reactions
• Sensitivity


  The ability of an organism to detect and respond to stimuli in its surroundings
• Sensitivity responses in animals

  The nervous system and endocrine system allow humans to respond to their environment
• Sensitivity responses in plants


  Responses are controlled by chemicals and are usually much slower, e.g. geotropism and phototropism
• Movement


  An action by an organism causing a change of position or place
• Plants cannot move from place to place but can change their orientation, e.g. sunflowers tracking the sun
• Control


  Living organisms must control their internal environment in order to keep conditions within required limits, known as homeostasis
• Homeostasis in humans


  Mechanisms to control body temperature, blood glucose levels, and water levels
• Homeostasis in plants


  Plants use transpiration to maintain a suitable temperature
• Reproduction


  The process that leads to the production of more of the same kind of organism
• Types of reproduction


  • Sexual reproduction
  • Asexual reproduction
• Sexual reproduction


  The male and female gametes fuse together to form a zygote with DNA from both parents
• Asexual reproduction


  Cells or whole organisms can reproduce without the fusion of gametes, producing an exact clone of the parent
• Growth


  A permanent increase in size
• In animals, an individual grows larger between the zygote and adult stage with changes in proportion or shape
• In plants, an individual grows larger throughout their whole life with new shoots, leaves, branches etc forming year after year
• Eukaryotic organisms


  Animals, plants, fungi and protoctists, made up of cells that contain a nucleus with a distinct membrane
• Prokaryotic organisms


  Bacteria, single-celled organisms without a distinct membrane-bound nucleus
• Main features of animals


  • Multicellular
  • Cells contain a nucleus with a distinct membrane
  • Cells do not have cellulose cell walls
  • Cells do not contain chloroplasts
  • Feed on organic substances made by other living things
  • Often store carbohydrates as glycogen
  • Have nervous coordination
  • Able to move from place to place
• A typical animal cell
• Cell Structures Found in Both Animal and Plant Cells