Zoology 121 - Introduction to Zoology Notes

Introduction to Zoology

  • Zoology is the science studying animal life, focusing on:
  • Animal structure and internal processes.
  • Modes of life and evolution.
  • Interaction between species and their environments.
  • Growth, reproduction, inheritance principles, and distribution of life over time.

Subdivisions of Zoology

  • Main Areas:
  • Taxonomy
  • Ecology
  • Zoogeography
  • Animal evolution
  • Structural Studies:
  • Anatomy
  • Comparative Anatomy
  • Histology
  • Cytology
  • Embryology
  • Paleontology
  • Experimental Studies:
  • Experimental Zoology
    • Genetics
    • Experimental Morphology
    • Embryology
  • Molecular Biology
    • Biochemistry
    • Genetics
    • Chemistry of Macromolecules
  • Subcategories by Subject:
  • Entomology (insects)
  • Herpetology (amphibians and reptiles)
  • Ornithology (birds)
  • Parasitology (parasites)
  • Ichthyology (fish)
  • Mammalogy (mammals)

Theories of the Origin of Life

  1. Theory of Special Creations:
  • Life forms created by a supernatural power, immutable since creation.
  • Supported by Christianity with a specific creation timeline from the Bible.
  1. Abiogenesis:
  • Life originated from non-living matter (spontaneous generation) about 3.5 billion years ago.
  • Proposed by Aristotle with examples of organisms arising from decay and filth.
  • Experimentally rejected by Francisco Redi in 1668.
  1. Biogenesis:
  • States that life arises from pre-existing life.
  • Confirmed by Redi's experiment where maggots only arose from eggs laid by flies.
  1. Cosmozoic Theory:
  • Life came to Earth from another planet (panspermia).
  • Proposed by Richter and Arrhenius but lacks explanation for survival during space travel.
  1. Modern Chemical Theory:
  • Developed by Oparin and Haldane, suggesting life arose under primitive Earth conditions due to chemical reactions driven by solar and UV energy.
  1. Theory of Catastrophism:
  • Life originates and evolves through a cycle of creation and catastrophic events leading to extinction.

Characteristics of Living Things

  1. Order:
  • Highly organized structures (cells, tissues, organs).
  1. Irritability or Sensitivity:
  • Response to stimuli. Examples include hunger responses in organisms.
  1. Reproduction:
  • Ability to produce new organisms, either asexually or sexually, passing on genetic information.
  1. Growth and Development:
  • Organisms grow and develop based on genetic instructions.
  1. Metabolism:
  • Chemical processes essential for life, including nutrient transport and energy production.
  • Photosynthesis and cellular respiration are key processes.
  1. Homeostasis:
  • Ability to maintain stable internal conditions despite environmental changes. Example: thermoregulation in polar bears.
  1. Evolution:
  • Capacity of living beings to evolve over generations via natural selection, affecting species survival based on advantageous traits.