Study of Life 1,2,3

• Properties of life


  • DNA – heritable information
  • Reproduction: Life comes only from life
  • Growth and development
  • Energy utilisation
  • Response to environment
  • Homeostasis/Regulation
  • Evolutionary adaptation
• Certain natural entities have some but not all properties of life: Virus
• DNA


  • Hereditary material
  • Encodes biological information and transmit from one generation to the next
  • Continuity of life = heritable information
• Reproduction


  1. Asexual reproduction (bacteria)

  2. Sexual reproduction (higher eukaryotes)
• Asexual reproduction


  Offspring arise from a single parent (e.g. binary fission)
• Sexual reproduction


  Creates a new organism by combining the genetic material of two organisms (meiosis, gametes, fertilisation)
• Growth and development


  DNA directs the pattern of growth & development to produce organism that is characteristic to its species
• Energy utilisation


  • Organisms transform energy
  • They exchange energy with their environment (Food chain)
  • Chains of biochemical reaction to create & maintain order
  • Generate building blocks and energy
• Homeostasis/Regulation


  • Regulation by feedback mechanisms to achieve homeostasis (steady state physiological condition of the body)
  • Eg: Temperature sensing and response in human at warm environments (positive feedback, negative feedback)
• Life can be classified into many orders
• Taxonomy


  Practice and science of classification
• Nomos


  Law or science
• Evolution


  Life evolved from fewer, simpler organisms to many, more complex organisms
• Father of Taxonomy


  Carl Linnaeus
• Evolution


  Differs from religious views (Creation)
• Linnaean Classification consists of a hierarchy of groupings (taxa)
• Kingdom


  Largest and most inclusive grouping
• Evolutionary studies


  • Seek to understand the diversity and complexity of living organisms - their origin and history
  • Seek to understand the processes by which diversity has developed (formation of new species) and that act to maintain diversity
• Lamarck's theory of evolution


  Organisms change slowly and gradually over time into new species. Lamarckian "transformism"
• Species


  Smallest and most exclusive grouping
• Darwin's theory of evolution


  On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life in 1859
• Imperium Naturae - 3 kingdoms


  • Regnum Animale (Animal)
  • Regnum Vegetabile (Vegetables/Plants)
  • Regnum Lapideum (Minerals)
• In a small, intimately related group, there exist gradation and diversity (variation within the same species)
• Whittaker's Classification


  Based on difference in nutrition and structure - 5 Kingdoms
• All species living today are descendents of ancestral species: descent with modification
• 5 Kingdoms in Whittaker's Classification


  • Autotrophic (photosynthesis): Plants
  • Heterotrophic: Animals
  • Saprotrophs (break down and absorb surrounding materials)
  • Protista: Unicellular or multicellular without specialised tissues
  • Monera: Unicellular, no nucleus
• Darwinian evolution is more popular than Lamarckian evolution
• Darwinian evolution claims strong races can form species
• Woese's three domain system


  • 3 domains: Archaea, Bacteria, and Eukarya
  • 6 kingdoms: Archaebacteria (ancient bacteria), Eubacteria (true bacteria), Protista, Fungi, Plantae and Animalia
  • Based on differences in 16S (prokaryotic) and 18S (eukaryotic) rRNA genes
• Natural selection and evolutionary adaptation


  • Galapagos finches
• Binomial system of nomenclature


  Combination of a genus name and the species name to uniquely identify each species of organism
• Populations of the same species on different islands had some differences from each other
• Differences between populations on different islands developed into different species based on different environments
• Binominal nomenclature


  Scientific name/Latin
• Homologous bones


  • Seal, human, horse and bird
• The correct way of representing a binomial name is in print (italised) or in handwriting (underlined)
• Darwin's argument


  • Individuals show variation. Those best adapted have a greater chance of survival (natural selection)
  • More individuals are produced than can survive
  • Struggle for existence
  • Principle of inheritance. Selected varieties will produce offspring similar to themselves so these varieties will become more abundant in subsequent generations
• Binomial nomenclature of human beings


  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Primates
  • Family: Hominidae
  • Genus: Homo
  • Species: Homo sapiens
• Natural selection ignores reproduction
• Natural selection is a tautology i.e. it essentially says the survival of the survivors