BIOLOGY

• This book is written for students following the Pearson Edexcel International Advanced Subsidiary (IAS) Biology specification
• This book covers the full IAS course and the first year of the International Level (IAL) course
• The book contains full coverage of IAS units (or exam papers) 1 and 2
• Each unit in the specification has two topic areas
• The topics in this book, and their contents, fully match the specification
• Students can prepare for the written Practical Skills Paper (unit 3) by using the IAL Biology Lab Book
• Each topic is divided into chapters and sections to break the content down into manageable chunks
• Each section features a mix of learning and activities
• Learning objectives


  Each chapter starts with a list of key assessment objectives
• Specification reference


  The exact specification references covered in the section are provided
• Exam hints


  Tips on how to answer exam-style questions and guidance for exam preparation. Orange Learning Tips help you focus your learning and avoid common errors
• Biodiversity is a measure of the variety of living organisms and their genetic differences
• Biodiversity is an important concept because the Earth's biodiversity is reducing rapidly
• Classification


  A means of organising the variety of life based on relationships between organisms using differences and similarities in phenotypes and in genotypes, and is built around the species concept
• The result of millions of years of evolution is an enormous variety of living organisms
• An internationally recognised way of referring to any living organism is essential
• Scientists can monitor changes in the populations of different types of organism if they know the numbers that there are in a particular habitat
• It is important for biologists to understand how different types of living organism are related to each other
• Taxonomy


  The science of describing, classifying and naming living organisms
• The aim of a classification system is to group organisms to accurately identify them and represent their ancestral relationships
• A valid classification system must be based on careful observation and the use of homologous structures - that is, structures that genuinely show common ancestry
• Carolus Linnaeus developed the first scientifically devised classification system in the 18th century
• The main taxonomic groups

  • Domain
  • Kingdom
  • Phylum (division, for plants)
  • Class
  • Order
  • Family
  • Genus
  • Species
• The Archaea domain contains one kingdom: Archaebacteria
• The Swedish botanist Carolus Linnaeus (1707-78) developed the first scientifically devised classification system


  18th century
• We still use many of Linnaeus' principles and his basic naming system today, but we can now add many more modern techniques to the simple but detailed observation of organisms that he introduced
• The main taxonomic groups from largest to smallest

  • Domain
  • Kingdom
  • Phylum (division, for plants)
  • Class
  • Order
  • Family
  • Genus
  • Species
• The Archaea domain contains one kingdom

  • Archaebacteria: ancient bacteria thought to be early relatives of the eukaryotes
• The Bacteria domain contains one kingdom

  • Eubacteria: the true bacteria are what we normally think of when we are describing the bacteria that cause disease, and which are so useful in the digestive systems of many organisms and in recycling nutrients in the environment
• The Eukaryota domain contains four kingdoms


  • Protista: a very diverse group of microscopic organisms, some heterotrophs, some autotrophs
  • Fungi: all heterotrophs, most saprophytic and some parasitic, with chitin in their cell walls
  • Plantae: almost all autotrophs, making their own food by photosynthesis
  • Animalia: all heterotrophs that move their whole bodies around during at least one stage of their life cycle
• Binomial system of naming organisms

  Every organism is given two Latin names - the genus name and the species or specific name which identifies the organism precisely
• There are certain rules to writing binomial names: use italics, the genus name has an upper-case letter and the species name a lower-case letter, and after the first use, binomial names are abbreviated to the initial of the genus and then the species name
• Genus


  A group of species that all share common characteristics
• Genus Vanessa


  • Painted Lady Vanessa cardui
  • Red Admiral Vanessa atalanta
  • Indian Red Admiral Vanessa indica
• It is not always so easy to tell the difference between species within a genus
• Full classification of four different organisms

  • Escherichia coli (common bacterium in the intestines)
  • Equus caballus (domestic horse)
  • Amanita muscaria (fly agaric)
  • Oryza sativa (rice)
• Whichever side you choose, your argument must be backed up by good scientific evidence
• The cell cycle includes interphase and mitosis. Mitosis has four phases: prophase, metaphase, anaphase and telophase
• The photograph below shows plant root cells at various stages of the cell cycle
• The graphs below show changes in the DNA content of cells during the cell cycle in two different plants, A and B