Unifying Principles of Life Notes

Cell Theory and Key Discoveries

• Cell Theory Principles:

  • All biological organisms are composed of cells.

  • Cells are the fundamental unit of life.

  • All cells arise from preexisting life.

  • Proposed by Matthias Jakob Schleiden and Theodor Schwann.

• Key Historical Discoveries:

  • Robert Hooke: Discovered cells.

  • Anton Van Leuwenhoek: Discovered protozoa and bacteria.

  • Robert Brown: Discovered the cell nucleus.

  • Albert Von Kolliker: Discovered mitochondria.

  • Schleiden and Schwann: Proposed cell theory.

  • Evans and Kauffman: Discovered Embryonic Stem Cells from mice.

  • James Thomson: Discovered Embryonic Stem Cells from humans.

  • Camillo Golgi: Discovered the Golgi apparatus.

  • Joseph Beinaime Caventou and Pierre Joseph Pelletier: Discovered chlorophyll.

Cell Classification and Structure

• Eukaryotic Cells:

  • Contain a nucleus enclosed within a nuclear membrane.

  • Form large and complex organisms classified under the kingdom Eukaryota (protozoa, fungi, plants, and animals).

• Prokaryotic Cells:

  • Single-celled organisms belonging to the domains Bacteria and Archaea.

  • Significantly smaller than eukaryotic cells, lacking a nucleus and membrane-bound organelles.

  • Encased by a cell wall; many feature a polysaccharide capsule or slime layer.

Gene Theory

• Core Concepts:

  • Proposed by Gregor Mendel.

  • States that characteristics of living organisms are controlled by genes passed from parents to offspring.

  • Genes are segments of DNA containing instructions to encode specific proteins.

  • Located on chromosomes inside every cell.

  • Humans possess approximately $20{,}000$ protein-coding genes.

Homeostasis

• Regulatory Mechanisms:

  • Defined as a dynamic, self-regulating process that maintains internal stability while adjusting to changing external conditions.

  • Represents an essential balance across physical systems required for proper organismal function and survival.

Evolution and Adaptation

• Theory of Evolution:

  • Based on the concept that all species are related and change gradually over time through genetic variation.

  • Formulated by Charles Darwin with three main components:

  • Random variation within members of a species.

  • Inheritance of traits by offspring.

  • Struggle for existence favoring individuals with favorable traits for survival.

• Adaptations:

  • Characteristics that enhance an organism's ability to survive and reproduce in a specific environment.

  • Example: The star-nosed mole possesses tactile tentacles on its nose to detect prey by touch in total underground darkness.