The Variety of Life

• Living organisms vary in


  • Size
  • Complexity
  • Structural and functional features
• Living organisms


  • Plants (flowering and non-flowering)
  • Animals (vertebrates and invertebrates)
  • Other organisms (principally bacteria)
• Classifying living organisms


  • Makes it easier to identify organisms
  • Helps scientists communicate with each other
  • Organisms are given scientific names
• Scientific name


  Always two words, e.g. Homo sapiens (human), Ranunculus acris (meadow buttercup). The first name is the genus and the second name is the species.
• Types of adaptations


  • Morphological (structural)
  • Behavioural
• Behavioural adaptations


  • Time of day when an animal is active
  • Type of food it eats
• Plants have very limited "behaviour", so behavioural adaptations mostly apply to animals
• Resources needed by living things


  • Light
  • Food
  • Water
  • Oxygen
  • Carbon dioxide
  • Minerals
• Light


  Needed by plants to make food for energy
• Food


  Needed by animals for energy
• Water, oxygen, carbon dioxide, minerals


  Needed by all living organisms for the chemical reactions that take place in cells
• Competition for resources occurs between members of the same species and between organisms of different species with similar needs
• Competition puts a limit on the potential size of a population
• Competition only occurs when a particular factor (e.g. food) is in limited supply
• Predation, disease and pollution all contribute to the death rate in a population, and so also limit its size
• Biodiversity


  The number of different species (of all types) in a particular area, and the number of animals and plants of each species
• Importance of biodiversity


  • Leads to stable environments that can resist potentially harmful situations
  • Habitats are more interesting to humans for scientific and leisure purposes
  • Potential for extracting new medicines from plants
  • Can strengthen current breeds of domestic and farm animals and crops by crossbreeding with ancient breeds
• The more biodiversity there is in an area, the more options each species has if a source of food is wiped out, and so the environment is more stable
• Ways to maintain biodiversity


  • Breeding and release programmes
  • Active conservation of habitats of threatened species
  • Recreation of habitats that have declined
  • Control of invasive species
  • Legislation to protect habitats or individual species
  • Controlling pollution or other factors that might be threatening species or their habitats
• Legislating to protect habitats or species can be difficult as wildlife needs may conflict with human needs
• Principles of sampling to get data about biodiversity


  • The sample must be big enough to be representative of the area as a whole
  • The sample must be randomly selected
  • The sample must be taken from the same place each time to allow comparison
• Getting data about biodiversity - quadrats


  1. Divide the area into a numbered grid

  2. Use a random number generator to choose squares to sample

  3. Place the quadrat on each numbered square

  4. Identify, count and record the species within the quadrat

  5. Use the numbers to calculate the total for the area
• Quadrats cannot be used to sample animal populations where the animal moves
• Getting data about biodiversity - animal populations


  1. Capture a number of individuals

  2. Mark them so they can be distinguished

  3. Release them back into the habitat

  4. Capture another sample

  5. Calculate the total population using the proportion of marked individuals
• Capture-recapture technique


  N = MC/R, where N is the estimate of total population size, M is the number of animals captured and marked on the first visit, C is the total number of animals captured on the second visit, and R is the number of animals captured on the first visit that were then recaptured on the second visit
• The capture-recapture technique will only give accurate results when certain conditions apply
• An alien species is one that is not normally found in a country or geographical area, but has been introduced from a different part of the world
• Introducing an alien species can create problems such as having no predators, competing with existing species, preying on existing species, or carrying diseases
• Biological control


  Using living organisms (often predators) instead of chemical pesticides to control pest species
• In the early days of biological control, the process sometimes went wrong, and the introduced predator itself caused a problem
• Scientists now understand the possible problems of introducing biological control agents and detailed research and extensive trials are now used before introducing any control species