D. Introduction to Life Science

• Evolution and Adaptation


  • All biological beings must be able to adapt to their environment in order to survive living in their environment
• Adaptation


  Any structure, behavior, or internal process that allows response to a stimulus. It gives better chance of survival for an organism
• Evolution


  Gradual accumulation of adaptations over time
• Natural selection


  Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest
• Descent with modification


  Each living species has descended, with changes, from other species over time. This is a result of natural selection over a long period of time, which produces organisms that have different structures, establish different niches, or occupy different habitats
• Stimulus


  Any condition in the environment that requires an organism to adjust
• Response


  Reaction to stimulus
• Homeostasis


  Stable level of internal conditions
• Types of organism by cell organization

  • Unicellular – organism is made up of one cell
  • Multicellular – organism is made up of more than one cell
• Differentiated cells


  Different cells in one organism have different functions. Examples are the heart cells and lung cells
• Metabolism


  The chemical process by which a plant or an animal uses food, water, etc., to grow and heal and to make energy
• Categories of living things according to food source

  • Autotrophic – an organism that uses energy from the sun for photosynthesis to make its own food (plants)
  • Heterotrophic – an organism that ingests food to receive energy (animals, fungi, etc.)
• DNA (Deoxyribonucleic acid)


  Contains the hereditary material of a cell; the blueprint of reproduction, growth and development
• Growth


  An increase in the amount of living material
• Development


  All changes that an organism undergoes in its lifetime
• Ecology


  The study of the interaction of organisms with their environment
• Energy flow in an ecosystem

  Energy from the sun - is passed from one organism to another producers (plants) to herbivore (plant eater) to carnivore (meat eater) to decomposers (breakdown dead organisms)
• Factors that determine interdependence, survival, and growth of an organism in an environment

  • Abiotic factors – non-living factors such as air, water, energy, soil, temperature, and minerals are needed for survival
  • Biotic factors – include all living things on earth
• Special Creation


  Life-forms may have been put on earth by supernatural or divine forces. The theory of special creation says that a divine God created life which is at core of most major religions. It is the oldest hypothesis about life's origins and is the most widely accepted
• Extraterrestrial Origin


  Life may not have originated on earth at all; instead, life may have infected earth from some other planet. Also known as the theory of panspermia, it proposes that meteors or cosmic dust may have carried significant amounts of complex organic molecules to earth, which started the evolution of life
• Spontaneous Origin


  Most scientists tentatively accept the spontaneous origin. This theory states that living organisms can originate from inanimate objects
• Reducing atmosphere


  We refer to the early atmosphere as a reducing atmosphere because of ample availability of hydrogen atoms and their electrons. In such a reducing atmosphere, it would not take as much energy as it would today to form the carbon rich molecules from which life evolved
• Deep in the earth's crust


  Life might have formed as a by-product of volcanic activity, with iron and nickel sulfide minerals acting as chemical catalysts to recombine gases spewing from eruptions into the building blocks of life
• Volcanic activity


  Iron and nickel sulfide minerals acting as chemical catalysts to recombine gases spewing from eruptions into the building blocks of life
• Clay hypothesis


  Life is the result of silicate surface chemistry, with the surface of clays having positive charges to attract organic molecules and exclude water, providing a potential catalytic surface on which life's early chemistry might have occurred
• Deep-sea vents hypothesis


  Life originated at deep-sea hydrothermal vents, with the necessary prebiotic molecules synthesized on metal sulfides in the vents
• Miller-Urey experiment


  Early attempt to see what kinds of organic molecules might have been produced on the early earth, carried out by Stanley L. Miller and Harold C. Urey
• Bubble theories


  Theories that the location where life started is at "ocean's edge", with bubbles playing a key role in the evolution of cells
• Protobionts


  Chemical concentrating bubble-like structures proposed by Alexander Oparin as the precursors to cells
• microfossils - (fossilized forms of microscopic life) that are said to be 3.5 billion years old, and resemble present-day bacteria or prokaryotes
• Archaebacteria


  The first major group of bacteria, representing the surviving representatives of the first ages of life on earth, found in oxygen-free depths or high temperature environments, lacking peptidoglycan in their cell walls
• Eubacteria


  The second major group of bacteria, having very strong cell walls and a simpler gene architecture, including cyanobacteria that are photosynthetic and played a role in increasing oxygen levels in the atmosphere