Introduction to Biology

Definition of Biology

• Biology is the study of life, focusing on living organisms and their vital processes.
• It encompasses the structure, function, growth, origin, evolution, and distribution of life forms.

Properties of Life

• Organization: Living things exhibit a complex structure with specialized functions at various levels including:

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Individuals
  • Populations/Communities
  • Ecosystems

• Energy: Essential for performing work, energy exists in two forms:

  • Potential Energy
  • Kinetic Energy

• Growth and Development:

  • Growth refers to an increase in size.
  • Development involves changes in shape or form.

• Reproduction: The process through which new living organisms are created, categorized into:

  • Sexual reproduction
  • Asexual reproduction

• Response and Adaptation: Organisms have unique adaptations that enhance their survival in specific environments.

Cell History

• 1650: Invention of the first microscope by Hans and Zacharias Janssen.
• 1665: Robert Hooke studied cells by examining cork under a microscope.
• 1674: Anton van Leeuwenhoek discovered "animalcules" (microorganisms) in water.
• 1833: Robert Brown identified the nucleus as the cell's central part.
• 1838: Mathias Schleiden established that plants are made of cells.
• 1839: Theodore Schwann confirmed that animals consist of cells, contributing to the Cell Theory.
• 1858: Rudolph Virchow declared that all living cells arise from pre-existing cells, dismissing the notion of spontaneous generation.

Cell Theory

• Cells are the fundamental unit of structure and function in all organisms.
• All living creatures comprise one or more cells.
• Cells arise only from previously existing cells through the process of cell division.

Modern Version of Cell Theory

• Energy flow occurs within cells.
• Hereditary information, conveyed by DNA, is passed from cell to cell.
• All cells share a common basic chemical composition.