Biology Edexcel IGCSE

• The criteria for something to be considered 'living' are:

  • Movement
  • Respiration
  • Sensitivity
  • Control
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• Viruses are an example of non-living particles/agents
• Organisms must obtain food to provide energy
• Plants use sunlight, carbon dioxide, and water to produce oxygen and glucose in photosynthesis
• Animals consume other living organisms to obtain the energy they require
• Respiration is a chemical reaction carried out in all living organisms
• Energy is released from glucose either in the presence of oxygen (aerobic respiration) or the absence of oxygen (anaerobic respiration)
• Excretion is the removal of toxic materials and substances from organisms
• Waste products excreted by animals include carbon dioxide, water, and urea
• Waste products excreted by plants include oxygen, carbon dioxide, and water
• The sensitivity of an organism refers to its ability to detect and respond to stimuli in its surroundings
• In humans, the nervous system provides a complex system of receptors, neurones, and effectors to detect and respond to different stimuli
• In plants, responses are controlled by chemicals and are usually much slower
• Movement is an action by an organism causing a change of position or place
• Living organisms must control their internal environment in order to keep conditions within required limits
• Reproduction is the process that leads to the production of more of the same kind of organism
• Sexual reproduction involves the fusion of male and female gametes
• Asexual reproduction involves creating exact copies of the parent cell
• Growth is defined as 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 forming year after year
• Common Features of Eukaryotic Organisms:
• Living organisms can be classified into five kingdoms, including animals, plants, fungi, protoctists, and prokaryotes
• Animals, plants, fungi, and protoctists are all eukaryotic organisms, which means they can be multicellular or single-celled and have cells with a distinct membrane-bound nucleus
• Animals:
• Prokaryotic organisms, such as bacteria, are separate from eukaryotes, always single-celled, and do not contain a nucleus
• Plants:
• Main features of animals include being multicellular, having cells with a distinct membrane-bound nucleus, lacking cellulose cell walls and chloroplasts, feeding on organic substances, storing carbohydrates as glycogen, having nervous coordination, and being able to move
• Fungi:
• Main features of plants include being multicellular, having cells with a distinct membrane-bound nucleus, having cell walls made of cellulose, containing chloroplasts for photosynthesis, feeding by photosynthesis, storing carbohydrates as starch or sucrose, and lacking nervous coordination
• Protoctists:
• Main features of fungi include being usually multicellular, having cells with a distinct membrane-bound nucleus, having cell walls made of chitin, lacking chloroplasts, feeding by secreting extracellular digestive enzymes onto food, some being parasitic, storing carbohydrates as glycogen, and lacking nervous coordination
• Protoctists are a diverse kingdom of organisms that are mainly microscopic and single-celled, with some forming larger forms like colonies or filaments
• Protoctists have cells with a distinct membrane-bound nucleus and can exhibit features of animal cells or plant cells, some photosynthesizing and others feeding on organic substances
• Examples of protoctists include amoeba, Paramecium, Plasmodium, and Chlorella
• IGCSE Biology Edexcel exam
• Characteristics of Living Organisms:

  • Living organisms must fulfill specific criteria to be considered 'living'
  • Criteria can be remembered using the acronym MRS C GREN (Movement, Respiration, Sensitivity, Control, Growth, Reproduction, Excretion, Nutrition)
  • Viruses are non-living particles/agents
• Nutrition:

  • Organisms must obtain food for energy
  • Plants use sunlight, carbon dioxide, and water for photosynthesis to produce oxygen and glucose (autotrophic)
  • Animals consume other living organisms for energy and break down molecules through digestion (heterotrophic)
• Respiration:

  • Chemical reaction in all living organisms
  • Energy released from glucose in the presence (aerobic) or absence (anaerobic) of oxygen
  • Results in the production of carbon dioxide and water as waste products
  • Energy transferred in the form of ATP
• Excretion:

  • Metabolic reactions in living cells produce waste products
  • Excretion is the removal of toxic materials from organisms
  • Animals excrete carbon dioxide, water, and urea
  • Plants excrete oxygen, carbon dioxide, and water