Biology ch1

• Biology is the study of living things
• Biology is a branch of science and a way of understanding nature
• Biologists deal with the living part of nature and with the non-living things which affect the living things in any way
• Biologists strive to understand, explain, integrate and describe the natural world of living things
• Biology


  The study of life
• It is very difficult to define life
• There are certain aspects of life that lie beyond the scope of the science of biology like the answers to the questions: what is the meaning of life? Why should there be life?
• These questions are not usually taken up by Biologists and are left to philosophers and theologians
• Biologists mainly deal with the matters relating to how life works
• Living organisms


  • Highly organized, complex entities
  • Composed of one or more cells
  • Contain genetic program of their characteristics
  • Can acquire and use energy
  • Can carry out and control numerous chemical reactions
  • Can grow in size
  • Maintain a fairly constant internal environment
  • Produce offspring similar to themselves
  • Respond to changes in their environment
• Any object possessing all these characteristics simultaneously can be declared as a living thing and is an object for biological studies
• The science of biology is a very wide based study
• It includes every aspect of a living thing
• It is but natural to divide this science into quite a number of branches for our convenience of comprehending and studying biology
• Branches of biology


  • Ecology
  • Embryology
  • Physiology
  • Morphology (external and internal)
  • Palaoeontology
  • Histology
  • Evolution
  • Genetics
  • Cell Biology
  • Zoogeography
  • Molecular Biology
  • Microbiology
  • Marine Biology
  • Environmental Biology
  • Freshwater Biology
  • Parasitology
  • Human Biology
  • Social Biology
  • Biotechnology
• Molecular biology


  A branch of biology which deals with the structure of organisms, the cells and their organelles at molecular level
• Environmental biology


  The study of organisms in relation to their environment, including interaction between the organism and their inorganic and organic environment, especially as it relates to human activities
• Microbiology


  The study of microorganisms which include Bacteria, Viruses, Protozoa and microscopic algae and fungi
• Freshwater biology


  The branch of biology that deals with the organisms living in freshwater bodies i.e., rivers, lakes etc and physical and chemical parameters of these water bodies
• Marine biology


  The study of life in seas and oceans, including the study of the marine life and the physical and chemical characteristics of the sea acting as factors for marine life
• Parasitology


  The branch of biology which deals with the study of parasites, including their structure, mode of transmission, life histories and host-parasite relationships
• Human biology


  The study of man, including form and structure, function, histology, anatomy, morphology, evolution, genetics, cell biology and ecological studies
• Social biology


  The branch of biology which deals with the study of social behaviour and communal life of human beings
• Biotechnology


  The use of living organisms, systems or processes in manufacturing and service industries
• Hundreds of chemical reactions are involved in maintaining life of even the simplest organism
• Of the 92 naturally occurring chemical elements, only 16 are commonly used in forming the chemical compounds from which living organisms are made
• These 16 elements and a few others which occur in a particular organism are called bioelements
• The six commonest bioelements that account for 99% of body mass

  • Oxygen (65%)
  • Carbon (18%)
  • Hydrogen (10%)
  • Nitrogen (3%)
  • Calcium (2%)
  • Phosphorus (1%)
• Other bioelements (about 1%)

  • Potassium (0.35%)
  • Sulphur (0.25%)
  • Chlorine (0.15%)
  • Sodium (0.15%)
  • Magnesium (0.05%)
  • Iron (0.004%)
  • Copper (trace)
  • Manganese (trace)
  • Zinc (trace)
  • Iodine (trace)
• The fact that the same 16 chemical elements occur in all organisms, and the fact that these elements are arranged in similar ways, suggests that all life has a common biochemical basis
• Types of ecological relationships

  • Commensalism
  • Mutualism
  • Competition
• Biome


  A large regional community primarily determined by climate
• The major type of plant determines the other kind of plants and animals in a biome
• Biomes have been named after the type of major plants or major feature of the ecosystem
• The living world is enormous in size and has been reproducing and evolving since its origin on this planet
• Today almost all parts of the world abound in living organisms
• The distribution of organisms in space can be studied through biomes